Towards Terawatt Sub-Cycle Long-Wave Infrared Pulses via Chirped Optical Parametric Amplification and Indirect Pulse Shaping

Yanchun Yin,Andrew Chew,Zenghu Chang,Yi Wu,Xiaoming Ren,Yang Wang,Jie Li

doi:10.1038/srep45794

Abstract

We present an approach for both efficient generation and amplification of 4–12 μm pulses by tailoring the phase matching of the nonlinear crystal Zinc Germanium Phosphide (ZGP) in a narrowband-pumped optical parametric chirped pulse amplifier (OPCPA) and a broadband-pumped dual-chirped optical parametric amplifier (DC-OPA), respectively. Preliminary experimental results are obtained for generating 1.8–4.2 μm super broadband spectra, which can be used to seed both the signal of the OPCPA and the pump of the DC-OPA. The theoretical pump-to-idler conversion efficiency reaches 27% in the DC-OPA pumped by a chirped broadband Cr2+:ZnSe/ZnS laser, enabling the generation of Terawatt-level 4–12 μm pulses with an available large-aperture ZGP. Furthermore, the 4–12 μm idler pulses can be compressed to sub-cycle pulses by compensating the tailored positive chirp of the idler pulses using the bulk compressor NaCl, and by indirectly controlling the higher-order idler phase through tuning the signal (2.4–4.0 μm) phase with a commercially available acousto-optic programmable dispersive filter (AOPDF). A similar approach is also described for generating high-energy 4–12 μm sub-cycle pulses via OPCPA pumped by a 2 μm Ho:YLF laser.

Highlights

Isolated attosecond pulses as short as 67 as have been generated via high harmonic generation (HHG) driven by few-cycle near infrared pulses at ~800 nm[1]
We present a design that enables generating, for the first time to the best of our knowledge, mJ-level, CEP-stable [4,5,6,7,8,9,10,11,12] μm pulses through dual-chirped optical parametric amplification (DC-OPA)[22,23,27,28,29,30], and compressing such pulses to sub-cycle duration through indirect pulse shaping
We first present the experimental generation of a μJ-level super broadband spectrum, which covers 1.8–4.2 μm generated by difference frequency generation (DFG) in a BIBO crystal, followed by discussions on how to tailor the phase matching of Zinc Germanium Phosphide (ZGP) in order to achieve [4,5,6,7,8,9,10,11,12] μm parametric bandwidth and on indirect pulse shaping toward sub-cycle pulses

Summary

Introduction

Isolated attosecond pulses as short as 67 as have been generated via high harmonic generation (HHG) driven by few-cycle near infrared pulses at ~800 nm[1]. Two-cycle mJ-level driving lasers around 1.7 μm has been used to generate high-flux soft X-ray pulses in the water-window region (280 to 530 eV)[4,5], supporting 10 as transform limited pulses. To significantly increase both center photon energy and bandwidth of high harmonics for generating shorter attosecond or even zeptosecond X-ray pulses, the development of high-energy few-cycle pulses further into the mid-infrared (mid-IR) region is in demand. High-energy few-cycle infrared pulses are primarily enabled by optical parametric chirped pulse amplification (OPCPA) pumped by few-picosecond lasers, which allows a trade-off between the gain bandwidth and the damage threshold of nonlinear crystals[14,15]. The second-order phase of high-energy [4,5,6,7,8,9,10,11,12] μm pulses can be compensated by using NaCl, which has a very small n2 and a high damage threshold; the higher-order phase can be compensated indirectly by controlling the signal phase with a commercially available acousto-optic programmable dispersive filter (AOPDF)

Results

Discussion

Conclusion