High-power semiconductor red laser arrays for use in photodynamic therapy

Semiconductor laser ridge arrays emitting 250 mW at a wavelength of 635 nm are designed for photodynamic therapy applications. Although ridge laser arrays are less efficient than broad area lasers, they are more reliable and can produce higher power from the same lateral width due to thermal considerations. An analytic expression for the active layer temperature of the laser array as a function of the ridge spacing, number of ridges, and width is derived and has excellent agreement with a finite-element analysis. This analytic expression allows optimization of the laser and the submount geometry to minimize the active region temperature with the constraint of a small submount, heat sink, and package.