Edge-pumped Composite Power Amplifiers

Advanced amplifier designs that are durable, efficient, light weight, and compact are required for the next generation heterodyne laser radar systems such as the Advanced Discriminating Ladar Technology Program. We propose to address the need for improved amplifier technology through the use of a side-pumped composite structure to convert low brightness pump sources into usable population inversion. The pump sources will be coupled to the laser medium crystal using simple optics and scaling of the pump power will be achieved by using stacked diode laser bars. One potential component of the composite structure, ceramic Nd:YAG, will allow for flexibility in the active ion doping density (up to 6% Nd) for efficient pump absorption over short lengths. In our proposed design, heat is removed from the composite laser structure by direct contact to heat sinks; flowing liquid contacting the crystal is not required as it is in many high-average-power laser schemes, allowing the use of a wide variety of cooling techniques. Thermal lensing, which can cause aberration of the output beam, is kept low by spreading the heat load over a large area and minimizing the distance between the heat load and heat sinks.