At Yokohama National University in Hodogaya, Japan, researchers have demonstrated that the application of a Bragg grating to a microdisc laser enables the device to operate with a threshold of 17 µW and to display a quality factor (Q) of 4300. They reported the development in the March 25 issue of Applied Physics Letters.The team employed inductively coupled plasma etching and selective wet etching to create 16- to 24-line gratings around the circumference of the 2.2- to 3.2-µm-diameter GaInAsP/InP discs, creating "microgear" structures. A 980-nm laser diode served as the pump source. The addition of the Bragg grating decreased the threshold of the device by 33 percent and increased its Q by 43 percent, compared with an unetched microdisc laser.