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

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Abstract
Cryogenic optical data links require an efficient optical source with temperature-insensitive continuous-wave (CW) operation at low temperatures. Also, to simplify optical alignment, it is desirable to obtain CW operation over a broad temperature range that spans both the low and high temperatures. By the use of vertical-cavity surface-emitting lasers (VCSELs) with chirped (nonuniform) multiple quantum wells (MQWs) to broaden the optical gain spectrum, CW operation has been achieved from 5-350 K, with improved characteristics in both the high- and low-temperature regimes. In particular, temperature-insensitive, submilliampere threshold current was achieved at temperatures from 5-50 K, with a threshold current density of 350 A/cm/sup 2/, and a threshold voltage that is below 3 V.