Semiconductor optical amplifier using energy from single-transverse-mode vcsels to amplify optical signal

Abstract

A vertically lasing semiconductor optical amplifier (SOA) apparatus for amplifying an optical signal and related methods are described. The SOA comprises an integrated plurality of vertical cavity surface emitting lasers (VCSELs) having a common gain medium layer, and a signal waveguide extending horizontally through the VCSELs near the gain medium layer such that the optical signal is amplified while propagating therethrough. Although integrated onto a common substrate, the VCSELs are functionally isolated from each other, each building up its own distinct lasing field responsive to a distinct electrical pump current therethrough. Each VCSEL is configured and dimensioned to achieve smooth, single transverse mode lasing action for promoting spatially uniform and temporally stable gain of the optical signal as it propagates along the signal waveguide. Preferably, the SOA comprises several dozens to several hundreds of functionally isolated VCSELs, each providing only a small portion of the overall signal gain. If a local defect arises during device fabrication that causes a hot spot or other lasing non-uniformity to occur at nominal bias levels, the spatial and operational scope of that defect is limited to its particular VCSEL, with overall device performance being reduced by only a minor amount.