A $\chi^{(2)}$-based AlGaAs Phase Sensitive Amplifier with Record Gain, Noise and Sensitivity

TL;DR

This paper reports the first successful demonstration of a $ ext{AlGaAs}$-based phase sensitive amplifier with record gain, low noise, and high sensitivity, advancing on-chip quantum and classical optical signal processing.

Contribution

It introduces a novel $ ext{chi}^{(2)}$-based semiconductor PSA using efficient phase matching and pulsed pumping in AlGaAs waveguides, achieving record performance metrics.

Findings

Achieved on-chip in-phase gain and 0.005 photons per pulse sensitivity.

Approached the theoretical minimal noise figure of 0 dB.

Demonstrated operation with sub-single photon signals.

Abstract

Phase sensitive amplifiers (PSAs) have the potential to empower substantial advances in emerging generations of optical communication systems as well as classical and quantum on-chip signal processing. The core building block of a PSA is a nonlinear medium. While the second-order nonlinearity ($\chi^{(2)}$) is stronger than the third-order nonlinearity ($\chi^{(3)}$), it is used less often in semiconductors for parametric amplification owing to the challenges of effectively phase matching the interacting waves as well as two-photon absorption of the pump. In this work, we demonstrate the successful design, fabrication, and characterization of the first $\chi^{(2)}$-based semiconductor PSA using an efficient phase matching approach and a pulsed pump, based on an aluminium gallium arsenide (AlGaAs) waveguide platform. Non-centrosymmetric semiconductors such as AlGaAs offer appreciable $\chi^{(2)}$. Such waveguides also achieve more than one order of magnitude greater pump field confinement when compared to other materials with large $\chi^{(2)}$ such as Periodically Poled Lithium Niobate (PPLN). Our AlGaAs PSA achieves an on-chip in-phase gain, a sensitivity of 0.005 photons per pulse, and approaches theoretical minimal noise figure (NF) of 0~dB. With the capability of operating on signal states with sub-single photons per pulse, our PSA could usher in a new era of on-chip quantum circuits.