High-quality Cavity Research Articles

Smooth GaN membranes by polarization-assisted electrochemical etching

III-nitride membranes offer promising perspectives and improved device designs in photonics, electronics, and optomechanics. However, the removal of the growth substrate often leads to a rough membrane surface, which increases scattering losses in optical devices. In this work, we demonstrate membranes with etched surface roughness comparable to that of the as-grown epitaxial material, accomplished by the implementation of a properly designed built-in polarization field near the top of the sacrificial layer from an AlInN interlayer, which is polarization-mismatched to GaN. This leads to a steeper reduction in free carrier density during the electrochemical etching of the sacrificial layer, limiting the etching current and thus causing an abrupter etch stop. As a result, the root mean square roughness is reduced to 0.4 nm over 5 × 5 μm2. These smooth membranes open attractive pathways for the fabrication of high-quality optical cavities and waveguides operating in the ultraviolet and visible spectral regions.

Design and Modeling of High-Performance DBR-Based Resonant-Cavity-Enhanced GeSn Photodetector for Fiber-Optic Telecommunication Networks

In this work, we present a novel distributed Bragg reflector (DBR)-based resonant-cavity-enhanced (RCE) GeSn photodetector on Si substrates to achieve high-performance photodetection in terms of responsivity and 3-dB bandwidth (BW) for the short-wave infrared (SWIR) high-speed applications. The proposed structure consists of Si/SiO2 distributed Bragg reflectors (DBRs) to enhance the performance of the device. The top and bottom DBRs create a high-quality ( ${Q}$ ) optical cavity to enable multiple pass reflection schemes to increase the responsivity and also high wavelength selectivity with a sharp response. In addition, with an increase in Sn concentration in the active ( i- GeSn) layer, the photodetection range extends to longer wavelengths due to the shrinkage of bandgap energy. The calculated result shows an enhanced 3-dB BW and responsivity as compared to the existing p-i-n PDs. Therefore, the proposed DBR-based RCE GeSn PD can be a promising device for high-speed SWIR photodetection applications.

Optical Microfluidic Waveguides and Solution Lasers of Colloidal Semiconductor Quantum Wells.

The realization of high-quality lasers in microfluidic devices is crucial for numerous applications, including biological and chemical sensors and flow cytometry, and the development of advanced lab-on-chip (LOC) devices. Herein, an ultralow-threshold microfluidic single-mode laser is proposed and demonstrated using an on-chip cavity. CdSe/CdS@Cdx Zn1- x S core/crown@gradient-alloyed shell colloidal semiconductor quantum wells (CQWs) dispersed in toluene are employed in the cavity created inside a poly(dimethylsiloxane) (PDMS) microfluidic device using SiO2 -protected Ag mirrors to achieve in-solution lasing. Lasing from such a microfluidic device having CQWs solution as a microfluidic gain medium is shown for the first time with a record-low optical gain threshold of 17.1 µJ cm- ² and lasing threshold of 68.4 µJ cm- ² among all solution-based lasing demonstrations. In addition, air-stable SiO2 protected Ag films are used and designed to form highly tunable and reflective mirrors required to attain a high-quality Fabry-Pérot cavity. These realized record-low thresholds emanate from the high-quality on-chip cavity together with the core/crown@gradient-alloyed shell CQWs having giant gain cross-section and slow Auger rates. This microfabricated CQW laser provides a compact and inexpensive coherent light source for microfluidics and integrated optics covering the visible spectral region.

Substantiation of parameters of mine working drivage with blasting technique and cleaning charges in advance cutting holes

Drilling and blasting operations (D&B) are the most difficult and laborious operations in the process of mineral extraction, requiring permanent development and upgrading of methods and equipment. The aim of the study is to substantiate the parameters of drilling and blasting drivage of horizontal and inclined (up to 12o) mine workings on the basis of high-performance self-propelled equipment and new designs of box cuts with cleaning explosive charges (0.2 kg of 6ZhV ammonite), placed in advance holes of 65 to 105 mm in diameter. The paper presents the results of the analysis of practical experience and scientific achievements in the field of drilling-andblasting rupture of solid media and continuum mechanics. The need for new designs of box cuts, reliability of which in the formation of high-quality (clean) cut cavity reaches 0.95-1.00, was substantiated. New design options of box cuts have been developed, the peculiarity of which consists in provision of sufficient compensation (peripheral) volume with the use of blast hole cut charges for blasting rupture of trapezoidal partitions, with the compensation volume factor of 2.50 to 1.34. Promising areas of research were shown using the example of complicated structure ore deposits and large faults in the Kirovograd ore district and crystalline rocks of the Ukrainian shield at the following mines of Ukraine: PJSC KZhRK, CJSC Sukhaya Balka (Kryvyi Rih), Vostok-Ruda LLC, SE VostGOK (Zheltye Vody), CJSC ZZhRK, etc. Promising areas of research were proposed using the example of complicated structure ore deposits typically formed at the junction of large faults; besides, the use of environmentally friendly emulsion explosives and self-propelled emulsion explosive chargers was recommended.

Photo-Triggered Logic Circuits Assembled on Integrated Illuminants and Resonant Nanowires

High-performance photo-triggered electronic devices have already become an abiding target of optoelectronics. Current results, involving high-sensitivity phototransistors with the enhancement of material properties or the modification of electrical field, need an independent external light-source system. Nevertheless, few research studies inform of circuits in which the logic channel can be directly light controlled by a fully integrated photogate. In this paper, nanowire-based photon-effect transistors (PETs) combined with organic light-emitting diode (OLED) gates, and the photo-triggered nanowire circuits (PTNCs) are exhibited. The nanowire channels are manifested as high-quality optical cavities coupled by reflective electrodes for forming standing wave resonance. With the function of resonance, the nanowire channel under the illumination of the OLED gate can reach a high on/off ratio of ∼107, and under the different interconnected configuration of OLED gates, the functions of PETs can separately be realized as P-type and N-type of CMOS-like transistors. Then, a PTNC inverter that includes two nanowire channels with the respective OLED gates is operated utilizing electrical input voltage and logic opposite output signal. NAND and NOR gates as PTNC have also been demonstrated and indicate their corresponding outstanding arithmetic logic operation. PTNCs can effectively represent an innovative step toward multipurpose photonic circuits as to programmable logic components and photo-triggered computing.

Excitonic Lasers in Atomically Thin 2D Semiconductors

Two-dimensional (2D) atomically thin transition-metal dichalcogenides (TMD) and their van der Waals (vdW) heterostructures offer a platform with tightly bound intralayer/interlayer excitons for the on-chip fabrication of ultracompact nanolasers. Excitons in 2D TMD materials present a considerable binding energy of up to hundreds of meV, which permits a high Mott transition density of 1014 cm–2 and stable excitonic lasing under room-temperature operation and high pump fluences. Here, we review the recent progress on the lasing emission from intralayer excitons in TMD monolayers and interlayer excitons in vdW heterostructures incorporated with various high-quality optical cavities, including photonic-crystal, whispering-gallery-mode, distributed-feedback, distributed-Bragg-reflector cavities. Lasing emissions in TMD monolayers and heterostructures have been demonstrated by narrow emission peaks, a clear threshold for nonlinear amplification, time- and spatial coherence under either continuous-wave or pulsed light pumping. Finally, prospective and frontier research topics, including large-scale on-chip integration of TMD nanolasers, electrically pumped lasers, spin-polarized nanolasers, and exciton–polariton Bose–Einstein condensation (BEC) are highlighted.

Dynamical Casimir effect in cavities with two modes resonantly coupled through a qubit

We revisit the dynamical Casimir effect in high-quality multimode cavities, namely, generation of photons from vacuum due to fast external variation of system parameters. In one-dimensional case the spectrum of modes is equidistant, so for harmonic modulation an infinite number of modes become excited. But only one mode is usually excited in cavities with nonequidistant spectrum, apart from some exceptional configurations for which two or three modes are populated. Here is unveiled another scenario in which a small number of photons is generated from vacuum in two specific modes of a cavity with special spectrum profile. The scheme relies on strongly coupling the field to an initially unexcited qubit, whose frequency undergoes a weak harmonic perturbation. When the ratio between two modes' frequencies is accurately tuned in the vicinity of 3, these modes and the qubit can be driven to tripartite entangled states due to narrow three-photon resonances.

Developing a photonic hardware platform for brain-inspired computing based on 5 × 5 VCSEL arrays

Brain-inspired computing concepts like artificial neural networks have become promising alternatives to classical von Neumann computer architectures. Photonic neural networks target the realizations of neurons, network connections and potentially learning in photonic substrates. Here, we report the development of a nanophotonic hardware platform of fast and energy-efficient photonic neurons via arrays of high-quality vertical cavity surface emitting lasers (VCSELs). The developed 5 × 5 VCSEL arrays provide high optical injection locking efficiency through homogeneous fabrication combined with individual control over the laser wavelengths. Injection locking is crucial for the reliable processing of information in VCSEL-based photonic neurons, and we demonstrate the suitability of the VCSEL arrays by injection locking measurements and current-induced spectral fine-tuning. We find that our investigated array can readily be tuned to the required spectral homogeneity, and as such show that VCSEL arrays based on our technology can act as highly energy efficient and ultra-fast photonic neurons for next generation photonic neural networks. Combined with fully parallel photonic networks our substrates are promising for ultra-fast operation reaching 10 s of GHz bandwidths, and we show that a single non-linear transformation based on our lasers will consume only about 100 fJ per VCSEL, which is highly competitive, compared to other platforms.

Deterministic quantum entanglement between macroscopic ferrite samples

We show how macroscopic magnetic samples like yttrium iron garnet samples are excellent candidates for producing deterministic quantum entanglement and, thus, providing a platform for quantum information science. This requires strong coupling with a high quality cavity, which, in turn, provides an effective coupling between the two samples. For modest values of the squeezing of the pump, we obtain significant entanglement between the two garnet samples. This is the principal feature of our scheme. We present a number of tests for entanglement in terms of the experimentally observed quantities and, in this way, unfold a paradigm for producing entanglement. We also generate quantum states of collective magnon variables.

Design of an overmoded resonant cavity-based reactor for ceramic matrix composites production

The use of high-quality resonant cavities in microwave-assisted reactors is highly desirable. Thanks to the low losses in the cavity walls and to the possibility to reach critical coupling conditions, high energy efficiency can indeed be achieved.This paper describes the design, building, and test of a microwave-assisted Chemical Vapor Infiltration reactor at a pilot scale, based on an overmoded resonant cavity operating at 2.45 GHz.First, a general design method is proposed, in which the dimensions of the cavity are chosen in order to obtain a defined mode density and a high fraction of microwave power dissipated in the sample. Among the modes of this cavity, the most efficient one for the microwave heating of the sample is then determined by means of rigorous numerical analysis.In the graphite reactor cavity built using this approach, the condition of critical coupling is met in a large variety of samples and operating conditions. Moreover, a good agreement between experimental and simulated heating dynamics is obtained, which confirms the validity of the proposed method.As a result, disc-shaped samples with a diameter of the order of 10 cm and a thickness of the order of 1 cm can be brought to an infiltration temperature of about 900 °C within 5 min, using a microwave power of 1000 W, with a well controllable and reproducible temperature variation. In the infiltration of Nicalon preforms, more than 60% of the microwave power is dissipated in the sample.

Polariton Microlasers: Multiphoton‐Pumped Highly Polarized Polariton Microlasers from Single Crystals of a Dye‐Coordinated Metal–Organic Framework (Adv. Funct. Mater. 32/2020)

In article number 2003294, Wei Ji and co-workers introduce an archetypical polariton laser, for the first time, based on single-crystalline metal-organic framework microplates, which possess the potential to be titled “next-generation laser.” The discovery of polariton lasing from bare metal-organic framework microplates, without the need to be embedded in a high-quality optical cavity, eliminates all fabrication complexities usually involved in realizing polaritons.

The field-field and dipole-dipole coupling effects on the entanglement of the interaction between two qutrits with a two-mode field

In this paper we study the interaction between two qutrits ([Formula: see text]-type three-level atoms) with a two-mode field in a high quality cavity, considering the field-field (F-F) correlation and dipole-dipole (D-D) interaction. By defining a Hamiltonian corresponds to D-D interaction related to the two three-level atoms, we introduce a generalized Hamiltonian of Jaynes-Cummings model for the desired system and then the associated Schrödinger equation is solved. Finally, by achieving the reduced density matrix and then the linear entropy as a criterion for the entanglement, we investigate the influence of the F-F and D-D coupling on the degree of entanglement of the system. Our results show that there exists specific initial superposition of atomic states wherein the stable value of linear entropy is accessible. In addition, in such cases the F-F correlation and D-D interaction have not considerable effect on the entropy. Moreover, in general, as we have shown, the entanglement can be tuned appropriately by choosing the parameters involve in the model.

Linear cavity tapered fiber sensor using mode-tracking phase-shift cavity ring-down spectroscopy

Phase-shift cavity ring-down spectroscopy (PS-CRDS) is an alternative CRDS approach that allows the detection of minute changes in cavity losses by measurement of the phase shift experienced by a modulated laser as it propagates through a high-quality factor cavity. Fiber loop resonators and microresonators have been employed in previous PS-CRDS demonstrations for liquid phase applications. Here we employ a tapered fiber-based linear fiber cavity for the demonstration of a highly sensitive sensor for sucrose concentration in water using PS-CRDS. Our linear fiber cavity has a small cavity length ( ∼ 1.25 m ) that enables the observation and tracking of individual cavity modes in transmission and phase spectra recorded during laser sweeps. Hence, we eliminate the need for Pound–Drever–Hall locking of the laser source to the cavity resonance and thus provide a simpler experimental scheme. We analyze the recorded data sets to track the changes in phase shifts observed only when the laser wavelength is in resonance with the cavity modes. Such a mode-tracking PS-CRDS approach reveals limit of detection values less than around 400 µM, better than the performance of previously demonstrated PS-CRDS sucrose concentration sensors employing fiber loop resonators. The sensitivity of our sensor critically depends on the fiber taper diameter and can reach up to around 6°/1 mM Suc. for 3.2 µm taper diameter at 6 MHz modulation frequency using fiber Bragg gratings (FBGs) with reflectivities around 86%. This value can be further increased by employing FBGs with higher reflectivities or fiber tapers with smaller diameters provided that the cavity loss due to water absorption is compensated with an amplifier.

Method for Accurately Preparing Cavities on Cortical Bones Using Picosecond Laser.

Objective: This study was conducted to (1) evaluate a new method for accurately and automatically preparing dental implant cavities; (2) investigate the quantitative relationships between the number of focal-plane additive pulse layers (n) in two-dimensional ablation, the Z-axis feed rate, and the ablation depth (d) during cortical-bone ablation using a numerically controlled three-axis picosecond laser; and (3) establish appropriate methods for precise ablation control. Materials and methods: Two-dimensional ablation was performed on swine-rib blocks in the focal plane on a preset circular path using a picosecond laser device and an in-house-developed three-axis numerically controlled micro-laser galvanometer scanner. The maximum two-dimensional d and the quantitative relationship between n and d within the maximum d were consequently obtained. The measured and theoretical values of the ablated cavities were then compared to obtain n and d values corresponding to the minimum difference, and to evaluate the error in d, resulting in a higher-accuracy d value (i.e., single-step ablation depth) being obtained. Results: The diameter and deep errors between the measured and design data for 24 cavities were 2.76 ± 1.51 and 10.23 ± 4.82 μm, respectively. Thus, high-quality cortical-bone cavities preparation was achieved using a picosecond laser with the parameters employed in this study. Conclusions: Precise control of cortical-bone ablation using a picosecond laser can be attained by optimizing the single-step ablation parameters.

Tunneling time of the ultracold atoms: effects of the injected atomic coherence and field statistics

We inspect the tunneling characteristics of ultraslow atoms through the coherent field of a high quality cavity. The potential offered by the cavity is due to multiple barriers and well constituents that dictate propagation of the atoms through the cavity. We examine tunneling time of the traversal corresponding to the maximal constructive/destructive interference by tuning parameters of the injected coherence. It is found that the sub- superclassical character of the tunneling time can be efficiently controlled through the phase of the injected atomic coherence. Further, mazer action (i.e. the scattering like aspect of the interaction) may be obtained for somewhat faster atoms by employing an intense cavity field. For one of the dressed state (), our system offers a free transmission as the incident atoms examine zero potential.

Strain-modulated high-quality ZnO cavity modes on different crystal orientations

Dynamically regulated coherent light emission offers a significant impact on improving white light generation, optical communication, on-chip photonic integration, and sensing. Here, we have demonstrated two mechanisms of strain-induced dynamic regulation of ZnO lasing modes through an individual ZnO microbelt and microrod prepared by vapor-phase transport method. We systematically explained the dependence on externally applied strain and crystal orientation. Compared with the reduced size of resonant cavity played a major role in the microbelt, the resonant wavelength variation of the microrod under tensile stress is affected by the change in both the cavity size and the refractive index, which tends to antagonize in the direction of movement. It shows that the refractive index can be effectively regulated only when the stress is in the same direction along the c-axis. The results on the linear relationship between the resonance wavelength variation and applied strain imply the capacity of the devices to detect tiny stresses due to the ultra-narrow line width of the cavity mode with a high-quality factor of ∼104. It not only has a positive influence in the field of the modulated coherent light source, but also provides a feasible strategy for implementing color-resolved non-contact strain sensors.

Ultrahigh sensitive gas sensors based on slotted photonic wire-based structures including optical microcavities

In this paper, we investigated two-dimensional (2D) and three-dimensional (3D) finite element method (FEM) simulations to provide ultrasensitive gas sensors based on silicon-on-insulator (SOI) slotted photonic wire structures in the mid-IR spectral region, tuned for the wavelength 3.392 $$\upmu \hbox {m}$$. The proposed optical microstructures have the ability to detect methane gas in the environment in addition to sensing the gas flux from the hole/slot regions with a very high sensitivity ($${S} = 2.97$$) through a very high confinement of the electric field in the photonic wire slot region that leads to an increase in the interaction of light with gas. To further boost the sensitivity of the SOI slotted photonic wire structure to the methane gas, we designed an optical microcavity in the photonic crystal (PhC) slotted structure. This microcavity can sense the smallest methane gas level $$(0.36062\,\upmu \hbox {m}^{2})$$ with high sensitivity ($${S}= 27.45$$), by means of strengthening the high-quality factor cavity mode and reduction of effective modal volumes. In addition, the ultra-wide bandgap ($$1.9\,\upmu \hbox {m}$$) obtained from Bragg mirrors of the simulated microcavity structures can facilitate us to extend the sensing in a wide range of wavelengths.

Squeezed Light Induced Symmetry Breaking Superradiant Phase Transition.

We theoretically investigate the quantum phase transition in the collective systems of qubits in a high quality cavity, where the cavity field is squeezed via the optical parametric amplification process. We show that the squeezed light induced symmetry breaking can result in quantum phase transition without the ultrastrong coupling requirement. Using the standard mean field theory, we derive the condition of the quantum phase transition. Surprisingly, we show that there exists a tricritical point where the first- and second-order phase transitions meet. With specific atom-cavity coupling strengths, both the first- and second-order phase transition can be controlled by the nonlinear gain coefficient, which is sensitive to the pump field. These features also lead to an optical switching from the normal phase to the superradiant phase by just increasing the pump field intensity. The signature of these phase transitions can be observed by detecting the phase space Wigner function distribution with different profiles controlled by the squeezed light intensity. Such superradiant phase transition can be implemented in various quantum systems, including atoms, quantum dots, and ions in optical cavities as well as the circuit quantum electrodynamics system.

Synthetic gauge fields for phonon transport in a nano-optomechanical system.

Gauge fields in condensed matter physics give rise to nonreciprocal and topological transport phenomena and exotic electronic states1. Nanomechanical systems are applied as sensors and in signal processing, and feature strong nonlinearities. Gauge potentials acting on such systems could induce quantum Hall physics for phonons at the nanoscale. Here, we demonstrate a magnetic gauge field for nanomechanical vibrations in a scalable, on-chip optomechanical system. We induce the gauge field through multi-mode optomechanical interactions, which have been proposed as a resource for the necessary breaking of time-reversal symmetry2-4. In a dynamically modulated nanophotonic system, we observe how radiation pressure forces mediate phonon transport between resonators of different frequencies. The resulting controllable interaction, which is characterized by a high rate and nonreciprocal phase, mimics the Aharonov-Bohm effect5. We show that the introduced scheme does not require high-quality cavities, such that it allows exploring topological acoustic phases in many-mode systems resilient to realistic disorder.

Frequency-Selective Limiters Using Triple-Mode Filters

This paper presents the first frequency-selective limiter (FSL) with both power-activation and user-prompted override that also features a reconfigurable threshold power and frequency tuning with closed-loop feedback. The FSL is based on a tunable absorptive bandstop-to-all-pass filter with integrated electronics. Three distinct modes are available: user-defined bandstop, power-activated bandstop, and all-pass mode. In the user-defined bandstop mode, the FSL presents a measured notch of 45-55 dB at an user-defined center frequency within 1.5-2 GHz tuning range. The out-of-band insertion loss is less 0.8 dB. In the power-activated mode, the FSL switches intrinsically between its bandstop and all-pass responses based on the incident power level at any user-defined power threshold and frequency within the 1.5-2 GHz range. In the all-pass mode, the measured loss is less than 3.1 dB at the user-defined center frequency and less 0.8 dB elsewhere. The measurements are conducted including the two SMA connectors and the associated connector-to-microstrip transitions. The threshold power level is tunable in the -45 to +8 dBm range. The filter is designed and fabricated with high-quality substrate-integrated cavities with an extracted resonator unloaded quality factor (Qu) of 300. The unique features and the measured RF performance of the presented FSL are state-of-the-art results.