Integrated Nonreciprocal Photonic Devices with Dynamic Modulation

Abstract

Nonreciprocal components, such as isolators and circulators, are crucial components for photonic systems. In this article we review theoretical and experimental progress towards developing nonreciprocal photonic devices based on dynamic modulation. Particularly, we focus on approaches that operate at optical wavelengths and device architectures that have the potential for chip-scale integration. We first discuss the requirements for constructing an isolator or circulator using dynamic modulation. We review a number of different isolator and circulator architectures, including waveguide and resonant devices, and describe their underlying operating principles. We then compare these device architectures from a system-level performance perspective, considering how their figures of merit, such as footprint, bandwidth, isolation, and insertion loss, scale with respect to device degrees of freedom.

Nonreciprocity in Bianisotropic Systems with Uniform Time Modulation

“…To date, all the known approaches for obtaining nonreciprocal wave propagation in time-modulated systems can be boiled down to the following three fundamental classes [31,32]: Travelling-wave modulators (indirect photonic transitions) [17,29,33,34], tandem phase mod- * These authors contributed equally.…”

“…In both cases, it is necessary to use a series of time-modulated elements which have to be precisely synchronized with each other, which greatly increases the complexity of the biasing networks. The third approach requires either asymmetric modulation function profile of the real part of permittivity [32,38] or modulating both its real and imaginary parts [37]. However, in both cases the system exhibits reciprocal transmission for the fundamental frequency since waves incident from the opposite directions "sense" effectively the same structure (nonreciprocity manifests itself only in nonreciprocal frequency conversion).…”

“…Interestingly, although the metasurface described by the circuit in Fig. 1 is nonreciprocal, it obeys the generalized time-reversal symmetry [32]. Under substitution v(t) → v(−t) and η 0 → −η 0 (reversal of the current direction in the circuit, rather than replacing loss by gain), relations ( 6) and ( 7) do not change their forms, providing that C(t + ∆t) = C(−t + ∆t) for some specific gauge time translation ∆t.…”

Extreme Non-Reciprocal Near-Field Thermal Radiation via Floquet Photonics

“…Equations (3,4) extend the standard treatment of thermal radiation to periodically modulated photonic circuits and provide a bridge with the field of Floquet engineering [51,53,54]. It turns out that time-dependent perturbations could induce non-reciprocal transmittance T F α,β (ω) = T F β,α (ω) [55][56][57] whose origin is traced to interference effects between different paths in the Floquet ladder [51]. At the same time, Eqs.…”

“…In the absence of any modulation ω n = ω 0 , and due to rotational symmetry, the system has two degenerate right/left-handed modes (1, e ±2iπ/3 , e ±4iπ/3 ) T / √ 3 with frequency ω L(R) = ω 0 − k and a mode (1, 1, 1) T / √ 3 with frequency ω C = ω 0 + 2k. The situation is different in the presence of periodic modulations [55][56][57]. Guided by previous Floquet engineering studies performed in the scattering framework [53,54] we have implemented a driving protocol that involves the time-modulation of the n = 2, 3-resonators with ω n = ω 0 − δ 0 [cos(Ωt + φ n ) + cos(Ωt + φ 0 )], combined with the driving of the coupling constant k 23 = k 32 = k + δ 0 cos(Ωt + φ 0 ).…”