High-power single mode GaSb-based 2 μm superluminescent diode with double-pass gain

Abstract

We report a broadband superluminescent diode operating around a 2 μm wavelength, optimized for high-power broadband operation. The high power operation is achieved by using a GaInSb/AlGaAsSb heterostructure positioned in a ridge waveguide with a J-shaped layout to form a double-pass geometry. To avoid lasing at high current while enabling high gain, a cavity suppression element is used. This combination allows demonstration of an output power as high as 120 mW for continuous-wave (CW) operation at room temperature, with a spectral full width at half maximum of about 43 nm. The maximum power spectral density was measured to be 1.8 mW/nm, which is about a fourfold increase compared to the state-of-the-art results for this wavelength range. To avoid heating, the diode was also driven with low duty-cycle current pulses; in this case, a peak power of more than 300 mW was achieved without any sign of roll-over (power was limited by the current injected). For CW operation, the central emission wavelength could be tuned by current injection between 1900 nm at 200 mA and 2027 nm at 2000 mA. Devices produce a Gaussian output beam that is suitable for coupling to single mode waveguides.