Bragg Reflector Research Articles

Generation of broadband chaotic laser based on a four-segment InP-based monolithically integrated chaotic semiconductor laser

Aiming at the problems of limited bandwidth and obvious time-delay signature (TDS) of monolithically integrated chaotic semiconductor lasers, this paper proposes a four-segment InP-based monolithically integrated chaotic semiconductor laser. The laser structure is composed of a distributed feedback (DFB1) laser region, a semiconductor optical amplifier (SOA) region, a distributed Bragg reflector (DBR) grating region and a distributed feedback (DFB2) laser region. Mutual injection between the two DFB laser regions effectively enhances the bandwidth of power spectrum. The DBR grating region is used to form a complex multi-feedback cavity to suppress the TDS caused by the fixed external cavity structure. The simulation results show that the chaotic signal with the standard bandwidth of 29.2 GHz and the TDS value of 0.094 is generated. The research in this paper can further improve the performance of monolithically integrated chaotic laser, and provide a high-quality chaotic laser source for secure optical communication, chaotic lidar and distributed optical fiber sensing.

Enhanced collection efficiency of quantum emitter mediated by extra ordinary optical transmission in a plasmonic cavity

Abstract Manipulation of light-matter interaction has played a key role in developing modern quantum optical technologies. We have designed a plasmonic cavity by placing a gold film over a dielectric layer of PMMA (spacer layer) placed on the distributed Bragg reflector (DBR) with a high reflection band between 550 to 750 nm using computational models. We then introduced periodic holes of subwavelength dimension in the gold film and a quantum emitter (QE) is placed inside the spacer layer. When QE interacts with the periodic array of nano-holes, it shows an enhanced light transmission through them due to the extraordinary optical transmission (EOT) phenomenon, which arises due to surface plasmon polariton excitations in the metallic structures. When the QE emission is coupled with these modes, EOT will help its emission to propagate into the far-field domain. We find an average Purcell enhancement of 3 times with 50% collection efficiency without using an antenna. The results have the potential to develop better single-photon coupling interfaces, quantum communication systems, and other quantum technologies.

Experimental analysis and modeling of the penetration depth of uniform and apodized integrated Bragg reflectors

Experimental analysis and modeling of the penetration depth of uniform and apodized integrated Bragg reflectors

Impact of cut-off frequency effect on resonance energy transfer and Casimir–Polder interaction

Abstract Using the Green’s function approach, we investigate the resonance energy transfer (RET) rate between two parallel, identical two-level atoms in the presence of three types of cylindrical system: a distributed Bragg reflector (DBR), a perfectly reflecting wall (PRW), and a two-layer silicon fiber. Our analysis, incorporating the cut-off frequency condition, reveals significant suppression of the RET rate for atoms positioned along the axis of the cylinder with the PRW. In contrast, for atoms located within the DBR, the RET rate is enhanced in the far zone. Additionally, we find that for atoms oriented radially are placed inside or near the surface of the silicon fiber, the RET rate is entirely inhibited. We also investigate the Casimir–Polder (CP) interaction between a cut-off-frequency DBR and an excited atom, discovering a fully attractive potential towards the surface for the atom within the waveguide.

Nanoring Tamm cavity in the telecommunications O band

Quantum and classical telecommunications require efficient sources of light. Semiconductor sources, owing to the high refractive index of the medium, often exploit photonic cavities to enhance the external emission of photons into a well-defined optical mode. Optical Tamm States (OTSs) in which light is confined between a distributed Bragg reflector and a thin metal layer have attracted interest as confined Tamm structures are readily manufactureable broadband cavities. Their efficiency is limited however by the absorption inherent in the metal layer. We propose a nanoring Tamm structure in which a nanoscale patterned annular metasurface is exploited to reduce this absorption and thereby enhance emission efficiency. To this end, we present designs for a nanoring Tamm structure optimized for the telecommunications O band and demonstrate a near doubling of output efficiency (35%) over an analogous solid disk confined Tamm structure (18%). Simulations of designs optimized for different wavelengths are suggestive of annular coupling between the Tamm state and surface plasmons. These designs are applicable to the design of single photon sources, nano-LEDs, and nanolasers for communications.

Dual-Phase Singularity at a Single Incident Angle with Spectral Tunability in Tamm Cavities.

The phase singularity, a sudden phase change occurring at the reflection zero is widely explored using various nanophotonic systems such as metamaterials and thin film cavities. Typically, these systems exhibit a single reflection zero with a phase singularity at a specific incident angle, particularly at larger angles of incidence (>50 degrees). However, achieving multiple phase singularities at a single incident angle remains a formidable challenge. Here, the existence of a dual-phase singularity is experimentally demonstrated at a lower incident angle using a tunable Tamm plasmon polariton (TPP) cavity that consists of gold-coated ultralow-loss phase change material Sb2S3-based distributed Bragg reflector. It can excite narrowband TPP resonances from normal incidence to a wide angle of incidence for both s- and p-polarizations of light. Notably, this TPP cavity shows dual-phase singularity at lower angles of incidence since the excited TPP for s- and p-polarizations exhibits zero reflection at slightly different wavelengths for the same incident angle. A TPP cavity-based scalable hydrogen sensor is proposed and shows that the dual-phase singularity can further improve the sensitivity of singular phase-based sensing approaches. Moreover, spectrally tunable dual-phase singularity is experimentally demonstrated at a lower incident angle using a metal-free Tamm cavity.

High power GaSb-based distributed feedback laser with laterally coupled dielectric gratings at 1.95 µm

Traditional distributed feedback (DFB) or distributed Bragg reflector (DBR) lasers typically have commonly employed buried gratings as frequency-selective optical feedback mechanisms. However, the fabrication of such gratings often requires regrowth processes, which introduce significant technical challenges, particularly for material systems such as GaAs and GaSb. While metal gratings have been implemented in GaSb-based lasers, they incur additional absorption losses, thereby constraining the device's efficiency and achievable output power. Herein, we introduce a laterally coupled dielectric Bragg grating structure, which enables highly controllable, deterministic, and stable coupling between the grating and the optical mode. Our device demonstrates a continuous-wave output power of 47.02 mW at room temperature, exhibiting stable single-mode operation from 300 to 1000 mA and a maximum side mode suppression ratio of 46.7 dB. These results underscore the innovative lateral coupled dielectric grating as a feasible and technologically superior approach for fabricating DFB and DBR lasers, which hold universal applicability across different material platforms and wavelength bands.

Tailoring Second Harmonic Generation via Strong Coupling in a One‐Dimensional Photonic Crystal Heterostructure

Controlling harmonic generation is crucial for nonlinear optics and nanophotonic devices. Herein, a 1D photonic crystal heterostructure is theoretically proposed comprising a metal film, a lithium niobate layer, and a distributed Bragg reflector with a defect layer. The Tamm state and the defect state for dual‐band second‐harmonic generation (SHG) enhancement simultaneously are numerically investigated. Finite‐element method simulations indicate that SHG efficiencies based on Tamm plasmons and the defect state are 6.85 × 10−6 and 3.28 × 10−4, respectively. Intriguingly, the strong coupling between the defect state and Tamm plasmons enables spatial energy exchange, leading to the SHG switching between them. In the strong coupling region with Rabi splitting energy up to 5.5 meV, the SHG conversion efficiency reaching 5 × 10−5 is observed for both two new hybridized states. During the entire anticrossing Rabi splitting process, the SHG efficiency difference between two resonances can be modulated by up to two orders of magnitude. The coupling strength between two resonances is adjusted by varying the position of the defect layer. Simulation results are consistent with the coupled oscillator model. This work not only offers a platform for studying nonlinear frequency conversion but also establishes a new method of using strong coupling to tailor SHG.

Microcavity-assisted multi-resonant metasurfaces enabling versatile wavefront engineering

Metasurfaces have exhibited exceptional proficiency in precisely modulating light properties within narrow wavelength spectra. However, there is a growing demand for multi-resonant metasurfaces capable of wavefront engineering across broad spectral ranges. In this study, we introduce a microcavity-assisted multi-resonant metasurface platform that integrates subwavelength meta-atoms with a specially designed distributed Bragg reflector (DBR) substrate. This platform enables the simultaneous excitation of various resonant modes within the metasurface, resulting in multiple high-Q resonances spanning from the visible to the near-infrared (NIR) regions. The developed metasurface generates up to 15 high-Q resonant peaks across the visible-NIR spectrum, achieving a maximum efficiency of 81% (70.7%) in simulation (experiment) with an average efficiency of 76.6% (54.5%) and a standard deviation of 4.1% (11.1%). Additionally, we demonstrate the versatility of the multi-resonant metasurface in amplitude, phase, and wavefront modulations at peak wavelengths. By integrating structural color printing and vectorial holographic imaging, our proposed metasurface platform shows potential for applications in optical displays and encryption. This work paves the way for the development of next-generation multi-resonant metasurfaces with broad-ranging applications in photonics and beyond.

Toward 10-watt-level single-frequency fiber laser oscillators

High-power single-frequency laser oscillators are in great demand for some specific applications, such as quantum information and laser interferometer gravitational-wave observatories, where 10-watt or even 100-watt-level narrow-linewidth lasers with extremely low noise levels are required. In this paper, we present numerical investigations on the power scalability of single-frequency distributed Bragg reflector (DBR) ytterbium-doped phosphate fiber lasers and identify the low-quantum-defect operation approach to 10-watt single-frequency laser oscillators with the best figure of merit, defined by the ratio of the laser efficiency to the quantum defect. This research offers valuable insights for the design and development of high-power single-frequency DBR fiber laser oscillators at many other wavelengths.

Numerical simulation of electrically pumped active vertical‐cavity surface‐emitting lasers diodes based on metal halide perovskite

AbstractMetal halide perovskites (MHP)‐based electrically pumped vertical‐cavity surface‐emitting lasers (EPVCSEL) are promising candidates in optoelectronics due to low‐carbon footprint solution processing method. However, significant challenges impede MHP‐EPVCSEL manufacturing: (1) Distributed Bragg Reflectors (DBRs) composed of typical electron transport layers (ETLs) and hole transport layers (HTLs) are not conductive enough. (2) Due to large mobility difference of typical ETLs and HTLs, carriers‐unbalanced injection leads to severe performance degradation. Herein, we propose a potential strategy to address such challenges using MAPbCl3 and CsSnCl3 as carrier transport layers with mobility 3 orders larger than typical ETLs and HTLs. Via transfer matrix method calculations, we find that the reflectance of DBRs composed of MAPbCl3 (130.5 nm)/CsSnCl3 (108 nm) is larger than 91% with 10 pairs of DBRs. Furthermore, the proposed EPVCSEL device simulation shows that MHP‐EPVCSEL has the potential to achieve room temperature continuous wave lasing with a threshold current density of ∼69 A cm−2 and output optical power ∼10−4 W. This work can provide a deep insight into the practical realization of MHP‐EPVCSEL.

Ultrahigh quality factor cavity based on double dielectric nanocylinder metasurfaces

An optical cavity with a high quality factor (Q-factor) is essential for a wide range of applications, including lasers, single-photon sources, optical filters, and sensors. A high Q-factor cavity can enhance the interaction between light and materials, thereby improving the performance of optical devices. The Fabry–Pérot (FP) cavity is a typical optical device capable of achieving a high Q-factor; however, it often relies on distributed Bragg reflectors, which increase the size of the optical device. In recent years, Mie scattering-based metasurfaces with high reflectivity have been studied as alternatives to distributed Bragg reflectors. We propose a scattering-based FP cavity consisting of two metasurface layers. In our structure, a FP cavity with high reflectivity is formed by back-forward scattering from a single dielectric cylinder array. Our findings show that the structure exhibits a Q-factor of 4.36 × 1010 when the period and gap size are 658.8 nm and 740 nm, respectively. This high Q-factor is maintained even with misalignment between the two layers. Additionally, we confirmed that a high Q-factor of 2.6 × 106 appears in the low-index substrate structure, with the Q-factor increasing with the number of double cylinders in the finite structure. We also observed a strong directionality in the z-axis direction when examining the far field. We designed the dielectric FP cavity with a subwavelength thickness, is expected to significantly contribute to enhancing the Q-factors of various types of optical cavities.

Structure Design of UVA VCSEL for High Wall Plug Efficiency and Low Threshold Current

Vertical-cavity surface emitting lasers in UVA band (UVA VCSELs) operating at a central wavelength of 395 nm are designed by employing PICS3D(2021) software. The simulation results indicate that the thickness of the InGaN quantum well and GaN barrier layers affect the emission efficiency of UVA VCSELs greatly, suggesting an optimal thicknesses of 2.2 nm for the well layer and 2.7 nm for the barrier layer. Additionally, an overall consideration of threshold current, series resistance, photoelectric conversion efficiency, and optical output power results in the optimized thickness of the ITO current spreading layer, ~20 nm. Furthermore, by employing a five-pair Al0.15Ga0.85N/GaN multi-quantum barrier electron blocking layer (EBL) instead of a single Al0.2Ga0.8N EBL, the device shows a ~51% enhancement in the optical output power and a ~48% reduction in the threshold current. The number of distributed Bragg reflector (DBR) pairs also plays crucial roles in the device’s photoelectric performance. The device designed in this study demonstrates a minimum lasing threshold of 1.16 mA and achieves a maximum wall plug efficiency of approximately 5%, outperforming other similar studies.

Spectrally narrowband simultaneous dual-wavelength emission from Y-branch DBR diode lasers at 785 nm

Y-branch distributed Bragg reflector (DBR) diode lasers with a stable narrowband emission in simultaneous dual-wavelength operation with spectral distances below 3.2 nm are presented. The Y-branch laser consists of two laser branches with different DBR gratings serving as wavelength-selective rear-side mirrors. Therefore, two emission wavelengths with a spectral distance defined by the DBR grating periods can be generated simultaneously. A Y-coupler combines the two ridge waveguide (RW) branches into a single straight output RW. Devices with a spectral distance of 0.6 nm and 2.0 nm emitting around 785 nm are manufactured. Selecting the operation parameters carefully, stable narrowband emission for both wavelengths is obtained. Resistors serving as heaters implemented next to the DBR gratings allow for wavelength adjustment and a tuning of the spectral distance. At an optical output power of 100 mW, the spectral distance can be shifted from 0 to 1.55 nm (0–0.76 THz) for the former device or from 1.00 to 3.15 nm (0.49–1.54 THz) for the latter device, respectively. This makes the Y-branch DBR diode laser particularly interesting for the generation of THz beat-note signals, needed to generate THz radiation via photo-mixing.

Red-color-modulated perovskite solar cells with copper(I) thiocyanate/cellulose acetate–based distributed Bragg reflectors

Abstract This study investigates the development of perovskite solar cells (PSCs) equipped with distributed Bragg reflectors (DBRs) through a coating-based fabrication technique. The incorporation of DBRs enhanced the esthetic appeal and improved the light absorption properties of PSCs, rendering them suitable for building-integrated photovoltaics (BIPV). The DBRs, composed of 3–11 layers of copper(I) thiocyanate and cellulose acetate, exhibited peak reflectance at 700 nm. However, as the number of DBR layers increased, there was a corresponding decrease in short-circuit current density (Jsc) and power conversion efficiency (PCE) due to greater light reflection. Specifically, compared with PSCs without DBRs, those with 11-layer DBRs showed 41.2% and 39.0% reduction in Jsc and PCE, respectively. Despite these reductions, this study highlights the potential of colored PSCs for practical BIPV applications, achieving a balance between esthetics and efficiency.

High-Efficiency and Stable Emission Wavelength Red InGaN Light-Emitting Diodes with Porous Distributed Bragg Reflectors on Si Substrates

High-Efficiency and Stable Emission Wavelength Red InGaN Light-Emitting Diodes with Porous Distributed Bragg Reflectors on Si Substrates

High Efficiency Ultra-Narrow Emission Quantum Dot Light-Emitting Diodes Enabled by Microcavity.

A wide-color-gamut display enableby a narrow emission linewidth facilitates a visually immersive experience akin to the real world. Quantum dot light-emitting diodes (QLEDs) with excellent color purity and high efficiency hold great promise as future candidates for high-definition displays. However, most devices typically exhibit emission linewidths exceeding 20nm, and lack a universal strategy for further enhancing the color purity. In this study, a planar microcavity structure for realizing ultra-narrow emissions is developed by incorporating a distributed Bragg reflector into normal electroluminescent devices. By leveraging the strong optical resonance effect derived from this microcavity structure, red QLEDs are successfully fabricated with an extraordinary full width at half maximum of 11nm in the normal direction, beyond the BT.2020 color coordinates. The fabricated red-microcavity QLEDs exhibit a considerable enhancement in the external quantum efficiency, which increases from 28.2% to 35.6%, together with an extended operating lifetime. The strategy adopted herein will serve as an effective reference for achieving ultra-narrow emission and high-efficiency QLEDs.

Simulation model to enhance Bragg reflector assisted GeSn SACM-SPAD performance for 1550 nm LIDAR applications in autonomous vehicles

A safe 3-D lidar sensor for autonomous vehicle creates a high demand on 1550 nm SPADs detectors. Due to the limitation of the energy band gab and absorption coefficient of Si and Ge, their photodetectors have low efficiency at the 1550 nm wavelength. Doping Ge with Sn reduces its bandgap and enables higher efficiency in this range while adding Bragg reflector represents a smart way to increase absorption area effective thickness. Here a simulation model for Ge(1-x)Snx SACM SPAD is proposed to work as a 1550 nm laser detector. Two Bragg reflectors are built using Si\\SiGe and Si\\SiGeSn layers. Results show a significant enhancement on detector optical properties. PDP reaches 38 % at room temperature and the increase in Pdp due to Bragg reflector reaches 66 %. Although DCR also increases, it can be handled with proper dead time configuration.

Efficient single-frequency Tm:YAG crystal-derived silica fiber laser at 1.7 µm.

A single-frequency distributed Bragg reflector (DBR) fiber laser operating at 1720 nm has been demonstrated for the first time using a Tm:YAG crystal-derived silica fiber (TCDSF), to the best of our knowledge. A single-frequency laser with an over 220 mW output power was achieved from a 1.5-cm-long TCDSF when being in-band pumped by a homemade 1610 nm fiber laser. The slope efficiency reached 25.30% for the absorbed pump power. The optical signal-to-noise ratio (OSNR) of the laser was ∼69.78 dB, and the laser linewidth was ∼84.5 kHz. Additionally, the measured relative intensity noise (RIN) remained at -130 dB/Hz at frequencies above 9 MHz. The experimental results indicate that the TCDSF is a promising gain medium for single-frequency lasers at 1.7 µm.

Self-referencing refractive index sensor based on graphene-assisted TAMM plasmon cavity resonance.

In this Letter, we report TAMM plasmonic polaritons (TPPs) generated by few-layer MoS2 with a distributed Bragg reflector (DBR) structure in the terahertz frequency region by utilizing the transfer matrix method (TMM) and finite element method (FEM). By inserting a mono-graphene embedded cavity layer, we realize the graphene-induced mode strong coupling (GCM), which is a strategy of a refractive index sensor by optimizing the cavity layer spacing. By adjusting the chemical potential of graphene, GCM is modulated. μc = 0.1 eV and μc = 0.9 eV are selected as the on-off-state parameters, respectively. The difference in reflectance spectra presents a differential signal and a self-reference operation. The sensitivity of the designed refractive index sensor is 7.8 THz/RIU and a figure of merit (FOM) of 882 RUI-1 can be obtained. The proposed structure in our Letter demonstrates its potential application in high-performance self-reference refractive index sensors.