Aicong Geng

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.

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.

Highly efficient tunable tapered-polymer-fiber lasers

A highly efficient tunable tapered-polymer-fiber (TPF) laser was demonstrated by use of a compound parabolic TPF doped with Rhodamine-6G (R6G) dye. The tuning ranges over 40 nm at the visible region for laser output with the maximum output energy of 600 mu J at 570 nm and the optical-optical conversion efficiency of 23% were achieved by a prism as a spectrally selective element. Moreover, the coupling efficiency for the taper exceeded 90%. Compared to traditional polymer fibers with a micrometer-size core diameter, the taper allows for a higher pump to be launched without damaging the fiber endfaces, and it can efficiently couple the light into the fiber and alleviate the alignment difficulty. So, the TPF laser not only possesses all of the advantages of traditional polymer-fiber lasers, and it can also obtain higher output energy and higher efficiency. Additionally, it is insensitive to geometrical displacements. (c) 2005 American Institute of Physics.

Power scaling analyses of optical parametric amplifier

Thermally induced rupture of a nonlinear crystal is the primary limiting factor to the attainment of High average power (HAP) in an optical parametric amplifier (OPA). In this paper, HAP scaling behavior in an OPA is addressed in detail by combining thermally induced phase mismatching with thermally induced rupture. Expressions for thermally induced stress are derived and analyzed that can give directions for a HAP-OPA design. When an OPA generates the maximum average output power, the dependence of flaw size on thermo optical material parameters of nonlinear crystals is obtained that is very useful for surface processing, material selecting, properties improving of a nonlinear crystal and new HAP nonlinear crystals developing.