Liang Xiaoyan

Efficient Spherical Wavefront Correction near the Focus for the 0.89 PW/29.0 fs Ti:Sapphire Laser Beam

We demonstrate a new loop system of the spherical wavefront (SW) correction near the beam focus to effectively improve the focusability of 0.89 PW/29.0 fs Ti:sapphire chirped pulse amplification laser. After wavefront correction, the Strehl ratio is improved to reach 0.91, and the focal spot size using the f/4 off-axis parabola is reduced to 6.34 ? 6.94 ?m2 (corresponding to 1.63 ? 1.78 times diffraction limitation). With full peak power of 0.89 PW, the peak intensity of 2.59 ? 1021 W/cm2 is obtained. The experimental results show that the SW correction scheme near the beam focus is comparatively simple, economic and high-efficient.

High and Stable Conversion Efficiency Obtaining in Single-Stage Multi-Crystal Optical Parametric Chirped Pulse Amplification System

An optical parametric chirped-pulse amplification system is demonstrated to provide 32.9% pump-to-signal conversion efficiency . Special techniques are used to make the signal and pump pulses match with each other in both spectral and temporal domains. The broadband 9.5-mJ pulses are produced at the repetition rate of 1 Hz with the gain of over 1.9 x 10(8). The output energy fluctuation of 7.8% is achieved for the saturated amplification process against the pump fluctuation of 10%.

Diode-Pumped Soliton and Non-Soliton Mode-Locked Yb:GYSO Lasers

Diode-pumped soliton and non-soliton mode-locked Yb:(Gd1−x Yx)2SiO5(x = 0.5) lasers are demonstrated. Pulses as short as 1.4 ps are generated for the soliton mode-locked operation, with a pair of SF10 prisms as the negative dispersion elements. The central wavelength is 1056 nm and the repetition rate is 48 MHz. For the non-soliton mode locking, the output power could achieve ~1.2 W, and the pulse width is about 20 ps. The critical pulse energy in the soliton-mode locked operation against the Q-switched mode locking is much lower than the critical pulse energy in the non-soliton mode-locked operation.

Wavefront Correction of Pettawat Laser System by a Deformable Mirror with 50 mm Active Aperture

We firstly propose and demonstrate a new economical approach that can correct the wavefront of the petwatt Ti:sapphire laser system with a beam size of 150mm. By using a deformable mirror with 50mm active aperture in the end of the laser, the focal spot size is reduced effectively. The experimental results show that the new approach is simple, less-expensive and valid from a technical and economical point. This technique could be applied to correct the wavefront of a large optical beam with a smaller aperture deformable mirror.

Red and Blue Light Generation in an LiTaO3 Crystal with a Double Grating Domain Structure

The Pd39Ni10Cu30P21 bulk metallic glass is isothermally relaxed under various pressures. The degree of the structural relaxation is evaluated in terms of the enthalpy recovery behaviours involved in the irreversible glass transition processes by using a temperature-modulated differential scanning calorimetry technique. A roughly Linear increase of the recovery enthalpy is observed within the experimental pressure range fi-om 2.67 to 4.45 GPa, which reflects the release of the frozen-in enthalpy in the as-quenched glass with increasing relaxation pressure. The pressure dependence of the timescale of the enthalpy recovery processes is also exhibited.

An ultra-broadband spatially dispersed regenerative amplifier free from spatial chirp

An ultra-broadband Ti:sapphire regenerative amplifier based on spatially dispersed amplification is demonstrated experimentally. Departing from previous reports, a new design of the cavity gets the amplified pulse free from spatial chirp. Utilizing this new regenerative amplifier, chirped pulses with bandwidth (FWHM) of about 80 nm are obtained, and the bandwidth is limited only by that of the incident seed pulses.

Generation of 17-TW 23-fs Pulses with a Two-Stage Ti：Sapphire Amplifier at Repetition Rate 10 Hz

We have developed a two-stage Ti:sapphire amplifier system which can produce 17-TW/23-fs pulses at a repetition rate 10 MHz. A birefringent plate is used in the regenerative amplifier to alleviate gain narrowing, while an all-reflective cylindrical-mirror-based pulse stretcher and an acousto-optic programmable dispersive filter (AOPDF) are used to compensate for the higher order dispersion of the system.

Violet to Infrared Multiwavelength Generation in Periodically Poled Lithium Niobate Pumped by a Q-Switched Nd:YVO4 Laser

Six output wavelengths from violet to infrared have been observed simultaneously from an all-solid-state laser pumped optical parametric oscillator in a periodically poled lithium niobate crystal. The output wavelengths can be tuned by varying the quasi-phase matched period and/or temperature. The pump laser is a diode-pumped passive Q-switched Nd:YVO4 laser operated at 1064 nm. Using a crystal with a 29.9 µm grating period, we measured six wavelengths at 448, 515, 532, 630, 773 and 1546 nm and obtained efficient output. We explain the multiwavelength generation by multiwave coupling theory. This phenomenon may have novel applications in photonic devices.

Comparison of Laser Performances of 5at.% Yb:Gd2xY2(1?x) SiO5 Crystals between Different Cutting Directions

We investigate the laser actions of 5at.% Yb:Gd2xY2(1-x)SiO5 (Yb:GYSO; x = 0.1) crystals with different cutting directions, parallel and vertical to the growth axis. Our results show that the cutting direction of the sample plays an astonished role in the laser operation. The sample cut vertically to the growth axis possesses the favourable lasing characteristics. Its output power reaches 3.13W at 1060nm with a slope efficiency of 44.68% when the absorbed pump power is 8.9 W. In contrast, the sample cut parallel reaches only 1.65 W at 1044 nm with a slope elLiciency of 33.76% with absorbed pump power of 7.99 W. The absorption and emission spectra of the two samples are examined and the merit factor M is calculated. Our analysis is in agreement well with the experimental results. The wavelength tuning range of the superior sample covers from 1013.68 nm to 1084.82 nm.

Dispersion Analysis and Compensation of Collinear Optical Parametric Chirped Pulse Amplification Systems

In an optical parametric chirped pulse amplification (OPCPA) laser system, residual phase dispersion should be compensated as much as possible to shorten the amplified pulses and improve the pulse contrast ratio. Expressions of orders of the induced phases in collinear optical parametric amplification (OPA) processes are presented at the central signal wavelength to depict a clear physics picture and to simplify the design of phase compensation. As examples, we simulate two OPCPA systems to compensate for the phases up to the partial fourth-order terms, and obtain flat phase spectra of 200-nm bandwidth at 1064?nm and 90-nm at 800?nm.