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 RF linewidth. Relying on a quantum-well active region, this design avoids complex epitaxial engineering and furnishes a low-cost, high-power, broad-band OFC source.