Qihua Zhu

Accurate measurement and control of delay variation between two ultra-short laser pulses based on cross-correlation

A method based on cross-correlation is proposed for measurement and control of accurate delay variation between two ultra-short laser beams. The accuracy can reach to a few femtoseconds.

Preliminary results of Ti:sapphire ultrahigh-power laser facility

A multihundred-terawatt Ti:sapphire laser facility was built at China Academy of Engineering Physics which could deliver femtosecond pulses at three power levels of 5TW, 30TW and hundreds TW to targets. Near-diffraction-limited focal spots were measured and it was found for the first time that alignment errors of grating groove parallelisms in compressors could be the major mechanism for producing elongated far fields. Pulse durations of 35fs were obtained with a Fastlite-produced AOPDF for spectral compensation.

Measurement and control of micro-errors on components-tiling and beams-combination

To meet the needs of some physical experiments for high energy short pulse laser, TGC (tiled gratings compressor) technology and beams-combination technology are required. Progress of TGC and beams-combination at CAEP is introduced. On TGC technology, interference pattern and far field distribution is used to initially eliminate the tiling error, and displacement sensor is used as feedback to maintain the posture of the sub-gratings. As for beams-combination a preliminary method of feedback control in subsections is proposed and will be expected to be used in an integrated test-bed.

THz surface plasmon polaritons propagation along metal nanowire

Terahertz (THz) surface plasmon polaritons (SPPs) propagation along metal wire of nanometer scale is studied. An analytical theory is deduced to describe the propagation properties of THz SPPs. Formulae describing the propagation attenuation and the phase velocity intuitionally relate to the nanowire radius and the THz frequency.

Terawatt femtosecond laser storage cavity with cholesteric liquid crystals for an x-ray source based on Compton scattering

In laser Compton scattering systems, the limitation to higher average brightness is the low repetition rate of high-power lasers. We propose and demonstrate for the first time, as far as we know, a simple method by which x-ray yield could be enhanced nearly 2 orders of magnitude per second. The method, utilizing cholesteric liquid crystals as the entrance mirror of the laser storage cavity, can be used not only for storing femtosecond laser pulses with a peak power of several terawatts, but also to make high coupling efficiency and energy utilization efficiency accessible.

Tolerance analysis and experiment of injection double lens in high power solid laser facility

The injection lens of the high power solid laser facility built soon was designed as double lens. The tolerance of the double lens was analyzed, and the optical performance of which was detected in experiment.

Arbitrary spectral shaping using optical parametric chirped pulse amplification

It is demonstrated that arbitrary spectral shaping can be achieved with pump pulse time shaping in optical parametric amplification. This result is confirmed with our high energy PW front end laser system.

Generation of broad-bandwidth femtosecond 270-nm light by third-order nonlinear coupling with focusing beams in a single crystal of BBO

By third-order nonlinear coupling and tightly focusing the beams in a single crystal of BBO, high intensity broad-bandwidth femtosecond pulses are used to generate 50&mgr;J of light at 270nm (up to 1% THG efficiency). And it is proved that the major contribution to the THG observed is the third-order process, not the cascaded second-order process.

The art for broad-bandwidth direct third-harmonic generation focusing beams in a single crystal of BBO

By third-order nonlinear coupling and tightly focusing the beams in a single crystal of BBO, high intensity broad-bandwidth femtosecond pulses are used to generate 50μJ of light at 270nm (up to 1% THG efficiency). It is proved that the major contribution to the THG observed is the third-order process, not the cascaded second-order process. And the primary reasons why THG efficiency is about 1% is that 1ωlight is frequency-chirp beams and BBO crystal isnt tuned to optimized angle. At last, the methods to improve the third harmonic conversion efficiency have been put forward.