Nanosecond pulse, injection laser bar stack driver

Injection laser diode bars consisting of 50 or more injection lasers in parallel are used primarily for pumping of solid state lasers such as Nd:YAG. These injection laser bars are commonly stacked in electrical series to increase the conduction voltage drop. The bar stacks are commonly pulsed for several hundred microseconds such that the average optical power from an individual laser bar is on the order of tens of watts. A ten-bar stack thus produces a relatively steady state optical power on the order of 100 watts. The thermalization or temperature equalization time for the energy dissipated in the injection laser structure and the thermal energy removed via a cooling system is on the order of 200 ns. This paper describes the design of a very high speed driver for an injection laser bar stack that produces a 10 ns pulse with less than I ns rise and fall times. The current and optical pulse length is much less than the time required for the laser structure to reach equilibrium so that the laser´s output power and thus the thermal dissipation can exceed that possible in the steady state conditions. In this manner, the laser bar stack can produce a peak optical power of over 1000 watts. The circuit design and modeling are presented and components for the circuit are specified.