Single-mode semiconductor lasers fabricated by standard photolithography for direct modulation.

The output characteristics, modal properties, far-field profiles, and dynamic modulation responses of semiconductor lasers with surface higher-order gratings fabricated by the standard photolithography are presented. Single-mode semiconductor lasers with 20th- and 37th-order gratings for the 1.55 µm wavelength range are realized. The single-mode semiconductor lasers with 20th-order gratings have lower threshold currents and higher slope efficiencies than those with 37th-order gratings. The surface higher-order grating placed closed to the output facet can deteriorate the vertical far-field profile of the semiconductor laser. However, the properties of the semiconductor laser's single-mode operation are not affected by the surface higher-order grating's position in the ridge waveguide. The -3 dB bandwidth of these single-mode semiconductor lasers can achieve 9 GHz at 100 mA, which is the highest, to the best of our knowledge, for such a kind of single-mode semiconductor laser with a surface higher-order grating.