When the light incident on your detector needs to be manipulated, the best course of action may be to apply a coating or filter specific to your application. For maximum signal, AR coatings can be applied to one or both sides of windows, and also to the photodiode chip itself.
Band-pass or long-pass filters can be applied to windows to tailor the working wavelength range of the detector system. In high-power scenarios, partially reflective coatings can attenuate optical power to a manageable level.
Where reflections are undesirable, absorptive filters can often be used for attenuation in place of a traditional glass window.
GPD uses well-selected coatings for many of our standard products, and we are happy to discuss the requirements of your project so we can offer the best solution.