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In this paper, we propose helicity-dependent switching (HDS) of magnetization in Co/Pt for an energy efficient optical receiver. Designing a low-power optical receiver for optical-to-electrical signal conversion has proven to be very challenging. Current day optical receivers use a photodiode that produces a photocurrent in response to input optical signals, and power hungry transimpedance amplifiers are required to amplify the small photocurrents. These limitations can be overcome by using light helicity-induced switching of magnetization which can avoid the requirement of photodiodes and subsequent transimpedance 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 has recently been demonstrated which shows a one-to-one correspondence between light helicity and the magnetization state. We use these phenomena to directly switch the magnetization state of a thin Co/Pt ferromagnet layer at the receiver via circularly polarized laser pulses. The circular polarization is controlled in accordance with digital input data which establishes a one-to-one correspondence between the transmitted data and output magnetization state. The Co/Pt layer is used as the free layer of an MTJ, the resistance of which is modified by the laser pulses. Since the output magnetization state is controlled by the input data, the MTJ resistance is directly converted to a digital output signal. Our device-to-circuit level simulation results indicate that HDS-based optical receiver circuit consumes only 0.124 pJ/bit energy, which is much lower than existing techniques. [ABSTRACT FROM AUTHOR]

Optical interconnect has emerged as the front-runner to replace electrical interconnect especially for off-chip communication. However, a major drawback with optical interconnects is the need for photodetectors and amplifiers at the receiver, implemented usually by direct bandgap semiconductors and analog CMOS circuits, leading to large energy consumption and slow operating time. In this letter, we propose a new optical interconnect architecture that uses a magnetic tunnel junction (MTJ) at the receiver side that is switched by femtosecond laser pulses. The state of the MTJ can be sensed using simple digital CMOS latches, resulting in significant improvement in energy consumption. Moreover, magnetization in the MTJ can be switched on the picoseconds time-scale and our design can operate at a speed of 5 Gb/s for a single link. [ABSTRACT FROM AUTHOR]