Signal and noise in magneto-optical readout

For a magneto-optical readout system which uses the Kerr effect, the power spectral density of the read signal has been derived. The noise components originating in the photodetection and amplification stages appear as additive terms in the expression for the overall spectral density, enabling us to define a signal to noise ratio for the readout system. Adjustable parameters of the system are then optimized and a multilayer disk structure is introduced which enhances the Kerr effect and, consequently, results in an increased signal to noise ratio.