Photodetectors are devices used for the detection of light. They are used primarily as an optical receiver to convert light into electricity. A commonly used photodetector is the photodiode. A photodiode is a type of photodetector that is used to convert light into current so that optical power can be measured. You have been given the task of designing a photodetector for an optical local area network which uses GaAs laser diode light source (free space wavelength , 850 nm). You decide to use a silicon photodiode, which responds well at this wavelength. Silicon has relative permittivity &, = 11.9 air D=? 1 TiO) material=? (SiO, or silicon To improve the photo response, you decide to add an antireflection coating to the photodiode as shown in figure. You have equipment that can deposit either Sio, (refractive index n = 1.45) or TiO2 (refractive index n = 2.25) coating. Determine which of the two available materials gives the best antireflection coating and determine the optimum thickness for the coating.