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In this study, we have successfully demonstrated a high-energy subpicosecond Yb:YAG laser system based on chirped-pulse regenerative amplification. Our experimental results demonstrate a pulse energy of 3 mJ with a pulse duration of 829.8 fs and a repetition rate of 1 kHz. Additionally, we conducted an extensive investigation into the system's recompression capability under various modulation and seeding conditions. Our findings suggest that the system can achieve effective recompression over a broad range of parameters, with the ability to compensate for a considerable degree of chirp. Our study provides valuable insights into the fundamental physic of high-energy laser systems and the performance characteristics of chirped-pulse regenerative amplification. [ABSTRACT FROM AUTHOR]

We present an effective approach to realize a highly efficient, high-power and chirped pulse amplification-free ultrafast ytterbium-doped yttrium aluminum garnet thin-disk regenerative amplifier pumped by a zero-phonon line 969 nm laser diode. The amplifier delivers an output power exceeding 154 W at a pulse repetition rate of 1 MHz with custom-designed 48 pump passes. The exceptional thermal management on the thin disk through high-quality bonding, efficient heat dissipation and a fully locked spectrum collectively contributes to achieving a remarkable optical-to-optical efficiency of 61% and a near-diffraction-limit beam quality with an M2 factor of 1.06. To the best of our knowledge, this represents the highest conversion efficiency reported in ultrafast thin-disk regenerative amplifiers. Furthermore, the amplifier operates at room temperature and exhibits exceptional stability, with root mean square stability of less than 0.33%. This study significantly represents advances in the field of laser amplification systems, particularly in terms of efficiency and average power. This advantageous combination of high efficiency and diffraction limitation positions the thin-disk regenerative amplifier as a promising solution for a wide range of scientific and industrial applications.

In this study, we have successfully demonstrated a high-energy subpicosecond Yb:YAG laser system based on chirped-pulse regenerative amplification. Our experimental results demonstrate a pulse energy of 3 mJ with a pulse duration of 829.8 fs and a repetition rate of 1 kHz. Additionally, we conducted an extensive investigation into the system’s recompression capability under various modulation and seeding conditions. Our findings suggest that the system can achieve effective recompression over a broad range of parameters, with the ability to compensate for a considerable degree of chirp. Our study provides valuable insights into the fundamental physic of high-energy laser systems and the performance characteristics of chirped-pulse regenerative amplification.

• Design of high optical efficiency dual-pass resonant cavity. • Picosecond laser regenerative amplifier without compression. • Good beam quality ultrafast laser system. • Zero-phonon line pumping technology with low quantum loss and thermal effects. This paper introduces a CPA-free Yb:YAG thin-disk regenerative amplifier laser system. The seed pulse is generated by a passive mode-locked picosecond oscillator based on a semiconductor saturable absorber mirror, with a center wavelength of 1030.7 nm, a pulse width of 7.7 ps, and a repetition frequency of 26.3 MHz. After stretched and pre-amplified by an all-fiber front stage, the seed with a pulse width of 201.3 ps and a pulse energy of 15.2 nJ was obtained, then injected into the thin-disk regenerative amplifier. Yb:YAG crystal was chosen as the material for the thin-disk, with 100 μm thickness, 9 mm diameter and 7 at.% doping rate. In order to increase the one-way round-trip gain of the thin-disk regenerative amplifier, a symmetrical dual-pass resonant cavity was designed to double the number of passing through the crystal on a round trip in the regenerative resonant cavity to reduce the times of cycles, intra-cavity loss and improve optical efficiency. We used a 969 nm fiber-coupled semiconductor laser as the pump source to pump the Yb:YAG thin-disk crystal. With zero-phonon line pumping technology, the quantum loss and thermal effect were reduced. In the end, we obtained a regenerative amplification output with an average power of 104.5 W, a repetition frequency of 200 kHz, a pulse width of 143.9 ps, and a spectrum width of 0.39 nm. The amplified pulse had quite good beam quality with M x 2 = 1.09 and M y 2 = 1.14. [ABSTRACT FROM AUTHOR]

Picosecond pulse laser is the main light source for satellite laser ranging. In this paper, a 10 kHz repetition rate picosecond green laser with an average output power of 5.3 W is demonstrated. The laser generates a pulse width of 18.6 ps at a center wavelength of 532.20 nm with a spectral width of .066 nm. The beam quality is well preserved with M2 of 1.1 with the beam divergence measured to be .62 mrad and pointing stability of 7 μrad over 30 min of operation. The laser system was then applied to measure the BeiDou satellite (Compass-I3) and generated a single range accuracy of 3.2 mm, which is the highest reported range accuracy for synchronous orbit satellite laser ranging.

In this study, the designing method of multi-beam regenerative amplifiers with the repetitive rate was proposed and demonstrated. To obtain multi-beam regenerative amplifiers with uniform performance, the disparities in output energy, energy stability, and mode size were analyzed, and the detailed optimizing method was presented. With the designs, eight-beam regenerative amplifiers were developed. The output performances of eight-beam regenerative amplifiers were uniform. The output energies were in the range of 25.4–28.8 mJ, and the energy stabilities over two hours were in the range of 2.4%–5.1% (PV) and 0.3%–0.9% (RMS).

Free-electron lasers (FELs) have been designed to operate over virtually the entire electromagnetic spectrum, from microwaves through to X-rays, and in a variety of configurations, including amplifiers and oscillators. Oscillators can operate in both the low and high gain regime and are typically used to improve the spatial and temporal coherence of the light generated. We will discuss various FEL oscillators, ranging from systems with high-quality resonators combined with low-gain undulators, to systems with a low-quality resonator combined with a high-gain undulator line. The FEL gain code MINERVA and wavefront propagation code OPC are used to model the FEL interaction within the undulator and the propagation in the remainder of the oscillator, respectively. We will not only include experimental data for the various systems for comparison when available, but also present, for selected cases, how the two codes can be used to study the effect of mirror aberrations and thermal mirror deformation on FEL performance. [ABSTRACT FROM AUTHOR]

We present a regenerative amplifier (RA) based on Yb:YAG single-crystal fiber (SCF) and nonlinear amplifying loop mirror (NALM) fiber oscillator. The home-made all-fiber NALM oscillator is constructed with polarization maintaining (PM) fibers for improved environmental stability, delivering a stable pulse train. The seed is directly amplified in a single stage without using CPA technique. 21 W, $105~\mu \text{J}$ , 2.4 ps at 200 kHz repetition rate with beam quality of 1.3 has been achieved. A remarkable optical gain of 57.4 dB is obtained with a seed injection of 190 pJ. Further increase in average power is expected. [ABSTRACT FROM AUTHOR]

• Beam mutation in thin-disk regenerative amplifiers is proposed for the first time. • It is proved experimentally that beam mutation appears together with period doubling bifurcation and deterministic chaos. • A Yb:YAG thin-disk regenerative amplifier with stable beam and single-energy pulse is realized by reducing the gate length. • The peak power is 250 MW, which is the highest intra-cavity peak power at repetition rates above 1 kHz reported. Beam mutation in thin-disk regenerative amplifiers is proposed here, to the best of our knowledge, for the first time. It is proved to appear together with period doubling bifurcation and deterministic chaos experimentally. The suppression of beam mutation is achieved by reducing the gate length of the regenerative amplifier. With the gate length of 1.88 μs, a Yb:YAG thin-disk regenerative amplifier with stable beam and single-energy pulse is realized. The maximum pulse energy is 145 mJ with the optical-optical efficiency of around 10 %. The repetition rate and the pulse width are 1 kHz and 580 ps respectively. [ABSTRACT FROM AUTHOR]

Free-electron lasers (FELs) have been designed to operate over virtually the entire electromagnetic spectrum, from microwaves through to X-rays, and in a variety of configurations, including amplifiers and oscillators. Oscillators can operate in both the low and high gain regime and are typically used to improve the spatial and temporal coherence of the light generated. We will discuss various FEL oscillators, ranging from systems with high-quality resonators combined with low-gain undulators, to systems with a low-quality resonator combined with a high-gain undulator line. The FEL gain code MINERVA and wavefront propagation code OPC are used to model the FEL interaction within the undulator and the propagation in the remainder of the oscillator, respectively. We will not only include experimental data for the various systems for comparison when available, but also present, for selected cases, how the two codes can be used to study the effect of mirror aberrations and thermal mirror deformation on FEL performance.

This paper presents a calibration-free 12-bit 50-MS/s full-analog SAR analog-to-digital (A-to-D) converter (ADC) in 40-nm CMOS, which integrates the functions of comparator, SAR logic, and digital-to-analog converter (DAC) switches into multiple feedback zero-crossing detectors (FB-ZCDs). By eliminating all the digital circuits, the full-analog bit conversions operate with the asynchronous amplification-to-regeneration (A-to-R) operation that highly relaxes the requirements of the analog circuits and reference generator. This paper is implemented without any calibration, where the non-ideal effects (offset mismatch, insufficient residue, and noise) are mitigated and eliminated with the proposed techniques as follows. The offset mismatches among the FB-ZCDs are covered by the redundancies of the sub-radix DAC arrangement in the coarse ADC. The bottom-plate coupling compensators (BPCCs) are proposed to correct the consecutive SAR decision errors as quantizing the insufficient residue. The shared FB-ZCD with capacitor coupling decision (CCD) network is developed to obtain the identical offset in the fine ADC. Amplification extension (AE) technique is proposed to enhance the precision of the shared FB-ZCD by reconfiguring as a complementary inverter-based amplifier with the extended amplification period to enhance the output SNR. This paper occupies an active area of 0.01 mm2 and achieves the Nyquist-rate signal-to-noise-and-distortion ratio (SNDR), spurious-free dynamic range (SFDR), Walden figure-of-merit (FoMW), and Schreier FoM (FoMS) of 64.1, 75.6 dB, 5.3 fJ/conversion step, and 172.8 dB, respectively. [ABSTRACT FROM AUTHOR]

Abstract In general, misalignment, surface quality of optical components, thermal and nonlinear properties, doping level and inhomogeneity in the gain material can induce unexpected pulse propagation effects on intnese femtosecond laser pulses. Among them, the thermal lens in a thermally loaded material is more serious since it limits power scaling and degrades maximum achievable intensity at the focus by introducing distortion into the wavefront. Thereby, an understanding of thermally distortion wavefront is of great importance for optimum design of high power laser amplifiers and efficient serving femtosecond lasers in various specific applications. In this paper, we experimentally studied beam quality and wavefront distortion in a longitudinally pumped two-stage chirped pulse high power Ti:sapphire amplifier laser at 1 kHz operation in terms of pump power. The amplifier crystals are cooled thermoelectrically to below −10 °C. A simple formula for coupling the thermal lens in a two-stage amplifier consists of a regenerative amplifier followed by a single-pass amplifier pumped equally by the Nd:YLF laser at 527 nm with maximum average output power of 44 W and 130 ns pulse duration at 1 kHz is presented. The wavefront curvature of the compressed laser pulses with ∼40 fs pulse duration and center wavelength of 800 nm is evaluated directly by Shack-Hartmann Wavefront Sensor (SHWS) with help of the Zernike polynomials. While the beam radius and spatial beam quality M2 factor are estimated by knife-edge testing. Also, the optical wavefront distortion caused by an iris inserted into the beam path of a high power laser for quick spot size adjustment has been presented. When diameter of the iris is about 75% of the laser beam size (corresponding to 67% fraction transmission), laser beam distortion associated with the iris is negligible. [ABSTRACT FROM AUTHOR]

We report a stable optical fiber pumped Nd:YVO4 all solid state regenerative amplifier with all fiber picosecond laser as seed source. 888 nm Yb optical fiber lasers was chosen as pump source to reduce quantum defect for improved thermal performance. At the repetition rate of 99.6 kHz, maximum power of 19.63 W with 36 ps pulse duration were achieved when seeded by a 150 mW picosecond oscillator. The wavelength delivered was 1064.07 nm with spectral width of 0.14 nm.

An average power of 3 W green picosecond laser at a pulse repetition frequency of 1 kHz was reported. At the Shanghai satellite laser ranging (SLR) station, many satellites were measured with this laser and a narrow spectrum filter in the daytime. Satellites of the Beidou satellite navigation system for the Chinese, Global navigation satellite system for the Russian and Galileo satellite navigation system for the Europe were measured respectively. Especially ranging precision root mean square was up to 19.4 mm for the satellite of compassi5 about 37,000 km far from the earth. A Nd:YVO 4 mode-locked laser with an etalon, a dual-length of Nd:YAG regenerative amplification cavity, single-pass two Nd:YAG modules amplifier and nonlinear optical materials LiB 3 O 5 frequency doubling were designed. An average power of 3 W in 532 nm was obtained with pulse width of 30 ps, and angle of divergence was 0.8 mrad. Using the dual-length of regenerative cavity would greatly decrease the laser's volume and improve stability of picosecond laser. A narrow spectrum filter can reduce a lot of optics noise from the sun, and so all the satellites were almost be measured with this laser in the daytime at the Shanghai SLR station. [ABSTRACT FROM AUTHOR]

This paper presents a new understanding of the gain narrowing mechanism in short-pulse amplification. Spectral and temporal bandwidth measurements of the amplified pulse, extracted from a chirped pulse amplification system, indicates clearly that gain narrowing occurs during the initial roundtrips in a regenerative amplifier, but during the later round trips, the pulse gains spectral bandwidth. This evolution of the pulse and its spectrum in a Nd:glass regenerative amplifier has been explained with a simulation code. The simulation is based on the Frantz–Nodvik model that has been generalized to a spectral domain and applied to Nd:glass, the active medium of the regenerative amplifier. The results also confirm the inhomogeneous gain profile of the active medium and the slow cross relaxation rates. [ABSTRACT FROM AUTHOR]

X-ray free-electron lasers (FELs) rely on SASE due to the lack of seed lasers and the difficulty in obtaining mirrors. Progress in diamond crystal Bragg mirrors enables the design of x-ray FEL oscillators. Regenerative amplifiers (RAFELs) are high gain/low- Q oscillators that out-couple most of the optical power. An x-ray RAFEL based on the LCLS-II at SLAC using a six-mirror resonator out-coupling 90% or more through a pinhole in the first downstream mirror is analyzed using the MINERVA simulation in the undulator and OPC for the resonator. Results show substantial powers at the fundamental (3.05 keV) and 3rd harmonic (9.15 keV).

A non-pulse-leakage optical fiber pumped 100-kHz level high beam quality Nd:YVO4 picosecond amplifier has been developed. An 80 MHz, 11.5 ps mode-locked picosecond laser is used as the seed with single pulse energy of 1 nJ. By harnessing the double β-BaB2O4 (BBO) crystal Pockels cells in both the pulse picker and regenerative amplifier, the seed pulse leakage of the output is suppressed effectively with an adjustable repetition rate from 200 to 500 kHz. Through one stage traveling-wave amplifier, a maximum output power of 24.5 W is generated corresponding to the injected regenerative amplified power of 9.73 W at 500 kHz. The output pulse duration is 16.9 ps, and the beam quality factor M2 is measured to be 1.25 with near-field roundness higher than 99% at the full output power. [ABSTRACT FROM AUTHOR]

We report, to the best of our knowledge, a chirped pulse amplification laser system based on the Nd,Y:SrF 2 crystal for the first time. The incorporation of Y 3+ nonactive ions can significantly improve laser properties of Nd:SrF 2 crystal, including broader emission linewidth, larger cross-section as well as longer fluorescence lifetime. Pulse laser with 5.1 mJ (uncompressed), 3.7 mJ (compressed) energy, 1.6 ps duration at 5 Hz repetition rate is demonstrated. The results indicate that the Nd,Y:SrF 2 crystal is a potential candidate with excellent laser and thermal performance for developing ultra-intense laser with high repetition rate. [ABSTRACT FROM AUTHOR]

A diode-pumped Yb:YAG MOPA-System for the unprecedented generation of transform limited pulses with variable pulse duration in the range between 10 ps and 100 ps is presented. First applications relying on unique pulse parameters as modulation free spectrum, tunability and coherence length, namely the direct laser interference patterning (DLIP) and laser cooling of stored relativistic ion beams are highlighted. Pulses are generated by a mode-locked fs-oscillator while the spectral bandwidth is narrowed in the subsequent regenerative amplifier by an intra-cavity grating monochromator. Two alternative booster amplifiers were added to increase the pulse energy to 100 μJ and 10 mJ, respectively. [ABSTRACT FROM AUTHOR]

An analytical model is presented describing the temporal intensity contrast determined by amplified spontaneous emission in high-intensity laser systems which are based on the principle of chirped pulse amplification. The model describes both the generation and the amplification of the amplified spontaneous emission for each type of laser amplifier. This model is applied to different solid state laser materials which can support the amplification of pulse durations [ABSTRACT FROM AUTHOR]

A non-pulse-leakage optical fiber pumped 100-kHz level high beam quality Nd:YVO4 picosecond amplifier has been developed. An 80 MHz, 11.5 ps mode-locked picosecond laser is used as the seed with single pulse energy of 1 nJ. By harnessing the double β-BaB2O4 (BBO) crystal Pockels cells in both the pulse picker and regenerative amplifier, the seed pulse leakage of the output is suppressed effectively with an adjustable repetition rate from 200 to 500 kHz. Through one stage traveling-wave amplifier, a maximum output power of 24.5 W is generated corresponding to the injected regenerative amplified power of 9.73 W at 500 kHz. The output pulse duration is 16.9 ps, and the beam quality factor M2 is measured to be 1.25 with near-field roundness higher than 99% at the full output power.

We report a stable optical fiber pumped Nd:YVO4 all solid state regenerative amplifier with all fiber picosecond laser as seed source. 888 nm Yb optical fiber lasers was chosen as pump source to reduce quantum defect for improved thermal performance. At the repetition rate of 99.6 kHz, maximum power of 19.63 W with 36 ps pulse duration were achieved when seeded by a 150 mW picosecond oscillator. The wavelength delivered was 1064.07 nm with spectral width of 0.14 nm. [ABSTRACT FROM AUTHOR]

We report on a picosecond laser system produced by grating stretcher and regenerative amplifier. Firstly, mode-locked pulses with 8.5 ps and around 160 mW at the repetition rate of 143.8MHz were obtained by semiconductor saturable absorber mirrors (SESAM). Secondly, we successfully got the pulses stretched with grating stretcher from 160 mW and 8.5 ps to 90 mW and 99.9 ps. Finally, by using multi-pulse regeneration amplifier system we got a pulse sequence has each of five pulses as a group which output energy about 28.0 mJ at the repetition rate of 1 kHz and 1064 nm in single pulse width. INSET: 15. [ABSTRACT FROM AUTHOR]

A third-harmonic-generation picosecond pulse with several millijoules per pulse at 355 nm has been achieved by nonlinear optical materials LiB3O5 (LBO). The single pulse energy of third harmonic was up to 2 mJ at the repetition rate of 1 kHz. The conversion efficiency was up to 33.3% from 1064 to 355 nm with the M² factor of 2.4. The system is based on a Nd:YAG regenerative amplifier with a simple double-pass post-amplifier. [ABSTRACT FROM AUTHOR]

A diode dual-end-pumped Nd:YVO4 regenerative amplifier is reported. The influence of the cavity stability on the performance of the regenerative amplifier is studied. The experimental results match well with the analysis at high pump power. The mode locking seed pulses with 15 ps pulse width and 10 nJ single pulse energy at 86 MHz are amplified up to 4.7 mJ at 1 kHz, corresponding to the maximum amplification about 0.5 x 106, by our regenerative amplifier. And an average power of 4.7 W is obtained at the repetition rate from 1 kHz to 10 kHz. [ABSTRACT FROM AUTHOR]

The three-dimensional heat deposition of the cryogenic Yb:YAG regenerative amplifier, which is yielded by pulsed pumped laser, is derived in details based on the theory of quasi-three-level rate equations. Furthermore, the transient temperature field, stress, and strain induced by the thermal gradients in the laser crystal are analyzed by use of the finite element method. Then the thermally induced lens and depolarization in the cryogenic regenerative amplifier are theoretically studied. We find that for the pump and cooling structure which has been designed, the focal length of the thermally induced lens is about 15 m and the depolarization rate could be ignored. The maximum output energy 10.2 mJ at a repetition rate of 10 Hz with nearly TEM00 mode profile is obtained using the designed pump and cooling structure. [ABSTRACT FROM PUBLISHER]

Abstract: Since many years shortening of pulse duration down to femtosecond regime is propagated as a recipe for achieving higher precision in micro machining with lasers. The drawback of this approach is a loss in productivity which cannot be accepted when large work pieces such as rolls, cylinder liners or solar panels have to be treated. A novel development tool based on disk technology will be presented allowing finding application specific highest productivity at still acceptable inaccuracy. [ABSTRACT FROM AUTHOR]

Synchronized signal (650 ps) and pump (1.3 ns) pulses were generated using 4-pass geometry in a grating pair based pulse stretcher unit. The pump pulse has been further amplified in a high gain regenerative amplifier. This amplified pulse was used as the pump in an optical parametric chirped pulse amplification based Nd:glass laser system. As the chirped signal pulse and the pump pulse originated from the same oscillator, the time jitter between the pump pulse and the signal pulse can be <50 ps. [ABSTRACT FROM AUTHOR]

The article focuses on the development of a high-efficiency Yb:YAG regenerative amplifier and the estimation of its performance by theoretical calculations. It states that the experiment is aimed at developing an industrial laser system into a commercial product. It mentions that the Frantz-Nodvik equation was applied in order to calculate the regenerative pulse amplification, and the results of theoretical calculation was compared with experimental data.

Abstract: A diode-pumped Master Oscillator Power Amplifier (MOPA) laser system based on cryogenic cooled Yb:YAG has been designed, developed and its output performance characterised. The laser system consists of a fibre oscillator, an active mirror regenerative amplifier and a four pass main amplifier. 2.4mJ, 10ns, 100Hz seed pulses from the fibre oscillator/regenerative amplifier arrangement were amplified up to pulse energies of over 200mJ by using the four pass main amplifier arrangement. As a further study we have obtained an increased slope efficiency of 40% and an optical-to-optical efficiency of 30% using a pinhole vacuum spatial filter/image relay for laser mode control. With 1.8mJ input seed pulses, output pulse energies of around 150mJ were achieved. [Copyright &y& Elsevier]

An Yb:YAG dual-crystal regenerative amplifier was developed. The thermal effects were largely decreased by the dual-crystal configuration and optimized cavity design. The chirped pulse was amplified to 3.5 mJ with excellent energy stability (root mean square ∼ 0.95%) and beam quality (M2 < 1.1) at a repetition rate of 1 kHz using chirped pulse amplification (CPA) systems. A single space-saving simple-to-align chirped volume Bragg grating (CVBG) was used as a stretcher/compressor, which yielded 2-mJ pulses with a pulse duration of 1.9 ps after compression with an efficiency of 94.3%. A low-cost highly compact kilohertz high-energy ultrafast laser system solution was obtained. • To the best of our knowledge, this is first regenerative amplifier with Yb:YAG dual-crystal configuration. • A single space-saving simple-to-align chirped volume Bragg grating (CVBG) was used as a stretcher/compressor. • Achieve 2-mJ pulses with a pulse duration of 1.9 ps after compression with an efficiency of 94.3%. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we discuss extending the operating wavelength range of tunable Regenerative Amplifier FELs to shorter wavelengths than current design proposals, notably into the XUV regions of the spectrum and beyond where the reflectivity of broadband optics is very low. Simulation studies are presented which demonstrate the development of good temporal coherence in generic systems with a broadband radiation feedback of less than one part in ten thousand. [Copyright &y& Elsevier]

Abstract: We present a diode-pumped, chirped-pulse Yb:S-FAP regenerative amplifier. This regenerative amplifier was developed as a first amplifier in an all-solid-state Yb:S-FAP laser system for laser-Compton X-ray generation. The amplifier delivers pulse energies above 24mJ at a repetition rate of 50Hz. Pulse compression reduces pulse widths to approximately 2.0ps. [Copyright &y& Elsevier]

We describe a design and a construction of a TW-class 12-fs Ti:sapphire chirped-pulse amplification system. We developed a broadband pulse stretcher, a broadband gain-narrowing compensator, broadband high-energy mirrors, high-energy dichroic chirped mirrors, a dispersion compensator, and a broadband pulse compressor for ∼10-fs pulse generation. Utilizing these optical devices, we demonstrated a generation of 12-fs pulses from a 10-Hz-repetition-rate Ti:sapphire chirped-pulse multipass amplifier system and a 1-kHz-repetition-rate Ti:sapphire chirped-pulse regenerative amplifier system. Optimized designs of broadband Ti:sapphire amplifiers with multilayer gain-narrowing compensators and an adaptive dispersion compensator with a spatial light modulator contribute to the shorter pulse amplification. [ABSTRACT FROM PUBLISHER]

We demonstrate direct simultaneous seeding of a few-cycle optical parametric chirped pulse amplifier (OPCPA) in the 700-1000-nm spectral range, and of a Nd:YLF amplifier emitting 30-ps pulses at 1053 nm by use of a chirped-mirror 6-fs Ti:sapphire oscillator. This approach of employing a single master oscillator to drive two power amplifiers simplifies the pump laser design and is applied to eliminate the timing jitter between the seed and the pump pulses in the OPCPA chain. We show that 10 mJ fundamental picosecond pump pulses with the intensity contrast in excess of 104 relative to the nanosecond Q-switched background can be achieved with the seed intensity available in the edge of the oscillator spectrum around 1053 nm. Cross-correlation measurements between the picosecond pump and femtosecond oscillator pulses reveal no traceable timing jitter between the OPCPA pump and seed pulses. The estimated long-term jitter of 0.3 ps is attributed to the thermal expansion of the cavity of the Nd:YLF regenerative amplifier. [ABSTRACT FROM PUBLISHER]

We demonstrated accurate pulse shaping of amplified femtosecond optical pulses by modulating the amplitude and phase prior to regenerative chirped-pulse amplification. We measured the amplitude and phase of amplified pulses using a spectral interferometer with a well-defined reference pulse. Based on these measurements, the pulse shaper was adjusted only a few times to compensate for a transfer function of the amplifier consisting of the gain narrowing and self-phase modulation. [ABSTRACT FROM PUBLISHER]

• Acousto-optic modulation of amplified chirped laser pulses is commissioned experimentally. • Modulation rise/fall time below 4 ps was obtained for the 3 mJ pulses. • Modulation rise/fall time depends on the SOD sign induced by the pulse shaper. The paper belongs to the field of ultrafast optics. Acousto-optic pulse shaping has been studied experimentally for binary intensity modulation in a chirped pulse amplification laser system. Direct time-domain measurement of modulation rise/fall time with a picosecond streak camera was performed for a Ti:sapphire regenerative amplifier. It was discovered that the sign of the second order dispersion produced by the acousto-optic dispersion delay line affects the modulation rise/fall time. Two algorithms for synthesis of ultrasonic waveforms for feeding the delay line, dispersive Fourier synthesis and the Gerchberg-Saxton algorithm, were compared. Minimum modulation rise/fall time of 3.6 ps for 3 mJ pulses with the linear chirp of 6.2 ps/nm at the wavelength of 795 nm was obtained. [ABSTRACT FROM AUTHOR]

This work is focused on experiments showing enhancements in power extraction efficiency and spectral control of a W-band Free Electron Laser oscillator (FELo) using ramping of the electron beam energy. The FELo operates at 1.4 MeV with electron beam currents of 1–2 A with pulse duration 10–20 μ s. Changing the beam energy post-laser-saturation of the initially unbunched continuous electron beam changes the phase-space oscillation trajectory between the beam energy and trapping ponderomotive wave. This enables very significant increases in output power with just 2% changes in beam energy, cases of 39%, and 100% are presented. Unlike in previous work a variable delay has been introduced between the start of the electron beam and the ramp in electron beam energy such that the effect can be observed unambiguously despite significant system jitter from shot-to-shot. In addition to increasing radiative efficiency, where desirable this could be used to rapidly modulate the power without a need to modify parameters such as the beam current or resonator out-coupling. This effect is shown to pull the locked longitudinal modes up or down depending on the direction of the ramp allowing fine frequency control and influence over mode-competition and mode-hops. To complement the experiments simulations were run to map the full range of beam-energy-ramping against resonator out-coupling and beam current for the experimental system. [ABSTRACT FROM AUTHOR]

A real-time two-photon fluorescence microscope with a microlens-array scanner using a regenerative amplifier is presented. The regenerative amplifier generates pulsed laser lights with extremely high peak power and produces brighter two-photon-induced fluorescence compared with that produced without the amplifier. Experimental results obtained from the observation of some biological samples with the proposed microscope are given. [ABSTRACT FROM AUTHOR]

We review the linear and nonlinear optical properties of crystals transparent near and below 200 nm and suitable for up conversion of femtosecond Ti:sapphire laser sources, β-BaB2O4 , the crystal with the largest birefringence of all presently available materials, is investigated experimentally as a quadrupler by mixing the fundamental and the third harmonic both using a 1-kHz repetition rate Ti:sapphire regenerative amplifier and a 82-MHz mode-locked Ti:sapphire laser. Milliwatt average powers near 200 nm are achieved in both cases. The sub-200-fs pulses at the fourth harmonic are almost bandwidth limited. Sum-frequency generation as a method for upconversion of femtosecond pulses is experimentally studied by mixing the fourth harmonic generated down to 189 nm by the regenerative amplifier with a parametrically generated femtosecond pulse in the infrared. Pulse energies at the microjoule level are produced with LiB 3O5 above 180 nm. Li2B4O7 shows superior performance in the 170-180-nm range, and the shortest wavelength achieved with KB5 O8·4H2O is 166 nm [ABSTRACT FROM PUBLISHER]