Flip-chip bonded, back-emitting, microlensed arrays of monolithic vertical cavity lasers and resonant photodetectors

We present flip-chip bonded arrays of monolithically integrated vertical-cavity lasers (VCLs) and resonant photodetectors. The VCLs and photodetectors are integrated using a novel structure that allows through-the-substrate emission and detection without compromising device performance. Substrate-side microlenses have been integrated to take advantage of the through-the-substrate architecture. Flip-chip bonded VCLs exhibit threshold currents as low as 135 μA with differential efficiencies of 53%. The detectors have the same operating wavelength as the VCLs and responsivities of 0.48 A/W, corresponding to 60% absorption, with optical bandwidths of 7 nm. The VCLs exhibit maximum small-signal modulation bandwidths, which are limited by parasitics, of ~9.5 GHz at 20°C and ~8.4 GHz at 70°C. The VCLs have the lowest reported bias currents required to reach bandwidths of up to ~8 GHz. A free-space optical link is demonstrated with these flip-chip bonded arrays of microlensed, monolithically integrated VCLs and detectors. The link is found to be tolerant to temperature differences of ±75°C between the VCL and detector, with error free (BER<10^-12) data transmission demonstrated in each case