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Output Characteristics of a Semiconductor Laser Diode with Double Ring Cavities and a Y-Junction Coupler

We demonstrated an InGaAlP multiple-quantum-well semiconductor laser diode with double circular ring cavities and its output characteristics. It was found that the optical confinement factor of the ridge waveguide plays an important role in the output emission of this device, and superluminescence emission can be achieved with a low-confinement ridge waveguide. Spatial solitons can be generated in the ridge waveguide of 8 µm width and 0.9 µm depth owing to a nonlinear photorefractive effect. When the injection current in the circular ring cavity increases, the feedback light from the Y-junction coupling section continuously enhances the excitation through the soliton waveguide. In addition, the double-ring cavities provide wavelength filtering and feedback control from the Y-junction coupling section to achieve a superluminescent mode or lasing mode output operation. Results of light–current (L–I) and spectral measurements of the devices with various waveguide properties were presented to explore the mechanism of the output from this circular ring laser diode.