An integrated circuit includes a photodetector. The photodetector includes a circular optical grating formed in an annular trench in a semiconductor substrate. The circular optical grating includes dielectric fins and photosensitive fins positioned in the annular trench. The circular optical grating is configured to receive incident light and to direct the incident light around the annular trench through the dielectric fins and the photosensitive fins until the light is absorbed by one of the photosensitive fins.