Modulation and free-space link characteristics of monolithically integrated vertical-cavity lasers and photodetectors with microlenses

We present temperature, modulation, and free-space link characteristics of monolithically integrated vertical-cavity lasers (VCLs) and resonant photodetectors. The devices have been integrated using a novel structure that makes it possible to fabricate devices with through-the-substrate emission and detection. Taking advantage of the substrate emitting/detecting architecture, we monolithically integrate microlenses on the substrate side of the devices and flip-chip bond arrays without via processes or substrate removal. Low-threshold high-efficiency VCLs exhibit maximum small-signal modulation bandwidths, which are limited by parasitics, of /spl sim/9.5 GHz at 20/spl deg/C and /spl sim/8.4 GHz at 70/spl deg/C. The VCLs have the lowest reported bias currents required to reach bandwidths of up to /spl sim/8 GHz. A free-space optical link is demonstrated with flip-chip-bonded arrays of microlensed, monolithically integrated VCLs and detectors. The link is found to be tolerant to temperature differences of /spl plusmn/75/spl deg/C between the VCL and detector, with error free (BER<10/sup -12/) data transmission demonstrated in each case.