Extended tuning and single-mode operation of an anti-reflection-coated InGaN violet laser diode in a Littrow cavity

An InGaN laser diode operating at 398 nm and with output facet coated with a multi-layer anti-reflection coating has been operated within Littrow external cavities. A maximum manual tuning range of 6.3 nm has been achieved and a continuous tuning range of 0.8 GHz with a single piezo control. Stable single-longitudinal-mode operation has been obtained with a linewidth less than 11 MHz. The effects on total tuning range due to the orientation of the diode output facet within the Littrow cavity are discussed.