Broadband 2-μm superluminescent diodes with GaSb-based variable-thickness quantum wells

A GaSb-based superluminescent diode (SLD) operating near the 2-μm wavelength region, employing quantum wells with variable thicknesses to achieve broadband emission, is reported. The gain region incorporates two Ga_0.73In_0.27Sb/Al_0.27Ga_0.73As_0.02Sb_0.98 quantum wells with identical composition but significant difference in the thicknesses of 7 and 13 nm, exhibiting broadband amplified spontaneous emission. To minimize reflections from the output facet and to enable operation at high current injection, we employed a J-shaped ridge waveguide. For an injection current of ∼200 mA, the device delivers a continuous-wave output power of ∼1.2 mW at room temperature exhibiting a bimodal emission spectrum with a combined bandwidth of ∼132 nm. Increasing the injection current to 1000 mA results in a maximum output power of ∼40 mW, accompanied by emission bandwidth narrowing to ∼40 nm. In general, the broad amplified spontaneous emission spectrum demonstrates the capacity of variable-thickness quantum wells to further engineer the emission properties extending the bandwidth and the output power in GaSb-based SLDs and opens a path for practical applications in advanced optical coherence tomography, spectroscopy, and microscopy.