Abstract

Dense wavelength-division multiplexing (WDM) is a promising approach to the improved utilization of the terahertz capacity of optical fibers for which integrated laser arrays with uniform wavelength separations are necessary. Because of its two-dimensional integrability, a surface-emitting laser array can greatly increase the number of channels that can be wavelength multiplexed. Two-dimensional VCSEL arrays with uniformly graded emission wavelengths have been achieved by using molecular beam epitaxial (MBE) growth techniques and have been used in WDM system demonstrations.1 We have shown that because of MOCVD's unique ability to continuously grade all the hetero-interfaces, it can produce VCSELs with a significantly lower series resistance and thermal dissipation, which is important to the realization of a dense VCSEL array. Here we report the first demonstration, to our knowledge, of spatial grading of MOCVD grown VCSEL emission wavelength. By using two-dimensional spatial mappings of reflectance spectra we have seen gradients of 16 nm/cm over a square centimeter area. Through tracking the positions of the cavity mode and of the reflection band and comparing them to theoretical results, the relation between wavelength shifts in the reflectance spectra and the variations in the thickness of the layers is determined. This data was used in our predictions of and comparison with the experimental lasing wavelengths of individually pumped VCSELs.

© 1992 Optical Society of America