Cavity Design Research Articles

Lithographically-defined cavities with high quality and purcell factors

Abstract We introduce and analyze a lithographically defined cavity (Li-cavity) incorporating a buried mesa defect in a planar vertical structure, which induces transverse photonic confinement while enabling compatibility with electrical injection. We systematically investigate the influence of key cavity parameters on optical behavior and fundamental properties using a comprehensive three-dimensional optical model. Our analysis reveals that the Li-cavity exhibits low optical scattering, resulting in high Q and Purcell factors, even at sub-wavelength dimensions. Furthermore, the Li-cavity supports single-mode operation within a broader aperture size range compared to conventional cavity designs, promising enhanced optical power of single-mode emission. Adequately designed structures demonstrate superior Q and Purcell factors at wavelength scale sizes,- outperforming conventional micropillar cavities. These improved properties and customizable device characteristics stem from a simple fabrication process that precisely controls the cavity size, shape, and optical mode. Superior characteristics, along with its adaptability to diverse materials, wavelengths, and photonic integration platforms, promise a broad range of applications and potential adaptation of this design to diverse photonic devices.

Design of topological micropillar cavities for Purcell enhanced single photon emission from semiconductor quantum dots

Design of topological micropillar cavities for Purcell enhanced single photon emission from semiconductor quantum dots

Optimizing Solar Dish Concentrator Efficiency with Nanofluids and Diverse Cavity Design

Optimizing Solar Dish Concentrator Efficiency with Nanofluids and Diverse Cavity Design

Conventional soliton and noise-like pulse emissions at 1.98μm utilizing tungsten trioxide as mode-locker

In this paper, we experimentally demonstrate the dual pulse emissions of conventional soliton (CS) and noise-like pulse (NLP) in thulium-holmium co-doped fiber laser using tungsten trioxide saturable absorber (WO3-SA). The CS pulse delivered 2[Formula: see text]ps width, centered at 1982.8[Formula: see text]nm. Increasing the pump power and alteration of polarization states switched the CS to the NLP regime with 1990.0[Formula: see text]nm central wavelength, 17.2[Formula: see text]nm spectral bandwidth, and 396[Formula: see text]fs spike width riding on top of a wide picosecond pulse pedestal in the time domain. This work suggests the capability of WO3-SA as a pulse initiator for future dual-source ultrashort pulses based on an all-fiber laser cavity design.

Photomechanical investigation on the impact of endodontic cavity design on the biomechanical response in mandibular posterior teeth

The traditional endodontic cavity (TEC) facilitates canal preparation, but may increase susceptibility to root fracture; conservative endodontic cavities (CEC) aim to preserve tooth structure to maintain the structural integrity of root-filled teeth. The objective of this study was to evaluate the effect of access cavity design and the degree of pulp chamber roof removal on the microstrain distribution patterns under different levels of functional loading using digital moiré interferometry (DMI). Twelve extracted human teeth (N=12) were included, comprising of mandibular premolars (n = 6) and mandibular first molars (n = 6). Specimens were subjected to physiologic levels of compressive loading ranging from 10 to 50N for each group. DMI fringe patterns were acquired three times for each pecimen: prior to endodontic cavity preparation (control group (CG)), after conservative endodontic cavity preparation (CEC), and following traditional endodontic cavity preparation (TEC). The acquired fringe patterns were used to determine the microstrain distribution at the coronal and cervical dentin. The data was analyzed qualitatively and quantitatively using one-way ANOVA and T-tests (P< 0.05). The intact crowns of CG teeth showed significantly less microstrain, when compared to CEC and TEC with a distinct shift in coronal microstrain in both CEC and TEC groups. There were significant differences between both the coronal and cervical microstrain in the CG, CEC, and TEC groups. The roof of the pulp chamber contributes to a distinct biomechanical response in posterior teeth. The microstrain at the coronal and cervical level increased significantly following de-roofing of the pulp chamber in both CEC and TEC groups, with the TEC resulting in higher coronal microstrain compared to CEC group.

Resonant cavity structural design of carbon-based intrinsic metamaterial absorbers for broadening the effective absorption bandwidth

The effective absorption bandwidth (EAB) of absorptive materials has always been a bottleneck limiting their applications. Particularly, the combination of macroscopic structural design and the loss functions at the microscopic level of materials provides an efficient solution to this issue. Herein, a novel approach was proposed, integrating macroscopic structural design with microscopic loss functions to broaden the effective absorption bandwidth (EAB) through designing an intrinsic metamaterial absorber composed of a uniform blend of carbon-based absorbing materials and polydimethylsiloxane. A key innovation lies in the dual cubic resonant cavity design, where the multiple dimensions of the resonant cavities enable the absorber to achieve effective impedance matching across a wide frequency range. Additionally, the generation of a bottom ring current induces a magnetic field, which enhances the metamaterial absorber’s capability for further attenuation of electromagnetic wave energy. These innovative designs enable traditional carbon-based absorbing materials to achieve exceptional absorption performance, with the EAB being 2.37 times that of the skin structure, addressing the narrow EAB issue of traditional carbon-based absorptive materials. Experimental results demonstrate that the prepared samples achieve an absorption rate of 90 % for electromagnetic waves in the frequency range of 5.74 to 18 GHz under normal incidence, consistent with the simulation results. This absorber boasts advantages of broadband, with an equivalent thickness of only 2.94 mm. Its structure is easy to manufacture, demonstrating certain potential applications, and providing valuable insights for the work of other researchers.

Exploring the criterion for the self-pulsing suppression of mid-IR intracavity OPO with self-Raman scattering.

The stimulated Raman scattering (SRS) from the Nd:YVO4 gain medium is originally employed to eliminate the self-pulsing effect from the intracavity optical parametric oscillator (OPO) for achieving a continuous-wave (CW) mid-infrared output. The SRS with a second-order pump-wave power depletion is applied as the damping for the coupling between OPO pump-wave relaxation oscillation and signal-wave depletion. The SRS threshold conditions for different cavity and diode-pumped mode size designs are theoretically and experimentally explored. By using different resonators, the CW mid-infrared output from 120 mW to 1.56 W at the diode pump power from 3 to 19.3 W can be successfully demonstrated.

Watt-level long-term stable ultra-narrow linewidth 1064 nm single-longitudinal-mode ring cavity fiber oscillator

This study presents a high-power, single-longitudinal-mode (SLM) fiber oscillator with a ring cavity design, operating at 1064 nm. Utilizing a double-cladding ytterbium-doped fiber as the gain medium, the system incorporates a fiber Bragg grating Fabry-Perot cavity and a dual coupler ring for step-by-step filtering to achieve SLM operation. With a pump power of 4.19 W, the oscillator delivered an output power of 1.01 W and narrowed the linewidth to 147 Hz, with the potential for further power increase. The oscillator demonstrated excellent longitudinal-mode stability, maintaining mode-hop-free operation for 8.7 hours after temperature stabilization. To the best of our knowledge, this work represents the longest duration of mode-hop-free operation and the narrowest laser linewidth achieved by a free-running ring-cavity SLM fiber oscillator at watt-level output powers.

Coherent Perfect Absorption of Arbitrary Wavefronts at an Exceptional Point.

A coherent perfect absorber exploits the interferometric nature of light to deposit all of a light field's incident energy into an otherwise weakly absorbing sample. The downside of this concept is that the necessary destructive interference in coherent perfect absorbers gets easily destroyed both by spectrally or spatially detuning the incoming light field. Each of these two limitations has recently been overcome by insights from exceptional-point physics and by using a degenerate cavity, respectively. Here, we show how these two concepts can be combined into a new type of cavity design, which allows broadband exceptional-point absorption of arbitrary wavefronts. We present two possible implementations of such a massively degenerate exceptional-point absorber and compare analytical results with numerical simulations.

Comparative analysis of inlet and outlet cavity designs on the thermal-hydraulic performance of compact heat exchangers for combustion engine exhaust heat recovery

ABSTRACT Improving the Internal Combustion Engines (ICEs) overall thermal efficiency is crucial to reduce fuel consumption and emissions. To achieve this goal, waste heat recovery from exhaust gases remains the most promising strategy, which involves the utilization of compact heat exchangers. This study evaluates the performance of novel Monolithic Integrated Thermal Exchange Matrixes (MITEMs) designs for recovering exhaust heat from a 70 hp diesel engine, focusing on the impact of inlet/outlet cavities. Computational Fluid Dynamics simulations were employed to analyze the heat transfer rate, pressure drop, and overall thermal-hydraulic performance of different MITEM designs. The Rectangular Channels with Large Cavities (RCLC) design exhibited superior performance, enhancing the heat transfer rate by 14.7% compared to the baseline design while limiting pressure drop increase to 9.2%. The RCLC design increased local Nusselt numbers and heat transfer coefficients by up to 60%, achieving peak velocities of 98 m/s within cross-sectional planes. These findings provide valuable insights for optimizing exhaust heat recovery systems in diesel engines.

Integrated chirped photonic-crystal cavities in gallium phosphide for broadband soliton generation

Chirped mirrors have underpinned advances in ultra-fast lasers based on bulk optics but have yet to be fully exploited in integrated photonics, where they could provide a means to engineer otherwise unattainable dispersion profiles for a range of nonlinear optical applications, including soliton frequency comb generation. The vast majority of integrated resonators for frequency combs make use of microring geometries, in which only waveguide width and height are varied to engineer dispersion. Here, we present an integrated photonic-crystal Fabry–Pérot resonator made of gallium phosphide (GaP), a material exhibiting a Kerr nonlinearity 200 times larger than that of silicon nitride and a high refractive index that permits the creation of strongly chirped photonic-crystal mirrors. Leveraging the additional degrees of freedom provided by integrated chirped mirrors, we disentangle optical losses from dispersion. We obtain an overall dispersion that is more anomalous than that achievable in both silicon nitride and gallium phosphide ring resonators with the same free-spectral range (FSR), while simultaneously obtaining higher quality factors than those of GaP ring resonators. With subharmonic pulsed pumping at an average power of 23.6 mW, we are able to access stable dissipative Kerr frequency combs in a device with a FSR of 55.9 GHz. We demonstrate soliton formation with a 3-dB bandwidth of 3.0 THz, corresponding to a pulse duration of 60 fs. This approach to cavity design based on photonic-crystal reflectors offers nearly arbitrary dispersion engineering over the optical transparency window of the nonlinear material.

Energy-managed soliton fiber laser

Ultrafast fiber lasers constitute a flexible platform to investigate new solitary wave concepts. To surpass the low energy limitation of the conventional solitons generated in standard telecom fibers, successive breakthroughs have promoted the usage of an important frequency chirping within fiber oscillators. This lead to original solitary wave regimes such as stretched-pulse, all-normal-dispersion, and self-similar dynamics. We here revisit ultrafast fiber lasers built from standard optical fibers featuring solely anomalous dispersion. We propose a new cavity design enhancing key dissipative effects with contained frequency chirping and demonstrate the generation of high energy pulses in the few-picoseconds regime. The involved intracavity dynamics blends conventional and dissipative soliton features in an unseen way with low- and high-energy propagation regions, allowing an increased flexibility and novel scalability prospects.

All-solid continuous-wave Nd: YVO4-diamond intracavity Raman laser

We demonstrated a continuous intracavity diamond Raman laser operating by linear-cavity and V-cavity design. The diamond crystal as the Raman medium and Nd: YVO4 as the laser gain medium was utilized to achieve high beam quality Stokes output with narrow line width. By employing linear and V-shaped cavity, we achieved Stokes light outputs of 1.68 and 2.26 W, respectively. Compared to the linear cavity, the V-shaped cavity has a higher conversion efficiency of 11.07% and a narrower linewidth of 0.07 nm. Mechanism for linewidth of different cavity design and methods for further increasing power range and high quality are discussed.

A fast quadrupole-based analytical model for solving transient heat transfer in ventilated double-skin walls and assessing their energy saving potential

This research proposes a fast and accurate method for modeling transient heat transfer in ventilated double-skin façades (VDFs) with forced ventilation to predict their energy-saving potential. Using the thermal quadrupole formalism, the method solves the VDF problem in the Laplace domain while considering the full transient nature of the heat transfer; the only approximation is in space. The solution involves obtaining a general transfer function that predicts heat transfer rates or air temperatures at ventilated cavity's exit. The quadrupole method is validated against computational fluid dynamic numerical simulations conducted under similar meteorological, design and boundary conditions. A very good agreement was found (less than 3 % average deviation) with a significant reduction in computation time (less than 3s against 6h for CFD calculations). The model is computationally efficient and can consider important factors such as the opacity of the walls, construction materials, and air cavity design parameters. Finally, the model allows the assessment of the energy-saving potential of VDFs under various scenarios compared to conventional systems, which helps contributing to more sustainable building design practices. The energy efficiency of a VDF configuration was compared against a conventional wall system. Energy savings of 8.4 and 5.2 % were obtained, in cold and hot climates respectively.

Influence of Endodontic Cavity Design on Interfacial Voids, Class II Resin Composites Sealing Ability and Tooth Fracture Resistance: An In Vitro Study.

Objective: The aim of this in vitro investigation is to study the effect of endodontic cavity design on interfacial voids, class II resin composite sealing ability, and fracture resistance in mandibular premolars. Methods: A total of 48 single-rooted mandibular premolars received compound class II preparations with either traditional flare access cavities (group A) or contracted endodontic cavity preparations (group B). Each study group was subdivided according to the coronal restoration into two sub-groups as α and β. In the α group, a microhybrid composite was used after etch-and-rinse bonding technique using an MDP-containing universal adhesive. In the β group, a self-adhesive composite was used as coronal restoration after endodontic treatment (n = 12) for each subgroup. A micro-CT analysis was performed to assess the obturation interfacial voids and tracing of class II cervical interfacial adaptation. The tooth fracture resistance testing was then performed adding an extra group of 12 sound non-prepared teeth, which were tested as the control for fracture strength testing. A one-way ANOVA and post-hoc testing were used together with descriptive statistics for an analysis of the mean values of obturation interfacial voids. A two-way ANOVA was used to assess the fracture resistance test results, and to find the influence of endodontic access design and the type of composite material on the fracture resistance testing. Chi-square testing was employed to analyze the cervical interfacial seal of the class II restorations. Results: A one-way ANOVA revealed that there were no statistically significant differences between test groups in the amount of obturation interfacial voids (p > 0.05). There were no statistically significant differences between test groups in terms of cervical interfacial sealing ability (p > 0.05). A two-way ANOVA revealed that no statistically significant differences between test groups including the control group existed in terms of the fracture resistance testing (p > 0.05). Conclusions: Although it does not improve tooth fracture resistance, the contracted endodontic access cavity does not deteriorate the quality of obturation in terms of the interfacial porosity. The self-adhesive composite does not improve the efficiency of cervical interfacial adaptation or tooth fracture resistance regardless of the endodontic access cavity shape, yet it revealed a substantial load-bearing capacity.

Direct extraction of optical constants of organic semiconductors in ultrastrongly coupled microcavities and their application in antireflection design for polariton devices

The strongly bound Frenkel excitons in organic semiconductors enable strong or even ultrastrong exciton-photon coupling in room-temperature cavities, with the resulting polariton states typically resolved through reflectance measurements. This paper demonstrates that the distinct features of exciton and polariton modes in the reflectance spectra of strongly/ultrastrongly coupled organic microcavities can be effectively utilized to extract the optical constants and physical thickness of the embedded organic semiconductor. We investigate metal-clad microcavities based on two prototype conjugated polymers, poly[2-methoxy-5-(3,7-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV) and poly(3-hexylthiophene) (P3HT), both exhibiting ultrastrong coupling characteristics. The (n,k) spectra and thickness of these polymer films are determined by fitting the normal incidence reflectance spectra of organic microcavities, using Kramers-Kronig transformation and transfer-matrix calculations with varying optical and thickness parameters. We also examine the individual effects of the main fitting parameters on the spectrum, establishing a close correlation with the underlying polariton properties. Moreover, we analyze the optical admittance at exciton and polariton modes to understand reflectance variations with different parameters, which facilitates precise control of optical properties at specific modes through cavity design. Finally, using the extracted optical constants of MDMO-PPV and P3HT, we propose optimized microcavity designs that exhibit antireflection at the lower polariton mode for potential luminescence and photodetection device applications.

Formation and conversion of high-peak-power structured beams by an Nd:YVO4/Cr4+:YAG laser subject to tight-focusing off-axis pumping

A compact Nd:YVO4/Cr4+:YAG passively Q-switched laser in a near-hemispherical resonator is exploited to realize high-peak-power pulsed beams with high spatial degrees of freedom. Beneficial from the advantages of strong intracavity beam focusing as well as the point-like excitation condition for the proposed cavity design, various high-order structured pulses as coherent superpositions of multiple degenerate eigenmodes are stably generated under different off-axis pump schemes. Besides, by employing external-cavity astigmatic mode conversion (AMC), the oval-shaped and chessboard-like structured pulses under on-axis and 1D off-axis pumping are transformed into exotic modes with polygonal and figure-eight-shaped envelopes to further enrich the spatial complexity of the generated fields. With well-defined beam structures that are reconstructed using the analytical resonant wave functions of the resonator, the phase structures of AMC pulsed fields are numerically resolved to present a variety of singularity arrays. Experimental results reveal that the overall peak power of the on-axis and off-axis generated structured pulses respectively exceeds 600 W and 1 kW while maintaining good pulse train stability with peak-to-peak amplitude fluctuation to be less than 10% and 15%.

Review of Innovative Cavity Designs in Metal–Insulator-Metal Waveguide-Based Plasmonic Sensors

AbstractPlasmonic sensors utilizing metal–insulator-metal (MIM) waveguides represent a significant advancement in sensing technology due to their high sensitivity and versatility. These sensors leverage surface plasmon polaritons to detect minute changes in the surrounding environment, making them highly effective for a range of applications. For instance, they can precisely measure variations in the Refractive Index, which is crucial for monitoring chemical concentrations and biological interactions. Additionally, MIM waveguides can be adapted to sense temperature fluctuations, pressure changes, and the presence of specific gases, providing valuable insights in fields such as environmental surveillance, medical diagnostics, and industrial processes. In recent years, a variety of sensor cavity shapes have been proposed to enhance sensor performance. This review examines how these innovative geometries optimize sensor cavities to achieve unprecedented levels of resolution and sensitivity, underscoring their transformative potential across a broad spectrum of scientific and practical applications.

Prototype optical enhancement cavity for steady-state microbunching.

The innovative mechanism of steady-state microbunching (SSMB) promises a potent light source, featuring high repetition rate and coherent radiation. The laser modulator, comprising an undulator and an optical enhancement cavity, is pivotal in SSMB. A high-finesse prototype optical enhancement cavity for SSMB with an average power of 55 kW is described in this paper. Preliminary design of the laser modulator, experimental setup, and methods to address frequency degeneracy and power coupling issues are discussed. D-shaped mirrors are utilized to successfully suppress the modal instability. This study is the first to illustrate the finesse reduction caused by high-order mode damping during experiments. The experimental and simulation results match closely. A cavity power coupling model is established, and the experimental results verify the correctness of the coupling model. A method for estimating the absorption coefficient through thermal-induced evolution of cavity mode has been implemented. Experimental results demonstrate a high-average-power enhancement cavity with a finesse of 16 518 ± 103 and an estimated average absorption coefficient of 12 ppm for the cavity mirrors. The findings contribute to the advancement of SSMB by providing insights into the design and operation of high-power optical enhancement cavities.

Development and tests of the 499.8 MHz srf cryomodules for HEPS

A 499.8 MHz single-cell superconducting cavity has been proposed as the active third-harmonic cavity for the High Energy Photon Source (HEPS), a 6 GeV diffraction-limited synchrotron light source currently under construction in Beijing. Two 499.8 MHz cryomodules are required to provide a total of 3.5 MV of rf voltage and 400 kW of beam power. A mechanically enhanced cavity design, based on the original KEKB-type cavity, was developed to meet the specifications of HEPS. Three cryomodules have been assembled and subjected to horizontal tests. A comprehensive clean-assembly procedure was developed, resulting in excellent rf performance maintained from vertical tests to horizontal tests at cryogenic temperatures. The unloaded quality factors of all three modules exceeded 2.45×109 at 1.75 MV, significantly surpassing the design goal. No field emissions were observed throughout the tests. These are the highest-performing 500 MHz modules treated by buffered chemical polishing, also outperforming the average performance of their electropolished counterparts. Following dedicated analyses and multiple road tests, one cryomodule was successfully transported in its entirety from the test platform to the HEPS tunnel, with well-controlled accelerations on delicate components. Vacuum integrity and performance were well maintained. The module has been accelerating electron beams since August 2024 for the HEPS commissioning. This paper presents the design, fabrication, assembly, cryogenic tests, and transportation of the mechanically improved 499.8 MHz single-cell srf cryomodule.