Shanghai Jiao Tong University

Fudan University

Liejia Qian

Peng Yuan

Guoqiang Xie

Jingui Ma

Jing Wang

Yongzhi Wang

Bingjie Zhou

Zhipeng Qin

Dongfang Zhang

Daolong Tang

Heyuan Zhu

Lingchen Kong

Dianyuan Fan

Fuyong Wang

Zhen Qiao

Ultrafast group-velocity control method and device thereof comprising a signal path successively comprising a seed laser source, a pulse stretcher, and a first pulse compressor; a pump path comprising a pump laser source; an amplifier comprising a nonlinear crystal with chirped poled-period; and an idler path successively comprising a spectral filter and a second pulse compressor after amplifier. Both chirped signal pulse from the pulse stretcher and pump pulse from the pump source incident into the amplifier, where energy continuously transfers from the pump pulse to the chirped signal pulse and a newly generated idler pulse. The amplified chirped signal pulse is directly compressed by first pulse compressor and the generated idler pulse is firstly filtered by the spectral filter and then compressed by the second pulse compressor. After amplification and compression, both signal and idler are delayed, and group delay is adjusted by the pump intensity.

Method and device for ultrafast group-velocity control via optical parametric amplification in chirped quasi-phase-matching structure

A high-average-power OPCPA amplifier comprising a pump laser, a signal laser, and a nonlinear crystal amplifier. The pump laser includes an Nd:YVOlaser oscillator-regenerative amplifier, an Nd:YAG boost amplifier, a frequency-doubling convertor, and a frequency-tripling convertor. The signal laser includes a supercontinuum generator, a pulse stretcher, and a pulse compressor. The chirped signal and the pump laser is intersected with a noncollinear angle of 3.0&#xb0; to 4.0&#xb0; in the nonlinear crystal amplifier and the temperature of the crystal amplifier is set at higher than 320K for simultaneous temperature- and wavelength-insensitive phase-matching.

Multi-parameter noncollinear phase-matching for high-average-power optical parametric chirped-pulse amplifier

A method for generating femtosecond vortex beams with high spatial intensity contrast, where a noncollinearly pumped HG beam femtosecond laser generates femtosecond HG beam and a cylindrical lens mode converter converts the femtosecond HG beam to femtosecond LG vortex beam. The HG beam femtosecond laser comprises a pump source, a gain medium, a saturable absorption mirror as mode-locker, and an output coupler with a noncollinear angle between the laser beam and the pump beam in the gain medium, which enables the laser to generate pure, order-tunable femtosecond HG beams. Femtosecond vortex beams obtained after the cylindrical lens converter have high-intensity-contrast, and are topological charge-tunable.

Method for generating femtosecond vortex beams with high spatial intensity contrast

A simultaneous temperature- and wavelength-insensitive parametric amplifier comprising a pump laser, a signal laser, and a crystal amplifier. The pump laser system on a first optical pathway includes a Nd:YVOlaser oscillator-regenerative amplifier and a Nd:YAG boost amplifier. The pump laser beam is generated from the pump laser system, passes through the first image-relay system, and is frequency-doubled in the frequency-doubling crystal. The signal laser system on a second optical pathway comprises a Ti:sapphire regenerative amplifier and generates the signal laser beam, which passes through the pulse stretcher and is temporally chirped and imposed with an angular dispersion by the first grating. The chirped signal beam and pump laser beam are intersected with a noncollinear angle of &#x3e;5&#xb0; in the crystal amplifier for temperature-insensitive phase-matching (PM). By optimizing grating constant of the first grating, the chirped signal is imposed with appropriate amount of angular dispersion for wavelength-insensitive PM.

Noncollinear achromatic phase matching based optical parametric chirped-pulse amplifier with insensitivity to temperature and wavelength

Quasi-parametric chirped-pulse amplifier comprising a signal path, a pump path, and an amplifier. A dedicated nonlinear crystal doped with rare-earth-ions is used which has strong absorption around the idler waveband. Both the chirped signal pulse and the pump pulse incident into the amplifier, where energy continuously transfers from the pump pulse to the signal pulse and a newly generated idler pulse. The energy of the generated idler pulse is continually absorbed by the rare-earth ions doped in the amplifier.

Quasi-parametric chirped-pulse amplifier

A spatiotemporally resolved far-field pulse contrast measuring device includes a plano-convex cylindrical lens, a nonlinear correlation crystal, a plano-convex imaging lens and a signal-receiving system. The signal-receiving system includes a fiber array, a photomultiplier and a digital oscilloscope. A measuring method of the device includes steps of: focusing an under-test beam in x dimension to make a focus of the under-test beam fall onto a front surface of the nonlinear correlation crystal; making a spatial correlation and a temporal correlation respectively in two transverse spatial dimensions (x-y) of the nonlinear correlation crystal by the far-field under-test beam and a sampling beam; generating a two-dimensional correlating signal by the spatiotemporal correlation; imaging the two-dimensional correlating signal by an imaging system onto a detection surface of a receiver system; and measuring the x-dimensional and y-dimensional intensity distributions of the correlating signal highly dynamically by the receiver system.

Spatiotemporally resolved far-field pulse contrast measuring method and device

A method for generating ultrashort femtosecond pulses in the optical parametric oscillator pumped by long pulses, comprising governing dispersion and nonlinearity in the optical parametric oscillator, forming linearly-chirped long pulses with broad bandwidth in the optical parametric oscillator, compressing the linearly-chirped long pulses to femtosecond pulses by a second-order dispersion outside the optical parametric oscillator cavity. The ultrashort femtosecond pulse is generated in the OPO with long pulse pumping.

Method for generating ultrashort femtosecond pulses in optical parametric oscillator pumped by long pulses

A method for filtering noises in an optical parametric chirped-pulse amplifier by a spatial-chirp-dressed seed beam is provided. The various noises that grow during amplification course, including parametric super-fluorescence, pump distortion-induced noise and surface-reflection-initiated pre-pulses, will not have the spatial and temporal chirp. After dechirping amplified signal with a compressor, a main pulse having its spatial and temporal chirp removed completely is produced, while the noises acquire an additional spatiotemporal coupling, making themselves highly distinguishable from signal in space, and hence supporting noise filtering effectively and expediently in spatial domain that would not be possible otherwise. The method has capabilities of an order of magnitude reduction in noise energy and several orders of magnitude enhancement in temporal contrast.

Method for filtering noises in optical parametric chirped-pulse amplifier and device therefor

A single-shot pulse contrast measuring device based on non-harmonic long-wavelength sampling pulse includes a long-wavelength sampling light generation unit, a large-angle non-collinear sum-frequency cross-correlation unit and a high sensitivity signal receiving unit. The long-wavelength sampling light sum-frequency cross-correlator can allow that the beams are interacted with each other at the large non-collinear angle in the quasi-phase matching crystal, match the measuring window of the high sensitivity signal receiving system, and is in favor of eliminating the scattered light noise, thereby achieving the single measurement of the pulse contrast with large temporal window and high dynamic range. The single-shot pulse contrast measuring device of the present invention has good extensibility at the temporal window and dynamic range, and is adapted for measuring the contrast of the high-power laser with various wavelengths.

Single-shot pulse contrast measuring device based on non-harmonic long-wavelength sampling pulse

A high-fidelity device for single-shot pulse contrast measurement based on quasi-phase-matching includes a generating unit of sampling pulse, a high-fidelity cross-correlation unit of nonlinear SFG and a high-sensitivity signal detecting unit. An innovatively designed dot-mirror or dot-attenuator and correlating crystal. The dot-mirror or dot-attenuator is adopted to suppress the scattering noise, which is mainly induced by air scattering of the main peak of the correlation beam, to a level below the real pulse background. While the crystal is introduced into the device as a nonlinear correlation crystal to move two kinds of artifacts introduced by a correlation process respectively out of the temporal window and behind the main pulse, so that effects of the artifacts on the contrast measurement in a pulse leading edge are removed, without obviously affecting other parameters. The device is also fit for measuring contrasts of high-power lasers of various wavelengths.

High-fidelity device for single-shot pulse contrast measurement based on quasi-phase-matching (QPM)

A system for detecting single-shot pulse contrast includes a correlator generating a correlation signal, a spectral filter filtering light signals having wavelengths different from the correlation signal, a fiber array comprising a plurality of fibers with different lengths for transmitting the correlation signal in parallel forming parallel correlation signals, and a fiber bundle bounding the fibers at the end thereof for converging the parallel correlation signals, wherein due to different lengths of the fibers, the parallel correlation signals are converted into serial correlation signals at end of the fibers, a plurality of fiber attenuators spliced into at least one of the fibers respectively for attenuating the parallel correlation signals, a detector for detecting the serial correlation signals to produce analog signals, an A/D convertor converting the analog signals to digital signals, and a computer for processing the digital signals for retrieving the single-shot pulse contrast.

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Shanghai, China

Liejia Qian