1.55 μm single mode lasers with complex coupled distributed feedback gratings fabricated by focused ion beam implantation

Complex coupled GaInAsP/InP distributed feedback lasers were developed based on maskless focused ion beam lithography. By combining implantation enhanced wet chemical etching and implantation induced thermal quantum well intermixing a refractive index grating was defined self-aligned to a gain grating forming a complex coupled grating lateral to a ridge waveguide. The devices show single mode emission at wavelengths around 1.55 μm with linewidths ≪2 MHz and side mode suppression ratios of more than 40 dB for continuous wave operation at room temperature. A high single mode yield (≫90%) over a large tuning range (88 nm) was achieved. © 1999 American Institute of Physics.