This paper describes the design of polarization insensitive InP-based arrayed waveguide gratings (AWGs), and the characteristics of fabricated devices. The use of a deep-ridge waveguide structure made the fabrication of compact polarization-insensitive AWGs possible. As a result, a low crosstalk (-30 dB) 8-channel AWG and a large-scale (64 channel) AWG with 50 GHz channel spacing could be fabricated. An integrated circuit containing an 8-channel AWG with photodetectors is also described.

We studied three types of lasers emitting narrow beam divergence of output light: 1) a spot-size converter integrated laser diodes (SS-LDs) with a vertically tapered waveguide, 2) one with a laterally tapered waveguide, and 3) one consisting of a small cross section of active region. We compared them with regard to their performance in coupling efficiency to a cleaved single mode fiber, threshold current, output power, and reliability. Both the spot-size converted integrated lasers with vertically and laterally tapered waveguide repeatedly provided low threshold currents of as low as 6 mA and low coupling loss to the fiber of 1.2 to 2.5 dB in two inch wafer processes. As a result of the aging test, the SS-lasers were predicted to have the same degradation rate as a conventional buried heterostructure laser. The laser having a small cross section of active layer also has low coupling loss and high efficiency up to 85.