VCSELs with nonuniform multiple quantum wells for a very wide temperature range of CW operation

Summary form only given. The temperature range over which CW operation of vertical-cavity surface-emitting lasers (VCSELs) exhibit a low current threshold can be extended by broadening the gain spectrum. This can be achieved through the use of nonuniform multiquantum wells (MQWs) in the active region, which allows the lasing mode to be aligned to the gain peak over a wider range of temperatures. To achieve efficient lasing operation, it is essential that the gain of each quantum well be sufficiently high to compensate for the reduced gain contributions from other wells at the lasing wavelength. This is easily satisfied at lower temperatures, where the differential optical gain is significantly increased and the quantum efficiency is high (>80%). We have previously demonstrated efficient CW lasing operation at cryogenic temperatures (6 K to 250 K) using a VCSEL with uniform multiple quantum wells that achieved optimal gain-mode alignment at /spl sim/100 K. By use of multiple quantum wells of different thicknesses (nonuniform MQWs), and thereby obtaining a broadened gain spectrum, the CW performance of the laser has improved and the overall temperature range of operation has increased.