Semiconductor optical amplifier monolithically integrated with an electroabsorption modulator and dual-waveguide spot-size converters

We have demonstrated an electroabsorption modulator and semiconductor optical amplifier monolithically integrated with novel dual-waveguide spot-size converters (SSC) at the input and output ports for low-loss coupling to planar light-guide circuit silica waveguide or cleaved single-mode optical fiber. The device was fabricated by means of selective-area MOVPE growth, quantum well intermixing and asymmetric twin waveguide technologies with only a three steps low-pressure MOVPE growth. For the device structure, in SOA/EAM section, double ridge structure was employed to reduce the EAM capacitances and enable high bit-rate operation. In the SSC sections, buried ridge structure (BRS) were incorporated. Such combination of ridge, ATG and BRS structure is reported for the first time in which it can take advantage of easy processing of ridge structure and the excellent mode characteristic of BRS. At the wavelength range of 1550~1600nm, lossless operation with extinction ratios of 25 dB dc and more than 10 GHz 3-dB bandwidth is successfully achieved. The beam divergence angles of the input and output ports of the device are as small as 8.0°×12.6°, resulting in 3.0 dB coupling loss with cleaved single-mode optical fiber.