High-contrast, high-intensity laser pulse generation using a nonlinear preamplifier in a Ti:sapphire laser system

We report a high-contrast, high-intensity Ti:sapphire chirped-pulse amplification system that incorporates a nonlinear preamplifier based on optical parametric chirped-pulse amplification (OPCPA). By cooling the Ti:sapphire crystal in the final amplifier down to 77 K, the chirped-pulses are amplified to 2.9 J at a 10 Hz repetition rate without a thermal lensing effect. Pulse compression down to 19 fs duration obtained after amplification indicates a peak power of 80 TW. With the OPCPA, the temporal contrast is significantly improved to better than 7x10(-9) in a few picoseconds interval prior to the main laser pulse.     

Generation of high-contrast and high-intensity laser pulses using an OPCPA preamplifier in a double CPA, Ti:sapphire laser system

We demonstrate a high-contrast, high-intensity double chirped-pulse amplification (CPA) Ti:sapphire laser system using an optical parametric chirped-pulse (OPCPA) pre- amplifier. By injecting cleaned microjoule seed pulses into the OPCPA, a temporal contrast greater than 10¹⁰ within picosecond times before the main femtosecond pulse is demonstrated with an output pulse energy of 1.7 J and a pulse duration of 30 fs, corresponding to a peak power of 60 TW at a 10 Hz repetition rate. This system uses a cryogenically-cooled Ti:sapphire final amplifier and generates focused peak intensities in excess of 10²⁰ W/cm².     

TW级Ti：Al2O3飞秒激光放大器

报道ＴＷ（１０＾１２Ｗ）级Ｔｉ：Ａｌ２Ｏ３飞秒激光放大器的研究，采用Ｔｉ：Ａｌ２Ｏ３自锁模激光振荡器和脉冲啁啾放大技术，获得了能量为８４ｍＪ，脉宽为７５ｆｓ的放大光脉冲，峰值功率达到ＴＷ量级。     

High-average-power kilohertz-repetition-rate sub-100-fs Ti:sapphire amplifier system

We report on a femtosecond Ti:sapphire laser amplifier system that generates pulse energies >5 mJ at a 1-kHz repetition rate. The system consists of regenerative and multipass amplifiers and uses the technique of chirped-pulse amplification. When the system was seeded with 70-fs pulses at 800 nm from a self-mode-locked Ti:sapphire oscillator, amplified pulses of 94-fs duration at a repetition rate of 1 kHz and an average output power of 5.4 W were produced. The amplified pulse-repetition rate is variable from 250 Hz to 3 kHz. Pulse energies of >7.5 mJ were obtained at 500 and 250 Hz.     

Experimental demonstration of joule-level non-collinear optical parametric chirped-pulse amplification in yttrium calcium oxyborate

In this Letter, we report on what is, to our knowledge, the first experimental demonstration of yttrium calcium oxyborate (YCOB) for joule-level and broadband non-collinear optical parametric chirped-pulse amplification centered at 800 nm. Based on a Ti:sapphire chirped-pulse amplification front end, an amplified signal energy of 3.36 J was generated with a pump of 35 J in the crystal. Compressed pulse duration of 44.3 fs, with a bandwidth of 49 nm, was achieved. The results confirm that YCOB crystal is another potential alternative as a final amplifier besides Ti:sapphire in a petawatt laser at 800 nm.     

基于交叉偏振波产生的脉冲净化技术研究与应用

本文利用交叉偏振波产生技术(XPW)对800 nm波段钛宝石飞秒激光器输出的激光脉冲进行时域净化, 提高脉冲时域对比度, 并测量验证了10¹¹对比度的脉冲, 达到测量仪器的动态范围极限, 比初始脉冲时域对比度有三个量级的提高, XPW的效率为22%. 同时发现净化后脉冲光谱宽度也得到一定展宽, 进一步利用啁啾镜对和补偿片对净化后的脉冲进行色散补偿, 得到25 fs脉宽的脉冲. 利用该净化后的激光脉冲作为种子注入已有的太瓦级钛宝石啁啾脉冲放大系统中, 在输出脉冲能量250 mJ, 宽度50 fs, 对应峰值功率5 TW的情况下, 在主脉冲前100 ps以外的范围内测量验证了10¹¹的脉冲对比度.     

High-energy, high-contrast, multiterawatt laser pulses by optical parametric chirped-pulse amplification

We describe a compact, reliable, high-power, and high-contrast noncollinear optical parametric chirped-pulse amplifier system. With a broadband Ti:sapphire oscillator and grating-based stretching and compression, the chirped pulses are amplified from 0.1 nJ to 122 mJ in type I beta-barium borate optical parametric chirped-pulse amplifiers with a total gain of over 10(9) at 10 Hz repetition rate. Pulse compression down to 19-fs duration achieved after amplification indicates a peak power of 3.2 TW at an average power of 0.62 W. The prepulse contrast is measured to be less than 10(-8) on picosecond time scales.     

High-repetition-rate 12 fs pulse amplification by a Ti:sapphire regenerative amplifier system

We demonstrate the direct generation of 12 fs pulses from a Ti:sapphire regenerative amplifier system at a 1 kHz repetition rate utilizing properly designed broadband components for chirped-pulse amplification. Optimized designs of a regenerative amplifier with a multilayer gain-narrowing compensator and an adaptive dispersion compensator with a spatial light modulator contribute to the shorter pulse amplification.     

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.     

飞秒激光脉冲的高效率放大研究

介绍了采用多通放大的飞秒脉冲掺钛蓝宝石激光放大系统,分析讨论了提高放大效率及缩短脉冲宽度的技术方法。在仅用能量２９０ｍＪ的倍频Ｎｄ：ＹＡＧ激光泵浦下,得到了输出峰值功率大于１．４ＴＷ、脉宽２５ｆｓ、重复频率１０Ｈｚ的超短超强激光脉冲。     

飞秒激光脉冲的高效率放大研究

 介绍了采用多通放大的飞秒脉冲掺钛蓝宝石激光放大系统,分析讨论了提高放大效率及缩短脉冲宽度的技术方法。在仅用能量290mJ的倍频Nd:YAG激光泵浦下,得到了输出峰值功率大于1.4TW、脉宽25fs、重复频率10Hz的超短超强激光脉冲。     

Proton acceleration to 40 MeV using a high intensity, high contrast optical parametric chirped-pulse amplification/Ti:sapphire hybrid laser system

Using a high-contrast (10(10):1) and high-intensity (10(21) W/cm(2)) laser pulse with the duration of 40 fs from an optical parametric chirped-pulse amplification/Ti:sapphire laser, a 40 MeV proton bunch is obtained, which is a record for laser pulse with energy less than 10 J. The efficiency for generation of protons with kinetic energy above 15 MeV is 0.1%.     

Compact, high-throughput expansion-compression scheme for chirped pulse amplification in the 10 fs range

A novel pulse stretching-compression system suitable for kHz-rate chirped-pulse amplification of ≈10 fs pulses in Ti:sapphire systems is demonstrated. The material dispersion of the system components used for pulse selection and isolation broadens the wide-band seed pulses by a factor of ≈300, allowing amplification up to the submillijoule energy range. The compressor consists of a pair of prisms and newly-developed chirped multilayer dielectric mirrors for compensating high order dispersion. Using this simple scheme a recompression of unamplified pulses down to 15 fs with a throughput as high as 80% is demonstrated.     

An 11-fs, 5-kHz optical parametric/Ti:sapphire hybrid chirped pulse amplification system

We developed a noncollinear optical parametric/Ti:sapphire hybrid chirped pulse amplification system, which consists of a two-pass optical parametric amplifier and multipass Ti:sapphire amplifiers with adaptive phase control. The use of the parametric amplifier instead of a regenerative amplifier broadened the final spectrum significantly, resulting in 11-fs pulses with a peak power of 18 GW at 5 kHz. PACS 42.55.-f; 42.65.Re; 42.65.Yj     

Long-term carrier-envelope-phase stabilized fiber-bulk hybrid laser with millihertz linewidth and 50 W average power

Long-term carrier-envelope-phase stabilization was demonstrated in high-power large-modearea fiber chirped-pulse spectral fraction amplification at 1030 nm of a broadband femtosecond Ti:sapphire laser. The carrier enveloped phase was stably controlled with the maximum average power up to 50 W by pre-compensating the carrier-envelope phase changes in the high-power fiber amplifiers. The locked in loop and out of loop frequency fluctuation was measured to be 1.44 and 46 mHz within half an hour. The locked carrier-frequency exhibited an in loop and out of loop beat signal linewidth of 1.66 and 2.27 mHz, accordingly accumulated phase jitter was estimated to be 0.22 and 0.73 rad, respectively, with the integration range from 10 mHz to 100 kHz. The phase stabilization was measured to change little as the output power increased, confirming negligible amplitude-to-phase noise conversions in the linear high-power fiber chirped pulse amplification.     

Contrast and phase characterization of a high-peak-power 20-fs laser pulse

We fully characterize a high-peak-power, ultrashort laser pulse in a Ti:sapphire chirped-pulse amplification laser system. The contrast, temporal, and spectral phases of the 20-fs pulse are determined by using high-dynamic-range cross-correlation and frequency-resolved optical gating techniques. Minimization of the total phase error can be achieved by balancing the phase terms of the group delay dispersion and quartic. The laser system is currently being applied to perform high-field atomic ionization experiments at 10²⁰ W/cm².     

采用环形再生腔结构的飞秒激光啁啾脉冲放大研究

采用环形再生腔结构的啁啾脉冲放大技术方案, 在重复频率100 Hz,单脉冲能量33.1 mJ的532 nm激光抽运下, 从钛宝石激光中获得了单脉冲能量9.84 mJ的放大输出, 对应的斜效率达33.1%.在重复频率10 Hz的情况下, 同样获得了单脉冲能量为9.64 mJ, 对应斜效率达36.8%的高效率放大结果. 通过色散补偿压缩该啁啾激光脉冲后的单脉冲能量为6.36 mJ, 脉冲宽度为59.7 fs. 测量结果表明典型的能量不稳定度为1.85%. 关键词： 啁啾脉冲放大 再生放大 飞秒激光 环形腔     

Multimillijoule chirped parametric amplification of few-cycle pulses

The concept of optical parametric chirped-pulse amplification is applied to attain pulses with energies up to 8 mJ and a bandwidth of more than 100 THz. Stretched broadband seed pulses from a Ti:sapphire oscillator are amplified in a multistage noncollinear type I phase-matched beta-barium borate parametric amplifier by use of an independent picosecond laser with lock-to-clock repetition rate synchronization. Partial compression of amplified pulses is demonstrated down to a 10-fs duration with a down-chirped pulse stretcher and a nearly lossless compressor comprising bulk material and positive-dispersion chirped mirrors.     

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.     

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.