Epitaxial III-V semiconductor quantum dots (QDs) integrated with nanophotonic structures are promising on-demand sources of indistinguishable single photons for quantum photonic circuits. Close proximity of QDs to etched sidewalls in such structures, however, may induce excitonic linewidth broadening, reducing photon indistinguishability. Here, we design and demonstrate GaAs photonic crystal cavities based on multimode nanobeam waveguides that maximize QD separation from etched surfaces beyond an empirically determined threshold that suppresses spectral broadening, while enabling QD access through higher-order waveguide modes. Although multimode propagation adds design complexity, simulations predict quality factors Q approximate to 103 and mode volumes V/(lambda/n)3 approximate to 2 for Purcell radiative rate enhancements of Fp approximate to 100. Fabricated devices containing QD ensembles exhibit resonances consistent with these predictions, and single-QD measurements yield Fp<5 for 11 randomly located emitters. Monte Carlo simulations of spatially dependent Fp distributions indicate that slow carrier capture and relaxation dynamics, rather than QD placement, primarily limit the observation of higher Purcell factors. These results highlight the potential of our cavities for integrating epitaxial QDs while clarifying key constraints on observation of radiative rate enhancement.

A key element for on-chip quantum photonic systems is a reliable source of on-demand, indistinguishable, waveguided single photons that can be seamlessly integrated with photonic circuits. While epitaxial semiconductor quantum dots have the potential to fulfill such needs, optical excitation that is resonant with the quantum dot ensures maximum single-photon indistinguishability. To date, a majority of waveguided quantum dot sources that allowed resonant excitation have relied on free-space excitation beams. Free-space excitation requires significant experimental overhead, especially if multiple sources need to be addressed. waveguided resonant excitation, in contrast, has not been extensively explored, and yet enables simplified, plug-and-play operation of single and even multiple sources on chip. Here, we show design steps for what we believe to be a novel, modular nanophotonic structure that, relying on inversely designed components, allows waveguided resonant quantum dot excitation with high single-photon waveguide collection efficiencies (> 85 %) and low multi-photon probability (<10-3), many favorable trade-off possibilities, and reasonable robustness to quantum dot positioning.

We fabricate an inversely-designed nanophotonic quantum dot polarization de-multiplexer and observe the coupling of single embedded InAs quantum dot to two orthogonal output waveguides.

Single solid-state quantum emitters offer consid-erable potential for the implementation of sources of single indistinguishable photons, which are central to many photonic quantum information systems. Nanophotonic geometry optimiza-tion with multiple performance metrics is imperative to convert a bare quantum emitter into a single-photon source that approaches the necessary levels of purity, indistinguishability, and brightness for quantum photonics. We present an inverse design methodology that simultaneously targets two important figures-of-merit for high -performance quantum light sources: the Purcell radiative rate enhancement and the coupling efficiency into a desired light collection channel. We explicitly address geometry-dependent power emission, a critical but often overlooked aspect of gradient-based optimization of quantum emitter single-photon sources. We illustrate the efficacy of our method through the design of a single-photon source based on a quantum emitter in a GaAs nanophotonic structure that provides a Purcell factor Fp = 21 with a 94% waveguide coupling efficiency, while respecting a geometric constraint to minimize emitter decoherence caused by etched sidewalls. Our results indicate that multiobjective inverse design can yield competitive performance with more favorable trade-offs than conventional approaches based on a pre-established waveguide or cavity geometries.

Distributed Bragg reflectors (DBRs) have found applications in various fields, including optical communications, light generation, solar cells, and sensors. DBRs are also crucial in open-access Fabry‐Pérot microcavities for enhanced and spectrally tunable light-matter interactions. This document presents the inverse design, fabrication, and optical characterization of aperiodic Ta2O5/SiO2 multilayer DBR mirrors targeting a sharp reflectivity spectrum. The results were confirmed through simulations and experimental measurements. The proposed inverse design methodology can be used to develop DBRs for important technologies such as single-photon sources, polaritonic systems, and random laser generation.

We develop a single-photon source based on single InAs/GaAs quantum dots in a nanobeam photonic crystal cavity engineered to allow waveguided resonant dot excitation, high Purcell radiative rate enhancements and efficient out-coupling into an on-chip waveguide.

Inverse design for photonic integrated circuits is becoming increasingly attractive, but can be computationally heavy for realistic devices. Here, we demonstrate inverse design enhanced by a hardware-accelerated electromagnetic solver and automatic differentiation, with the specific example of a large-area, CMOS-compatible grating coupler.

Epitaxial quantum dots can emit polarization-entangled photon pairs. If orthogonal polarizations are coupled to independent paths, then the photons will be path-entangled. Through inverse design with adjoint method optimization, we design a quantum dot polarization demultiplexer, a nanophotonic geometry that efficiently couples orthogonally polarized transition dipole moments of a single quantum dot to two independent waveguides. We predict 95% coupling efficiency, cross talk less than 0.1%, and Purcell radiative rate enhancement factors over 11.5 for both dipoles, with sensitivity to dipole misalignment and orientation comparable to that of conventional nanophotonic geometries. We anticipate our design will be valuable for the implementation of triggered, high-rate sources of path-entangled photon-pairs on chip.

We use inverse design to develop an optimized nanophotonic geometry for efficient, Purcell-enhanced, waveguide-coupled, path-entangled photon pair sources based on single embedded quantum dots.

We demonstrate a new, multi-objective inverse design strategy for single-photon sources based on single quantum emitters, and show that it can produce comparable performance, with more favorable trade-offs, than conventional design based on pre-existing nanophotonic geometries.

Due to recent development of growing and processing techniques for high-quality single crystal diamond, the large scale production of diamond optomechanical crystal cavities becomes feasible, enabling optomechanical devices that can operate in higher mechanical frequencies and be coupled to two-level systems based on diamond color centers. In this paper we describe a design optimization method to produce diamond optomechanical crystal (OMC) cavities operating at the high-cooperativity regime (close to unity) at room temperature.

We demonstrate hybrid quantum photonic circuits comprising Si3N4 waveguides featuring losses in the dB/m range, with directly integrated quantum dot based single-photon sources.

Nanobeam photonic crystal cavities are engineered to provide large Purcell ra-diative rate enhancements for single quantum dot single-photon emitters while minimizing spectral broadening induced by etched sidewalls.

In this work, we study a diamond nanobeam design in which two nearly-degenerated mechanical modes are coupled to a single optical mode in a high-cooperativity regime. Both modes’ resilience was tested against fabrication defects.

In this work, we developed a method for design optimization to maximize the cooperativity of a diamond-based nanobeam. Our optimized cavity is sideband-resolved and can reach the high-cooperativity regime with only 40 intracavity photons.

The color viewing angles of diffractive-plasmonic reflective color filters are assessed using BFP microscopy images and numerical simulations. The results indicate an asymmetric color response useful for data privacy enhancement in display applications.

Photonic crystal (PhC) slabs with a lower-index material surrounding the core layer are an attractive choice to circumvent the drawbacks in the fabrication of membranes suspended in air. In this chapter, we summarize and expand a numerical study performing a design protocol for nanophotonic devices based on an oxide-cladding aluminum nitride PhC slab. We show the design of an ideal structure and analyze the effects of material dispersion based on a first-order correction perturbation theory approach, in which the dielectric functions obtained by experimental measurements of the thin film materials were employed. This bulk PhC slab was then used as a host medium for the study of an optimized nanocavity, as well as for the development of a slow light waveguide that can compose a Mach–Zehnder electro-optic modulator. The study also includes modeling and analysis of the effects of fabrication-induced disorder, such as deviation in sizes and positions of holes, in the performance of the photonic devices. The results show that the oxide-cladding AlN PhC can be a promising platform for the development of integrated photonic devices.

The desire to reproduce vivid colors such as those found in birds, fishes, flowers, and insects has driven extensive research into nanostructured surfaces especially because of their high spatial resolution. Using a periodic silicon-patterned structure coated with aluminum, we combine two distinct and yet interconnected effects to produce bright and vivid color surfaces. A genetic algorithm optimization process was used to fine-tune both the diffraction and plasmonic effects to obtain reflective color filters for the red, green, and blue colors. The obtained structures are suitable for displays, image applications, color sensors, and optical filters.

Colors observed in nature are very important to form our perception of an object as well as its design. The desire to reproduce vivid colors such as those found in birds, fishes, flowers and insects has driven extensive research into nanostructured surfaces. Structural colors based on surface plasmon resonance (SPR) have played an important role in this field due to its high spatial resolution. Creating vivid color reflecting surfaces is still a major challenge and could revolutionize low power consumption image displays. Here we combine diffraction and plasmonic effects to design bright and vivid-color reflecting surfaces. The periodic reflection patterns are designed through genetic algorithm optimization and are defined in aluminum coated silicon chips.

Slow light propagation throughout photonic crystal slab waveguides have great potential to reduce the size and power consumption of active silicon photonic devices. A great effort has been done to understand the slow light mechanisms and their relations with the waveguide geometrical parameters. In this way, it is expected to control the waveguide dispersion characteristics and exploit the effects produced when slowing down light propagation speed, but avoiding, at the same time, the high group velocity dispersion (GVD) level drawbacks such as pulse broadening and distortion. Here, we present a concise methodology to perform an efficient near-zero GVD slow light photonic crystal waveguide oriented-design. We use a slow light flatness parameter for enabling a systematic comparison of slow light waveguide structures regarding their average group velocity and group index slope within a limited bandwidth. The results show the feasibility of obtain near-zero GVD slow light photonic crystal waveguide structures with slowdown factors up to 40, normalized delay-bandwidth products over 0.2, and dispersion lengths at the millimeter scale.