Showing papers on "Regenerative amplification published in 2020"

Multi-millijoule, few-cycle 5 µm OPCPA at 1 kHz repetition rate

Abstract: A table-top midwave-infrared optical parametric chirped pulse amplification (OPCPA) system generates few-cycle pulses with multi-10 GW peak power at a 1 kHz repetition rate. The all-optically synchronized system utilizes ZnGeP2 nonlinear crystals and a highly stable 2 µm picosecond pump laser based on Ho:YLiF4. An excellent energy extraction is achieved by reusing the pump pulse after the third parametric power amplification stage, resulting in 3.4 mJ idler pulses at a center wavelength of 4.9 µm. Pulses as short as 89.4 fs are achieved, close to only five optical cycles. Taking into account the pulse energy, a record high peak power of 33 GW for high-energy mid-IR OPCPAs beyond 4 µm wavelength is demonstrated.

Laser with 1.2 ps, 20 mJ pulses at 100 Hz based on CPA with a low doping level Yb:YAG rods for seeding and pumping of OPCPA.

Abstract: We report on a picosecond two-stage double-pass chirped pulse amplifier based on a low doping level Yb:YAG rods. After compression, it provides output pulses with a pulsewidth of 1.15 ps and an energy of more than 20 mJ at a repetition rate of 100 Hz with a beam quality of M2 ∼1.05. These pulses were frequency doubled in a two-cascaded second harmonic converter based on LBO and BBO crystals with an output energy of 12 mJ and 5 mJ at 515 nm, suitable for simultaneously pumping OPCPA cascades.

High-power passively mode-locked cryogenic Yb:YLF laser

Abstract: We report, to the best of our knowledge, the first mode-locked operation of Yb:YLF gain media at cryogenic temperatures. A saturable Bragg reflector was used for initiating and sustaining mode locking. Once aligned, the system was self-starting and quite robust. Using output couplers in the 10–40% range, 3–5 ps long pulses with an average power as high as 28 W were achieved. The repetition rate was 46.45 MHz, and the corresponding pulse energy and peak power were as high as 602 nJ and 126.5 kW, respectively. The central wavelength of the mode-locked pulses could be tuned in the 1013.5–1019 nm range using an intracavity birefringent filter. The achieved output power performance is two to three orders of magnitude higher than previous room-temperature Yb:YLF systems.

Pure-rotational 1D-CARS spatiotemporal thermometry with a single regenerative amplifier system.

Abstract: We report spatiotemporal pure-rotational coherent anti-Stokes Raman spectroscopy (CARS) in a one-dimensional imaging arrangement obtained with a single ultrafast regenerative amplifier system. The femtosecond pump/Stokes photon pairs, used for impulsive excitation, are delivered by an external compressor operating on a ∼35% beam split of the uncompressed amplifier output (2.5 mJ/pulse). The picosecond 1.2 mJ probe pulse is produced via the second-harmonic bandwidth compression (SHBC) of the ∼65% remainder of the amplifier output (4.5 mJ/pulse), which originates from the internal compressor. The two pump/Stokes and probe pulses are spatially, temporally, and repetition-wise correlated at the measurement, and the signal generation plane is relayed by a wide-field coherent imaging spectrometer onto the detector plane, which is refreshed at the same repetition rate as the ultrafast regenerative amplifier system. We demonstrate 1 kHz cinematographic 1D-CARS gas-phase thermometry across an unstable premixed methane/air flame-front, achieved with a single-shot precision <1% and accuracy <3%, 1.4 mm field of view, and an excellent <20µm line-spread function.

Thin-disk laser-pumped OPCPA system delivering 4.4 TW few-cycle pulses.

Abstract: We present an optical parametric chirped pulse amplification (OPCPA) system delivering 4.4 TW pulses centered at 810 nm with a sub-9 fs duration and a carrier-envelope phase stability of 350 mrad. The OPCPA setup pumped by sub-10 ps pulses from two Yb:YAG thin-disk lasers at 100 Hz repetition rate is optimized for a high conversion-efficiency. The terawatt pulses of the OPCPA are utilized for generating intense extreme ultraviolet (XUV) pulses by high-order harmonic generation, achieving XUV pulse energies approaching the microjoule level.

20-mJ, sub-ps pulses at up to 70 W average power from a cryogenic Yb:YLF regenerative amplifier.

Abstract: We report, what is to our knowledge, the highest average power obtained directly from a Yb:YLF regenerative amplifier to date. A fiber front-end provided seed pulses with an energy of 10 nJ and stretched pulsewidth of around 1 ns. The bow-tie type Yb:YLF ring amplifier was pulse pumped by a kW power 960 nm fiber coupled diode-module. By employing a pump spot diameter of 2.1 mm, we could generate 20-mJ pulses at repetition rates between 1 Hz and 3.5 kHz, 10 mJ pulses at 5 kHz, 6.5 mJ pulses at 7.5 kHz and 5 mJ pulses at 10 kHz. The highest average power (70 W) was obtained at 3.5 kHz operation, at an absorbed pump power level of 460 W, corresponding to a conversion efficiency of 15.2%. Despite operating in the unsaturated regime, usage of a very stable seed source limited the power fluctuations below 2% rms in a 5 minute time interval. The output pulses were centered around 1018.6 nm with a FWHM bandwidth of 2.1 nm, and could be compressed to below 1-ps pulse duration. The output beam maintained a TEM00 beam profile at all power levels, and possesses a beam quality factor better than 1.05 in both axis. The relatively narrow bandwidth of the current seed source and the moderate gain available from the single Yb:YLF crystal was the main limiting factor in this initial study.

2.05 µm chirped pulse amplification system at a 1 kHz repetition rate—2.4 ps pulses with 17 GW peak power

Abstract: Ho-doped yttrium lithium fluoride chirped pulse amplification (CPA) is implemented with a high-gain regenerative amplifier (RA) and a two-stage booster amplifier. We demonstrate the generation of 52.5 mJ pulses with a duration of 2.4 ps at a 1 kHz repetition rate. A peak power of 17 GW is achieved for the 2050 nm pulses. The CPA displays a remarkably high stability with a pulse-to-pulse rms as low as 0.23%. The RA operates without any signs of bifurcation and delivers 12 mJ pulses. Seeding the booster amplifier with the RA output scales the pulse energy linearly up into the 50-60 mJ range. The amplifier system is operated at room temperature and shows a high optical-to-optical efficiency of 20.3% with respect to the optical pump power.

Programmable generation of terahertz bursts in chirped-pulse laser amplification

Abstract: Amplified bursts of laser pulses are sought for various machining, deposition, spectroscopic, and strong-field applications. Standard frequency- and time-domain techniques for pulse division become inadequate when intraburst repetition rates reach the terahertz (THz) range as a consequence of inaccessible spectral resolution, requirement for interferometric stability, and collapse of the chirped-pulse amplification (CPA) concept due to the loss of usable bandwidth needed for safe temporal stretching. Avoiding the burst amplification challenge and resorting to lossy post-division of an isolated laser pulse after CPA leaves the limitations of frequency- and time-domain techniques unsolved. In this Letter, we demonstrate an approach that successfully combines amplitude and phase shaping of THz bursts, formed using the Vernier effect, with active stabilization of spectral modes and efficient energy extraction from a CPA regenerative amplifier. As proof of concept, the amplified bursts of femtosecond near-infrared pulses are down-converted into tunable THz-frequency pulses via optical rectification.

Power and energy scaling of rod-type cryogenic Yb:YLF regenerativeamplifiers

Abstract: We numerically investigate the power and energy scaling potential of cryogenic Yb:YLF regenerative amplifiers in rod geometry. Our approach is based on solving the coupled set of equations describing thermal behavior of the material and its effect on spectroscopic properties, gain, and overall amplification. The approach is first benchmarked with earlier experimental data. By carefully analyzing the sensitivity of the system to operation parameters, we see that the relatively low gain nature of the Yb:YLF and the onset of thermal effects are the main factors that limited the performance in earlier experimental work. We show that usage of dual-rod geometry promises much improved performance. Specifically, we demonstrate that sub-250 fs pulses with an average power of up to 270 W and a peak power above 500 GW can be extracted directly from a single-stage Yb:YLF regenerative amplifier employing dual Yb:YLF rods. We further show that by adjusting the spot size in the regenerative amplifier, one can operate the amplifier in either high-energy mode (>100mJ at 1 kHz) or high-average-power mode (>25mJ at 10 kHz, with >250W). We also discuss pros and cons of Yb:YLF with respect to Yb:YAG, and underline the need for measurement of population and photo-elastic-effect-induced lensing in Yb:YLF to obtain a better understanding of Yb:YLF systems. The findings presented in this work can be used for the design and development of next-generation high-average and peak-power Yb:YLF amplifier systems.

Bifurcation suppression in regenerative amplifiers by active feedback methods.

Abstract: The performance of regenerative amplifiers at high repetition rates is often limited by the occurrence of bifurcations induced by a destabilization of the pulse-to-pulse dynamics. While bifurcations can be suppressed by increasing the seed energy using dedicated pre-amplifiers, the availability of adjustable filters and control electronics in modern pulse amplifiers allows to exploit feedback strategies to cope with these instabilities. In this paper, we present a theoretical and experimental analysis of active feedback methods to stabilize otherwise unstable operational regimes of regenerative amplifiers. To this end, the dynamics of regenerative amplifiers are investigated starting from a general space-dependent description to obtain a generalization of existing models from the literature. Suitable feedback strategies are then developed utilizing measurements of the output pulse energies or the transmitted pump light, respectively. The effectiveness of the proposed approach is highlighted by experimental results for a Yb:CaF2-based regenerative amplifier.

Eight-pass Yb:YLF cryogenic amplifier generating 305-mJ pulses

Abstract: We report record output pulse energies from a cryogenic 8-pass Yb:YLF amplifier system operating at 10 Hz repetition rate. When seeded with 20-mJ, 1-ns stretched pulses, the amplifier produced output pulses with 305 mJ of energy at 1018.5 nm with a spectral width supporting sub-ps pulse-duration. The output beam profile was quite symmetric and had a measured beam quality factor (M2) of ∼1.45. To achieve this performance, the diameter of the beam inside the gain element is gradually increased via an adjustable telescope from around 4.6 mm to 6.2 mm. This enables adjustment of the fluence to a moderate value in subsequent passes: high enough for efficient extraction and low enough to prevent laser induced damage. To our knowledge, this is the highest pulse energy reported from cryogenically cooled Yb:YLF amplifiers to date. Further scaling in peak power and repetition rate is anticipated in future work.

Ultra-broadband high conversion efficiency optical parametric chirped-pulse amplification based on YCOB crystals.

Abstract: We present a high efficiency and ultra-broadband optical parametric chirped-pulse amplification (OPCPA) system fully based on yttrium calcium oxyborate (YCOB) crystals. The OPCPA properties of YCOB at 808 nm are studied for both high gain and saturated amplification. The non-collinear angle is finely tuned to study the variation of gain spectrum at a certain phase-matching angle of YCOB crystals. After amplification by four YCOB crystals, a total signal gain of 0.9×109 is obtained and the FWHM spectral bandwidth is still over 100 nm. An amplified signal pulse of 182 mJ is achieved with pump energy of 440 mJ in the saturated amplification stage and the conversion efficiency is about 40%. After a four-grating compressor, a pulse duration of 20 fs is measured by a second-order autocorrelator.

Recent Progress on the Shanghai Superintense Ultrafast Laser Facility (SULF) at SIOM

Abstract: SULF laser based on chirped pulse amplification (CPA) was built in Shanghai. The amplified energy of 422 J was achieved at repetition rate of one shot per 3 minutes. After compressor, the pulse duration was measured to be 23.4 fs with a throughput efficiency of 71.3%, which correspond to a peak power of 12.9PW.

640-nm Pr:YLF regenerative amplifier seeded by gain-switched laser diode pulses.

Abstract: We demonstrated the regenerative amplification of picosecond laser pulses generated by a gain-switched laser diode at 640 nm with a Pr:YLF crystal that was continuously pumped by a multimode blue laser diode. A 0.7-pJ seed pulse energy sufficiently suppressed the self-oscillation in the amplifier. The amplified pulse energy reached 33 µJ at a repetition rate of 10 kHz. The spatial beam quality was nearly TEM00. We also demonstrated second- and third-harmonic generation and obtained 320- and 213-nm pulse energies of 18 and 0.83 µJ at 10 kHz.

0.4 J / 35 ps Nd:YAG laser for Lunar Laser Ranging

Abstract: We developed a 0.4 J diode-pumped 1064 nm Nd:YAG MOPA laser with pulse duration of 35 ps. The master oscillator was based on laser scheme with regenerative amplification of DFB laser diode radiation. The two-pass two-stage power amplifier was built on two Nd:YAG laser rods. The SHG efficiency up to 83% was achieved in 17x17x7 mm3 LBO crystal.

Comparison of multi-pass and regenerative strategies for energetic high-gain amplifiers based on Yb:CaF2.

Abstract: Yb-doped materials, due to their high saturation fluence and consequently their low gain, represent a challenging choice for high-energy amplifiers. In this Letter, we study two original amplifier designs adapted to a large number of passes capable of operating in the 100 mJ energy range at repetition rates up to 100 Hz using Yb:CaF2 crystals as active media. Amplification geometries based on double-head active-mirror configurations are presented. We confront two alternative strategies suitable for amplification of large beams: regenerative and geometrical multi-pass amplifiers. This Letter consists of finding the pivot point, allowing us to discriminate the specific interest of each strategy. We present compensation methods of the thermal lens adapted to each amplifier configuration with and without cavity, and we demonstrate that despite similar laser heads and pumping conditions, the thermal lens impacts differently the optimal performance for multi-pass or regenerative strategy. We perform amplification up to 66 mJ pulses at 10 Hz with the regenerative amplifier and 52 mJ at 100 Hz with the multi-pass amplifier.

High Energy Cryogenic Yb:YAG and Yb:YLF Chirped Pulse Amplifiers

Abstract: We present cryogenically cooled, high repetition-rate Yb-based regenerative and multipass amplifiers that provide pulse energies up to 1.2 J and average power up to 600W. Different design approaches depending of the gain crystal material are discussed.

High gain amplification up to 100 mJ to 3 J using Yb3+:YAG slab-based cat's-eye cavities under variable seed and operating conditions

Abstract: We demonstrate the optical architecture of a fairly compact design at 1030 nm for linear amplification, which enables the combination of very high gains and output energies in a single stage to be operated at room temperature. Gains and energies are experienced in the nanosecond regime up to 20 dB and 120 mJ, respectively, at the same time. This design makes use of a thick slab of Yb3+:YAG in a scalable cat’s-eye cavity, provided there is uniform edge-pumping and fine control of a number of relevant spatial characteristics regarding the pump and the cavity. Highly variable operating conditions are considered for a comprehensive benchmark of the optical performance. They involve single 3 ns long seed pulses with an energy of 1 mJ, accordingly to more or less gain saturation, together with long bursts of stretched picosecond-long pulses. This gives access to kilowatt-class pulse trains of duration 3–5 ms, with a total energy of up to 3 J and an optical efficiency of 20%–25%, prior to more complete gain saturation.

Generation of Continuously-Tunable, Narrowband THz Pulses from Phase-Locked Femtosecond Pulse Bursts

Abstract: We demonstrate generation of continuously-tunable, narrowband THz pulses from phase-locked multi-millijoule femtosecond pulse bursts by optical rectification in a tilted-pulse-front setup. Experimental results indicate advances in both, femtosecond pulse burst and high-energy THz source technology.

Pipelined-interpolating analog-to-digital converter

Abstract: Analog-to-digital converter (ADC) circuitry to convert an analog signal to a digital signal is disclosed herein. The ADC circuitry can utilize pipelined-interpolation analog-to-digital converters (PIADCs) with adaptation circuitry to correct regenerative amplification cells of the PIADCs. The PIADCs can implement a rotational shuffling scheme for correction of the regenerative amplification cells, where the correction implemented by the regenerative amplification cells allows for offsetting of latches of the regenerative amplification cells.

Sub 5-cycle pulse generation from mode-locked Cr:ZnS laser using mid-IR resonant SWCNTs

Abstract: We demonstrate the excellent saturable absorption of single-walled carbon nanotubes with resonance around 2.4 µm, realizing 36-fs oscillation in a Cr:ZnS oscillator. Introducing a two-stage single pass amplifier, the output exceeds 100 nJ.

High repetition rate OPCPA driving an attosecond pump-probe beamline

Abstract: A high power optical parametric amplifier operating at 100 kHz repetition rate has been integrated into an attosecond pump-probe beamline. Attosecond pulses with high photon flux are generated and characterized in pump-probe experiments.

70 W Yb:YLF Cryogenically-Cooled Regenerative Amplifier

Abstract: We demonstrate a cryogenically-cooled Yb:YLF regenerative amplifier delivering 20-mJ pulses at 3.5 kHz corresponding to 70 W average power. The pulses possess 2.1 nm spectral bandwidth centered at 1019 nm supporting sub-ps pulses.

Generation of Continuously-Tunable, Narrowband THz Pulses from Phase-Locked Femtosecond Pulse Bursts

Abstract: We demonstrate generation of continuously-tunable, narrowband THz pulses from phase-locked multi-millijoule femtosecond pulse bursts by optical rectification in a tilted-pulse-front setup. Experimental results indicate advances in both, femtosecond pulse burst and high-energy THz source technology.

All-fiber high-energy pulse regeneration and amplification device and method based on 2 * 3 optical switch

Abstract: The invention discloses an all-fiber high-energy pulse regeneration and amplification device based on a 2 * 3 optical switch. The device comprises the 2 * 3 optical switch, an all-fiber regeneration and amplification resonant cavity composed of the 2 * 3 optical switch, an ultrashort pulse laser seed source, a pulse broadening device, a pulse compression device and a detection and feedback controldevice. The 2 * 3 optical switch selectively inputs the pulse of the regenerative amplification resonant cavity and outputs the pulse from different ports. The input pulse of the all-fiber regenerative amplification resonant cavity is circularly amplified for multiple times in the resonant cavity, and the locking of the repetition frequency of the ultrashort pulse laser seed source and the all-fiber regenerative amplification resonant cavity and the synchronization between a 2 * 3 optical switch control signal and the ultrashort pulse laser seed source are ensured by using a detection and feedback control device. The high-energy pulse regeneration and amplification device can effectively replace a multi-stage amplification and frequency reduction structure in traditional high-power optical fiber laser amplification, the cost of high-energy ultrafast laser is reduced, and research and application of the ultrafast laser can be promoted.

Laser-induced polarization-dependent birefringence in sodium borate glasses

Abstract: The possibility of femtosecond laser-induced polarization-dependent birefringence was demonstrated for the first time in the bulk of sodium-borate glass. The dependence of retardance of laser-induced birefringence on alkali content was studied.

Mid-infrared supercontinuum generation in polarization maintained ZBLAN fibers using a femtosecond Tm:YAP laser

Abstract: Mid-infrared supercontinuum generation in polarization-maintained fluoride fibers has been demonstrated. The coherence of the supercontinuum is dramatically im-proved by reducing the round trip number of the 2 µm Tm:YAP regenerative amplifier.

High Power Cryogenic Yb:YLF Regenerative Amplifier

Abstract: We present a cryogenic Yb:YLF regenerative amplifier which can reach 70 W average power and 20 mJ output energy at 3.5 kHz operation. The output beam quality factor is better than 1.05 in both axes.

Luminosity Enhancement in Laser-Compton Scattering by Crab Crossing

Abstract: X-ray enhancement by the crab crossing of electrons and laser photons in laser-Compton scattering (LCS) is studied. Current status of our crab crossing LCS experiment and the development of thin-disk regenerative amplifier is reported.