Repetitive Mode-Locking in Thermally Compensated Phosphate Glasses at 5 Hz and Above

Abstract

The passively mode-locked Neodymium (Nd)-glass laser is an important source of high energy pulses for studies requiring temporal resolution below the 25 ps obtainable with Nd-YAG. On the other hand, the thermal conductivity of glass is over an order of magnitude smaller than that of YAG, and previous studies involving glass lasers have encountered thermal distortions and damage as repetition rates were increased beyond 0.2 Hz (1 to 10 pulse trains per minute) [1,2]. In addition, the low cross-section for stimulated emission and, also, the low dye concentrations required to avoid self-focusing and rod damage have caused irreproducible mode-locking with “misfirings” and multiple pulsing. As a result many experimentalists have turned from glass, its shorter pulses notwithstanding, and have elected to use YAG with its higher data rate, in order to reduce set up and alignment time, increase the size of statistical samples obtainable within realistic time limits, and improve detectivity through better signal-to-noise discrimination.