Describe the Faraday magneto-optic effect. How can it be used for impressing information on a beam of light? A cylindrical rod of magneto-optic material, of length L with Verdet constant V at the wavelength of light to be used, is placed wholly within an N-turn solenoid, also of length L, so that the rod and solenoid axes are parallel. A beam of Iaser light, with power P watts, passes through the rod along its axis. The light entering the rod is linearly polarized in the vertical direction. The light emerging from the rod is passed through a polarization analyser whose acceptance direction is vertical, and then on to a photodiode which has a sensitivity of S amps watt-^1.

A current ramp is applied to the solenoid, of the form:

i = kt

where i is the current at time t, and k is a constant. Assuming that optical losses are negligible for the arrangement, derive expressions for the amplitude and frequency of the AC component of the signal delivered by the photodiode.