Minimum temperature sensitivity of 1.55 μm vertical-cavity lasers at -30 nm gain offset

Double-fused vertical-cavity surface-emitting lasers (VCSELs) have demonstrated the highest temperature performance of any 1.5 mu m VCSEL, but further optimization is needed to reduce their temperature sensitivity, We present and analyze threshold current measurements of these devices between -90 degrees C and 30 degrees C stage temperature, Despite a zero gain peak offset from the emission wavelength at room temperature, the pulsed threshold current has its minimum near -50 degrees C corresponding to about -30 nm gain offset, This is in contrast to a common VCSEL design rule. Temperature effects on the optical gain of the strain-compensated InGaAsP/InP active region are found to be the main cause for the disagreement. A design rule modification is proposed. Numerical simulation of an optimized 1.55 mu m VCSEL shows that gain offset improvements are counteracted by loss mechanisms, (C) 1998 American Institute of Physics.