Oxide-relief and Zn-diffusion 850-nm vertical-cavity surface-emitting lasers with extremely low energy-to-data-rate ratios for 40 Gbit/s operations

We demonstrate novel structures of a vertical-cavity surface-emitting laser (VCSEL) for high-speed (∼40 Gbit/s) operation with ultralow power consumption performance. Downscaling the size of oxide aperture of VCSELs is one of the most effective ways to reduce the power consumption during high-speed operation. However, such miniaturized oxide apertures (∼2 μm diameter) in VCSELs will result in a large differential resistance, optical single-mode output, and a small maximum output power (< 1 mW). These characteristics seriously limit the maximum electrical-to-optical (E-O) bandwidth and device reliability. By the use of the oxide-relief and Zn-diffusion techniques in our demonstrated 850-nm VCSELs, we can not only release the burden imposed on downscaling the current-confined aperture for high speed with low-power consumption performance, but can also manipulate the number of optical modes inside the cavity to maximize the E-O bandwidth and product of bit-rate transmission distance in an OM4 fiber. State-of-the-art dynamic performances at both room temperature and 85 °C operations can be achieved by the use of our device. These include extremely high D-factors (∼13.5 GHz/mA ^1/2), as well as record-low energy-to-data ratios (EDR: 140 fJ/bit) at 34 Gbit/s operation, and error-free transmission over a 0.8-km OM4 multimode fiber with a record-low energy-to-data distance ratio (EDDR: 175.5 fJ/bit.km) at 25 Gbit/s.