Self-mixing interference (SMI) effects have been widely used in measuring the distance and displacement and velocity. Conventional methods are fringe counting and phase analysis. The former method has a precision of λ/10 in a multi-mode LD pumped solid-state laser (LDPSSL), while the latter has a precision of nearly λ/50 concerning the multiple reflections. Theoretical analysis and simulation calculations are presented.
A solid-state laser source with flat-top wide beam profile was designed and made. The laser source was mainly made up of an Nd:YAG solid-state laser at 1064 nm and a maximum 267 x collimating telescope. A 2 W laser diode (LD) pumped Nd:YAG laser with flat-concave cavity was adopted as the primary laser source at 1064 nm. Then the output laser (1064 nm) was injected into a collimating telescope. We designed three schemes according to spherical wave theory and chose the best one based on our experiments. We found out the spherical aberration (including axial and off-axial points) must be corrected. At last, an output laser beam with 80 mm diameter, 0.4 mrad divergence angle, > 50 mW output power, and ±10% intensity distribution of cross section, was obtained.
During design and experiments, multi-diode-laser -module was employed to pump a double AO switched Quasi-CW YAG laser with KTP or LBO crystal as frequency doubler. Thermal lensing effect in laser rod and frequency doubling crystal were both considered. Cavity design with ABCD law and crystal thermal compensation given in detail by numerical calculation. High average power output was achieved.
We have describe a simple diode-side-pumped high-power and high efficiency Nd:YAG laser that produces 240 W of power continuous-wave(CW) with 33% optical-optical efficiency. We used the technology of diode laser close-couple to realize high pumping efficiency ,We measured the thermal lensing focal length to design the laser resonator, which decrease the rod thermal effect. By changing the resonator parameters ,we can adjust the fundamental mode size and the output beam quality.
A high power intracavity frequency doubled Nd:YAG laser with KTP crystal and A-O Q-switcher pumped by 1600 Watt-808 nm laser diodes and its thermal effect are discussed. Also we proved that the title angle of KTP crystal can be to compensate for the phase mismatching and to solve the problem of the drop of green laser output power along with the increasing temperature of KTP crystal. Then based on optical parametric oscillator (KTP-OPO) pumped by 532 nm laser and their frequency doubling (with KTP and BBO) a Watt-level red and blue laser system which would be provided as RGB laser projection display are described.
Thermal lens effect is a very important factor in designing stable resonators for high-power solid-state laser pumped by laser diodes. In a symmetric plane-parallel resonator , if the thermal lens of the laser crystal is close to a thin lens, according to the theory of transfer matrix we can get that there is a critical hollow point where the resonator changes from stable region to unstable state, then back to stable region. So we can measure the ultrashort thermal focal length of high-power solid-state laser based on this fact. We used this method to measure the ultrashort thermal focal length of a 100W magnitude Nd:YAG laser. The experimental results have shown this is a simple and effective technique.