Abstract
Nonreciprocal components are essential in photonic systems for protecting light sources and for signal routing functions. Acousto-optic methods to produce nonreciprocal devices offer a foundry-compatible alternative to magneto-optic solutions and are especially important for photonic integration. In this paper, we experimentally demonstrate a dynamically reconfigurable nonreciprocal acousto-optic modulator at the telecom wavelength with a peak contrast of 8 dB and a 3 dB bandwidth of 1.1 GHz. The modulator can be arranged in a multitude of reciprocal and nonreciprocal configurations by means of an external RF input. The dynamic reconfigurability of the device is enabled by a new cross-finger interdigitated piezoelectric transducer that can change the directionality of the reciprocity-breaking acoustic excitation based on the phase of the RF input. The methodology we demonstrate here may enable new avenues for direction dependent signal processing and optical isolation.
Highlights
Optical isolators and circulators are crucial components in photonic circuits for protecting light sources from backscattering and for achieving direction dependent signal routing.[1,2,3] These functions can be only achieved by components that are nonreciprocal, i.e., that have asymmetric scattering matrices that imply different port-toport propagation in opposing directions
Nonreciprocal components are essential in photonic systems for protecting light sources and for signal routing functions
A nonreciprocal modulator can be obtained through intermodal scattering between two optical modes of the photonic system that are distinct in both frequency and momentum space.[11,17,18]
Summary
Optical isolators and circulators are crucial components in photonic circuits for protecting light sources from backscattering and for achieving direction dependent signal routing.[1,2,3] These functions can be only achieved by components that are nonreciprocal, i.e., that have asymmetric scattering matrices that imply different port-toport propagation in opposing directions. An alternative approach is to use spatiotemporal modulation or momentum-biasing of the medium to produce magnetless nonreciprocity This class of method, of which specific approaches employ synthetic magnetism,[7,8,9] interband photonic transition,[10,11,12,13,14,15,16,17,18,19] angular momentum biasing,[20,21,22] and phase modulation,[23,24,25,26,27,28] is APL Photon. In this context, we previously demonstrated an on-chip nonreciprocal modulator[17] that uses a traveling acoustic wave to produce indirect interband transitions in a photonic resonator. With the approach demonstrated here, the level of transparency (in terms of whether or not the signal is modulated) or opacity in the forward and backward directions can be set independently
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