Simultaneous Light-Hole and Heavy-Hole Emission from an Intra-Cavity Contact Cryo-VCSEL with Dual-Wavelength Operation

The first demonstration of a single-active-region vertical-cavity surface-emitting laser (VCSEL) exhibiting dual-wavelength lasing under cryogenic operation is reported. At temperatures below 40 K, and most prominently at 8 K, the device emits at 830 nm and 867 nm from the same electrically pumped InGaAs quantum well active region. Through combined optical modeling, edge-emitting electroluminescence spectroscopy, polarization-resolved measurements, and k\cdot p-band structure analysis, we show that the two lasing wavelengths originate from distinct recombination pathways involving light-hole and heavy-hole transitions, respectively. Remarkably, the two wavelengths correspond to longitudinal cavity modes that are respectively anti-resonant and resonant with the quantum well gain region, demonstrating that conventional standing-wave gain enhancement is not a prerequisite for lasing in cryogenic VCSELs. The observed behavior is enabled by strong spectral broadening and increased radiative efficiency at cryogenic temperatures, which allow higher-order quantum well transitions to contribute significantly to laser gain. These results establish a new operating regime for VCSELs at cryogenic temperatures and open a route toward compact multiwavelength cryogenic VCSEL sources for wavelength-division multiplexed optical links in cryogenic computing and quantum information systems.