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Infrared (2–12 μm) Solid-State Laser Sources: A Review
Abstract
The infrared domain is very attractive for many applications owing to two unique features: (i) it contains several atmospheric transparency windows, (ii) it corresponds to the 'molecular fingerprint' region of the electromagnetic spectrum where various molecules have strong rovibrational absorption lines. In many cases, these applications (e.g. laser surgery, trace gas monitoring, remote sensing, nonlinear spectroscopy, countermeasures,...) require coherent light radiation as the one emitted by a laser source. In this context, the choice of the proper technology is a key issue. Depending on the selected application, it could be required the source to deliver tunable emission, narrow linewidth, nearly diffraction limited beam, pulsed or continuous-wave (CW) radiation, etc. This article briefly reviews the main technologies, restricted to CW and nanosecond pulsed sources emitting in the 2-12 mu m range. The technologies considered include rare-earth and transition-metal doped bulk and fiber lasers, semiconductor lasers, and optical parametric sources. Pros and cons of these technologies are then briefly discussed in the context of several selected applications.
... Mid-infrared (MIR) laser sources are of interest in various applications, including spectroscopy [1], laser ranging (LIDAR) [2], medical applications [3], material processing [4], and defense [4]. These applications require continuous-wave to ultra-fast pulsed sources [5,6]. High-energy laser sources of nanosecond pulses at 2-10 µm radiation are of particular interest for extreme ultraviolet (EUV) light generation in EUV lithography [7]. ...
... Possible sources at 2-µm wavelength fulfilling the aforementioned criteria are Tm 3+ /Ho 3+doped solid-state and fiber lasers [5]. An example is the high-energy Big Aperture Thulium (BAT) laser system operating at 1.9 µm-wavelength [9,10]. ...
A laser system generating high-energy pulses at 2-µm wavelength with pulse widths tunable from 10–24 ns is described. It comprises an optical parametric oscillator that generates mJ-level signal seed radiation and an optical parametric amplifier that boosts the output to 800 mJ of combined signal and idler when pumped with 2 J pulses of 1064-nm laser light. The system operated with KTP crystals and running at 10 Hz repetition rate is characterized in the spatial, temporal, and spectral domains. The effect of saturation leads to an output pulse approaching flat-top spatial and box-shaped temporal profiles, as desired in various applications. The amplified pulses can be imaged down to sub-100 µm diameters, making this laser system a suitable driver for plasma sources of extreme ultraviolet light.
... Depending on the laser parameters required, a wide choice of sources exists that emit in this portion of the "molecular fingerprint region". These include quantumcascade (QC) semiconductor lasers [3], Cr/Fe-doped II-VI chalcogenide solid-state lasers [4,5], and parametric frequency conversion sources [6]. Of the two direct emission routes, QC lasers are available across a wide spectral range (3-25 μm), but power scaling opportunities are limited. ...
... Similarly, Cr:CdSe/S lasers offer the potential for wide tuning at wavelengths >3 μm, but remain a relatively underdeveloped technology [7,8]. Alternatively, parametric wavelength conversion offers high average powers, supports large pulse energies, and wide spectral tunability dependent on the combination of pump source and nonlinear crystal [6,9]. Parametric sources based on a χ (2) nonlinearity can be realized using distinct architectures: optical parametric oscillators (OPOs), optical parametric amplifiers (OPAs) and optical parametric generators (OPGs). ...
... Solid-state lasers with wavelengths of 2-3 µm have important applications in lidar, microsurgery, processing of materials, gas sensing, and communications [1][2][3][4][5][6]. Generally, these lasers are based on bulk material doped with rare-earth ions (Tm, Ho, Er, Dy, etc.); however, the wavelength coverage of these lasers is limited by the emission spectrum of the active ions or the transmission range of the laser host materials [7][8][9][10]. ...
... This makes extending the 2 µm laser wavelength through the SRS effect more attractive. Over the last two decades, many Raman lasers have been investigated in the 2 µm wave band by using BaWO 4 , YVO 4 , KGd(WO 4 ) 2 , and diamond as Raman crystals [12][13][14][15][16][17][18][19][20][21]. ...
A dual-wavelength passively Q-switched Ho:GdVO4 self-Raman laser in the 2.5 µm wave band was demonstrated with Cr:ZnS as a saturable absorber. Synchronized dual-wavelength pulsed laser outputs at 2473 nm and 2520 nm were acquired, corresponding to Raman frequency shifts of 808 cm⁻¹ and 883 cm⁻¹, respectively. The maximum total average output power of 114.9 mW was obtained at an incident pump power of 12.8 W with a pulse repetition rate of 3.57 kHz and a pulse width of 16.36 ns. The maximum total single pulse energy was 32.18 µJ, corresponding to a total peak power of 1.97 kW. The power ratios of the two Raman lasers can be controlled by varying the incident pump power. To the best of our knowledge, this is the first time a dual-wavelength passively Q-switched self-Raman laser in the 2.5 µm wave band has been reported.
... Commonly, the Ho:LaF 3 gain mediums require an excitation light source at 1.9 µm, corresponding to the major emission peak of Tm 3+ [20,21]. Therefore, Tm 3+ ions, serving as sensitized ions, are frequently codoped with Ho 3+ to fabricate gain mediums. ...
In this paper, we explore the laser properties of a 2.1 µm Ho:LaF3 laser intracavity pumped by a LD-pumped Tm:YLF laser. Ho:LaF3 crystals, with a doping concentration of 2%, have been verified as a novel type of laser gain material, whose luminescence lifetime of the ⁵I7 level was up to 25.7 ms. The Ho:LaF3 laser achieved an average output power of 2.07 W with a slope efficiency of 16.2%. The dual-wavelength output centered at 2089 nm and 2093 nm and exhibited excellent spot quality with M²x and M²y values of 1.19 and 1.23, respectively. Our results effectively demonstrate the impressive capability of Ho:LaF3 crystals for generating high-power 2.1 µm mid-infrared lasers.
... High-power solid-state lasers in the 2-μm spectral range have been widely applied in various fields, including remote sensing, lidar, laser surgery and therapy, laser welding of transparent plastics, and pumping mid-infrared optical parametric oscillators (OPOs) for mid-IR frequency conversion [1][2][3][4]. Tm 3+ -doped, Ho 3+ -doped gain media provide the main approach to directly generate 2-µm high-power laser [5][6]. Compared to the Tm 3+ ions, the large emission cross section of Ho 3+ ions doped crystals makes it more ideal to achieve high power of 2-μm laser, for instance, yttrium aluminum garnet (Y3Al5O12, YAG) crystals doped with Ho 3+ ions have a gain cross section 7 times larger than Tm:YAG [7-8]. 1 presents an overview of CW Ho-lasers in the 2-µm spectral range [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26], containing Ho:YAG bulk, thin-disk, slab and Ho:fiber laser systems, illustrating the significant advances in terms of high power and efficiency that have been achieved in recent years. ...
... In the visible and near-infrared wavebands, many efficient Raman lasers whose conversion efficiency is close to the quantum limit have been reported [4][5][6][7]. The 2-3 µm mid-infrared Raman lasers have many important applications, such as medicine, gas spectroscopy, material processing, and environmental monitoring [8]. However, the Raman gain coefficient of Raman crystal evidently decreases as the fundamental laser wavelength increases, which limits the development of the 2-3 µm mid-infrared laser based on SRS effect [3]. ...
We demonstrate an efficient active Q-switched Ho:GdVO 4 self-Raman laser at 2500 nm for the first time, to our knowledge. Using Ho:GdVO 4 crystal as the gain medium for both the 2048nm fundamental laser and the 2500 nm Raman laser, the output performances of a new mid-infrared self-Raman laser were investigated. The maximum average output power of 1.45 W was achieved at an incident pump power of 22.5 W, with a slope efficiency of 25.8%, for an output transmittance of 30% and a pulse repetition frequency of 15 kHz. The maximum single pulse energy of 96.7 µJ with a pulse width of 11.35 ns was obtained, corresponding to the peak power of 8.5 kW. The beam quality was near diffraction limited with the M ² factors of 1.15 and 1.06 along the x and y directions. Moreover, adopting the two-end output way of the fundamental laser and the Raman laser, the Raman gain coefficient of Ho:GdVO 4 crystal was estimated to be 1.14 cm/GW at 2048nm. This work shows that Ho:GdVO 4 is an excellent self-Raman laser crystal for the generation of high power Raman laser at 2.5 µm.
... Lasers in the mid-infrared (MIR) 2 µm range with short pulses are promising for scientific research, medical diagnostics and environmental monitoring, among many other areas [1][2][3][4][5]. In order to obtain pulsed lasers with high power and short pulse width in the 2 µm wavelength range, the passively Q-switched (PQS) technique is one of the most effective methods used by researchers, due to its compactness and simplicity of design. ...
We have successfully achieved the synthesis of heterojunction consisting of WSe2 and BN, by using a liquid phase exfoliation method, and characterization of the prepared materials under the microstructure. The WSe2/BN heterojunction was used as a saturable absorber in the Tm:YAP laser for passively Q-switched operation, and a pulsed laser with an output wavelength around 2 µm range was successfully obtained. After comparing the effects of resonators composed of different cavity mirrors, it is concluded that when the curvature radius of the input mirror is 250 mm and the transmittance of the output coupler is 2.5%, the best output performance was obtained. The maximum average output power of 834 mW was achieved, with a pulsed repetition frequency of 43.51 kHz and a minimum pulse duration of 1.28 µs, corresponding to a peak power of 14.97 W and a maximum single pulse energy of 19.17 µJ.
... This implies that the ultra-broadband nature of IRSR still remains superior to any possible benchtop laser source. It is indeed undoubtable that the progresses in laser technologies opened new opportunities for laboratory-based IR spectroscopy and imaging, especially in the Mid-IR [12] and THz regime [13], but the Far-IR region is still uncovered by lasers. Taken into consideration the overcoming of the diffraction limited spatial resolution offered by wavelength-independent near field approaches nowadays available, IRSR offers a great opportunity for integrating spectroscopy-microscopy and nanoscopy IR programs at a DLSR, promoting also a better communication and overlap with nano-resolved Xray microscopy and imaging approaches. ...
... (b) signal power versus pump power at 300 Pa pressure with output light field shown in inset Fig. 8 Schematic diagrams of energy level transitions of Tm 3+ , Ho 3+ and Er 3+ (from left to right) [29] 综 述 Table 2 Tuning range and width of Tm 3+ doped laser with different substrates [30] Gain material Fig. 9 Overall experimental scheme [36] . (a) Energy level diagram of GSA and ESA dualwavelength pumped scheme; (b) experimental arrangement for GSA and ESA dualwavelength pumped Tm 3+ ∶YAP laser Fig. 10 Configuration of tunable multiwavelength Ho 3+ doped fiber laser [49] 综 述 Fig. 11 Diagrams of sidepumped Er 3+ ∶YSGG slab laser; (a) Top view; (b) side view [52] 综 述 Fig. 12 Schematic diagram of 140 W Cr 2+ ∶ZnSe laser system [67] 图 14 室温下 30. ...
... Ultrashort pulsed solid-state lasers operating in the 2 μm wavelength range could generate pulsed lasers with high peak power and typical narrow pulse width, and they not only in the safety range of the human eye, but also have a strong absorption capacity in water and human tissues. Therefore, solid-state lasers that generating ultrashort pulses of 2 μm are performing well in various industries, such as lidar, scientific research applications, environmental monitoring, aerospace, additive manufacturing, etc., and also play an extremely important role in social production activities such as precision medicine and industrial micromachining [1][2][3][4][5] . ...
We have successfully achieved the synthesis of heterojunction consisting of WSe2 and BN, by using a liquid phase exfoliation method，and characterization of the prepared materials under the microstructure. The WSe2/BN heterojunction was used as a saturable absorber in the Tm:YAP laser for passively Q-switched operation, and a pulsed laser with an output wavelength around 2 μm range was successfully obtained. After comparing the effects of resonators composed of different cavity mirrors, it is concluded that when the curvature radius of the input mirror is 250mm and the transmittance of the output coupler is 2.5%, the best output performance was obtained, and the output power is 834mW, with a repetition rate of 43.51 kHz and a minimum pulse duration of 1.28 µs, corresponding to a peak power of 14.97 W and a maximum single pulse energy of 19.17 µJ.
... Ultrafast laser sources emitting around 2 µm spectral region attract intense attention due to their promising applications in various fields, such as optical communication, remote sensing, laser surgery, material process, and nonlinear frequency conversion [1][2][3][4][5][6][7][8][9][10]. Moreover, such laser sources with high power and picosecond pulses can be used for improving the resolution in the laser range and reducing the damage densities in pumping optical parametric oscillators for the generation of frequency combs in the mid-IR spectral region. ...
A diode-end-pumped self-mode-locked Tm,Ho:LuLiF4 (LLF) laser is demonstrated for the first time, to the best of our knowledge. At the incident pump power of 3.4 W, the stable self-mode-locked operation of the Tm,Ho:LLF laser was realized without any additional devices in the resonator. Further increasing the incident pump power to 6.8 W, the maximum average output power of 1.07 W was achieved at 2068 nm with a pulse width of 746 ps and a repetition frequency of 468 MHz. The experimental results indicate that the Tm,Ho:LLF crystal is promising to generate the high-power self-mode-locked solid-state laser at 2 μm waveband. The self-mode-locked Tm,Ho:LLF laser has potential applications in optical communication, remote sensing, material process, and nonlinear frequency conversion.
... As we all know, mid-infrared (MIR) laser sources operating in the approximate 3.0 µm range have significant potential applications in the fields of environmental monitoring, optoelectronic countermeasures, oilfield exploitation, materials processing and scientific research, etc [1][2][3]. Furthermore, ∼3.0 µm wavelength laser, due to its strong absorption of water (absorption coefficient is about 10 4 cm −1 @3.0 µm) [4], has been proven to be an excellent soft tissue scalpel with powerful cutting capability. Holmium ion (Ho 3+ ) can yield laser oscillation at this wavelength by the 5 I 6 → 5 I 7 transition. ...
We demonstrate the thermal, spectroscopy and laser properties of Ho,Pr doped YAP crystal grown successfully by Cz method. The thermal expansion coefficient, thermal conductivity, absorption and emission spectra of Ho,Pr:YAP crystal are investigated in detail. Additionally, the level lifetimes suggest that Pr³⁺ is a suitable deactivating ion for Ho:YAP crystal. Particularly, the actual laser performance is optimized by doping active ion Ho with high concentrations and introducing deactivated Pr³⁺, resulting in decreased laser threshold, increased laser output power and slope efficiency. A 3.01 µm laser with output power of 502 mW, slope efficiency of 6.3% and beam quality factors of 1.42/1.43 is achieved in the Ho,Pr:YAP crystal, as far as we know this is the highest ∼3 µm CW laser power realized in Ho³⁺ doped oxide crystals.
... Each type of material and doping ion has its particularity and specificity. Their applications are also numerous and diversified, such as lighting applications, solid-state lasers, telecom, range-finding and remote sensing, plasma display panels, photoluminescence thermometry, without mentioning the numerous medical and military applications [1][2][3][4][5][6][7][8][9][10][11]. ...
... These high-brightness sources are essential in many fields such as sensing, metal and polymer processing, optical communications, defense systems, and medical applications. [1][2][3][4][5][6]. Absorption spectra of commonly used polymers in the plastics industry significantly increase in the 2.2-2.4-µm ...
This paper presents an all-passive external cavity KGW Raman laser in the 2- $\mathrm{\mu}$ μ m spectral range, pumped by a Tm:YLF laser at 1879.5 nm. The Raman laser emits two lines at 2197 nm and 2263 nm achieving maximum energy outputs of 1.86 mJ and 2.08 mJ, and conversion efficiencies of 40% and 45.3%, respectively. To the best of our knowledge, this laser performance is a new record in terms of energy per pulse and conversion efficiency, surpassing the two-mJ level for the first time by stimulated Raman scattering in the 2- $\mathrm{\mu}$ μ m range in an all-passive configuration.
... Ultrafast 2-µm lasers are in high demand for various applications, including frequency comb generation [1,2], spectroscopy, frequency downconversion to the mid-infrared spectral region using non-oxide nonlinear crystals [3,4], and high-harmonic generation toward the soft x ray region [5]. Tm 3+ -doped materials are well suited for high-power ultrafast 2-µm lasers. ...
We report on a continuous wave (CW) and Kerr-lens mode-locked (KLM) Tm³⁺:YScO3 single-crystal laser centered at 2.1 µm. Efficient CW laser operation with a maximum slope efficiency of 51% was achieved under in-band pumping by an Er:Yb fiber master oscillator power amplifier (MOPA). In KLM operation, pulses as short as 49 fs corresponding to seven optical cycles were achieved at a repetition rate of 96.7 MHz with an average output power of 126 mW. Such short pulse durations are enabled by the inhomogeneously broadened emission spectrum of Tm³⁺:YScO3 extending to above 2200 nm.
... Rare-earth (RE) ions are optically active elements that are sources of effective luminescence, and nanoparticles doped with these ions are characterized by high quantum yields, wide possibilities of tuning optical properties, and noticeable suppression of the effect of concentration quenching [12]. Therefore, luminescent glasses and glass ceramics based on rare-earth ions with a stoichiometric or non-stoichiometric composition are a promising replacement for phosphor single crystals [13]. ...
Samples of nanocrystalline PbF2 glass ceramics were obtained by heat-treating SiO2–GeO2–PbO–PbF2–CdF2 glasses. The Ho2O3 and Tm2O3 doping effects on the structural features of PbF2 nanoparticles were studied using small-angle X-ray scattering and X-ray diffraction methods. The enlargements of the average sizes of nanoparticles and the sizes of local areas of density fluctuations have been found to be correlated with an increase in concentrations of Ho2O3 and Tm2O3 in initial glasses. A variation in the concentrations of Ho2O3 and Tm2O3 does not affect the morphology and fractal dimension of the formed PbF2 nanoparticles.
... There are wide applications for the 1.5 μm middle infra-red laser generated by the Er 3+ doped laser materials: medical surgery, remote sensing ranging, and optical communication [18][19][20]. Due to the very rich energy level of Er 3+ , Er 3+ doped laser materials have wide absorption bands in the visible light and 1.5 μm region, easy to find an effective pump source. Considering the advantages of fluoride materials, the Er:SrF 2 ceramics can meet the requirements of infra-red laser materials such as the high thermal conductivity, high mid-infrared transmittance and low phonon energy et al. [21]. ...
Using the 1at.% Er:SrF2 nano-powders synthesized by the co-precipitation method as starting powders, 1at.% Er:SrF2 transparent ceramics were successfully prepared by air pre-sintering at different temperatures for 2 h combined with hot isostatic pressing (HIP) post-treatment at 600 oC for 2 h under 100 MPa Ar. The influences of the pre-sintering temperature on optical quality, microstructure, phase composition and EPR spectrum of ceramics were investigated. Among all the HIP post-treated 1at.% Er:SrF2 ceramics in the thickness of 2.5 mm, the sample pre-sintered at 650 oC shows the best optical quality, whose transmittance at 2500 nm and 1500 nm reaches 83.4% and 73.6%, respectively. Furthermore, the spectral characteristics of this ceramic sample were systematically analyzed. The fluorescence lifetime for the 1at.% Er:SrF2 ceramics at 1530 nm is 49.62 ms. The strongest absorption and emission cross section for the peaks at around 1530 nm are 6.20×10-21 and 3.47×10-21 cm2, respectively. In brief, the above findings indicate that the Er:SrF2 ceramics is a promising candidate as middle infra-red laser gain media.
... Myriads of middle-infrared (midIR, 1400-3000 nm) applications require either broadband ultra-short pulses or wide tunability. In recent years, lots of research have been conducted on solid-state laser materials emitting in the midIR spectral range (such as Tm 3+ , Ho 3+ , Cr 2+ or/and Er 3+ -doped materials) [1,2]. However, these active materials cannot directly generate few-cycles pulses (FCP) without a nonlinear (postcompression) stage [3,4]. ...
We present the simulation, fabrication, and characterization of large area microstructured fiber tapers which enables broadband phasematching conditions of the four wave-mixing process. These silica-based tapers are intended to serve as a nonlinear gain medium for intense and high average power Fiber Optical Parametric Chirped Pulse Amplifier emitting at 2 μm\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\upmu \hbox {m}$$\end{document} and strongly pumped at Yb wavelength. Different geometries (tapered/untapered, aspect ratio, etc.) are fabricated, analyzed and their broadening properties—key for supporting ultrashort pulses amplification—are compared and discussed. The characterization of nonlinear gain bandwidth of the tapers relies on a tunable source of stochastic pulses based on tunable amplified spontaneous emission in Yb-doped amplifiers. The strong overshoots of this source allows degenerate four-wave mixing process to occur thus generating broadband incoherent visible signal and mid-infrared idler waves at much lower average power than usually needed with coherent pumping. The idler centered around 1.85 μ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mu$$\end{document}m is broadened due to zero-dispersion wavelength shift along the taper.
... Over the past several decades, mid-infrared (MIR) solid-state lasers operating around 2.7-3 µm have received extensive attention for numerous applications in medicine surgery, communications, remote sensing, pollution monitoring, and military countermeasures, etc. [1][2][3][4][5]. Additionally, 2.7-3 µm lasers are suitable pump sources for longer wavelength mid-infrared or long-infrared (8-12 µm) laser applications utilizing the optical parametric oscillators [6,7]. ...
An efficient enhancement of 2.78 μm emission from the transition of Er3+: 4I11/2 → 4I13/2 by Tm3+ introduction in the Er/Tm: PbF2 crystal was grown by the Bridgman technique for the first time. The spectroscopic properties, energy transfer mechanism, and first-principles calculations of as-grown crystals were investigated in detail. The co-doped Tm3+ ion can offer an appropriate sensitization and deactivation effect for Er3+ ion at the same time in PbF2 crystal under the pump of conventional 800 nm laser diodes (LDs). With the introduction of Tm3+ ion into the Er3+: PbF2 crystal, the Er/Tm: PbF2 crystal exhibited an enhancing 2.78 μm mid-infrared (MIR) emission. Furthermore, the cyclic energy transfer mechanism that contains several energy transfer processes and cross-relaxation processes was proposed, which would well achieve the population inversion between the Er3+: 4I11/2 and Er3+: 4I13/2 levels. First-principles calculations were performed to find that good performance originates from the uniform distribution of Er3+ and Tm3+ ions in PbF2 crystal. This work will provide an avenue to design MIR laser materials with good performance.
... I n recent years, short-pulse solid-state lasers with narrow linewidths and high pulse energies have shown promise for applications in light detection and ranging (LIDAR), [1][2][3][4] precision laser microfabrication, 5) military, 6) and medical fields. 7) For instance, an injection-seeded Nd:YAG laser with a linewidth of 0.5 m −1 achieves a maximum wind velocity sensitivity of 1.09%/(m s −1 ) with respect to the Doppler LIDAR. 2) The types as well as the intracavity loss of a laser resonator cavity have been proven to be the main factors determining the linewidth of pulse solid-state lasers. ...
This work demonstrates that the Brillouin gain linewidth and pump power density are the primary factors affecting the linewidth of the Stokes pulse. As the pump power density increases, the Stokes linewidth tends to narrow and approaches the pump linewidth. This is the first study to reveal that the pump linewidth is the limiting factor in narrowing the Stokes linewidth. The Stokes linewidths of different liquid media were compared, and it was found that media with a wide Brillouin gain linewidth can be used to obtain lasers with a wider range of linewidths.
... [1][2][3][4][5][6][7] Therefore, many nonlinear optical crystals have intensively been studied and developed to produce laser sources of these ranges. 3,[8][9][10][11][12] Among these materials, special attention has been paid to those which can effectively convert the 1.060-1.064 mm emission from commercially available laser medium sources such as Nd:YAG, Nd:Cr:YAG, Nd:YLF, Nd:YVO 4 , and Nd:YCO. ...
The electronic and optical properties of an AgGaGeS4 crystal were studied by first-principles calculations, where the full-potential augmented plane-wave plus local orbital (APW+lo) method was used together with exchange-correlation pseudopotential described by PBE, PBE+U, and TB-mBJ+U approaches. To verify the correctness of the present theoretical calculations, we have measured for the AgGaGeS4 crystal the XPS valence-band spectrum and the X-ray emission bands representing the energy distribution of the electronic states with the biggest contributions in the valence-band region and compared them on a general energy scale with the theoretical results. Such a comparison indicates that, the calculations within the TB-mBJ+U approach reproduce the electron-band structure peculiarities (density of states-DOS) of the AgGaGeS4 crystal which are in fairly good agreement with the experimental data based on measurements of XPS and appropriate X-ray emission spectra. In particular, the DOS of the AgGaGeS4 crystal is characterized by the existence of well-separated peaks/features in the vicinity of −18.6 eV (Ga-d states) and around −12.5 eV and −7.5 eV, which are mainly composed by hybridized Ge(Ga)-s/p and S-p state. We gained good agreement between the experimental and theoretical data with respect to the main peculiarities of the energy distribution of the electronic S 3p, Ag 4d, Ga 4p and Ge 4p states, the main contributors to the valence band of AgGaGeS4. The bottom of the conduction band is mostly donated by unoccupied Ge-s states, with smaller contributions of unoccupied Ga-s , Ag-s and S-p states, too. The AgGaGeS4 crystal is almost transparent for visible light, but it strongly absorbs ultraviolet light where the significant polarization also occurs.
... Nanosecond pulsed lasers based on thulium-doped solid-state lasers and emission in the 1.9-2 μm band ( 3 F 4 → 3 H 6 ) have wide application values in laser ranging, spectroscopy, optical medicine, and metrology [1][2][3][4] . In the past two decades, passively Q-switched (PQS) lasers using saturable absorbers (SAs) have strongly promoted the development of high-quality pulsed lasers, largely due to the rapid development of SAs. ...
... Thulium (Tm) doped solid-state lasers operating in the 2-lm eye-safe spectral range are of interest for applications in photomedicine, laser ranging and infrared lidar [1]. Q-switched 2-lm lasers are especially important for pumping optical parametric oscillators (OPO) for efficient conversion into the mid-infrared [2]. By using active or passive Q-switch elements, pulsed 2-lm laser sources have been widely obtained. ...
... However, investigations of the combination of SRS and SRRS (SV-RRS) of hydrogen are sparse. The SV-RRS of hydrogen pumped by a 1064-nm laser can generate an ∼2.1-µm Raman laser, which is within an atmospheric transmission window, and a laser of this waveband can be used as a light source for remote sensing [19]. ...
A ${\sim}{{2}.{1 {\text-}}}\unicode{x00B5}{\rm m}$ ∼ 2 . 1 - µ m laser is within an atmospheric transmission window and can be used in remote sensing. In this work, a 1064-nm laser was used as the pump source, pressurized hydrogen was used as the Raman active medium, and a dual-wavelength ${\sim}{{2}.\rm{1{\text -}}}\unicode{x00B5}{\rm m}$ ∼ 2 . 1 - µ m Raman laser was generated. The 2147-nm laser was generated by a combination processes of stimulated vibrational Raman scattering and stimulated rotational Raman scattering, while a 2132-nm laser was generated by stimulated S-branch vibrational Raman scattering. Optimizing experimental conditions yielded a maximum pulse energy of 76.1 mJ, a peak power of ${\sim}{9.2}\;{\rm{MW}}$ ∼ 9.2 M W , and a photon conversion efficiency of 29.8%.
... To be established as an analytical technique, IR action spectroscopy must become independent from FELs and adopt solid-state table-top solutions. [155] Alternative mid-IR light sources are OPOs, [103] semiconductor-based quantum cascade lasers [156] and hybrid fiber-bulk chalcogenides based laser systems. [157] OPOs provide high intensities in a relatively large tuning range, and especially kHz and MHz OPOs were shown to provide high quality IRMPD spectra in the 3 μm range. ...
Lipids are small but complex biomolecules that feature an immense structural and functional diversity. The molecular structure and biological functions of lipids are intricately linked. Therefore, modern lipid analysis strives for complete structural elucidation and spatial mapping of individual species in tissues. Mass spectrometry is the uncontested key technology in lipidomics but cannot achieve this goal as a standalone technique. In particular, the distinction between frequently occurring isomers constitutes a major challenge. A promising step towards complete structural analysis of lipids consists in the coupling of mass spectrometry with laser light. Here we review recent advances in lipidomics applications employing laser‐induced ultraviolet and infrared photodissociation and ion spectroscopy, which substantially increase the gain in structural information. Fundamental concepts, instrumentation and promises of these powerful emerging techniques for future lipid analysis are outlined.
... Rare-earth ions are well-known optically active elements, which are sources of effective luminescence, and nanoparticles doped with these ions are characterized by high quantum yields, wide possibilities of tuning optical properties, and noticeable suppression of the effect of concentration quenching. Therefore, luminescent glasses and glass ceramics based on rare-earth ions with a stoichiometric or non-stoichiometric composition are a promising replacement for phosphors single crystals [12]. In this point of view, the up-conversion luminescent glass ceramics are of particular interest [13][14][15]. ...
... Mid-infrared pulsed fiber laser sources operating in the 2 and 3 μm spectral regions have remained a research hotspot attributed to their numerous applications in remote sensing, spectroscopy, free-space communications, and laser surgery [1][2][3][4][5][6]. Compared with actively modulated pulsed lasers, the passively modulated ones with saturable absorbers, such as passively Q-switched and passively modelocked lasers, show the merits of low cost and simple structure without the requirement of high-voltage and RF drivers. ...
We investigated 2 and 2.9 μm mid-infrared fiber lasers passively Q-switched by MIL-68(Al) and MIL-68(Fe), which were fabricated via the hydrothermal method. The modulation depth of MIL-68(Al) was found to be 9.12% at 1.99 μm. And the modulation depths of MIL-68(Fe) were found to be 18.89% and 15.79% at 1.99 μm and 2.87 μm, respectively. We report Q-switching pulse generation in both Tm ³⁺ -doped and Ho ³⁺ /Pr ³⁺ co-doped fiber lasers by using the as-prepared MIL-68 (M, M = Al ³⁺ , Fe ³⁺ ) as SAs. The center wavelengths were at 1.99 μm and 2.87 μm, respectively. These results indicate that MIL-68(M) has wideband nonlinear optical properties and promising application prospects in the field of optical modulators at 2- and 2.9-μm mid-infrared waveband. Work clearly accessible to a broad readership.
We review mid-infrared Er:ZBLAN fiber lasers and Fe:ZnSe lasers pumped by fiber lasers. We developed high-power Er:ZBLAN fiber lasers whose output power exceeds 30 W at 2.8 μm and applied 10-W-level fiber lasers for pumping Fe:ZnSe lasers that cover a wavelength range from 4 to 5 μm. We demonstrated that ZnSe crystals reach their highest potential with a high-beam-quality fiber laser. This laser technology paves the way for the development of powerful mid-IR sources for cutting-edge fields in industry, medicine, and science.
The acronym LIDAR stands for LIght Detection And Ranging, an optical analog of RADAR (RAdio Detection And Ranging). The conventional version of LIDAR requires a laser transmitter to launch short pulses of coherent light, which are scattered from atmospheric targets of interest back to an optical receiver, with a time delay that is determined by the range of the target. Optical phenomena in the Earth's atmosphere (e.g. Rayleigh scattering, Raman scattering, Mie scattering, refraction, and resonant absorption) contribute to the amplitude of optical signals returning to the receiver and their characteristic wavelength dependence allows us to measure the concentration and velocity distributions of different atmospheric molecules and aerosol particles. LIDAR backscattering in the infrared (IR) region, on which this article concentrates, is well suited to detecting aerosols (as in clouds or industrial particulate emissions). IR DIAL (DIfferential Absorption Lidar), a variant in which two or more wavelengths are used simultaneously to separate resonant molecular signals from background, enables many molecular species to be monitored by means of their IR absorption spectra. Closely related approaches comprise long‐path IR laser absorption and IPDA (Integrated Path Differential Absorption), with retroreflection from a topographic target (e.g. a strategically located mirror or a hard target, such as the ground in air‐borne applications); these approaches sacrifice optical range information but gain sensitivity because they integrate over all molecules in the optical column between the transmitter/receiver and the reflector or hard target. All of these techniques are vitally dependent on pulsed IR laser technology.
We report a high-power single-mode InP-based 2 μm distributed feedback (DFB) laser with a second-order buried grating and corrugated sidewalls. A second-order semiconductor grating is used for in-plane feedback and vertical out-coupling. The corrugated sidewalls are used to eliminate higher-order transverse modes. For the DFB laser with a 2 mm long cavity and 15 μm wide ridge, the maximum continuous-wave edge-emitting and surface-emitting single-mode powers at 300 K are up to 81 and 42 mW, respectively. A single-lobed far-field radiation pattern with a low divergence angle of approximately 8.6° is achieved by a device with a ridge width of 15 μm. The single-longitudinal-mode emission wavelength of the fabricated laser can be adjusted from 2003.8 nm at 288 K to 2006.9 nm at 313 K without any mode hopping. Robust single-mode emission with a side-mode suppression ratio of 30 dB is achieved under all injection currents and temperature conditions.
Modern infrared (IR) microscopy, communication, and sensing systems demand control of the spectral characteristics and polarization states of light. Typically, these systems require the cascading of multiple filters, polarization optics, and rotating components to manipulate light, inevitably increasing their sizes and complexities. Here, we report two-terminal mid-infrared (mid-IR) emitters, in which tuning the polarity of the applied bias can switch their emission peak wavelengths and linear polarization states along two orthogonal orientations. Our devices are composed of two back-to-back p-n junctions formed by stacking anisotropic light-emitting materials, black phosphorus and black arsenic-phosphorus with MoS2. By controlling the crystallographic orientations and engineering the band profile of heterostructures, the emissions of two junctions exhibit distinct spectral ranges and polarization directions; more importantly, these two electroluminescence (EL) units can be independently activated, depending on the polarity of the applied bias. Furthermore, we show that when operating our emitter under the polarity-switched pulse mode, the time-averaged EL exhibits the characteristics of broad spectral coverage, encompassing the entire first mid-IR atmospheric window (λ: 3-5 μm), and electrically tunable spectral shapes.
All passive Tm:YLF/KGW Raman laser at 2196 and 2262 nm is presented. Pulse energy of 1.1mJ was achieved, the highest energy per pulse reported using KGW at the SWIR with high conversion efficiency of 33%.
We present the laser characteristics of a 5 at.% Tm:YLF crystal using a modular setup at cryogenic temperatures emitting around 2 µm. Continuous-wave laser operation was achieved by pumping the laser crystal using a Volume Bragg Grating-stabilized laser diode emitting at 793 nm. A maximum output power of 6.5 W was achieved at 80 K corresponding to a slope efficiency of 66.0% with respect to the absorbed power with excellent beam quality.
Ho³⁺-doped CaY0.9Gd0.1AlO4 single crystal was successfully grown by the Czochralski technique for the first time. The polarized absorption spectra, polarized luminescence spectra and fluorescence decay curve of the crystal were investigated at room temperature. The spectroscopic parameters are calculated based on Judd–Ofelt theory, the values of Ω2,4,6 were calculated to be 3.16 × 10⁻²⁰ cm², 3.93 × 10⁻²⁰ cm², 0.91 × 10⁻²⁰ cm², respectively. The Ho:CaY0.9Gd0.1AlO4 crystal exhibits strong emission at 2013 nm for π- and 2032 nm for σ-polarizations with stimulated emission cross section of 6.64 × 10⁻²⁰ cm² and 1.90 × 10⁻²⁰ cm², respectively. The fluorescence lifetime of the ⁵I7 level was measured to be 6.60 ms. The continuous-wave (CW) laser operation of Ho:CaY0.9Gd0.1AlO4 crystal around 2 μm was demonstrated.
A ZnGeP>2 (ZGP) optical parametric oscillator (OPO) with wide mid-IR tunability has been demonstrated. The singly resonant angle-tuned ZGP OPO was pumped by 100-ns erbium laser pulses at λ =2.93μm and yielded output that was continuously tunable from 3.8 to 12.4 μm (type I phase matching) and from 4 to 10 μm (type II phase matching). An OPO pump threshold was less than 1 mJ in the whole 4–12 μm range of the output, and the quantum conversion efficiency reached 35%. An OPO linewidth was typically a few wave numbers; however, with a single intracavity etalon (uncoated Si plate) in a type II OPO it was narrowed to <0.5cm-1. We demonstrate the sensitive detection of N2O gas with the narrow-linewidth OPO.
We have carried out detailed optical and thermal simulations of quantum cascade laser (QCL) operation as a function of material and device parameters. The main objective of the study is to evaluate the potential for improvements in the cw wallplug efficiencies and output powers beyond the current state of the art, when such parameters as the internal loss, series resistance, doping level in the active region, number of QCL stages, ridge width, cavity length, current density, and operating temperature are varied within reasonable ranges. For the test case of a narrow-ridge λ = 4.8 μm QCL mounted epitaxial side down, we project that a maximum wallplug efficiency of >10% and cw output power of >1 W may be feasible at room temperature, if the net internal loss can be reduced by 30% from its best current value.
We have characterized 2.5-μm-wavelength InGaAsSb/AlGaAsSb/GaSb two-quantum-well diode lasers that emit 1 W continuous waves from a 100-μm-wide aperture at a temperature of 12 °C. The threshold current density is 250 A/cm2, and the external quantum efficiency near threshold is 0.36. The wall–plug efficiency reaches a maximum of 12% at a current of 2 A. Operating in the pulsed-current mode, the devices output nearly 5 W at 20 °C. These lasers exhibit internal losses of about 4 cm−1 and differential series resistances of about 0.1 Ω. A broad-waveguide design lowers internal losses, and highly doped transition regions between the cladding layers and the GaSb reduces series resistance. © 2002 American Institute of Physics.
We report the first chirped-mirror dispersion controlled KLM Cr:ZnSe laser, using a SESAM for starting and generating nearly transform-limited 80 fs pulses at 80 mW output power at 180 MHz rep-rate at 2.4 µm.
High-power quantum cascade lasers (QCLs) working in continuous wave (cw) above 400 K are presented. The material was grown by low-pressure metal organic vapor-phase epitaxy and processed into narrow buried heterostructure lasers. A cw output power of 204 mW was obtained at 300 K with an 8.38 mum wavelength, 3 mm long and 7.5 mum wide coated laser. The device operates in cw mode above 400 K, which exceeds the previous maximum cw temperature operation of QCLs by approximately 60 K. Preliminary reliability data obtained by accelerated aging tests indicate a remarkable robustness of the lasers.
A systematic investigation of the tunability and efficiency of non-critically phase-matched (NCPM) and critically phase-matched (CPM) KTA OPOs using x-and y-cut crystals orientations has been conducted for the first time. Using our previously developed tandem, KTA-CdSe, OPO technology, we demonstrate a multi-wavelength, mid-infrared source capable of simultaneously delivering tunable radiation in four broad bands covering the range from 1.5 to 10 µm with high conversion efficiency.
By pumping a mid infrared entangled cavity doubly resonant optical parametric oscillator with a micro-laser, we demonstrate the full potentialities of this widely tunable source : high spectral purity, compactness and low threshold of oscillation. ©2007 Optical Society of America OCIS codes: (190.4970) Parametric oscillators and amplifiers; (190.1900) Diagnostic applications of nonlinear optics.
We review progress in quasi-phase-matched optical parametric oscillators in bulk periodically poled LiNbO3. Using the electric-field poling process, we can reliably fabricate 0.5-mm-thick crystals with uniform domain structures over a 15-mm length. Periodically poled material retains the low-loss and bulk power handling properties of single-domain LiNbO3, and quasi phase matching permits noncritical phase matching with d33, the highest-valued nonlinear coefficient. Optical parametric oscillators pumped by 1.064-μm pulsed Nd:YAG lasers have been operated over the wavelength range 1.4–4 μm with tuning by temperature or by quasi-phasematched period. We have shown an oscillation threshold as low as 0.012 mJ with a Q-switched pump laser and pumping at greater than ten times threshold without damage. We have also demonstrated a cw doubly resonant oscillator near 1.96 μm pumped directly with a commercial cw diode laser at 978 nm. © 1995 Optical Society ofAmerica
We have developed a high-energy (>30mJ), narrow-bandwidth (<2nm) optical parametric system with large-aperture PPMgLN devices. The optical parametric system was employed in a ZnGeP2 difference frequency generation system and tunable mid-infrared generation was observed.
Broadly tunable infrared laser sources are of interest for a variety of applications including differential absorption lidar, differential scattering lidar, multi-spectral detection and imaging, hard target identification and discrimination, optical communications in poor visibility conditions, and spectroscopy. For chemical sensing applications, sources are particularly sought in the mid-wave infrared (MWIR) and long-wave infrared (LWIR) spectral regions. A variety of laser and nonlinear optical devices have been demonstrated that access these wavelengths. In particular, CTI is developing novel, tunable, narrow linewidth transmitters for coherent and direct detection lidar measurement applications. An example is a multi-watt Cr:ZnSe laser that is tunable over the 2.1 to 2.8 micrometers wavelength region. This laser has been used to pump-tune optical parametric oscillators (OPOs) that are broadly tunable across the MWIR and LWIR. We are also developing tunable Yb lasers that can be used to pump OPOs that emit signal beams in the eyesafe 1.55 micrometers region while generating idler beams that access the 3 to 4 micrometers MWIR band. This paper describes these sources.
We report >4.2-W mid-infrared (mid-IR) output (3.8 and 4.65 µm) and µ2.1 W at 3.5 µm in ZnGeP2 (ZGP) optical parametric oscillators (OPO) pumped by a holmium-doped yttrium aluminum garnet (Ho:YAG) laser, directly pumped by a diode-pumped 1.9-µm thulium-doped yttrium lithium fluoride (Tm:YLF) laser. Optical-to-optical efficiency achieved is >7.2% (laser diode to mid-IR). In addition, a Ho:YAG-pumped ZGP OPO operation is achieved over a Ho:YAG temperature range of 80 °C at the 8-W (Ho:YAG) and 3-W (ZGP OPO) power levels.
A CdSe optical parametric oscillator (OPO) pumped by a 2.79-μm , Cr, Er:YSGG laser yielded a 59% signal-plus-idler slope efficiency (η), a total idler output of 1.2–2.4mJ between 8.5 and 12.3 μm , and an idler beam that was 2.2–2.5 times the diffraction limit. A ZnGeP2 OPO operated with a lower threshold, η = 29% , and a forward idler output of 0.7–2.4 mJ from 6.9 to 9.9 µm . The signal and idler bandwidths were typically 4 cm-1 for each OPO.
We report the first observation of the room-temperature middle-infrared electroluminescence of n-type Cr doped bulk ZnSe crystals in the spectral range of 1800-2800 nm.
We report a high-brightness, rapidly-tunable Cr:ZnSe master-oscillator power-amplifier producing greater than 7 W of average power with near diffraction limited beam quality. The An 18.5 W Cr:ZnSe power oscillator was also demonstrated.
We report a high-brightness, rapidly-tunable Cr:ZnSe master-oscillator power-amplifier producing greater than 5 W of average power with near diffraction limited beam quality and 2 GHz linewidth. An 18.5 W Cr:ZnSe power oscillator was also demonstrated.
Room-temperature, continuous-wave laser action at 2.3 μm corresponding to the 3H4−3H5 transition in Tm3+-doped YLF is achieved. Output powers of 200 mW and a slope efficiency of 15% have been obtained for a pump power of 2 W at 0.78 μm. In addition, continuous tunability of this laser from 2.20 to 2.46 μm is obtained.
In this letter, high-power continuous-wave emission (>100 mW) and high temperature operation (358 K) at a wavelength of 10.6 μm is demonstrated using an individual diode laser. This wavelength is advantageous for many medium-power applications previously reserved for the carbon dioxide laser. Improved performance was accomplished using industry-standard InP-based materials and by careful attention to design, growth, and fabrication limitations specific to long-wave infrared semiconductor lasers. The main problem areas are explored with regard to laser performance, and general steps are outlined to minimize their impact.
The quantum cascade laser is an unipolar semiconductor laser source emitting in the mid-infrared range between 3.5 and 25 mum. During the past ten years after their invention, this technology has reached the level of maturity required for commercialization, and QC lasers have thus become very attractive for a large number of applications, including gas sensing, pollution detection, atmospheric chemistry, detection of compounds, non-invasive medical diagnostics, free-space optical data transmission or even LIDAR. Most common requirements are single-mode operation on thermoelectric cooler, high power and/or continuous-wave. Nowadays several high-power single-mode QC lasers are available at Alpes Lasers in the range from 4.3 to 16.5 mum, with a side-mode suppression ratio larger than 30 dB. We present here a specific high-average power Fabry-Perot quantum cascade laser and a distributed-feedback quantum cascade laser operating near 8 mum.
© 2000 Optical Society of America
Improvements in the generation of 8 – 12 µm radiation have been accomplished using the tandem OPO approach. Greater than 3 mJ/pulse at 5 Hz (η = 9%) was obtained from a AgGaSe2 OPO module consisting of a 10 x 10 x 25 mm3 crystal with direct contact AR coated ZnSe windows pumped at 1.54 µm. The idler beam quality was improved from 250 mm-mrad to 150 mm-mrad by a factor of four reduction in cavity Fresnel number.
© 2002 Optical Society of America
We report a 4-W, 2810-nm, diode-pumped, cw Er:YLF laser, to the best of our knowledge the highest power yet achieved for a cw Er-doped laser operating on the 4I11/2 - 4I13/2 transition. We tuned the laser on 11 different lines in the 2720-2840-nm region.
© 2001 Optical Society of America
High-Power 793nm diode-laser pumped thulium and holmium double-clad fibre lasers are reported. The 112 W Tm3+ and 83 W Tm3+:Ho3+ lasers have slope-efficiencies of 53% and 42%, respectively, both with M2 < 1.5
We have demonstrated 50 W of output power from a free-running Tm:YAlO3 laser at 1940 nm. We have also obtained Q-switched operation with 7 mJ of output energy at a 5 kHz repetition rate.
We present a two-stage system for parametric frequency conversion of high-energy Nd:YAG laser pulses to the 3-5 μm range. The first stage, which converts from 1.06 μm to about 2.1 μm, is based on KTiOPO4 (KTP) and has a master oscillator / power amplifier (MOPA) architecture, where the oscillator is an optical parametric oscillator (OPO) and the amplifier is an optical parametric amplifier (OPA). This architecture ensures that the 2.1 μm beam quality is good enough for pumping a ZnGeP2 (ZGP)-based OPO in the second stage. With 500 mJ from the Nd:YAG laser we obtain up to 138 mJ signal and 80 mJ idler in orthogonal polarizations at 2.1 μm. Using 86 mJ of the signal to pump the ZGP-OPO we have so far obtained 28 mJ in the 3-5 μm range.
Laser oscillation was realized in Tm:Y2O3 and Tm:Sc2O3 pumped with laser diodes. Peak emission cross sections are 8.8 10^-21cm2 at 1933nm in Y2O3 and 8.4 10^-21cm2 at 1992nm in Sc2O3. The emission wavelength could be tuned between 1930nm and 2090nm in Tm:Y2O3 and up to 2160nm in Tm:Sc2O3.
We report on a Cr:ZnSe laser pump-tuned, intracavity CdSe optical parametric oscillator (OPO) with signal and idler tunable from 3.2 to 3.8 µm and 8.2 to 8.5 µm respectively and output power of 2 W.
© 1997 Optical Society of America
We report an efficient, TEM00, Tm:fiber-laser-pumped, Ho:YLF laser producing 43 W cw power and 45 mJ of pulse energy in the Q-switched regime, the highest values yet reported for this material.
We report the theoretical analysis of an optical parametric oscillator that contains an intracavity crystal that generates the difference frequency between the signal and the idler produced by the optical parametric oscillator crystal. Phase mismatch in the difference-frequency mixer is considered. The cavity is singly resonant at the signal frequency. We find that high conversion efficiency of the difference and idler frequencies can be achieved over a large dynamic range of the incident pump intensity. A physical example that produces 3.192 μm from a 1.064-μm pump laser is predicted to produce 97.5% quantum efficiency in one polarization component and 197% quantum efficiency in the orthogonal-polarization component for a total power conversion efficiency of 98.2%.
The quantum cascade laser is a new light source based on resonant tunnelling and optical transitions between quantised conduction band states. In these semiconductor devices the principles of operation arise from the quantum engineering of electronic energy levels and tailoring of their wavefunctions. In recent years the performance of these devices has improved markedly and this semiconductor technology is now an attractive choice for the fabrication of mid-far infrared lasers in a very wide spectral range (3–80 μm). At present, quantum cascade lasers are capable of continuous-wave room temperature operation and can deliver 200–300 mW of average power (at λ∼9 μm) operating on a Peltier cooler. To cite this article: C. Sirtori, J. Nagle, C. R. Physique 4 (2003).
TEM00 Q-switched outputs of >100 mJ at 2.94 μm was generated using a dual rod oscillator. The output from the laser was used to pump ZGP, CdSe, and AgGaSe2 OPOs to generate output in the 3.5-12 μm spectral regions.
High-power and widely tunable Tm-doped silica fibre lasers cladding-pumped and core-pumped by a 1565 nm Er,Yb fibre laser are reported. Output power up to 19.2W was generated from the cladding-pumped cavity configuration for ~38.2W of launched pump power and with slope efficiency up to ~72% with respect to absorbed pump power. Wavelength tuning was realized by use of an external cavity containing a diffraction grating. A maximum output power of 17.4 W at 1941 nm was generated for 38.2 W of launched pump power and the operating wavelength could be tuned over 202 nm from 1859 to 2061 nm. In the core-pumped configuration, a maximum output power of 12.1 W was generated at 1851 nm for 23.1 W absorbed pump power using a simple free-running cavity configuration with only ~24 cm of Tm-doped fibre. By employing a tunable cavity configuration, the operating wavelength of the core-pumped Tm:fibre laser could be tuned over 250 nm from 1723–1973 nm at multi-watt power levels.
We report cw operation of buried heterostructure quantum-cascade lasers (lambda=6 mum) using a thick electroplated Au top contact layer and epilayer-up bonding on a copper heat sink up to a temperature of 333 K (60degreesC). The high cw optical output powers of 446 mW at 293 K, 372 mW at 298 K, and 30 mW at 333 K are achieved with threshold current densities of 2.19, 2.35, and 4.29 kA/cm(2) respectively, for a high-reflectivity-coated, 9-mum-wide and 3-mm-long laser. (C) 2004 American Institute of Physics.
We report on the design and fabrication of λ ∼ 5.25 μm quantum-cascade lasers (QCLs) for very high temperature continuous-wave (cw) operation. Cw operation is reported up to a maximum temperature of 90 °C (363 K). Cw output power is reported in excess of 500 mW near room temperature with a low threshold current density of 1.4 kA/cm2 at 298 K. Room temperature average power of over 540 mW is reported at 50% duty cycle. A high thermal conductance (Gth) of 340 W/K cm2 is reported for cw QCLs. A finite element thermal model is used to investigate the Gth and maximum cw operating temperature of the QCLs.
We report the cavity-length dependent high-temperature high-power cw characteristics in λ=6 μm quantum-cascade lasers with a thick electroplated Au top contact layer. For a high-reflectivity (HR) coated 15 μm wide and 3 mm long laser, the cw operation is achieved up to 313 K (40 °C) with an output power of 17 mW. At 298 K, a very high cw output power of 213 mW is obtained for a HR coated 15 μm wide and 4 mm long laser. Thermal resistance is analyzed at temperatures above 283 K for HR coated lasers with different cavities. © 2003 American Institute of Physics.
The fabrication and operating characteristics of lateral grating distributed feedback InP-based quantum cascade lasers emitting at λ ∼ 10 μm are reported. High performance, room temperature single mode lasers, utilizing double-sided lateral gratings, are achieved in InP-based material grown by metal organic phase epitaxy. These deeply etched gratings are made possible by the development of a high aspect ratio, multistage, inductively coupled plasma etch process. A threshold current density of ∼ 5.5 kA/cm2 is measured at room temperature and side mode suppression ratio >20 dB with a tuning coefficient of −0.067 cm−1 K−1 is observed over a temperature range of 190–330 K.
We report high-power continuous-wave (cw) operation of λ ∼ 9.5 μm quantum-cascade lasers to a temperature of 318 K. A high-reflectivity-coated 19-μm-wide and 3-mm-long device exhibits cw output powers as high as 150 mW at 288 K and still 22 mW at 318 K. In cw operation at 298 K, a threshold current density of 1.57 kA/cm2, a slope efficiency of 391 mW/A, and a maximum wall-plug efficiency of 0.71% are obtained. In pulsed operation, a maximum average power of 317 mW is achieved at 49% duty cycle. The emission wavelength in cw mode is shifted from 9.524 μm at 288 K to 9.547 μm at 313 K near 1.05 A drive current with a temperature tuning coefficient of 0.92 nm/K.
We report continuous-wave (cw) operation of quantum-cascade lasers (λ = 6 μm) using a thick electroplated Au top contact layer and epilayer-up bonding on a copper heat sink up to a temperature of 308 K (35 °C). The high cw optical output powers of 132 mW at 293 K and 21 mW at 308 K are achieved with threshold current densities of 2.29 and 2.91 kA/cm2, respectively, for a high-reflectivity-coated 15 μm wide and 2 mm long laser. © 2003 American Institute of Physics.
© 2002 Optical Society of America
A continuously tunable Cr2+:ZnSe laser is applied for photoacoustic gas detection in the wavelength range 2.0-3.1 μm. Trace-gas measurements in the 2.6-3.1 μm range with parts-per-billion sensitivity are reported for the first time.
The book describes the most advanced techniques for generating coherent light in the mid-infrared region of the spectrum. These techniques represent diverse areas of photonics and include heterojunction semiconductor lasers, quantum cascade lasers, tunable crystalline lasers, fiber lasers, Raman lasers, and optical parametric laser sources. Offering authoritative reviews by internationally recognized experts, the book provides a wealth of information on the essential principles and methods of the generation of coherent mid-infrared light and on some of its applications. The instructive nature of the book makes it an excellent text for physicists and practicing engineers who want to use mid-infrared laser sources in spectroscopy, medicine, remote sensing and other fields, and for researchers in various disciplines requiring a broad introduction to the subject.
We report obtaining room-temperature laser oscillation in a flashlamp-pumped (Cr,Yb,Ho):YSGG crystal. The laser action, which is due to the Ho3+ ions, is based on the cascade of transitions 5I6→5I7→5I8. We have measured the lifetimes of the working levels and the laser wavelength. The efficiency of the energy transfer process Cr3+→Yb3+→Ho3+ is 90%. We investigated the kinetics of the laser action and measured the lasing parameters for various types of output mirrors. We also measured the contribution of the laser transition 5I6→5I7 to the populating of the 5I7 level. For pump energies above 20 J, we observed saturation of the populations of the 5I6 and 5I7 levels of the Ho3+ ion. The cause of this saturation is assumed to be a stepwise sensitization of the Ho3+ ion. We obtained oscillation in a totally-reflecting resonator at 3-μm without self-limiting.
The operating points of pulsed dual-cavity doubly resonant optical parametric oscillators have been investigated, taking into account the influence of the optical dispersion. A diagram is proposed to determine the spectral separation of doubly resonant positions for any optical lengths of both cavities. From the analysis of the distribution of doubly resonant coincidences, original conditions for stable single-mode operation are specified. This approach is validated by use of a type II phase-matched β-barium borate crystal. Frequency stability and tuning characteristics are also reported. To our best knowledge, this is the first demonstration of single-mode operation that uses a dual-cavity doubly resonant optical parametric oscillator in the nanosecond pulsed regime.
Using a 2.8 m pump makes it possible to take full advantage of notable nonlinear optical properties of the infrared crystals ZnGeP 2 , CdSe, and GaSe to achieve efficient mid-infrared frequency downconversion. Traveling-wave optical parametric generators with angular tuning were pumped by single 100-ps 2.8-m Er,Cr:YSGG laser pulses. The continuous tuning range achieved was 3.9–10 m (ZnGeP 2), 3.57–4.3 and 8–13 m (CdSe), and 3.3–19 m (GaSe), with a quantum conversion efficiency of typically 10% and the lowest, to the author's knowledge, threshold ever obtained for a traveling-wave optical parametric generator. A dual-wavelength optical parametric generator was used for nonlinear spectroscopy of intersubband transitions of conduction-band electrons, quantum confined in semiconductor quantum wells, as well as for the study of intersubband-based resonantly enhanced (2) in quantum wells.