An integrated wavelength demultiplexer and pin detector array is reported for high density WDM detection at 1.5 mum. Signals spaced at 1 nm over the 1.48-1-55 mum wavelength range are separated and detected; channel passbands are 0-6-0.8 nm. Grown on a semi-insulating substrate, and providing a pseudoplanar device surface, the HD-WDM detector array is suitable for monolithic integration with high-speed multichannel receiver circuitry.