Study Of LD-End-Pumped Nd: YAG Laser And Solid-State Laser Sensor For Displacement Measurement

Compared with the traditional lamp-pumped solid-state lasers, the diode-pumped solid-state lasers (DPSSLs) have many advantages such as high efficiency, long lifetime, all-solid-state, small size and little heat effect, etc. Of many kinds of DPSSLs, laser diode (LD) end-pumped Nd:YAG laser plays an important role and has been found wide applicatins in industry, mainly because of its good mechanical and optical properties of Nd:YAG crystal and good mode matching to output a fundamental transverse mode.At first, this thesis introduces the progress, main characteristics and applications of LD pumped Nd:YAG laser. In term of the rate equation of Four-energy-level system, the theoretical expressions of threshold, output power, and slope efficiency of the laser has been deduced. The principle of operation and confirgurations of the laser as well as the theory of intracavity frequency doubling are also described briefly. Secondly, a design method for a LD-end-pumped Nd:YAG laser is offered on the base of approach of spatial-dependent rate equation analysis, for a certain pumping configuration, a useful guideline has been given for choosing the parameters including the oscilating laser mode size, transmission of output coupler, the pumping beam size, and the longitudinal position of focus spot of LD pumping beam. According to the guidline, two Nd:YAG lasers have been designed and set up, one is end-pumped by lower output power LD using a selfoc micro lens, and the other isend-pumped by high output power LD using a pair of lenses are designed, and the characteristics such as output power and power stabilization of both solid-state lasers are investigated. Thirdly, when an empty liquid crystal cell is inserted in the cavity of the Nd:YAG laser pumped by high power LD, the laser can operates in single axial mode. Finally, according to the relationship between the laser output power and the longnitudinal a LD-end-pumped Nd:YAG laser sensor for displacement measurement has been investigated theoretically and demonstrated experimently, the results indicate that when the mean radius of pumping inside the laser cavity is far less than that of the oscilating laser mode, the exponential of the output power is a Gauss function of the longitudinal positon of focused spot of LD pumping beam, both the measurement range and the sensitivity are dependent on the incident pumping power, as the incident pumping power is increased, the measurement range is enlarged and the sensitivity is improved. When the pumping power is 7.24W (corresponding to the maximum output power of 1.926 W), the measurement range and the sensitivity are 13. 045mm and 0. 148 mW/ m respectively.