The use of vertical-cavity surface-emitting lasers (VCSEL's) for optical detection of atmospheric oxygen is described. The VCSEL's were custom designed for single-mode emission in the 763-nm wavelength range, with low noise and narrow optical linewidth. Using standard wavelength modulation spectroscopy and a second-harmonic detection scheme with a 1-m air path, we determined an oxygen concentration resolution of 0.2%. Because of its small size, low power dissipation, and good tunability characteristics, the VCSEL promises to be an attractive light source for use in compact, low-cost optical sensor microsystems for trace gas detection.

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Coupled arrays of vertical-cavity surface-emitting lasers were realized by patterning the reflectivity of the top-distributed Bragg reflector using a phase-matching layer and a metal grid. For improved current injection and better heat dissipation the devices were selectively oxidized. Continuous-wave room-temperature operation of these arrays has been achieved at 960 nm. Near- and far-field measurements confirm the phase-coupling in a typical out-of-phase mode pattern. Analysis of the differential efficiency reveals a strong decrease when the number of lasing pixels and hence the mesa size is increased.

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