载波-包络相位稳定的周期量级近红外超短脉冲激光系统

利用光参量放大过程输出的闲置光载波-包络相位(CEP)被动稳定的特点,搭建了三级光参量放大(OPA)系统,获得了CEP稳定的近红外高能量超短激光脉冲(1.4 mJ/40 fs/1 kHz @ 1.8 μm),其CEP抖动为516 mrad(rms).经空心光纤展宽光谱和块体材料补偿色散,激光脉宽最终可被压缩至小于两个光学周期(<12 fs),脉冲能量达到0.54 mJ.该系统为单个阿秒脉冲的产生和其他高次谐波实验提供了优质的光源. 关键词： 光参量放大 周期量级近红外激光脉冲 载波-包络相位稳定     

Carrier envelope phase stabilization of a Yb:KGW laser amplifier

In this paper we report on the active stabilization of the carrier envelope phase (CEP) of a Yb:KGW chirped pulse amplifier laser system seeded by a Yb-doped solid-state Kerr-lens mode-locked oscillator. The regenerative amplifier delivers 180 fs CEP stable pulses of 30 μJ-1 mJ energy at a repetition rate tunable from 1 to 200 kHz. The bandwidth of the feedback loop was extended by a factor of 5 using a specially designed high-pass filter, which resulted in a dramatic decrease of CEP jitter below 0.45 rad after the amplifier.     

Compression of 2 mJ kilohertz laser pulses to 17.5 fs by pairing double-prism compressor: analysis and performance

A general expression of dispersion for pairing double-prism compressor with arbitrary apex angle is presented and a limitation to generate negative group-delay dispersion (GDD) for broadband spectrum is obtained. By use of this compressor with spectral shaping filters and chirped mirrors, 2 mJ, 17.5 fs pulses from a compact 10-pass kilohertz Ti:sapphire amplifier system are generated.     

Efficient hollow fiber compression scheme for generating multi-mJ,carrier-envelope phase stable,sub-5 fs pulses

We show that a standard hollow-core fiber (HCF) compressor device can be used to efficiently compress multi-mJ energy laser pulses down to few-cycle duration, when seeded with linearly chirped, circularly polarized pulses. With this approach, we routinely generate carrier-envelope phase (CEP)-locked, 1.6 mJ, 4.8 fs pulses using only 3 mJ, 25 fs pulses as the seed.     

High-power parametric amplification of 11.8-fs laser pulses with carrier-envelope phase control

Phase-stable parametric chirped-pulse amplification of ultrashort pulses from a carrier-envelope phase-stabilized mode-locked Ti:sapphire oscillator (11.0 fs) to 0.25 mJ/pulse at 1 kHz is demonstrated. Compression with a grating compressor and a LCD shaper yields near-Fourier-limited 11.8-fs pulses with an energy of 0.12 mJ. The amplifier is pumped by 532-nm pulses from a synchronized mode-locked laser, Nd:YAG amplifier system. This approach is shown to be promising for the next generation of ultrafast amplifiers aimed at producing terawatt-level phase-controlled few-cycle laser pulses.     

Generation of 0.1-TW optical pulses with a single-stage Ti:sapphire amplifier at a 1-kHz repetition rate

We present a kHz-rate all-solid-state Ti:sapphire oscillator-amplifier system producing 1.8 mJ sub-20 fs pulses using a single multipass amplifier stage pumped by ᄺ mJ pulses. Compensation for gain narrowing and high-order dispersion is provided by chirped dielectric multilayer optics. The focused peak intensity approaches 10¹⁸ W/cm², making this compact high-repetition-rate source attractive for a wide range of high-field applications.     

1.5 mJ, 6.4 fs parametric chirped-pulse amplification system at 1 kHz

We demonstrate an optical parametric chirped-pulse amplification (OPCPA) system with the pulse energy of 1.5 mJ at a 1 kHz repetition rate. The newly developed 100 ps Ti:sapphire pump laser system, which was optically synchronized with OPCPA seed pulses, delivered 10 mJ, 400 nm pump pulses. After three-stage parametric amplification, recompression of the amplifier output from 45 ps to 6.4 fs was performed. The pulse width of 6.4 fs is, to our knowledge, the shortest ever obtained by OPCPA, and the average power of 1.5 W (1.5 mJ, 1 kHz) is believed to be the highest among few-cycle OPCPA systems.     

All-fiber laser seeded femtosecond Yb:KGW solid state regenerative amplifier

A high efficiency compact Yb:KGW regenerative amplifier using an all-fiber laser seed source was comprehensively studied. With thermal lensing effect compensated by the cavity design, the compressed pulses with energy of 1 m J at 1 k Hz and 0.4 m J at 10 k Hz in sub-400-fs pulse duration using chirped fiber Bragg grating(CFBG) stretcher were demonstrated.A modified Frantz–Nodvik equation was developed to emulate the dynamic behavior of the regenerative amplifier. The simulation results were in good agreement with the experiment. Numerical simulations and experimental results show that the scheme can be scalable to higher energy of multi-m J, sub-300 fs pulses.     

低重复率的Ti:Al2O3飞秒激光放大器研究

本文报道了重复频率为10Hz的Ti:Al₂O₃飞秒激光放大器的研究.基于脉冲啁啾放大技术和采用再生/多通放大装置,得到了能量为8mJ的放大光脉冲,在该放大系统中,激光脉冲获M净增益约8×10⁷.     

Generation of 5 fs, 0.7 mJ pulses at 1 kHz through cascade filamentation

Two-cycle optical pulses with duration of 5 fs and energy of 0.7 mJ have been generated at 1 kHz by compressing the 38 fs laser pulses from a carrier-envelope phase (CEP) controlled Ti:sapphire laser system through a cascade filamentation compression technique. A simple and effective method is developed to suppress multiple filament formation and stabilize a single filament by inserting a soft aperture with an appropriate diameter into the driving laser beam prior to focusing, resulting in an excellent compressed beam quality. The good beam quality and potentially higher peak power make this ultrashort laser pulse source a significant tool for high-field physics applications.     

Self phase modulation in a femtosecond pulse amplifier with subsequent compression

The pulses from a colliding-pulse mode-locked dye laser (100 fs, 20 pJ) are amplified to 0.2 mJ and self phase modulated in an excimer laser pumped dye amplifier. Suitable chirp compensation leads to nearly bandwidth-limited pulses of about 50 fs duration.     

Fiber amplification of pulse bursts up to 20 μJ pulse energy at 1 kHz repetition rate

We demonstrate burst-mode operation of a polarization-maintaining Yb-doped fiber amplifier. Groups of pulses with a temporal spacing of 10?ns and 1?kHz overall repetition rate are amplified to an average pulse energy of ～20?μJ and total burst energy of 0.25?mJ. The pulses are externally compressed to ～400?fs. The amplifier is synchronously pulsed-pumped to minimize amplified spontaneous emission between the bursts. We characterize the influence of pump pulse duration, pump-to-signal delay, and signal burst length.     

Dual-wavelength chirped-pulse amplification system

We demonstrate a chirped-pulse amplification system that simultaneously amplifies two pulses from a dual-wavelength oscillator in a single regenerative amplifier. The two wavelengths can be tuned from 800 to 890 nm. The total energy of 1.5 mJ can be variably split between the two pulses. The pulses are 150 fs in duration and have 60-fs timing jitter.     

Hollow-fiber compression of 6 mJ pulses from a continuous-wave diode-pumped single-stage Yb,Na:CaF2 chirped pulse amplifier

Here, 200 fs 6 mJ pulses from a cw diode-pumped Yb,Na:CaF(2) amplifier are spectrally broadened in an Ar- or Ne-filled hollow-core fiber and recompressed to 20 fs (Ar) and 35 fs (Ne) using a prism pair. The results of spectral broadening and phase measurement are in excellent agreement with numerical modeling based on the generalized nonlinear Schr?dinger equation. The longer laser wavelength of 1030 nm permits favorable energy scaling for the hollow-fiber technique compared to ultrafast amplifiers operating at 800 nm.     

Bandwidth limited amplification of 220 fs pulses in XeCl

Transform limited pulses of 200–250 fs duration at 308 ns generated by a specially designed excimer laser pumped dye laser system have been amplified in a XeCl gain module. Simultaneous study of the spectrum and the temporal behaviour of the amplified UV pulses showed bandwidth limitation by the gain spectrum of XeCl. This effect is strongly dependent on the operational condition of the amplifier; in a single pass amplification scheme 0.5 mJ, 250 fs pulses, in a double pass arrangement 5 mJ, 220 fs pulses were obtained, with excellent reproducibility.     

Synchronously pumped femtosecond dye oscillator-amplifier system at 815 nm

A tunable dye oscillator-amplifier system that produces 0.25 mJ, 105 fs pulses at 815 nm is demonstrated. The system consists of a synchronously pumped femtosecond dye laser followed by a dye amplifier that is quasi-longitudinally pumped using the frequency-doubled output from a Nd:YAG regenerative amplifier.     

Sub-picosecond pulses at 100 W average power from a Yb:YLF chirped-pulse amplification system

We present a high-repetition-frequency, diode-pumped, and chirped-pulse amplification system operating at 106 W average output power with excellent beam quality (M(2)=1.3), based on cryogenically cooled Yb:YLF. 1 nJ seed pulses, derived from a mode-locked Ti:sapphire laser, are first amplified to 1 mJ pulse energy at 10 kHz repetition frequency in a regenerative amplifier. The second-stage, multipass amplifier increases the pulse energy to 10.6 mJ, resulting in a spectral width of 2.2 nm. The pulses are compressed to 865 fs in duration, which is 1.26 times the transform limit.     

Multi-millijoule, nonlinear preamplifier for high intensity femtosecond Yb:YAG chirped-pulse amplification lasers at 1030 nm

We report the highest energy broadband laser pulses at a center wavelength of 1030 nm based on optical parametric chirped-pulse amplification (OPCPA). We have demonstrated amplification of 1030 nm femtosecond laser pulses from a broadband Yb oscillator to over 6.5 mJ with a total gain of greater than 10⁷ achieved in a single pass through only 56 mm of gain material at a 10 Hz repetition rate. The amplified spectral bandwidth of 10.8 nm affords recompression to a 230 fs pulse duration following amplification. As an alternative to the regenerative amplifier (RA) this system is one of the more promising candidates for realizing compact, high intensity, direct diode-pumped, high repetition rate femtosecond Yb:YAG chirped-pulse amplification (CPA) in laser systems.     

Broadband high-energy diode-pumped Yb:KYW multipass amplifier

We report a diode-pumped Yb:KYW amplifier delivering up to 27 mJ pulses at a repetition rate of 100 Hz and a spectral bandwidth of 5.5 nm, centered at around 1030 nm. The system is based on a double-head multipass amplifier configuration where the pump thermal load is distributed over two relatively thin laser crystals, which permits a sufficiently large number of passes with minimal passive losses, thus maximizing the energy extraction efficiency. The amplified pulse bandwidth theoretically supports 340 fs pulses, and as a demonstration, a small fraction of the amplified pulses has been compressed to 560 fs.     

Experimental study on generation of high energy few cycle pulses with hollow fiber filled with neon

25 fs pulses with energy up to 0.8 mJ from a multi-pass amplifier system have been spectrally broadened from 460 nm to 950 nm due to strong self-phase modulation (SPM) effect in a gas filled hollow fiber. Using a set of chirped mirrors, the ultra-broadband dispersion compensation was achieved, and the compressed pulses reached their transform limit. Under optimized conditions we achieved pulses with duration of 5.1 fs and with energy of 400 μJ, corresponding to the peak power up to 80 GW. Supported by the National Natural Science Foundation of China (Grant Nos. 60608003, 60490280, 60225005 and 60621063)