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International Conference on Transparent Optical Networks

Engineering Non-Classical Light in Photonic Integrated Devices with Linearly Coupled and Uncoupled Resonators

Luca Zatti, John E. Sipe, Marco Liscidini

Published Jul 1, 2020• 0 citations
Publisher

Abstract

Integrated micro- and nanostructures allow for the efficient generation of photon pairs via parametric fluorescence, thanks to the enhancement of the light-matter interaction associated with light confinement in small volumes. Yet the advantages of using integrated devices go well-beyond the improvement of generation efficiency, for micro-structures can be designed to enable a precise control over the properties of the generated non-classical light. Particularly interesting are structures composed of more than one micro-resonator. In such systems one can control the spectral properties of the generated light, and suppress unwanted phenomena, with a careful engineering of the linear and nonlinear coupling of the resonant elements. Here we show that we can exploit this structure to generate photon pairs that are highly energy entangled or completely uncorrelated.

DOI
10.1109/icton51198.2020.9203496

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Integrated micro- and nanostructures allow for the efficient generation of photon pairs via parametric fluorescence, thanks to the enhancement of the light-matter interaction associated with light confinement in small volumes. Yet the advantages of using integrated devices go well-beyond the improvement of generation efficiency, for micro-structures can be designed to enable a precise control over the properties of the generated non-classical light. Particularly interesting are structures composed of more than one micro-resonator. In such systems one can control the spectral properties of the generated light, and suppress unwanted phenomena, with a careful engineering of the linear and nonlinear coupling of the resonant elements. Here we show that we can exploit this structure to generate photon pairs that are highly energy entangled or completely uncorrelated.
Integrated micro- and nano-structures allows for the efficient generation of photon pairs via parametric fluorescence, thanks to the enhancement of the light-matter interaction associated with light confinement in small volumes. For instance, the efficiency of spontaneous four wave mixing in a silicon micro ring resonator can range up to 10 orders of magnitude larger than in bulk silicon. Yet the advantages of using integrated devices go well beyond the sole efficiency improvement, for micro structures grant an unprecedented control over the properties of generated non-classical light. For instance, in a single photonic integrated circuit, one can exploit the interferences of many optical elements to construct complex multipartite states in a compact, stable, and scalable system. In this talk I will focus on the generation of photon pairs and show how their spectral properties can be engineered in an integrated device for use as building blocks in the construction of a whole variety of states, from heralded single-photons to multipartite states.
Optical nonlinear processes in linearly uncoupled resonators are being actively studied as a convenient way to engineer and control the generation of non-classical light. In these structures, one can take advantage of the independent combs of resonances of two linearly uncoupled ring resonators for field enhancement, with the phase-matching condition being significantly relaxed compared to a single resonator. However, previous implementations of this approach have shown a limited operational bandwidth along with a significant reduction of the generation efficiency. Here, we experimentally demonstrate that a Mach–Zehnder interferometer can be used to effectively linearly uncouple two resonators and, at the same time, allows for their efficient nonlinear coupling. We demonstrate that this structure can lead to an unprecedented control over the rings' interaction and can operate over more than 160 nm, covering the S-, C-, and L-telecom bands. In addition, we show that the photon pair generation efficiency is increased by a factor of four with respect to previous implementations.
Delicate engineering of integrated nonlinear structures is required for developing scalable sources of non-classical light to be deployed in quantum information processing systems. In this work, we demonstrate a photonic molecule composed of two coupled microring resonators on an integrated nanophotonic chip, designed to generate strongly squeezed light uncontaminated by noise from unwanted parasitic nonlinear processes. By tuning the photonic molecule to selectively couple and thus hybridize only the modes involved in the unwanted processes, suppression of parasitic parametric fluorescence is accomplished. This strategy enables the use of microring resonators for the efficient generation of degenerate squeezed light: without it, simple single-resonator structures cannot avoid contamination from nonlinear noise without significantly compromising pump power efficiency. We use this device to generate 8(1) dB of broadband degenerate squeezed light on-chip, with 1.65(1) dB directly measured.
Abstract Delicate engineering of integrated nonlinear structures is required for developing scalable sources of non-classical light to be deployed in quantum information processing systems. In this work, we demonstrate a photonic molecule composed of two coupled microring resonators on an integrated nanophotonic chip, designed to generate strongly squeezed light uncontaminated by noise from unwanted parasitic nonlinear processes. By tuning the photonic molecule to selectively couple and thus hybridize only the modes involved in the unwanted processes, suppression of parasitic parametric fluorescence is accomplished. This strategy enables the use of microring resonators for the efficient generation of degenerate squeezed light: without it, simple single-resonator structures cannot avoid contamination from nonlinear noise without significantly compromising pump power efficiency. We use this device to generate 8(1) dB of broadband degenerate squeezed light on-chip, with 1.65(1) dB directly measured.
The efficient and controllable generation of entangled photon pairs is a cornerstone for advancing quantum technologies, including quantum computing, communication, and sensing. Traditional methods, primarily relying on spontaneous parametric down-conversion (SPDC) or spontaneous four-wave mixing (SFWM) in bulk nonlinear crystals or waveguides, often suffer from low efficiency, bulky form factors, and limited control over the spectral and spatial properties of the generated photons. This paper explores a transformative approach leveraging resonant Bound States in the Continuum (BICs) within nanophotonic structures to overcome these limitations. BICs are extraordinary optical resonances characterized by theoretically infinite quality (Q) factors, enabling extreme light localization and immense field enhancement within subwavelength volumes. By integrating nonlinear optical materials into BIC-supporting structures, such as photonic crystal slabs or metasurfaces, the local electric field strength experienced by the nonlinear medium can be dramatically increased, boosting the efficiency of entangled photon generation. Furthermore, the sharp, tailor-able spectral response of BICs offers unprecedented control over the joint spectral amplitude of the photon pairs, promising high degrees of spectral purity and entanglement fidelity. This work outlines the theoretical underpinnings, potential device architectures, and anticipated advantages of BIC-enhanced entangled photon sources, paving the way for compact, high-brightness, and spectrally engineered quantum light sources critical for next-generation quantum technologies.