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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, the amplification of Ti: sapphire laser pulses in a regenerative amplifier with Z geometric arrangement has been demonstrated based on chirped pulse amplification method. Two pocket cells were used to transfer the seed pulses to the amplifier cavity and extract the amplified pulses. Build up time of the amplified pulses according to the energy of the pump laser has been studied, and the dynamic evolution of the pulses inside the amplifier cavity has been investigated. The pulse duration of the generated pulses inside the cavity without seed pulses is about 80 ns, and the buildup time is 38 ns. The 2 mJ amplified femtosecond laser pulses at a repetition rate of 10 Hz are obtained after 17 round trips using pump energy of 15 mJ at 532 nm. The amplified laser wavelength is 800 nm with 30 nm spectral bandwidth, which is 30 nm narrower than the oscillator bandwidth. The amplification efficiency relative to the pump energy is obtained at about 13%, and the amplification coefficient in this scheme reached 106.

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]