Temperature Control And Its Applications In SHG For All Solid-state Laser

Laser diode pumped all-solid-state laser and its frequency doubling is one of the mostimportant subjects in laser technology, which have potential applications in scientific research,industry, information and military areas. In high average power lasers, local heating offrequency doubling crystals induce by the residual absorption at the interacting frequenciesleads to the destruction of the perfect phase-matching condition, which drastically reduces theconversion efficiencies and stability of the second-harmonic generation. Frequency doublingefficiency and its stability depends on many factors, such as frequency doubling crystals andthe environment, of which the temperature varying in the crystals is the key factor[1]. Thetemperature stabilization and control and its application to the frequency doubling experimentare mainly discussed in this thesis. Self-heating effects in the double-axes crystal is analyzed using 2 D stable-state heatconduction equation and the temperature distribution in the crystals with laser turn-on isanalyzed. The simulation of temperature distribution in KTP crystal is given at differentcooling condition, different pumping power and different aperture, and how temperatureaffects the crystal refractive index is derived. The dependence of KTP crystal optimalphase-matching angle with temperature is calculated. A temperature control system for frequency doubling crystal in laboratory, which couldbe redeveloped, is developed by use of semiconductor cooler TEC to adjust the temperatureand an integrated temperature sensor AD590 as the temperature measurement component. Thecontrol circuit design, including circuit parameters calculation, architecture, systemintegration and system calibration, is analyzed in detail. The system has a temperatureaccuracy of 0.1 ℃. The temperature control system is successfully used in our LD pumped all-solid-statelaser frequency doubling experiment. With KTP crystal and at the fundamental wavelength of1064nm , SHG output power and stability change drastically with temperature, but has amaximum power when the temperature stabilized at 23 ℃.