Telecom Band Geometric Amplifier

Present-day devices for amplifying telecom laser light mostly produce gain by incoherently pumping a medium (optically or electrically), or by coherently pumping a nonlinear medium with a laser. Both approaches are technologically mature, and offer a range of performance tradeoffs. In contrast, geometric amplification is a gain mechanism that has only been recently proposed, and to date it has only been demonstrated in the acoustic domain [1]. However, the principle of geometric amplification can be applied to any domain. It can be realized using coupled resonators consisting only of linear, lossy components, so long as they can be modulated at a frequency comparable to the resonators’ decay rate [1]. In the telecom domain, this can be accomplished using a pair of fiber loops that include electrically tunable phase shifters that can be modulated at ~ 1 MHz. The adiabatic evolution associated with this relatively slow modulation (together with the components’ intrinsic loss) results in the accumulation of a geometric (Berry) phase [2,3] whose complex part can be engineered to provide gain [1,4,5]. Geometric gain differs existing forms of amplification in several respects, including that it achieves photon-number gain through rf modulation. This may offer practical advantages in terms of reduced device complexity, size, and power consumption.