arXiv subjects

Ricky Gibson

Publications and source records attributed to Ricky Gibson.

11 recordsLinked to original sources

arXiv2026

Frozen mode in coupled single-mode waveguides with gratings

We present a systematic methodology for designing slow-light photonic integrated circuits with a frozen mode based on a special kind of exceptional point of degeneracy (EPD) of order three named stationary inflection points (SIPs). This is realized through three-way coupled waveguides with lateral gratings operating at telecommunication wavelengths. We provide two designs and analyze sensitivity to geometric perturbations. We have fabricated a periodic waveguide with integrated taper loads and demonstrate reasonable agreement with full-wave simulations. These findings confirm the feasibility of integrating SIP-based delay functionalities in standard silicon photonic platforms.

physics.optics↗

arXiv2025

Lasing at a Stationary Inflection Point: erratum

This erratum provides an updated fitting function for the lasing threshold of finite-length cavities operating at a stationary inflection point (SIP) or regular band edge (RBE) resonance, clarifying their asymptotic scaling with the number of unit cells of the periodic cavity.

physics.optics↗

arXiv2025

Experimental Measurement of Enhanced Group Delay Silicon Photonic Waveguides Indicative of the Frozen Mode Regime Around the Stationary Inflection Point

The dispersion engineering of periodic silicon photonic waveguides presents opportunities for significant group delay enhancement compared to uniform waveguides of comparable length. We describe the spectral response characteristics for measured devices and compare their properties to modeled data. These waveguides support the frozen mode regime (FMR) around near infrared wavelengths and are expected to show enhanced group delays around the FMR resonances. Measurements of fabricated devices provide evidence for enhanced delays and spectral properties associated with the FMR. We study how perturbations to the waveguide model impact agreement with measurements and its meaning for these devices operating in the FMR.

physics.optics↗

arXiv2024

Epitaxial rare-earth doped complex oxide thin films for infrared applications

Rare earth dopants are one of the most extensively studied optical emission centers for a broad range of applications such as laser optoelectronics, sensing, lighting, and quantum information technologies due to their narrow optical linewidth and exceptional coherence properties. Epitaxial doped oxide thin films can serve as a promising and controlled host to investigate rare-earth dopants suitable for scalable quantum memories, on-chip lasers and amplifiers. Here, we report high-quality epitaxial thin films of Tm-doped CaZrO$_3$ grown by pulsed laser deposition for infrared optoelectronic and quantum memory applications. We perform extensive structural and chemical characterization to probe the crystallinity of the films and the doping behavior. Low temperature photoluminescence measurements show sharp radiative transitions in the short-wave infrared range of 1.75 - 2 \mu m.

physics.optics↗

arXiv2023

Broadband Thermal Imaging using Meta-Optics

Subwavelength diffractive optics known as meta-optics have demonstrated the potential to significantly miniaturize imaging systems. However, despite impressive demonstrations, most meta-optical imaging systems suffer from strong chromatic aberrations, limiting their utilities. Here, we employ inverse-design to create broadband meta-optics operating in the long-wave infrared (LWIR) regime (8 - 12 $\mu$m). Via a deep-learning assisted multi-scale differentiable framework that links meta-atoms to the phase, we maximize the wavelength-averaged volume under the modulation transfer function (MTF) of the meta-optics. Our design framework merges local phase-engineering via meta-atoms and global engineering of the scatterer within a single pipeline. We corroborate our design by fabricating and experimentally characterizing all-silicon LWIR meta-optics. Our engineered meta-optic is complemented by a simple computational backend that dramatically improves the quality of the captured image. We experimentally demonstrate a six-fold improvement of the wavelength-averaged Strehl ratio over the traditional hyperboloid metalens for broadband imaging.

physics.optics↗

arXiv2022

Frozen Mode Regime in an Optical Waveguide With Distributed Bragg Reflector

We introduce a glide symmetric optical waveguide exhibiting a stationary inflection point (SIP) in the Bloch wavenumber dispersion relation. An SIP is a third order exceptional point of degeneracy (EPD) where three Bloch eigenmodes coalesce to form a so-called frozen mode with vanishing group velocity and diverging amplitude. We show that the incorporation of chirped distributed Bragg reflectors and distributed coupling between waveguides in the periodic structure facilitates the SIP formation and greatly enhances the characteristics of the frozen mode regime. We confirm the existence of an SIP in two ways: by observing the flatness of the dispersion diagram and also by using a coalescence parameter describing the separation of the three eigenvectors collapsing on each other. We find that in the absence of losses, both the quality factor and the group delay at the SIP grow with the cubic power of the cavity length. The frozen mode regime can be very attractive for light amplification and lasing, in optical delay lines, sensors, and modulators.

physics.optics↗

arXiv2022

Design of a Modified Coupled Resonators Optical Waveguide Supporting a Frozen Mode

We design a three-way silicon optical waveguide with the Bloch dispersion relation supporting a stationary inflection point (SIP). The SIP is a third order exceptional point of degeneracy (EPD) where three Bloch modes coalesce forming the frozen mode with greatly enhanced amplitude. The proposed design consists of a coupled resonators optical waveguide (CROW) coupled to a parallel straight waveguide. At any given frequency, this structure supports three pairs of reciprocal Bloch eigenmodes, propagating and/or evanescent. In addition to full-wave simulations, we also employ a so-called ''hybrid model'' that uses transfer matrices obtained from full-wave simulations of sub-blocks of the unit cell. This allows us to account for radiation losses and enables a design procedure based on minimizing the eigenmodes' coalescence parameter. The proposed finite-length CROW displays almost unitary transfer function at the SIP frequency, implying a nearly perfect conversion of the input light into the frozen mode. The group delay and the effective quality factor at the SIP frequency show an $N^{3}$ scaling, where $N$ is the number of unit cells in the cavity. The frozen mode in the CROW can be utilized in various applications like sensors, lasers and optical delay lines.

physics.optics↗

arXiv2021

Controllable finite ultra-narrow quality-factor peak in a perturbed Dirac-cone band structure of a photonic crystal slab

We show that by using a perturbed photonic Dirac-cone, one can realize ultra-narrow and finite Q-factor peak in the wavevector space, with both the peak value and the width separately tunable. We also discuss a lower bound in the minimal viable width given a peak Q-value while maintaining sufficient Q differentiation among modes. The strong angular and frequency Q-selection finds applications in optical devices where strong angle- and frequency-selection is needed.

physics.optics↗

arXiv2021

500 W Peak Power Cavity Dumped 2-micron GaSb-Based VECSEL

A single transverse mode high pulse-energy VECSEL was developed. The GaSb based VECSEL emits at a wavelength of 2.04 microns with a peak power exceeding 500W while maintaining good beam quality. The cavity employs a Pockels cell combined with a low-loss thin film polarizer to selectively dump the intracavity energy into a 10ns pulse. The laser has promise for incoherent LiDAR, materials processing, gas sensing, and nonlinear optics.

physics.optics↗

arXiv2018

Experimental Observation of Strong Coupling Between an Epsilon-Near-Zero Mode in a Deep Subwavelength Nanofilm and a Gap Plasmon Mode

Strong coupling is a phenomenon which occurs when the interaction between two resonance systems is so strong that the oscillatory energy exchange between them exceeds all dissipative loss channels. Each resonance can then no longer be described individually but only as a part of the coupled, hybrid system. Here, we show that strong coupling can occur in a deep subwavelength nanofilm supporting an epsilon near zero mode which is integrated into a metal-insulator-metal gap plasmon structure. To generate an epsilon near zero mode resonance in the short-wave infrared region, an indium tin oxide nanofilm of ~lambda/100 thickness is used. A polariton splitting value of 27%, corresponding to a normalized coupling rate of 0.135, is experimentally demonstrated. Simulations indicate that much larger coupling rates, well within the ultra-strong regime where the energy exchange rate is comparable with the frequency of light, are possible.

physics.optics↗

arXiv2017

Polarization dependent femtosecond laser modification of MBE-grown III-V nanostructures on silicon

We report a novel, polarization dependent, femtosecond laser-induced modification of surface nanostructures of indium, gallium, and arsenic grown on silicon via molecular beam epitaxy, yielding shape control from linear and circular polarization of laser excitation. Linear polarization causes an elongation effect, beyond the dimensions of the unexposed nanostructures, ranging from 88 nm to over 1 um, and circular polarization causes the nanostructures to flatten out or form loops of material, to diameters of approximately 195 nm. During excitation, it is also observed that the generated second and third harmonic signals from the substrate and surface nanostructures increase with exposure time.

cond-mat.mtrl-sci↗