A quantum-well waveguide photodetector for high-precision wavelength monitoring about 1.55 μm

A two-segment InGaAsP rib waveguide photodetector is shown to function as a high resolution wavelength monitor in the 1.55-μm spectral region. For two in-line detector elements, the ratio of photocurrents produced is a sensitive function of the input wavelength near the material's absorption edge. This ratio varies rapidly with wavelength over a range from 1.53 to 1.565 μm and is independent of the optical input power. By utilizing the quantum confined Stark effect, the operating range of the device can be extended to over 50 nm. An average wavelength sensitivity of 3 pm is demonstrated.