Noncollinear Optical Parametric Chirped Pulse Research Articles

Generation and characterisation of few-pulse attosecond pulse trains at 100 kHz repetition rate

The development of attosecond pump–probe experiments at high repetition rate requires the development of novel attosecond sources maintaining a sufficient number of photons per pulse. We use 7 fs, 800 nm pulses from a non-collinear optical parametric chirped pulse amplification laser system to generate few-pulse attosecond pulse trains (APTs) with a flux of >106 photons per shot in the extreme ultraviolet at a repetition rate of 100 kHz. The pulse trains have been fully characterised by recording frequency-resolved optical gating for complete reconstruction of attosecond bursts (FROG-CRAB) traces with a velocity map imaging spectrometer. For the pulse retrieval from the FROG-CRAB trace a new ensemble retrieval algorithm has been employed that enables the reconstruction of the shape of the APTs in the presence of carrier envelope phase fluctuations of the few-cycle laser system.

Ultra-broadband all-OPCPA petawatt facility fully based on LBO

Abstract A petawatt facility fully based on noncollinear optical parametric chirped pulse amplification (NOPCPA) technology, Vulcan OPPEL (Vulcan OPCPA PEtawatt Laser), is presented. This system will be coupled with the existing hybrid-CPA/OPCPA VULCAN laser system (500 J, 500 fs beamline; 250 J, ns regime beamline) based on Nd:glass amplification. Its pulse duration (20 times shorter) combined with the system design will allow the auxiliary beamline and its secondary sources to be used as probe beams for longer pulses and their interactions with targets. The newly designed system will be mainly dedicated to electron beam generation, but could also be used to perform a variety of particle acceleration and optical radiation detection experimental campaigns. In this communication, we present the entire beamline design discussing the technology choices and the design supported by extensive simulations for each system section. Finally, we present experimental results and details of our commissioned NOPCPA picosecond front end, delivering 1.5 mJ, ~180 nm (1/e2) of bandwidth compressed to sub-15 fs.

Ultra-broadband near-infrared NOPAs based on the nonlinear crystals BiBO and YCOB

AbstractWe evaluate and demonstrate ultra-broadband near-infrared noncollinear optical parametric amplification in two nonlinear crystals, bismuth borate (BiBO) and yttrium calcium oxyborate (YCOB), which are not commonly used for this application. The spectral bandwidth is of the microjoule level; the amplified signal is ≥ 200 nm, capable of supporting sub-10 fs pulses. These results, supported by numerical simulations, show that these crystals have a great potential as nonlinear media in both low-energy, few-cycle systems and high peak power amplifiers for terawatt to petawatt systems based on noncollinear optical parametric chirped pulse amplification (NOPCPA) or a hybrid.

Generation and characterization of isolated attosecond pulses for coincidence spectroscopy at 100 kHz repetition rate

SynopsisAn attosecond pump-probe beamline with 100 kHz repetition rate for coincidence experiments has been developed. It is based on non-collinear optical parametric chirped pulse amplification and delivers 100 μJ sub-4 fs to an high-harmonic generation source. Details on the generation and characterization of isolated attosecond pulses will be presented.

Contrast improvement of sub-4 fs laser pulses using nonlinear elliptical polarization rotation.

Temporal-intensity contrast is crucial in intense laser-matter interaction to circumvent the undesirable expansion of steep high-density plasma prior to the interaction with the main pulse. Nonlinear elliptical polarization rotation in an argon filled hollow-core fiber is used here for cleaning pedestals/satellite pulses of a chirped-pulse-amplifier based Ti:Sapphire laser. This source provides ∼35 μJ energy and sub-4-fs duration, and the process has >50% internal efficiency, more than the most commonly used pulse cleaning methods. Further, the contrast is improved by 3 orders of magnitude when measured after amplifying the pulses to 16 TW using non-collinear optical parametric chirped pulse amplification with a prospect to even further enhancement.

Possible method for a single-cycle 100 petawatt laser with wide-angle non-collinear optical parametric chirped pulse amplification

A single-cycle (3 fs) 100 petawatt laser pulse is obtained theoretically by dramatically increasing the spectrum, accordingly reducing the pulse duration, of the optical parametric chirped pulse amplification (OPCPA) with a new designed wide-angle non-collinear OPCPA (WNOPCPA). While comparing with two other recent popular methods of the energy-further-increased single-beam femtosecond petawatt laser and the spatiotemporally coherent combination of multiple-beam femtosecond petawatt lasers, we believe that the proposed method is another choice for sub-exawatt lasers.

Sub-4 fs laser pulses at high average power and high repetition rate from an all-solid-state setup.

The generation of high average power, carrier-envelope phase (CEP) stable, near-single-cycle pulses at a repetition rate of 100 kHz is demonstrated using an all solid-state setup. By exploiting self-phase modulation in thin quartz plates and air, the spectrum of intense pulses from a high-power, high repetition rate non-collinear optical parametric chirped pulse amplifier (NOPCPA) is extended to beyond one octave, and pulse compression down to 3.7 fs is achieved. The octave-spanning spectrum furthermore allows performing straightforward f-to-2f interferometry by frequency-doubling the long-wavelength part of the spectrum. Excellent CEP-stability is demonstrated for extended periods of time. A full spatio-spectral characterization of the compressed pulses shows only minor asymmetries between the two perpendicular beam axes. We believe that the completed system represents the first laser system satisfying all requirements for performing high repetition rate attosecond pump-probe experiments with fully correlated detection of all ions and electrons produced in the experiment.

Optimizing the performance of non-collinear optical parametric chirped pulse amplification via multi-pass structure based on two geometry configurations.

We propose a method for multi-pass non-collinear optical parametric chirped pulse amplification (MNOPCPA) based on two geometries, tangent phase-matching (TPM) and Poynting vector walk-off compensation (PVWC), which optimize the performance of optical parametric chirped pulse amplification (OPCPA). A feasible design scheme is also presented for use in implementing this approach. Employing this design, we construct and perform a numerical simulation, showing that back-conversion from the signal and idler to the pump can be inhibited, and that the conversion efficiency can be boosted dramatically, approaching the theoretical limit of ~64%, when amplification is nearly saturated at full bandwidth. In the MNOPCPA scheme, the output signal has a wider spectrum and a corresponding shorter Fourier-limited pulse duration with the pump being continuously depleted. A barycenter shift of the signal spot results from a spatial walk-off effect due to the pump, which can be offset and corrected well. To the best of our knowledge, this is the first demonstration of a multi-pass non-collinear OPCPA method employed the scheme of regenerative amplification.

High-Stability High-Energy Picosecond Optical Parametric Chirped Pulse Amplifier as a Preamplifier in Nd:Glass Petawatt System for Contrast Enhancement**Supported by the National Natural Science Foundation of China under Grant Nos 11604350 and 61405211.

We demonstrate a novel picosecond optical parametric preamplification to generate high-stability, high-energy and high-contrast seed pulses. The 5 ps seed pulse is amplified from 60 pJ to 300 μJ with an 8.6 ps/3 mJ pump laser in a signal stage of short pulse non-collinear optical parametric chirped pulse amplification. The total gain is more than 106 and the rms energy stability is under 1.35%. The contrast ratio is higher than 108 within a scale of 20 ps before the main pulse. Consequently, the improvement factor of the signal contrast is approximately equal to the gain 106 outside the pump window.

Gain and bandwidth investigation in dual-pumped non-collinear optical parametric chirped pulse amplification

Dual-pumped non-collinear parametric amplification of a chirped laser pulse is numerically studied by employing the pump beams of different wavelengths. Our results reveal that the output bandwidth and the efficiency-bandwidth product are improved, when non-collinear angles and phase matching conditions are separately optimized for each individual pump beam. Moreover, by studying the dependence of the bandwidth of the amplified signal on the pump intensity, gain stability and its fluctuations are compared in small signal gain and saturation regimes. It is verified that the effective interaction length in this dual-pumped configuration is reduced as a consequent of increased bandwidth, compared to that in a single pump scheme.

Numerical investigation of output beam quality in efficient broadband optical parametric chirped pulse amplification

We theoretically analyzed output beam quality of broad bandwidth non-collinear optical parametric chirped pulse amplification (NOPCPA) in LiB3O5 (LBO) centered at 800nm. With a three-dimensional numerical model, the influence of the pump intensity, pump and signal spatial modulations, and the walk-off effect on the OPCPA output beam quality are presented, together with conversion efficiency and the gain spectrum. The pump modulation is a dominant factor that affects the output beam quality. Comparatively, the influence of signal modulation is insignificant. For a low-energy system with small beam sizes, walk-off effect has to be considered. Pump modulation and walk-off effect lead to asymmetric output beam profile with increased modulation. A special pump modulation type is found to optimize output beam quality and efficiency. For a high-energy system with large beam sizes, the walk-off effect can be neglected, certain back conversion is beneficial to reduce the output modulation. A trade-off must be made between the output beam quality and the conversion efficiency, especially when the pump modulation is large since. A relatively high conversion efficiency and a low output modulation are both achievable by controlling the pump modulation and intensity.

Numerical investigations of non-collinear optical parametric chirped pulse amplification for Laguerre–Gaussian vortex beam

We present for the first time a scheme to amplify a Laguerre–Gaussian vortex beam based on non-collinear optical parametric chirped pulse amplification (OPCPA). In addition, a three-dimensional numerical model of non-collinear optical parametric amplification was deduced in the frequency domain, in which the effects of non-collinear configuration, temporal and spatial walk-off, group-velocity dispersion and diffraction were also taken into account, to trace the dynamics of the Laguerre–Gaussian vortex beam and investigate its critical parameters in the non-collinear OPCPA process. Based on the numerical simulation results, the scheme shows promise for implementation in a relativistic twisted laser pulse system, which will diversify the light–matter interaction field.

SNR improvement based on non-collinear OPCPA with angular spectral dispersion in BBO crystal

The characteristics of the signal-to-noise ratio (SNR) improvement based on non-collinear optical parametric chirped pulse amplification (OPCPA) with angular spectral dispersion (ASD) was revealed and investigated. The angular dispersion formula was derived theoretically and the effects of crystal length, pump peak intensity, noise characteristics and angular dispersion on the SNR improvement and conversion efficiency were discussed. Furthermore, by optimizing the critical parameters, 35% conversion efficiency and more than 3 orders of magnitude of SNR improvement were achieved for the chirped signal pulse with a central wavelength of 800nm, pumped by 532nm in presented amplification scheme with BBO crystal.

Pump-seed synchronization for MHz repetition rate, high-power optical parametric chirped pulse amplification

We report on an active synchronization between two independent mode-locked lasers using a combined electronic-optical feedback. With this scheme, seed pulses at MHz repetition rate were amplified in a non-collinear optical parametric chirped pulse amplifier (OPCPA). The amplifier was seeded with stretched 1.5 nJ pulses from a femtosecond Ti:Sapphire oscillator, while pumped with the 1 ps, 2.9 µJ frequency-doubled output of an Yb:YAG thin-disk oscillator. The residual timing jitter between the two oscillators was suppressed to 120 fs (RMS), allowing for an efficient and broadband amplification at 11.5 MHz to a pulse energy of 700 nJ and an average power of 8 W. First compression experiment with 240 nJ amplified pulse energy resulted in a pulse duration of ~10 fs.

Broadband, high gain two-stage optical parametric chirped pulse amplifier using BBO crystals for a femtosecond high-power Ti:sapphire laser system

We design a two-stage non-collinear optical parametric chirped pulse amplifier using BBO crystals for a high-power Ti:sapphire laser system, and numerically analyze the output characteristics of the OPCPA system. We find optimal phase-matching conditions and calculate the parametric gains as a function of pump intensity and interaction length. By constructing a two-stage OPCPA system using two BBO crystals, we obtain 12 mJ output energy corresponding to a high gain of 107, a pulse duration of 37 fs, and a contrast ratio of 5×10−8.

On the efficiency of a multiterawatt optical parametric amplifier: numerical model and optimization

Numerical simulations and analysis of a very efficient and stable noncollinear optical parametric chirped pulse amplification (OPCPA) femtosecond system are presented. The system is optimized for a long (nanosecond), rectangular temporal profile and a flat-top spatial profile of the pump laser pulse. We show that a two-stage system consisting of a multipass preamplifier and a time-sheared power amplifier operating around 850 nm and pumped by a 532 nm pulse can achieve quantum efficiencies as high as 0.9. We also discuss practical schemes of the few-cycle multiterawatt OPCPA systems employing different nonlinear crystals. The results of the Monte Carlo simulations are used to balance the stability and efficiency of the parametric amplifier system.

Generation of energetic femtosecond green pulses based on an OPCPA-SFG scheme

Femtosecond green pulses were generated from broadband pulses centered at 800 nm and quasi-monochromatic pulses centered at 532 nm using noncollinear optical parametric chirped pulse amplification (NOPCPA) followed by sum frequency mixing. In addition to amplifying the 800-nm pulses, the NOPCPA stage pumped by a Q-switched, injection seeded Nd:YAG laser also provided broadband idler pulses at 1590 nm. The signal and idler pulses were sum frequency mixed using achromatic and chirp assisted phase matching yielding pulses near 530 nm with a bandwidth of 12 nm and an energy in excess of 200 μJ. The generated pulses were recompressed with a grating compressor to a duration of 150 fs. The technique is scalable to high energies, broader bandwidths, and shorter pulse durations with compensation for higher order chirps and dedicated engineering of the interacting beams.

Approaching the full octave: noncollinear optical parametric chirped pulse amplification with two-color pumping

We present a new method to broaden the amplification range in optical parametric amplification toward the bandwidth needed for single cycle femtosecond pulses. Two-color pumping of independent stages is used to sequentially amplify the long and short wavelength parts of the ultrabroadband seed pulses. The concept is tested in two related experiments. With multi-mJ pumping pulses with a nearly octave spanning spectrum and an uncompressed energy of 3 mJ are generated at low repetition rate. The spectral phase varies slowly and continuously in the overlap region as shown with 100 kHz repetition rate. This should allow the compression to the Fourier limit of below 5 fs in the high energy system.

2.4-Joule chirped pulse operation by a laser-diode-pumped slab laser for pumping non-collinear OPCPA

We present a diode-pumped chirped pulse amplification (CPA) system that generates multi-joule energy at a central wavelength of 1054 nm at a repetition rate of 10 Hz. The purpose of this laser is to serve as a pump source for non-collinear optical parametric chirped pulse amplification (NOPCPA). A Nd-doped glass slab with zigzag optical path was used as the gain medium of the main amplifier in this system to obtain multi-joule output with repeatable operation. The Nd:glass zigzag slab amplifier system consists of four-pass pre-amplification and four-pass power amplification. The seed pulse that is fed to the main amplifier was generated by a mode-locked fiber oscillator emitting at a 1053 nm central wavelength. The oscillator output was pulse-stretched to 2.7 ns duration with a 4.5 nm spectral bandwidth and amplified to 100 μJ by optical parametric amplification by use of type-I BBO crystals. After the main amplification, 2.4 J of energy in 3.7 nm of spectral bandwidth at 1 Hz repetition rate was obtained. This spectral bandwidth corresponds to a transform-limited pulse duration of 440 fs. This result indicates that our CPA laser is capable of delivering multi-joule pump light after pulse compression and frequency doubling for 30-TW NOPCPA system.

堆积脉冲光参量啁啾脉冲放大器

A compact,low cost,stable noncollinear optical parametric chirped pulse amplification system is studied,which is seeded by an Yb3+-doped self-starting passive mode-locked stacking pulse fiber laser centered at 1 053 nm.A gain higher than 1.1×107,single pulse energy exceeding 11 mJ with fluctuations less than 2% rms,8 nm amplified signal spectrum are achieved.Different pulse durations of amplified signal are obtained by adjusting the stacker of the Yb3+-doped self-starting passive mode-locked stacking pulse fiber laser.