Strong Wavelength Detuning of 850 nm Vertical-Cavity Surface-Emitting Lasers for High-Speed (>40 Gbit/s) and Low-Energy Consumption Operation

Abstract

The strong (>20 nm) wavelength detuning technique has been demonstrated to enhance the modulation speed and high-temperature characteristics (at 85 °C), as well as lower the required driving current density performance of oxide-relief 850-nm vertical-cavity surface-emitting lasers (VCSELs) for >40 Gbit/s operation. By increasing the wavelength detuning from 15 to 20 nm, a significant improvement in the electrical-to-optical (E-O) bandwidth (20 to 27 GHz) of the VCSEL can be observed. This detuning design (∼20 nm) is incorporated along with a Zn-diffusion structure into our oxide-relief VCSEL with a miniaturized oxide-relief aperture (∼3 μm). Highly single-mode, high-speed (26 GHz) operation, and moderate differential resistance (100 Ω) values can be simultaneously achieved. In addition, it is found that devices with a further larger detuning wavelength (>20 nm) and enlarged oxide-relief apertures (∼8 μm) can sustain the same maximum E-O bandwidth (26 GHz) as that of a miniaturized (∼3 μm) VCSEL, resulting in the lower driving current density (8 versus 18.8 kA/cm2) required for high-speed performance. Excellent transmission performance, which includes an extremely low energy-to-data rate ratio (EDR: 228 fJ/bit; over 100 m OM4 fiber) and record-low driving-current density (8 kA/cm2; 3.5 mA) has been successfully achieved for 41 Gbit/s error-free transmission for these VCSELs.