VCSEL Design Boosts Speed, Power

Semiconductor lasers have become one of the most important enablers of photonics-based technologies, allowing for indispensable science and a wide range of technologies. Vertical-cavity surface-emitting lasers (VCSEL), a critical class of semiconductor lasers, are gaining importance for their use as an optical source in high-speed, short-wavelength communications and sensors due to their form factor and optoelectronic performance.

Researchers present and demonstrate a new design of a VCSEL combining MTCCs, to improve slow-light optical feedback and thus extend the temporal laser bandwidth (speed) beyond the relaxation oscillation frequency limit.

They propose and demonstrate that a VCSEL cavity surrounded by MTCCs adiabatically provides direct slow-light feedback from each TCC to the main lasing cavity in their design. As a result, even if the direct feedback from each cavity is only moderate, it will redistribute the optical field density by funneling the slow-light mode into the central cavity, allowing sufficient feedback to be generated to extend the temporal laser bandwidth (speed).

Using this coupled cavity scheme, they demonstrate a modulation bandwidth in the 100 GHz range. They validate this novel laser design paradigm by demonstrating a VCSEL design using a hexagonal multi-cavity approach with a bandwidth of about 45 GHz, which is approximately five times better than ‘conventional’ VCSEL designs realized on the same wafer. Beyond speed, the MTCC paradigm can increase laser power output; for high-power single-mode operation, the Vernier effect in the hexagonal VCSEL can form a wider laser aperture.

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