Nonreciprocal transmission of multi-band optical signals in thermal atomic systems

Abstract

Multi-band signal propagation and processing play an important role in quantum communications and quantum computing. In recent years, optical nonreciprocal devices such as an optical isolator and circulator are proposed via various configurations of atoms, metamaterials, nonlinear waveguides, etc. In this work, we investigate all-optical controlled nonreciprocity of multi-band optical signals in thermal atomic systems. Via introducing multiple strong coupling fields, nonreciprocal propagation of the probe field can happen at some separated frequency bands, which results from combination of the electromagnetically induced transparency (EIT) effect and atomic thermal motion. In the proposed configuration, the frequency shift resulting from atomic thermal motion takes converse effect on the probe field in the two opposite directions. In this way, the probe field can propagate almost transparently within some frequency bands of EIT windows in the opposite direction of the coupling fields. However, it is well blocked within the considered frequency region in the same direction of the coupling fields because of destruction of the EIT. Such selectable optical nonreciprocity and isolation for discrete signals may be greatly useful in controlling signal transmission and realizing selective optical isolation functions.

Broadband tunable transmission non-reciprocity in thermal atoms dominated by two-photon transitions

“…In fact, most previous studies examine the non-reciprocal transmission of a single probe field due to limited natural linewidths of single-photon transitions, though it is possible to achieve the nonreciprocal bandwidths over 100 MHz and up to 1.0 GHz through nonlinear optical processes [41][42][43]. It is also known that the simultaneous manipulation of a vast number of light signals is required in all-optical networks, and wavelength division multiplexing (WDM) [51][52][53] is an effective technique for enlarging the information capacity of optical fiber communication [54][55][56][57][58][59]. Then, a specific question arises, whether the linear non-reciprocal transmission, if extended to systems dominated by two-photon transitions, can be realized in a wide enough frequency range appropriate for the WDM manipulation of multiple probe fields?…”