Design principles for high-power single-mode diode lasers are presented with emphasis on the design of constricted double-heterojunction large-optical-cavity (CDH-LOC) devices. In the CDH-LOC structure the lateral geometry allows oscillation in relatively large spots (1.7 µm × 7 µm), while providing strong discrimination against high-order mode operation via "anti-guiding" losses. Thus, operation in a single mode (spatial and longitudinal) is recorded to 40 mW/facet cw, the highest single-mode power ever reported for semiconductor lasers. Under 50% duty-cycle conditions, single spatial mode operation is recorded to 100 mW/facet. The beams have no astigmatism and typical half-power full widths of

. Preliminary room-temperature lifetests at 40 mW/facet initial power and 50% duty-cycle show relatively small changes after 10,000 hours of operation. For comparison, results from other types of high-power single-mode devices are presented and discussed.