Quantum-well semiconductor laser based on a dumbbell-taper-enhanced optical field for optical frequency combs

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Optical frequency combs (OFCs) with precise line spacing play a crucial role in modern optical communication systems.We propose and fabricate a dumbbell-shaped-taper (DST) quantum-well laser diode that generates a frequency-modulated (FM) optical frequency comb.Effective control of the optical field distribution can be achieved by adjusting the ridge width.In the ridge design, the wide section delivers high optical gain and a broadband spectral output, while the narrow section simultaneously serves as a high-order lateral-mode filter and provides strong optical nonlinearity.Compared with a conventional Fabry-Pérot structure, the device achieves an output power of 48 mW at a drive current of 420 mA and expands the 3 dB spectral bandwidth to 0.90 THz, along with a notable reduction in radio frequency linewidth.Relying on a quantum-well active region, this design avoids complex epitaxial engineering and furnishes a low-cost, high-power, and broadband OFC source.