Yong Bi

Double-end-pumped 11-W Nd:YVO4 cw laser at 1342 nm

A compact, high-power, and high-stability Nd:YVO4 laser at 1342 nm has been developed. As high as 11 W cw output for 35 W of incident pump power with a slope efficiency of about 31.4% has been obtained. It has been shown that a reasonable and effective way to improve the output power is to choose a pumping scheme that can effectively extend the range of the stable resonator region by choosing the optimal dopant concentration and length of the laser rod.

High-power and high-quality, green-beam generation by employing a thermally near-unstable resonator design

We have obtained green-beam quality of M2 = 6.2 at an average output power of 120 W by intracavity frequency doubling of a diode-side-pumped, Q-switched Nd:YAG rod laser with a repetition rate of 10 kHz and an optical-to-optical conversion efficiency of 15.2%. To achieve high-beam quality at high average power, the laser employs a thermally near-unstable resonator design with two-rod birefringence compensation in an L-shaped flat-flat cavity. The output power fluctuation of the green laser remains less than 0.9% in 4 h.

52% Optical-to-Optical Conversion Efficiency in a Compact 1.5 W 532 nm Second Harmonic Generation Laser with Intracavity Periodically-Poled MgO:LiNbO3

Intracavity second-harmonic generation of 1.56 and 1.52 W continuous-wave 532 nm green laser radiation was obtained by quasi-phase matching in periodically-poled MgO:LiNbO3 (MgO:PPLN) crystals with lengths of 2 and 1 mm, respectively. The maximum optical-to-optical efficiency achieved was 52%. The intracavity temperature bandwidth was 15 and 12°C for 1 mm crystal and 2 mm crystal, respectively.

High-power cw 671 nm output by intracavity frequency doubling of a double-end-pumped Nd:YVO4 laser.

We report on a high-power (cw) red laser at 671 nm by intracavity frequency doubling of a double-end-pumped 1342 nm Nd:YVO4 laser based on the nonlinear crystal LiB3O5. A red output power of 3.38 W is obtained for a pump power of 27 W, with corresponding optical-to-optical efficiency of 12.5%. The 671 nm beam is nearly diffraction limited.

Laser Digital Cinema Projector

The reason for wider color gamut of laser display systems rests on RGB laser lights whose color coordinates very approach the locus of gamut chart, which means the most saturated colors. A novel, practical and simplest method to reduce the laser speckle is developed. A laser digital cinema projector (LDCP) is manufactured for the first time in the world. The LDCP enjoys all benefits of 166% NTSC expanded color gamut, beyond 9 024 ANSI lumens light output, a minimum sequential contrast ratio of 2595:1, 2048 X 1080 display resolution, etc.

Image quality enhancement and computation acceleration of 3D holographic display using a symmetrical 3D GS algorithm.

The 3D Gerchberg-Saxton (GS) algorithm can be used to compute a computer-generated hologram (CGH) to produce a 3D holographic display. But, using the 3D GS method, there exists a serious distortion in reconstructions of binary input images. We have eliminated the distortion and improved the image quality of the reconstructions by a maximum of 486%, using a symmetrical 3D GS algorithm that is developed based on a traditional 3D GS algorithm. In addition, the hologram computation speed has been accelerated by 9.28 times, which is significant for real-time holographic displays.

Generation of 4.3-W coherent blue light by frequency-tripling of a side-pumped Nd:YAG laser in LBO crystals.

High average power nanosecond pulsed light is obtained using a compact all solid state Nd:YAG laser. The laser is operated in Q-switched mode at the 1.3 micron fundamental and internally frequency tripled using two LiB3O5 (LBO) crystals. 4.3 W average power at 440 nm was demonstrated at 3.5 kHz and a pulse width of 150+/-10 ns (FWHM). The beam quality of M2 value is 5+/-1 in both dimensions. The short-term average power stability of the light source is better than 5.6%. Spectral selecting is proposed to increase production efficiency at 440 nm.

Thermally near-unstable cavity design for solid state lasers

Conventionally, lasers are designed to operate at the middle of thermally stable zones, where the fundamental mode size is insensitive to thermal perturbation, but is inversely proportional to width of stability zone, which will give rise to inconvenience or even difficulty in practice when large mode size is required. We propose a new simple approach, namely thermally-near-unstable resonator. The laser is designed to operate at the border of stability zone instead, where it has large fundamental mode size at gain media. With increase of pump power, mode size would grow up automatically to a value suitable for monomode operation. Stability of cavity on whole pump range can also be easily guaranteed. And there is a point where the laser power is insensitive to driving perturbations. However, the laser beam quality is sensitive to driving and thermal perturbations for the mode size depends severely on thermal focusing. Large-scale improvement in beam quality is demonstrated experimentally.

Periodically poled self-frequency-doubling green laser fabricated from Nd:Mg:LiNbO 3 single crystal

Although a breakthrough in the fabrication of green laser diodes has occurred, the high costs associated with the difficulty of manufacture still present a great obstacle for its practical application. Another approach for producing a green laser, by combining a laser device and a nonlinear crystal, entails the fabrication of complex structures and exhibits unstable performance due to interface contact defects, thus limiting its application. In this work, we report the fabrication by domain engineering of high quality periodically poled LiNbO₃, co-doped with Nd³⁺ and Mg²⁺, which combines a laser medium and a high efficiency second harmonic conversion crystal into a single system that is designed to overcome the above problems. An 80 mW self-frequency doubling green laser was constructed for the first time from a periodically poled Nd:Mg:LiNbO₃ crystal of 16 mm in length. This crystal can be used for developing compact, stable, highly efficient mini-solid-state-lasers, which promise to have many applications in portable laser-based spectroscopy, photo-communications, terahertz wave generation, and laser displays.

High power green laser with PPMgLN intracavity doubled

The quasiphase matched PPMgLN crystal is used intracavity frequency doubled to obtain high power green laser, with a pump power of 20W at 808nm, 6.67W output power at 532nm is achieved.