High-quality factor microring resonators made from low-loss silicon nitride have offered tantalizing possibilities for nonlinear nanophotonics at modest optical powers. Here we discuss how they can be leveraged for generating quantum states such as squeezed light, and also introduce a scheme for high-dimensional on-chip Hamiltonian simulation using coupled microrings. Full-text article not available; see video presentation
High-quality factor microring resonators made from low-loss silicon nitride have offered tantalizing possibilities for nonlinear nanophotonics at modest optical powers. Here we discuss how they can be leveraged for generating quantum states such as squeezed light, and also introduce a scheme for high-dimensional on-chip Hamiltonian simulation using coupled microrings. Full-text article not available; see video presentation
Squeezed states, with their noise reduction below the standard quantum limit, are promising quantum states of light exploited for enhancing sensitivity in quantum sensing or as carriers of information in continuous variable quantum computing and communication. To make use of their quantum advantage, the main common challenge in generating these states is achieving high levels of squeezing in low loss setups.Over the years, several bulk optical nonlinear crystals and cavities have been employed for the generation of different types of high-quality squeezed states. However, recent progress in fabricating ultra-low loss integrated waveguides has shifted the interest of the community towards the integration of squeezing sources to gain advantages in terms of compactness, scalability, and reproducibility.The aim of this thesis is to investigate the main characteristics, limits, and requirements for the generation of vacuum and bright squeezed states by second- and third-order nonlinear devices, with more emphasis on integrated cavities. In particular, we demonstrate high on-chip intensity difference squeezing between bright mode pairs created in an engineered SiN microring resonator. In addition, we propose the use of the Ikeda map, a semi-classical simulation tool, for the investigation of two-mode quadrature squeezing generation in microresonators, discussing its competitiveness against standard quantum models. These results contribute to the optimization of engineered integrated devices with the aim of attaining high levels of squeezing sufficient to bring real advantages in classical and quantum applications.
Squeezed light is an essential nonclassical resource for quantum sensing, continuous-variable quantum information processing, low-noise optical communication, and new photonic computing systems. However, to make practical use of it, we need compact, low-power squeezed-light sources that can fit on a chip. In this work, we introduce a theoretical model of a dual-pump microring optical parametric amplifier for squeezed-light integrated photonics. The model outlines cavity-enhanced Kerr four-wave mixing among two pump fields, a signal mode, and the conjugate idler sideband. We use a linearized quantum Langevin approach under the undepleted-pump assumption. We derive the frequency-domain inputoutput relation and assess the output quadrature noise based on several factors: external coupling rate, intrinsic loss, pump power, signal detuning, nonlinear coefficient, and dispersion. First, we analyze a dispersion-engineered silicon nitride microring that operates in the telecom band. It shows that moderate external coupling offers the best trade-off between intracavity field enhancement and squeezed-field extraction. With the right pump detuning, the simulated silicon nitride resonator achieves over 10 dB of quadrature noise reduction at milliwatt-level input pump powers. We also compare AlGaAs and InP microring platforms, demonstrating that the squeezing performance is influenced not only by the nonlinear coefficient but also by the combined effects of material nonlinearity, cavity quality factor, loss, coupling, dispersion, and detuning. This framework gives design guidelines for low-power, chip-scale squeezed-light sources aimed at future quantum and AI-oriented photonic integrated circuits.
Integrated nonlinear microring resonators are promising sources of bright twin-beams exhibiting intensity difference squeezing. To take advantage of the noise reduction of these quantum states, many applications require high squeezing levels. However, the attainable on-chip squeezing is constrained by the ratio of intrinsic to coupling loss, which is strongly related to design and fabrication limits. Here, we demonstrate a silicon nitride microring resonator engineered to enable a set of periodic strongly overcoupled resonances from which the estimated on-chip intensity difference squeezing is 11.8 dB, exceptionally high for an integrated device. Due to significant setup loss, we directly measure 1.4±0.2 dB of squeezing, corresponding to an on-chip level of 9.2±5.1 dB. In addition, the new, to the best of our knowledge, design inherently suppresses mode competition in the modes surrounding the twin-beams, enabling a constant high squeezing level up to moderate powers. These results represent a significant step toward the miniaturization of integrated devices whose performance benefits from surpassing the quantum noise limit using squeezed states, with particular relevance to sensing applications.
The sub-wavelength optical confinement and low optical loss of nanophotonic devices dramatically enhances the interaction between light and matter within these structures. When nanophotonic devices are combined with an efficient optical coupling channel, nonlinear optical behavior can be observed at low power levels in weakly-nonlinear materials. In a similar vein, when resonant atomic systems interact with nanophotonic devices, atom-photon coupling effects can be observed at a single quanta level. Crucially, the chip based nature of nanophotonics provides a scalable platform from which to study these effects. This thesis addresses the use of nanophotonic devices in nonlinear and quantum optics, including device design, optical coupling, fabrication and testing, modeling, and integration with more complex systems. We present a fiber taper coupling technique that allows efficient power transfer from an optical fiber into a photonic crystal waveguide. Greater than 97% power transfer into a silicon photonic crystal waveguide is demonstrated. This optical channel is then connected to a high-Q (> 40,000), ultra-small mode volume (V 44% of the photons input to a fiber. This permits the observation of optical bistability in silicon for sub-mW input powers at telecommunication wavelengths. To port this technology to cavity QED experiments at near-visible wavelengths, we also study silicon nitride microdisk cavities at wavelengths near 852 nm, and observe resonances with Q > 3 million and V