1.3-$\mu$ m Laterally Tapered Ridge Waveguide DFB Lasers With Second-Order Cr Surface Gratings

We report the laterally tapered ridge waveguide InGaAsP-InGaAsP multiple quantum-well distributed-feedback (DFB) lasers with metal surface gratings, operating at λ ~1.3 μm, by holographic lithography. Single-tapered and double-tapered (bow-tie) ridge waveguide DFB structures with second-order Cr surface gratings are employed to enhance the coupling efficiency. The 600-μm-long laterally coupled DFB laser with a double-tapered ridge waveguide structure exhibits significantly improved single-mode operation without mode hopping, with a maximum sidemode suppression ratio of 42 dB and temperature-dependent wavelength shift up to d λ/dT ~0.071 nm/K.