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Schematic diagram for a QCW laser diode pumped Yb:YAG/YVO4 coupled-RML. M1 is the rear cavity mirror, M2 is the front cavity mirror, OC is the extra output coupler with partial reflectivity of 60%. tp, Pp, and R.R. are the pulse duration, pump power and repetition rate of QCW laser diode, respectively.
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Broadband lasers oscillating in multiple longitudinal modes have potential applications on high resolution interferometer, optical communication and laser spectroscopy. However, the bandwidth of the laser spectrum is limited by the spectral range of laser materials. Here, a broadband multi-longitudinal-mode laser with bandwidth of 22.4 nm at first-...
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... However, the repetition rate is low and the spectral range is narrow for these Q-switched Raman lasers owing to the etalon effect of optical elements and Q-switching element. Recently, broadband continuous-wave (CW) multi-longitudinal-mode Raman laser with bandwidth of 55.4 nm covering from 1041 to 1096.4 nm has been achieved in a Yb:YAG/YVO 4 Raman laser [13]. ...
Broadband self-pulsed Raman laser operating at sub-megahertz (sub-MHz) has been widely used in optical sensing, high-spectral-resolution lidar, frequency-division multiplexing, and optical communication. However, it is a big challenge for achieving stable self-pulsed Raman laser oscillation in a wide pump power range. Here, we construct a compact Yb:YAG/YVO4 Raman laser for generating broadband self-pulsed laser operating at high repetition rate. The effects of cavity length (LC) and Raman crystal length (LR) on the performance of self-pulsed Raman laser have been investigated. By utilizing a 1.5 mm-thick YVO4 crystal as a Raman crystal, the repetition rate increases dramatically from 62 to 280 kHz when the LC decreases from 10 to 4 mm. Meanwhile, the pulse width of 0.66 μs and peak power of 1.1 W are achieved for the self-pulsed Raman laser with LC = 4 mm. For the 4 mm-long Raman laser cavity constructed with a 2 mm-thick YVO4 crystal, the pump power range enable for self-pulsed Raman laser oscillation extends from 1.8 to 3.9 W, the repetition rate has been further increased from 258 to 467 kHz. While the peak power and pulse width are 0.6 W and 0.98 μs, respectively. The Yb:YAG/YVO4 self-pulsed Raman laser oscillates in broadband multi-longitudinal-mode, the spectral bandwidth is 27.4 nm covering from 1051.1 to 1078.5 nm. Utilization of a tilted 2 mm-thick YVO4 crystal as output coupler to construct compact Yb:YAG/YVO4 self-pulsed Raman laser dramatically expands the pump power range for generating high repetition rate self-pulsed Raman laser. Sub-MHz self-pulsed Raman lasers with a wide spectral bandwidth have potential applications in materials processing, quantum information processing, and optical communications.
... A 1g , B 1g , B 2g and E g . Under principal axial frame, Raman scattering tensors are: Stimulated Raman scattering (SRS) processes of multi-Raman modes based on a-cut and c-cut YVO 4 crystals have also been studied [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31]. For a-cut YVO 4 crystals, besides the most intensive Raman mode 895 cm −1 (A 1g ), SRS process of minor Raman modes 379 cm −1 (A 1g ) can be realized under a(cc)a or a(bb)a configuration [17], and that of 816 cm −1 (B 1g ) can be obtained under a(bb)a configuration [18][19][20][21]. ...
... In 2021, Y. Duan et al. realized AO Q-switched Nd:YAP/a-cut YVO 4 self-Raman lasers, and 1st Stokes of 816 and 890 cm −1 were generated [21]. For c-cut YVO 4 crystals, SRS processes of the most intensive Raman mode 895 cm −1 (A 1g ) and minor Raman mode 821 cm −1 (B 1g ) [22][23][24] can be realized under c(aa)c or c(bb)c configuration, and those of minor Raman mode 264 cm −1 (B 2g ) can be obtained under c(ba)c or c(ab)c configuration [23,[25][26][27][28][29][30][31] [30]. ...
LD end-pumped passively Q-switched a-cut Nd:YLF/Cr:YAG/c-cut YVO4 Raman laser is investigated for the first time, and SRS processes of 895 cm⁻¹(A1g), 821 cm⁻¹ (B1g) and 264 cm⁻¹ (B2g) modes are realized. Raman laser output power, temporal, spectral and polarization features are studied, and unusual phenomena of Raman laser output are observed for the first time. The maximum efficient Raman conversions of 895 cm⁻¹ (A1g), 821 cm⁻¹ (B1g) and 264 cm⁻¹ (B2g) modes are achieved with the linearly polarized direction of Ep to be about 45 degrees to a or b axis of c-cut YVO4 crystal. The optical axis orientation of c-cut YVO4 crystal significantly affect Raman laser spectra and polarization features. With experiments and analysis in-depth, these anomalies are attributed to optical axis direction deviation of c-cut YVO4 crystal. These findings can help design c-cut YVO4 multi-Raman mode lasers of high-performance, which have potential applications.
... For a-cut YVO 4 crystals, SRS processes of Raman shifts of 890 cm −1 (A 1g ), 816 cm −1 (B 1g ) and 379 cm −1 (A 1g ) were realized [2][3][4][5][6]. For c-cut YVO 4 crystals, SRS processes of Raman shifts of 890 cm −1 (A 1g ), 816 cm −1 (B 1g ), 259 cm −1 (E g ) and etc. were realized [7][8][9][10][11][12][13][14][15][16]. S. Fan et al. first realized SRS conversion of minor Raman mode separately in Nd:YVO 4 crystals [12]. ...
LD end-pumped passively Q-switched Nd:YLF/SrWO4/Cr⁴⁺:YAG Raman laser for multi-Raman-modes is investigated for the first time. Based on the main Raman mode (923 cm⁻¹), the maximum average output power of 0.462 W is achieved for 1st Stokes laser at 1159 nm. When the pumping power is 2 W, the maximum optical conversion efficiency of 17.4% is obtained with the pulse repetition frequency of 6.6 kHz and pulse width of 21 ns. By selecting an appropriate cavity mirror to suppress stimulated Raman scattering process of main Raman mode, SRS conversion of the minor mode (334.5 cm⁻¹) of SrWO4 crystal is realized separately for the first time in intracavity Raman laser. The maximum output power at 1085 nm obtained is 0.111 W. In experiments, multi-pulse phenomena of Stokes laser output with the main Raman mode (923 cm⁻¹) are observed, which are more obvious for smaller initial transmittance of saturable absorber and higher reflectivity of output coupler.
... In the context of this research, potential monolithic self-Raman Nd:KGW lasers may benefit from external-cavity tuning. Therefore, external-cavity investigations in Nd:KGW are necessary for tuning both laser and Raman conversion in compact monolithic self-Raman Nd: KGW lasers [17]. ...
We present a Nd:KGW laser with a wavelength selectable intracavity loss scheme comprising a notch filter and external-cavity feedback, which enables distinct continuous-wave laser oscillation regimes. Based on the spectroscopy of the 4F3/2 - 4I11/2 transition in Nd:KGW, we have achieved tunable laser oscillation at either 1067 nm, 1076 nm or 1085 nm corresponding to different spectral peaks of the emission cross-section. An adequate balance of the intracavity loss also allows for dual-wavelength operation at both 1067–1076 nm and 1076–1085 nm peaks, and the inclusion of an additional external reflector permits dual-wavelength oscillation in the vicinity of the main emission peak at 1067 nm. From the external-cavity laser theory perspective, in our approach, the tuning mechanism is treated as an effective intracavity loss instead of an effective reflectivity treatment. The key parameters for further improving the emission wavelength range and tunability are identified and discussed.
High‐order Hermite–Gaussian (HG) lasers oscillating at multiple wavelengths are extensively needed for generating vortex lasers carrying orbital angular momentum (OAM), which have wide applications on optical communication, high capacity storage, and high resolution imaging. Off‐axis pumping or off‐axis resonator has been used to generate high‐order HG0,n lasers, however, low optical efficiency limits practical applications of these lasers. Here, direct generation of multiple wavelength high‐order HG0,n lasers in a rectangular beam pumped Raman microchip laser constructed with Yb3+:Y3Al5O12 (Yb:YAG) and yttrium vanadate (YVO4) crystals is demonstrated. The order n of HG0,n mode lasers can be tuned from 1 to 9. HG0,n (n > 3) mode Raman lasers oscillate at multiple wavelengths and shift to longer wavelength with n. The output power is 137 mW for multiwavelength HG0,9 mode Raman laser when the input pump power is 2.7 W. The optical conversion efficiency is as high as 5.1%. Excellent beam quality with My2 close to theoretical values (My2 = 2n+1) for high‐order HG0,n lasers has been achieved. Topological charge tunable Laguerre–Gaussian (LG) vortex lasers with high beam quality are generated from HG0,n mode lasers with an astigmatic mode converter. This work demonstrates that rectangular beam pumping is an effective method for developing efficient multiwavelength high‐order HG0,n mode Raman lasers. Efficient, multiwavelength HG0,n lasers with n tunable from 1 to 9 have been demonstrated in a rectangular beam pumped Yb:YAG/YVO4 Raman microchip laser. High beam quality vortex lasers with topological charge tunable up to 9 have been achieved by using an astigmatic mode converter. The optical efficiency of five‐wavelength HG0,9 mode Raman laser is as high as 5.1%.
High‐order Laguerre‐Gaussian (LG0,n) petal‐like lasers are extremely important for manipulating microparticles, creating 3D optical trapping structures, and free space optical communication. However, it is difficult to expand the wavelength of LG0,n petal‐like lasers owing to the narrow fluorescence spectrum of laser gain media. Here, a Raman laser constructed with a Yb3+:Y3Al5O12 (Yb:YAG) crystal and a yttrium vanadate (YVO4) is demonstrated for achieving a high‐order LG0,n petal‐like laser with broadband laser wavelength and high beam quality. High‐order LG0,n petal‐like lasers with n tunable from 3 to 11 are obtained. The LG0,11 petal‐like Raman laser oscillates from 1075.4 to 1088.7 nm with 44 longitudinal modes, and the bandwidth of the Raman laser is 13.3 nm. The output power of the LG0,11 petal‐like Raman laser is 126 mW with an optical efficiency of 1.5%. High‐order LG0,n petal‐like Raman lasers with tunable n provide flexible choices for potential applications in manipulating microparticles and biological molecules. By using a yttrium vanadate (YVO4) crystal as Raman gain medium and a Yb3+:Y3Al5O12 (Yb:YAG) crystal as a gain medium, a broadband high‐order Laguerre‐Gaussian (LG0,n) petal‐like Raman laser with tunable n up to 11 is demonstrated in a Yb:YAG/YVO4 microchip laser by varying pump power. High beam quality, high‐order LG0,n petal‐like Raman lasers with controllable order n are promising sources for practical applications.
