SBIR-STTR Award

Optical Concepts, Inc. will use arrays consisting of one reference laser, and many signal lasers which are frequency offset locked to the reference, with different offsets. In this way, 10 or more channels can occupy a bandwidth of less than one nanometer, and the lasers can be tuned by small adjustments in bias current. Wavelength shifts of 1-2 nm in adjacent arrays can be fabricated by step-etching prior to top mirror deposition, as described in this report. In this way, large VCSEL arrays could ultimately provide densely-spaced channels covering the Erbium amplifier band. Realization of this system requires advancing the state of long-wavelength VCSELs, using design procedures described in this proposal. It also requires specifying power and linewidth requirements for these lasers, based on system calculations.

Phase I explored the feasibility of using long-wavelength vertical-cavity surface-emitting lasers (VCSELs) as sources in a densely spaced frequency-division multiplexed communication system. In this system, the subcarrier frequencies can extend up beyond 100 Ghz, limited by the speed of detectors, rather than by the modulation speed of laser. To extend the number of channels beyond the highest subcarrier, multiple groups of N lasers each can be used, centered at different optical wavelengths. For subcarriers up to 50 Ghz, we concluded that microwave circuitry could be purchased commercially, and detectors could be manufactured using existing techniques for InP/InGaAs pindiodes. Phase II will focus on realizing low-cost baseband and/or SCM digital systems using long wavelength VCSELs.