Fabrication and performance of InGaAlAs MQW distributed Bragg reflector lasers with grooved surface gratings formed by reactive beam etching

Abstract

Grooved surface grating distributed Bragg reflector lasers were fabricated by reactive beam etching after one-step growth of an InGaAlAs multiquantum well active layer and an InP cladding layer. A first-order diffraction grating with a 240 nm period was formed by utilising grooves etched into the cladding layer. The groove depths range between 550 to 900 nm. Single longitudinal mode operation was achieved for devices at all groove depths. DBR lasing with output power of up to 10 mA was obtained. The dependence of the lasing wavelength on device temperature is about 0.1 nm/°C, which indicates the same good stability as standard DBR/DFB lasers. Lasing performance (i.e. injection current against output light power and emission spectra) is discussed in terms of the groove depth of the grating. The relationship between the lasing wavelength shift and the groove depth was examined. The coupling coefficient of the Bragg reflectors are estimated to be about 80 – 180 cm-1 by using the relation between the threshold current density and the reflectivity of the laser cavity mirror.