Uncooled 100-GBaud Directly Modulated Membrane Lasers on SiC Substrate

We investigate the temperature dependence of the dynamic characteristics of a 1.3-μm InGaAlAs-based directly modulated membrane laser on a SiC substrate. The laser is fabricated by combining direct wafer bonding of SiC and InP substrates using a very thin (∼10 nm) oxide layer and epitaxial regrowth of a membrane InP layer on the InP/SiC template. The membrane laser structure on SiC with a high thermal conductivity (490 Wm
⁻¹
K
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) and a moderate refractive index (∼2.6) ensures both high thermal dissipation and a large optical confinement factor in the active region, which are ideal for increasing the relaxation oscillation frequency even at high operating temperatures. We further leverage the optical feedback effect from the output facet of a waveguide to enhance the bandwidth and enable signal modulation at 100 GBaud and beyond. Owing to the high relaxation oscillation frequency and the photon-photon resonance effect, it is possible to obtain a flat frequency response at temperatures ranging from 25 to 85 °C. The fabricated membrane laser on SiC with an active-region length of 50 μm exhibits 3 dB bandwidths of >110, 97, and 74 GHz at 25, 55, and 85 °C, respectively. We successfully demonstrate 2-km transmissions of 100-Gbit/s NRZ signals under uncooled conditions (25 to 85 °C). Furthermore, the laser is capable of 112-Gbit/s NRZ modulation at 85 °C.