Stacking chirped pulse optical parametric amplification

Stacking chirped pulse optical parametric amplification based on a home-built Yb³⁺-doped mode-locked fiber laser and an all-fiber pulse stacker has been demonstrated. Energic 11 mJ shaped pulses with pulse duration of 2.3 ns and a net total gain of higher than 1.1 × 10⁷ at fluctuation less than 2% rms are achieved by optical parametric amplification pumped by a Q-switched Nd:YAG frequency-doubled laser, which provides a simple and efficient amplification scheme for temporally shaped pulses by stacking chirped pulse.     

35 J broadband femtosecond optical parametric chirped pulse amplification system

We report on what is believed to be the first large-aperture and high-energy optical parametric chirped pulse amplification system. The system, based on a three-stage amplifier, shows 25% pump-to-signal conversion efficiency and amplification of the full 70 nm width of the seed spectrum. Pulse compression to 84 fs achieved after amplification indicates a potential of 300 TW pulse power for 35 J amplified pulse energy.     

高效三通光参量啁啾脉冲放大器

为了提高信号光与抽运光在时域上的匹配,提高放大系统的增益,提出了三通光参量啁啾脉冲放大的方法。实验中,信号光在一块晶体内被一抽运光在完全相位匹配的条件下放大了三次,总放大增益为3.7×107,能量晃动小于3%rms,放大后的信号光谱宽为30nm,压缩后的信号光脉宽为82fs。实验结果表明:采用三通光参量啁啾脉冲放大方法,有效地抑制了放大过程中参量荧光对放大过程的影响,在抽运光强为350MW/cm2时,参量荧光仅占输出总能量的1%。     

Numerical studies of optical parametric chirped pulse amplification

Based on the coupled wave equations, optical chirped-pulse parametric amplification (OPCPA) is simulated and its characteristics are investigated under the conditions of small-signal and pump depletion. The influence of the group-velocity mismatch and the phase mismatch among the three waves on the process of the amplification are discussed, respectively. Compared with the conventional chirped-pulse amplification system, synchronization between pump and signal-pulses is a crucial issue in OPCPA. The requirement on Δτ_p–s as well as the stability of the system is investigated.     

光参量啁啾脉冲放大过程中脉冲特性理论研究

 通过数值求解非线性三波耦合方程组,并利用色散致啁啾引起的瞬时频率与时间的关系,模拟了啁啾脉冲在光参量放大过程中的脉冲波形和频谱形状的变化关系,以及通过压缩器的脉冲形状。模拟结果表明：啁啾脉冲在光参量放大过程中的时域宽度和频谱有很小程度的加宽,但基本上不影响放大后脉冲的压缩及信噪比。     

光参量啁啾脉冲放大增益特性研究

 通过对非线性三波耦合方程组进行数值求解,研究了光参量放大的增益特性及饱和放大特性。给出了泵浦光、信号光参数对参量增益的影响及其与晶体饱和长度的关系。且OPA具有传统CPA系统所不具有的优点,将有可能取代传统的CPA系统而作为超短超强激光系统的新型前端。     

Ultrafast noncollinear optical parametric chirped pulse amplification in KTiOAsO4

Amplification of femtosecond pulses at 1.56 microm based on noncollinear parametric chirped pulse amplification in a potassium titanyl arsenate (KTA) crystal with pumping at 1.05 microm is reported. The 100 fs pulses of an erbium fiber laser are parametrically amplified while synchronously pumped by an amplified mode-locked Nd:YLF laser. This amplifier has a saturated gain of 65 dB with 30% conversion efficiency and has produced 160 fs pulses with peak powers of up to 0.75 GW. The system produced 380 mW before compression and can be readily scaled to the multiwatt range with bandwidths to support sub-100 fs pulses.     

Optical parametric chirped pulse amplification based on photonic crystal fibre

A compact two-stage optical parametric chirped pulse amplifier based on photonic crystal fibre is demonstrated.A 1064-nm soliton pulse is obtained in a home-made photonic crystal fibre (PCF) with femtosecond pulse pumping and then amplified to 2 mJ in an Nd:YAG regenerative amplifier.After the amplified pulses pass through the LBO crystal,the 532-nm double-frequency light with an energy of 0.8 mJ and a duration of over 100 ps at 10-Hz repetition rate is generated as a pump source in the following two-stage optical parametric amplification (OPA).The 850-nm chirped signal light gain from the stretcher is 1.5×10 4 in the first-stage OPA while it is 120 in the second-stage OPA.The total signal gain of optical parametric chirped pulse amplification (OPCPA) can reach 1.8×10 6.     

Generation of synchronized signal and pump pulses for an optical parametric chirped pulse amplification based multi-terawatt Nd:glass laser system

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.     

Contrast limitation due to pump noise in an optical parametric chirped pulse amplification system

The contrast ratio of the recompressed output pulses in an optical parametric chirped pulse amplification system can be limited by temporal noise on the pump pulse. We present a simple analysis which can be used to estimate both the contrast ratio of this background noise and the duration of its pedestal. The estimated values compare well quantitatively with values derived using a more accurate computer simulation code.     

Optimization of optical parametric chirped pulse amplification with different pump wavelengths

Optical parametric chirped pulse amplification with different pump wavelengths was investigated using LBO crystal, at signal central wavelength of 800 nm. According to our theoretical simulation, when pump wavelength is 492.5 nm, there is a maximal gain bandwidth of 190 nm centered at 805 nm in optimal noncollinear angle using LBO. Presently, pump wavelength of 492.5 nm can be obtained from second harmonic generation of a Yb:Sr₅(PO₄)₃F laser. The broad gain bandwidth can completely support ∼6 fs with a spectral centre of seed pulse at 800 nm. The deviation from optimal noncollinear angle can be compensated by accurately tuning crystal angle for phase matching. The gain spectrum with pump wavelength of 492.5 nm is much better than those with pump wavelengths of 400, 526.5 and 532 nm, at signal centre of 800 nm.     

Ultrafast laser system based on noncollinear optical parametric amplification for laser spectroscopy

We report the experimental demonstration of transform-limited sub-6 fs pulses at an optimal central wavelength by a tunable noncollinear optical parametric amplification(NOPA) source. Meanwhile, a white light continuum in the near-infrared(NIR) range from 900 to 1100 nm is also successfully generated by focusing the unconverted800 nm beam during NOPA generation on a sapphire rod. Both visible-pump/visible-probe and visible-pump/NIR-probe experiments are realized using the same laser system. As examples, ultrafast photo-induced exciton dynamics inside two kinds of materials are investigated by the visible-pump/visible-probe and visible-pump/NIR-probe spectroscopy, respectively.     

Generation of accurately synchronized pump source for optical parametric chirped pulse amplification

We demonstrate the generation of ultra-short pulses at 1064 nm by continuous-wave seeded non-collinear optical parametric amplification in a -barium borate crystal pumped by the second harmonics of a femtosecond Ti:sapphire laser. After two stages of seeded parametric amplifiers, the generated pulses at 1064 nm were accurately synchronized with the fundamental pump pulses, which could be used as seeding pulses for further amplification and then frequency doubling to produce an accurately synchronized pump source for optical parametric amplification of chirped pulses from the same Ti:sapphire laser. PACS 42.65.Re; 42.65.-k; 52.35.Mw     

Progress in chirped pulse optical parametric amplifiers

We discuss the main issues of optical parametric chirped pulse amplification and overview recent progress in the field. Although we distinguish between the two operating modes of modern chirped pulse parametric amplifiers, OPCPA and NOPA, we reveal that both represent the same technique and share a common concept. PACS 42.65.Yj; 42.65.Re     

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     

High-power and high-contrast optical parametric chirped pulse amplification in beta-BaB2O4 crystal

We have developed a high-power laser system based on optical parametric chirped-pulse amplification in a beta-BaB2O4 crystal. The system provides gain of 10(8), a conversion efficiency of approximately 23%, an output energy of -65 mJ, and good amplified beam quality. The prepulse ratio has been measured to be 1.5 x 10(-8) or less. The spectral width was as broad as 16.5 nm centered at 1053 nm.     

Analysis of ultra-broadband high-energy optical parametric chirped pulse amplifier based on YCOB crystal

A new type of optical parametric chirped pulse amplifier is designed and analyzed for the amplification of pulse centered at 808 nm.A novel crystal,yttrium calcium oxyborate YCa4O(BO3)3(YCOB),is utilized in the power amplification stage of optical parametric amplification(OPA).Noncollinear phase matching parameters in the xoz principle plane of YCOB,compared with those in BBO and DKDP,are analyzed by numerical simulation.The results show that YCOB rather than DKDP can be used in the power amplification stage of OPA to realize the amplification of chirped pulse to several joules with a gain bandwidth exceeding 100 nm.This can be used to gain a high intensity pulse of ～10 fs after the compressor.     

Multikilohertz optical parametric chirped pulse amplification in periodically poled stoichiometric LiTaO3 at 1235 nm

We demonstrate, for the first time to our knowledge, multikilohertz operation of a double-stage optical parametric chirped pulse amplifier with periodically poled stoichiometric LiTaO3 crystals, seeded by a homemade Cr:forsterite oscillator operating at 1235 nm. The repetition rate of the amplifier could easily be tuned without the use of electro-optic modulators by using a repetition-rate-tunable kilohertz pump laser operating at 532 nm and a time-synchronization unit. Amplified total (signal+idler) energies of 55.9 and 36.2 microJ were achieved at 1 and 5 kHz, respectively. After recompression, the pulse width of amplified idler pulses at 1235 nm amounted to 530 fs.     

Compact high gain double-pass optical parametric chirped pulse amplifier

A novel double-pass noncollinear optical parametric chirped pulse amplifier based on an Yb³⁺-doped passively mode-locked fiber laser has been demonstrated in this paper. The signal was double-pass amplified in a single nonlinear crystal by a long pump pulse, and the signal and pump pulses of each pass were completely phase matched in the plane of the maximum effective nonlinearity. Net saturated gain of 2×10⁶ was achieved and the superfluorescence was suppressed by increasing the overlap time between the signal and pump pulses.