Juerg Aus-der-Au

Spectra-Physics Rankweil · R&D

We present for the first time a thin-disk multipass amplifier delivering picosecond pulses with kW average power and highly-flexible MHz to multi GHz intra-burst repetition and at 100 kHz of burst repetition rate.

We present a high-power, single-crystal based, Yb:CALGO regenerative amplifier. The system delivers more than 50 W output power in continuous-wave regime, with diffraction limited beam quality. In Q-switching regime the spectrum is centered at 1043 nm and is 11 nm wide. In regenerative amplification experiments we achieved 34 W at 500 kHz with 12.7...

We report on a femtosecond high-power regenerative amplifier based on Yb : Lu 2 O 3 . Exploiting the excellent thermo-mechanical properties of this material, we were able to achieve up to 64.5 W in continuous-wave regime, limited only by the available pump power. In pulsed operation, 42 W of average output power at a repetition rate of 500 kHz with...

We report on a femtosecond high-power regenerative amplifier based on Yb:Lu₂O₃. Exploiting the excellent thermo-mechanical properties of this material, we were able to achieve up to 64.5 W in continuous-wave regime, limited only by the available pump power. In pulsed operation, 42 W of average output power at a repetition rate...

A detailed performance comparison of new interesting Yb-doped crystals in the same oscillator setup, with single-mode fiber-coupled diode laser pump is reported. We intended to assess the shortest pulses achievable with available SESAM technology, running a fair comparison with laser crystals Yb:KLuW, Yb:SSO, Yb:CALGO, Yb:CALYO and Yb:CaF2, very li...

We investigated the performance of the laser gain medium Yb:Lu2O3 in a low-power oscillator and a high-power regenerative amplifier. Almost Fourier transform limited 78-fs pulses were demonstrated in the low-power, SESAM mode-locked oscillator pumped with a single-mode fiber-coupled laser diode. Exploiting the excellent thermomechanical properties...

We obtained up to 42 W with 780 fs-long pulses at 500 kHz repetition rate with M2=1.2 in a Yb:Lu2O3 based regenerative amplifier. Also, sub-100-fs pulse generation in a low-power SESAM mode-locked oscillator are presented.

An Yb : CaF 2 laser pumped by two 400-mW single-mode laser diodes at 976 nm is reported to generate Fourier-limited 65-fs pulses, the shortest to date achieved with a semiconductor saturable absorber mirror (SESAM) mode-locking and this laser material to date. With a multimode pump diode, we have demonstrated higher average output powers of up to 1...

Yb:Sc2SiO5 has been investigated in a low-power laser femtosecond oscillator pumped by 400-mW single-mode fiber-coupled diode at 976 nm. Pulses as short as 71 fs were achieved. The same crystal was later employed in a regenerative amplifier, with an output power as high as 4.7 W at 500 kHz and sub-300-fs pulses.

Yb:CaYAlO4 has been investigated spectroscopically and compared to better known Yb:CaGdAlO4. It turns out that both materials show very similar spectroscopic parameters relevant to ultrafast lasers design. Employing single-mode fiber-coupled 400-mW laser diode at 976 nm we measured pulses as short as 43 fs, and broad tunability of 40 nm with a simp...

We report for the first time, to the best of our knowledge, an innovative design concept for intracavity pulse stretching in a regenerative amplifier, employing a single “grating-mirror” based on a leaky-mode grating-waveguide design. The very compact and flexible layout allows for femtosecond pulses to be in principle easily stretched up to nanose...

We study and compare the performance of Yb:CaAlGdO4- and Yb:CaF2-based regenerative amplifiers at low (5 to 10 kHz) and high (up to 500 kHz) repetition rates. Both materials allow for pulse energies of <1 mJ with sub-400-fs at low repetition rates and up to 9.4 W of average output power at 500 kHz. Thanks to the good thermal properties of Yb:CaF2 a...

We demonstrated for the first time, to the best of our knowledge a new intracavity pulse stretching design, employing a single grating-mirror based on a leaky-mode grating-waveguide design. The extremely compact and flexible layout allows for femtosecond pulses to be easily stretched up to nanosecond durations. The stretcher was implemented in a di...

We present an efficient, single-mode diode-pumped SESAM-mode-locked Yb:CaF2 laser with pulses as short as 65 fs. Higher average output power up to 1.4 W with 87-fs-long almost Fourier-transform limited pulses were demonstrated as well.

We investigated and compared Yb:CaAlGdO4 and Yb:CaF2 regenerative amplifiers at repetition rates 5-10 kHz, a frequency range interesting for industrial applications requiring relatively high pulse energy. Both materials allow for pulse energies close to 1 mJ with sub-400-fs pulses. The two laser materials offer comparable performance in the pump po...

High average power, high repetition rate femtosecond lasers with μJ pulse energies are increasingly used for material processing applications. The unique advantage of material processing with sub-picosecond lasers is efficient, fast and localized energy deposition, which leads to high ablation efficiency and accuracy in nearly all kinds of solid ma...

Yb:CaAlGdO4 (Yb:CALGO) is a very promising material for high power ultrashort pulse generation, due to its broad emission bandwidth and good thermal properties. Here we report, to the best of our knowledge, the highest power and shorter pulses ever demonstrated from a Yb:CALGO-based regenerative amplifier. The system layout consists of a Yb:CALGO o...

A new high-performance Yb : CaAlGd O 4 (Yb:CALGO) regenerative amplifier is demonstrated. Pumped by 116 W at ≈ 980 nm and seeded by means of a 92 fs oscillator, it generates as much as 36 W of average output power with chirped pulses, and 28 W with 217 fs compressed pulses at 500 kHz repetition rate. This corresponds to 56 μJ of pulse energy and 25...

In this paper, we present a simple, compact, and efficient Yb:CALGO laser system that can produce sub-100 fs pulses easily tunable over a 38 nm wide wavelength range between 1034 and 1072 nm. The laser is passively mode locked with a semiconductor saturable absorber and generates up to 90 mW output power (for 230 mW absorbed pump), using a single p...

High average power, high repetition rate femtosecond lasers with μJ pulse energies are increasingly used for bio-medical and material processing applications. With the introduction of femtosecond laser systems such as the SpiritTM platform developed by High Q Lasers and Spectra-Physics, micro-processing of solid targets with femtosecond laser pulse...

A regenerative bulk amplifier based on an Yb:CaAlGdO4 crystal is reported. Pulses as short as 165-fs, with output power up to 6.4-W, limited by the available pump power, are obtained.

We report the results of the investigation on a passively mode-locked Yb³⁺:CaGdAlO4 laser, pumped by a single transverse mode laser diode emitting 350 mW at 980 nm. This particular pump source allows efficient pumping with a nearly TEM00 beam and minimal thermal load, making the optimization of the mode-locking performance more straightforward than...

A picosecond regenerative amplifier with pulse on demand operation is demonstrated. The pulse energy is held constant for arbitrary pulse separation by employing an intracavity loss modulator. The loss modulator is controlled by a digital signal processor monitoring the gain of the laser material in real time. The gain is estimated from a measureme...

We report on the generation of 94-fs pulses with 12.5-W average output power from an 80-MHz Yb3+:CaGdAlO4(Yb:CALGO) oscillator with pulse energies and peak power levels higher than 150-nJ and 1.45-MW, respectively. To the best of our knowledge, this is the highest average power ever reported for a sub-100-fs bulk oscillator. Average output power le...

High average power, high repetition rate femtosecond lasers with μJ pulse energies are increasingly used for bio-medical and material processing applications. With the introduction of femtosecond laser systems such as the High Q femtoREGENTM UC platform, micro-processing of solid targets with femtosecond laser pulses have obtained new perspectives...

We present a compact and efficient single-mode diode-pumped, passively mode-locked Yb3+:CaGdAlO4 laser. Sub-100 fs pulses, tunable over 30 nm, with output power exceeding 50 mW at any operational wavelength were obtained.

High average power, high repetition rate ultrashort pulse (τ < 10 ps) laser systems with μJ pulse energies [1, 2] are increasingly used for bio-medical and material processing applications. Interesting applications for the ultrashort pulse laser systems are in the field of selective structuring of thin-films. Thin-film solar cells have shown a big...

High average power, high repetition rate ultrashort pulse (τ < 10 ps) laser systems with µJ pulse energies [1, 2] are increasingly used for bio-medical and material processing applications. Interesting applications for the ultrashort pulse laser systems are in the field of selective structuring of thin-films. Thin-film solar cells have shown a big...

An Yb:KYW oscillator has been cavity-dumped at 4.58 MHz, obtaining pulses as short as 264-fs and energies as high as 250 nJ. Up to 1.8 μJ and 234-fs have been achieved at 0.56 MHz.

Export Date: 7 October 2012, Source: Scopus, Art. No.: 4386293

We report on third-harmonic generation (THG) of biomolecular solutions at the fluid/glass interface as a means to probe resonant contributions to their nonlinear absorption spectra that could serve as contrast mechanisms for functional imaging. Our source was 100fs laser pulses whose center wavelength varied from 760 to 1000 nm. We find evidence of...

The simultaneous detection of third harmonic (THG), and multiphoton excitation fluorescence (MPF) or second harmonic (SHG) from the same focal volume has led us to the development of a nonlinear multimodal microscopic biological imaging tool. The multimodal microscope has been applied for imaging of isolated live cardiomyocytes, and investigation o...

Dynamic imaging of cardiomyocytes was performed with a simultaneous detection second harmonic generation (SHG), third harmonic generation (THG) and multiphoton excitation fluorescence (MPF) microscope. The fast scanning system of ~12 frames/second synchronized with multichannel detection provided the possibility of imaging three dimensional static...

Simultaneous detection of second harmonic generation (SHG), third harmonic generation (THG) and multiphoton excitation fluorescence with ultrafast laser pulses from a Nd:Glass laser was used to image isolated adult rat cardiomyocytes. The simultaneous detection enabled visualization of different organelles of cardiomyocytes, based on the different...

Simultaneous detection of second harmonic generation (SHG), third harmonic generation (THG) and multiphoton excitation fluorescence with ultrafast laser pulses from a Nd:Glass laser was used to image isolated adult rat cardiomyocytes. The simultaneous detection enabled visualization of different organelles of cardiomyocytes, based on the different...

We show that a simple plane wave analysis can be used even under tight focusing conditions to predict the dependence of third-harmonic generation on the polarization state of the incident beam. Exploiting this fact, we then show that circularly polarized beams may be used to spatially characterize the beam focus and temporally characterize ultrasho...

We demonstrate collinear, background-free, third harmonic spatial correlation, temporal correlation, and FROG techniques for characterizing the focus of high NA optics for the first time.

We show that a simple plane wave analysis can be used even under tight focusing conditions to predict the dependence of third-harmonic generation on the polarization state of the incident beam. Exploiting this fact, we then show that circularly polarized beams may be used to spatially characterize the beam focus and temporally characterize ultrasho...

We describe two novel parametric systems for wavelength-tunable ultrashort pulse generation in the spectral range around 1.5 µm. We demonstrate the first single-pass optical parametric generator (OPG) that is directly pumped by a mode-locked laser at the full laser repetition rate of 35 MHz, obtaining up to 500 mW of average signal power with a pul...

We demonstrate what is to our knowledge the first synchronously pumped high-gain optical parametric oscillator (OPO) with feedback through a single-mode fiber. This device generates 2.3-2.7 W of signal power in 700-900-fs pulses tunable in a wavelength range from 1429 to 1473 nm. The necessary high gain was obtained from a periodically poled LiTaO(...

We demonstrate a passively mode-locked thin-disk Yb:YAG laser that generates solitonlike pulses with durations that are continuously tunable in a very wide range from 3.3 to 89 ps or from 0.83 to 1.57 ps. The average powers are typically ~12 W . Previously [Opt. Lett. 25, 859 (2000)], only pulse durations in a narrow range near 0.7 ps could be obta...

Summary form only given. The Yb³⁺-doped potassium tungstates KY(WO₄)₂ (KYW) and KGd(WO₄) ₂ (KGW) are for several reasons of great interest for diode-pumped solid state lasers. Compared with Yb:YAG, they have a smaller quantum defect of only ~4% and higher absorption and emission cross sections....

Summary form only given. Synchronously pumped optical parametric oscillators (OPOs) are attractive sources of broadly wavelength-tunable ultrashort pulses as required for many applications, e.g. RGB display systems. We present a novel type of synchronously pumped OPO, which is based on feedback through a single-mode fiber in combination with a very...

We recently demonstrated that passive mode locking of a thin-disk Yb:YAG laser is possible and that this concept leads to sources of femtosecond pulses with very high average power. Here we discuss in detail the effect of spatial hole burning on the mode-locking behavior of such lasers. We have developed an efficient numerical model and arrive at q...

We demonstrate the first synchronously pumped high-gain optical parametric oscillator with feedback through a single-mode fiber. We obtained 2.7 W in 900-fs pulses at 1.45 μm. An active cavity length stabilization is not required.

Summary form only given. We present to our knowledge the first passively mode-locked Yb:KGd(WO₄)₂ (Yb:KGW) laser. This diode-pumpable gain material is vary suitable for high-power femtosecond lasers because it combines a broad amplification bandwidth (similar to Yb-doped glasses) with relatively large emission cross sections a...

We present a new concept which allows to build femtosecond lasers with very high average output powers. It is based on a thin disk Yb:YAG laser, passively mode-locked with a semiconductor saturable absorber mirror (SESAM). In a first step, we obtained 16 W of average power in near transform-limited soliton pulses with 730 fs duration, 0.47 μJ energ...

We demonstrate what is to our knowledge the first mode-locked Yb:KGd(WO(4))(2) laser. Using a semiconductor saturable-absorber mirror for passive mode locking, we obtain pulses of 176-fs duration with an average power of 1.1 W and a peak power of 64 kW at a center wavelength of 1037 nm. We achieve pulses as short as 112 fs at a lower output power....

We discuss in detail the effects of thermal lensing and thermally induced stress in end-pumped lasers with a strongly elliptical pump and laser mode and compare this situation with cylindrical rod geometries.

We demonstrate a power-scalable concept for high-power all-solid-state femtosecond lasers, based on passive mode locking of Yb:YAG thin disk lasers with semiconductor saturable-absorber mirrors. We obtained 16.2 W of average output power in pulses with 730-fs duration, 0.47-muJ pulse energy, and 560-kW peak power. This is to our knowledge the highe...

We discuss challenges arising from the quest for high average powers from passively mode-locked diode-pumped lasers. The recently obtained detailed understanding of Q-switching instabilities in passively mode-locked lasers turns out to be a crucial element on the way towards higher powers. We give an overview on results achieved with Nd:YAG (10.7 W...

We demonstrate a new scheme for dispersion compensation in femtosecond laser cavities, exploiting the observation that the negative dispersion from a Brewster interface can be strongly enhanced by the focusing effect of a curved surface on a prism or of a thermal lens in the gain medium. Based on this scheme, a high-power Nd:glass laser generated f...

© 2000 Optical Society of America

Optical parametric generation (OPG) in a single pass through a χ ⁽²⁾ nonlinear crystal is a simple way to generate ultrashort pulses which are tunable in a broad wavelength range.

Summary form only given. Femtosecond laser sources with multi-watt average powers and multi-kW peak powers are required for many applications. We have found a power-scalable concept to achieve this kind of performance directly with a diode-pumped passively mode-locked laser oscillator, not requiring any amplification stages. The concept is based on...

Summary form only given. We present the first optical parametric generator that is directly pumped with a mode-locked laser at the full laser repetition rate. The single-pass OPG scheme is significantly simpler than previous femtosecond parametric generators, which always required amplified pump sources, e.g, based on a mode-locked oscillator and a...

Optical parametric generation (OPG) in a single pass through a χ ⁽²⁾ nonlinear crystal is a simple way to generate ultrashort pulses which are tunable in a broad wavelength range. In contrast to an ultrafast optical parametric oscillator, OPG does not require an oscillator cavity which is synchronized to the laser. However, the required pump intens...

We demonstrate a power-scalable concept for femtosecond lasers with very high average powers. It is based on a thin disk Yb:YAG laser [1], passively mode-locked with a semiconductor saturable absorber mirror (SESAM) [2, 3]. In a first step, we obtained 16.2 W of average power in pulses with 730 fs duration, 0.47 μJ energy, and 560 kW peak power (Fi...

We obtained 74-kW peak power and 3.5-W average output power in 1-ps pulses from a diode-pumped Yb:YAG laser at 1030 nm that was passively mode locked with a semiconductor saturable-absorber mirror. Another laser produced 57-kW peak power and as much as 8.1-W average output power in 2.2-ps pulses, split into two nearly diffraction-limited beams (M2<...

We demonstrate passive mode locking of a Nd:vanadate (Nd:YVO4) laser to repetition rates of up to 13GHz. With Ti:sapphire pumping, we achieved mode locking at 13GHz with 310mW of average output power and pulse widths of 9.5ps. With diode pumping, we achieved mode locking at a repetition rate of 12.6GHz with 198mW of average output power and a pulse...

Summary form only given. Femtosecond laser sources usually require negative group delay dispersion (GDD) to compensate for the positive dispersion of the gain material and possibly other cavity elements. Various techniques to generate negative GDD from wavelength-dependent refraction at Brewster interfaces have been demonstrated. The resulting nega...

Femtosecond and picosecond pulses can find many applications if they can be produced with laser sources that are not only powerful and efficient but also compact and reliable. In continuous wave operation, diode pumping of solid-state lasers has allowed for a rapid progress towards powerful, compact and reliable sources, while the often used techni...

We have passively modelocked a diode-pumped Nd:YLF laser at 1.047 µm using semiconductor saturable absorber mirrors and achieved 1.3 W of average output power at 3.3 W pump power, which results in an optical efficiency of 39%. The pulse repetition rate was 50 MHz and pulse widths as short as 3.8 ps were obtained. We cavity-dumped single pulses from...

We demonstrate a new scheme for dispersion compensation in compact femtosecond laser cavities, strongly enhancing the negative dispersion obtained from a Brewster interface.

Femtosecond and picosecond pulses can find many applications if they can be produced with laser sources that are not only powerful and efficient but also compact and reliable. In continuous wave operation, diode pumping of solid-state lasers has allowed for a rapid progress towards powerful, compact and reliable sources, while the often used techni...

We report what we believe to be the first demonstration of a SESAM (semiconductor saturable absorber mirror)-based femtosecond Cr3+:LiSrAlF6 laser pumped by narrow-stripe AlGaInP laser diodes that have diffraction-limited output beams. A highly asymmetric, four-mirror laser cavity design is described for which 57 fs duration pulses at an average ou...

We investigate the differences in the dynamics of lasers mode-locked by fast and slow saturable absorbers. Slow saturable absorbers can already generate almost transform limited pulses much shorter than the recovery time of the absorber. If soliton-like pulse shaping is present in addition the pulses can be further compressed below the resulting ne...

We have demonstrated 175-fs pulses with 1 W and 300-fs pulses with 1.2 W of average output power at a pulse repetition rate of 117 MHz from a Nd:phosphate (Schott LG 760) glass laser pumped by a 1-cm-wide, 20-W diode laser bar. Stable soliton mode locking was achieved by use of an intracavity semiconductor saturable absorber mirror. We obtained mor...

We discuss the difference in the dynamics of solid-state lasers mode locked by fast or slow saturable absorbers with and without solitonlike pulse shaping, i.e., negative group delay dispersion (GDD) and self-phase modulation (SPM). We present simple relations that indicate when the single pulse per cavity round trip will break up into longer multi...

form only given. We report on a significant improvement in average output power of a diode-pumped Nd:glass laser, achieving >1 W mode locked and 2 W continuous wave. We used a 1-cm-wide, 806-nm 20-W diode bar and applied optimized mode matching (OMM) in the gain material in both the fast (i.e., sagittal) axis and the slow (i.e., tangential) axis of...

form only given. We report the operation of a low-threshold four-mirror laser using an AlGaAs semiconductor saturable absorbing mirror (SESAM) supplied by the Federal Institute of Technology, Zurich, to enable selfstarting femtosecond operation.

The combination of a GaAs semiconductor saturable absorbing mirror (SESAM) ¹ and a low-threshold laser geometry ² has allowed the efficient production of stable low-noise femtosecond pulses. The highly asymmetric 4-mirror Cr ³⁺ LiSAF laser was pumped by 2 polarisation-combined narrow-stripe AlGaInP laser diodes each providing a maximum available po...

We demonstrate 60-fs pulses with an average output power of 84 mW from a diode-pumped Nd:glass laser mode locked by a low-finesse antiresonant Fabry-Perot saturable absorber (A-FPSA). The mode-locked spectrum spreads over most of the available Nd:glass fluorescence bandwidth. At increased pulse energy fluence or decreased negative group-velocity di...

Intracavity semiconductor saturable absorber mirrors (SESAM's) offer unique and exciting possibilities for passively pulsed solid-state laser systems, extending from Q-switched pulses in the nanosecond and picosecond regime to mode-locked pulses from 10's of picoseconds to sub-10 fs. This paper reviews the design requirements of SESAM's for stable...

Thesis (doctoral)--Swiss Federal Institute of Technology Zurich, 2000.