Radiation detection systems and methods. In one approach, optical radiation can be detected by using the radiation to be detected as input to a high index contrast waveguide modulator that modulates a wavelength of light that falls within the detection band of a detector. In another approach, the optical radiation that is to be detected is combined with a high power CW boost mode signal in a waveguide, and the sum and/or difference frequencies are detected. In either approach, one can use grating couplers to couple the optical radiation of interest into a waveguide.