Room-temperature mid-infrared interband cascade vertical-cavity surface-emitting lasers

We report interband cascade vertical-cavity surface-emitting lasers (ICVCSELs) that operate in pulsed mode at temperatures up to 70 degrees C. Their emission at lambda approximate to 3.4 mu m extends considerably the previous longest wavelength of 3.0 mu m for an electrically-pumped vertical-cavity surface-emitting laser operating at room temperature. The output from mesas having diameters ranging from 30 to 60 mu m (with emission aperture diameters of 20-50 mu m) is circularly symmetric, and the threshold current densities at T = 25 degrees C are as low as 390 A/cm(2). However, the differential slope efficiencies are low, e.g., <= 50 mW/A at T = 25 degrees C, due to loss in the top and bottom mirrors and reduced current efficiency. The smallest device operates in a single spectral mode despite having an emission aperture much wider than the wavelength.