Highly efficient, diode-pumped, Q-switched Nd:YLF laser using an unstable resonator

We have developed a highly efficient Q-switched Nd:YLF oscillator. To achieve maximum electrical to optical efficiency in the Q-switched laser we use a side pumped, total internal reflection configuration and an unstable resonator with a uniform reflectivity output coupler. We believe that this is the first demonstration of a solid state laser using an unstable resonator with a uniform reflectivity output coupler or a TIR bounce configuration. Use of the uniform reflectivity output mirror is made possible by the TIR bounce configuration which eliminates all hard apertures within the cavity and thus the need for a graded reflectivity output coupler. This configuration allows for maximum energy extraction efficiency from the oscillator by providing for maximum and automatic overlap between the resonator mode and the stored energy. To date we have demonstrated 40% optical to optical efficiency in the long pulse mode with a flat top transverse profile.