GaAs DH injection laser (refractive index: 3.6) has an optical cavity of length 50 μm and width 20 μm. At normal operating temperature (300 K) the loss coefficient is 10 cm-1, the mirror reflectivity at each end of the optical cavity is 0.3 and the gain factor for the device is 3.76x10-2 cm/A. The device emits at a wavelength of 870 nm. 1.1 Calculate the frequency separation of the longitudinal modes and the number of longitudinal modes emitted by the device. 1.2 Determine the current threshold for the device at 300 K. 1.3 Determine the required threshold current when the diode is operated at a temperature of 60˚C.

GaAs DH injection laser (refractive index: 3.6) has an optical cavity of length 50 μm and width 20 μm. At normal operating temperature (300 K) the loss coefficient is 10 cm-1, the mirror reflectivity at each end of the optical cavity is 0.3 and the gain factor for the device is 3.76x10-2 cm/A. The device emits at a wavelength of 870 nm. 1.1 Calculate the frequency separation of the longitudinal modes and the number of longitudinal modes emitted by the device. 1.2 Determine the current threshold for the device at 300 K. 1.3 Determine the required threshold current when the diode is operated at a temperature of 60˚C.