Selective regrowth of a wide-bandwidth 1.3 mu m integrated lossless tap and optical preamplifier

The authors report the first monolithically integrated wide-bandwidth lossless tap-that is, an optical semiconductor amplifier followed by a colinear reverse-biased waveguiding photodetector with fiber-coupled input and output. The integration was achieved by using off-axis selective epitaxial growth of ridge waveguides on a patterned dielectric layer. The tilted facets produced by the off-axis growth, along with photodetector absorption, serve to reduce the effective facet reflectivity to -36 dB without any antireflection coating. By adjusting the length of the absorbing photodetector section, part or all of the amplified light may be absorbed, allowing the device to function respectively as a lossless tap or an optical preamplifier. A lossless tap with an electrical bandwidth of 7 GHz, a responsivity of 26 A/W, and a fiber-to-fiber gain of 3 dB is shown to have a receiver sensitivity of -22 dB at 3 Gb/s.<>