The Research On The Temperature Characteristics Of Microchip Laser

Since Theodore H.Maiman obtained 694 nm red laser by using flash-pumped synthetic ruby crystal in 1960,the laser technology has opened up the pace of rapid development,nowadays they are applicated in every aspect of modern social life.Compared to conventional lasers,microchip laser that use miniature and flaky doped crystals as gain medium has the advantages of small volume,high beam quality and large power per unit volume,which has a wide range of researchs and applications in many fields such as optical fiber communications,space communications,atmospheric research and medical equipment.Moreover,Dual-frequency microchip laser has become a competitive method in optical generation of millimeter wave.As with solid-state laser,the output performance of the microchip laser is also seriously affected by the thermal effect of the gain medium.In this paper,the thermal effect of microchip laser crystal is analyzed theoretically and stimulatingly,and the influence of laser spectrum characteristic caused by thermal effect of crystal is studied experimentally.The main contents can be summarized as follows:(1)The development of the Microchip laser is briefly overviewed,and the technology realization and application prospect of the optical generation of millimeter wave are introduced.Then,the research status of the foreign and domestic microchip laser is described respectively.(2)The causes of laser generation and the conditions of stable amplification are elaborated,and the various components of the laser are discussed.Then the several common materials of laser gain medium are introduced and compared.On the basis of deducing the steady-state rate equation of the microchip laser,the working characteristics of the microchip laser and their influencing factors are discussed,which provide a reference for improving the output beam quality of microchip laser.Based on the Theoretical analysis of microchip laser temperature drift phenomenon,the linear relationship between the laser wavelength and the crystal center temperature is obtained.(3)The thermal effect of microchip laser crystal is analyzed theoretically,and the heat transfer model of microchip laser crystal is studied by the finite element method.Theoretical analysis indicates that the thermal effect of the miscrochip laser crystal is due to the deposition of waste heat inside the crystal,the thermal effect will lead to the change of the cavity length and refractive index of the microchip laser crystal.The heat transfer model of microchip laser crystal was obtained by ANSYS thermal analysis.The results show that both LD pump power and the controlled temperature have linear relationship with the crystal center temperature.In the stimulation range,the thermal conductivity between the heat sink and the crystal only affects the crystal temperature difference,and a good cooling effect can be achieved by selecting the appropriate thermal conduction,but there is a heat limit.(4)The formation conditions of single longitudinal mode and double longitudinal mode are analyzed theoretically,and the temperature characteristics and spectrum matching of microchip laser are studied experimentally.The experiment results show that the power of single mode laser has a approximate negative linear relationship with the controlled temperature,for each 10 °C rise in controlled temperature,the laser power drops by about 18%.The wavelength of laser has linear relationship with the controlled temperature,the excursion rate in single mode laser is 9.4 nm/°C,and the excursion rate in double mode laser is 10.9 nm/°C,the feasibility of linearly shifting the laser wavelength is thus determined,and it is confirmed that thermal conductivity is not affected by temperature.Spectrum matching of single mode laser can be maintained when the pump current and temperature-controlled temperature satisfy a specific linear relationship: dT_o/dI=-16.8 °C/A.