Investigation of Mid-Infrared Type-Il 'W' Diode Lasers

摘要

We report an experimental investigation of 16 different mid-infrared diode laser samples with type-II "W" active regions.A number of design modifications were employed to study effects on the I-V characteristics,lasing threshold,and wallplug efficiency.Contrary to expectations,the threshold current density at low temperatures did not vary significantly with the number of active quantum-well periods,nor was there any clear correlation between lasing threshold and photoluminescence intensity.A shorter-wavelength device (3.2-3.6 mum) produced >500 mW of cw power at 80 K,and a second device displayed a wallplug efficiency >10%.The maximum lasing temperature was 317 K for pulsed operation and 218 K for cw operation.At T = 100 K,cavity-length studies indicated an internal loss of 7 cm~(-1) and nominal internal efficiency of 96%.Hakki-Paoli measurements of the gain spectrum implied an intrinsic line width enhancement factor of approx 1.3,which slightly exceeds the theoretical prediction.Longer-wavelength devices (lambda approx = 3.8-4.5 mum) showed similarly low threshold current densities at T = 80 K but degraded more rapidly with increasing temperature.