The University of British Columbia

Tremendous improvement in the performance of directly modulated 1.55 um Vertical Cavity Surface Emitting Lasers (VCSELs) has been obtained by using the Optical Injection Locking (OIL) technique. OIL uses a second laser to inject photons at a similar wavelength into the transmitter laser; the transmitter laser is thus locked (in wavelength and phase) to the master due to the coherent non-linear interaction in the cavity, which leads to significant changes in the dynamic properties of the laser. Specifically, the resonance frequency can increase from 5 GHz to over 50 GHz, thereby increasing the modulation bandwidth. Recently, our group has discovered that an OIL-VCSEL can function as a receiver, while the VCSEL forward-biased. This is a surprising effect, particularly since conventional reverse-biased VCSEL structures show a low responsivity and bandwidth. We have observed a small-signal modulation bandwidth of 20 GHz, and experimentally demonstrated large-signal digital modulation with a data-rate up to 12 Gb/s. Under an identical forward-bias condition, the OIL-VCSEL can function both as a transmitter and as a receiver, potentially with a similar bandwidth enhancement as previously reported for the transmitter case. This exciting discovery opens the possibility of high-speed bi-directional optical interconnects using a single directly-modulated laser.