Yulei Wang

Trends in stimulated Brillouin scattering and optical phase conjugation

An overview on current trends in stimulated Brillouin scattering and optical phase conjugation is given. This report is based on the results of the “Second International Workshop on stimulated Brillouin scattering and phase conjugation” held in Potsdam/Germany in September 2007. The properties of stimulated Brillouin scattering are presented for the compensation of phase distortions in combination with novel laser technology like ceramics materials but also for e.g., phase stabilization, beam combination, and slow light. Photorefractive nonlinear mirrors and resonant refractive index gratings are addressed as phase conjugating mirrors in addition.

High-quality near-field beam achieved in a high-power laser based on SLM adaptive beam-shaping system

We demonstrate a high-power laser system with a high-quality near-field beam by using a liquid-crystal spatial light modulator (SLM). An efficient spatial beam shaping algorithm is discussed which can improve the output nearfield beam quality effectively. Both small-signal and large-signal amplification situation of the laser are considered in the beam shaping algorithm. The experimental results show that the near field fluence modulation of output is improved from 1.99:1 to 1.26:1 by using the liquid-crystal SLM. Obvious uniform spatial fluence distribution and near-field beam quality improvement are observed.

Comparative study of LD-pumped Tm:YAG and Tim:LuAG lasers

Widely tunable performances of Tm:YAG and Tm:LuAG lasers near 2 μm are demonstrated. The emission spectra of Tm3+ in these two single crystals are reported and analyzed. The lifetimes of the 3F4 state in thulium-doped YAG and LuAG are 10.1 and 9.2 ms, respectively. In addition, it is proven that the Tm:YAG crystal with two bonded undoped YAG ends is promising for high-efficient operation.

Lasing Characteristics of a Single-Frequency Tm:YAG Laser

A single-frequency Tm:YAG laser at room temperature is presented. With two thin etalons as the intra-cavity tuning elements, the maximum output power 69.5 mW is obtained at room temperature. The slope efficiency is 10.2% and the optical to optical conversion efficiency of 4.02%. The central wavelength is 2012.5 nm. A temperature stability of 0.1 °C corresponds to a frequency stability of 74 MHz observed by wave meter in 50 s.

Double-clad Tm3+-doped silica fiber laser with Bragg grating inscribed directly into active core by femtosecond laser

We report for the first time to inscribe the Fiber Bragg Grating (FBG) in Tm3+-doped multimode double-clad silica fiber by 800 nm femtosecond laser with a phase mask. The 1.35 μm period Bragg grating is written into the fiber core, which is responded to the laser center wavelength located at nearly 1960 nm. Continuous wave total output power of 11.5 W is obtained under the launched pump power of 29.8 W, corresponding to a slope efficiency of 45.0% and a conversion efficiency of 38.6%.

Q-switch operation of a c-cut 2132-nm Tm, Ho:YAP laser pumped by a laser diode of 794.3 nm

Q-switch operation of a c-cut Tm (5 at %), Ho (0.3 at %):YAP laser at 2132 nm wavelength were reported in this paper. In the temperature of 77 K, the Tm, Ho:YAP crystal was double end-pumped by a 21.4-W fiber-coupled laser diode (LD) at the center wavelength of 794.3 nm. A 5.29-W Q-switch output power was acquired at pulse repetition frequency (PRF) of 10 kHz, corresponding to an optical-optical conversion efficiency of 24.7% and a slope efficiency of 28.1%. The energy per pulse of 3.57 mJ in 38 ns was achieved at 1.25 kHz with the peak power of 93.9 kW.

Holmium laser in-band pumped by a thulium laser in the same host of YAlO 3

We report on the room-temperature continuous-wave (CW) operation of a Ho:YAlO3 laser that is resonantly end pumped at 1.94 μm by a diode-pumped thulium-doped laser in the same host. Through the use of a 1 at % Ho3+-doped 20-mm-long YAlO3 crystal (b cut), the Ho:YAlO3 laser generated 1 W of linearly polarized (E//c) output at 2118 nm and 0.55 W of E//a output at 2128.5 nm for an incident pump power of 5 W, with an output coupler transmission of 14 and 3%, respectively. An optical-to-optical conversion efficiency of 20% and a slope efficiency of 33% were achieved at 2118 nm corresponding to an incident pump power.

Diode-pumped Q-switched Tm:YAP laser with a pump recycling scheme

We reported on a diode end-pumped AO Q-switched Tm:YAP laser at 1937 nm. The average output power was 3.9 W, with a slope efficiency of 29.4% and optical-optical conversion efficiency of 21.6% at a 5-kHz repetition rate. The temperature dependency of the output power and the pulse width at different repetition rates were investigated in details.

Using an active temporal compensating system to achieve the super-Gaussian pulses in high-power lasers

In high-power solid-state laser, initiative pulse shaping can help improve the output laser’s performance. The evaluation for output laser pulse is also incomplete. In this paper, we propose a method of initiative pulse shaping by using arbitrary waveform generator (AWG), and establish a relatively complete evaluation system for the output pulses shape simultaneously. It achieves the super-Gaussian pulse output with high SNR (signal-to-noise ratio). As a consequence, a square laser pulse with pulse adjustable width ~5ns, rising time 197ps is obtained. The power imbalance of the output square pulse is 3.72%. The similarity between the eight-order super-Gaussian pulse and the one we get from experiment reached 99%.

High stability, single frequency, 300 mJ, 130 ps laser pulse generation based on stimulated Brillouin scattering pulse compression

We obtained the output of single frequency laser pulses with an average pulse-width of 136 ps and the minimum of 123 ps based on stimulated Brillouin scattering pulse compression pumped by an 8xa0ns-pulse-width, 1064xa0nm-wavelength Q-switched Nd:YAG laser. The pulse-width stability of the output is about 4.1% while that of the pump pulses is about 1.1%, the highest energy conversion efficiency is about 85%, and the single pulse energy is above 300 mJ.