Directly Reflectivity Modulated Laser

Directly modulated lasers (DMLs) have been widely employed in data centers and other short-reach interconnect applications, thanks to their low cost and low power consumption. Nevertheless, these lasers have small wavelength tuning ranges and are limited to produce only intensity-encoded optical signals through modulating the gain in the active region. Therefore, it is difficult to use them in metro/long-haul applications, where tunable lasers and coherent modulation formats are preferred. In this paper, we propose and demonstrate a novel directly reflectivity modulated laser (DRML), which overcomes these limitations by modulating the reflectivity of the cavity mirror of a wavelength tunable laser. The DRML can offer wide wavelength tunability, low-chirp, and high-speed operation, and allows pure phase modulation. More importantly, the DRML still keeps the key benefit of traditional DMLs by requiring low RF drive powers. We experimentally demonstrate a DRML based on a hybrid silicon/III-V platform. About 25/40 Gb/s on-off-keying and 25 Gb/s binary phase-shift keying signals are generated and the wavelength tunability is >20 nm. This device shows a great potential for both short-reach and long-reach optical communications.