Optical Receiver with Helicity Dependent Switching of Magnetization

Abstract: In this work, we propose helicity-dependent switching (HDS) of magnetization of Co/Pt for energy efficient optical receiver. Designing a low power optical receiver for optical-to-electrical signal conversion has proven to be very challenging. Current day receivers use a photodiode that produces a photocurrent in response to input optical signals, and power hungry trans-impedance amplifiers are required to amplify the small photocurrents. Here, we propose light helicity induced switching of magnetization to overcome the requirement of photodiodes and subsequent trans-impedance amplification by sensing the change in magnetization with a magnetic tunnel junction (MTJ). Magnetization switching of a thin ferromagnet layer using circularly polarized laser pulses have recently been demonstrated which shows one-to-one correspondence between light helicity and the magnetization state. We propose to utilize this phenomena by using digital input dependent circularly polarized laser pulses to directly switch the magnetization state of a thin Co/Pt ferromagnet layer at the receiver. The Co/Pt layer is used as the free layer of an MTJ, the resistance of which is modified by the laser pulses. With the one-to-one dependence between input data and output magnetization state, the MTJ resistance is directly converted to digital output signal. Our device to circuit level simulation results indicate that, HDS based optical receiver consumes only 0.124 pJ/bit energy, which is much lower than existing techniques.