Optical Propagation Properties Research Articles

Singular optical propagation properties of two types of one-dimensional anti- PT -symmetric periodic ring optical waveguide networks

Two types of one-dimensional (1D) anti- PT -symmetric periodic ring optical waveguide networks, consisting of gain and loss materials, are constructed. The singular optical propagation properties of these networks are investigated. The results show that the system composed of gain materials exhibits characteristics of ultra-strong transmission and bidirectional reflection. Conversely, the system composed of loss materials demonstrates equal transmittance and reflectance at some frequencies. In both the systems, a new type of total reflection phenomenon is observed. When the imaginary part of the refractive indices of waveguide segments is smaller than 10−5, the system shows bidirectional transparency with the transmittance tending to be 1 and reflectivity to be smaller than 10−8 at some bands. When the refractive indices of the waveguide segments are real, the system will be bidirectional transparent at the full band. These findings may deepen the understanding of anti- PT -symmetric optical systems and optical waveguide networks, and possess potential applications in efficient optical energy storage, ultra-sensitive optical filters, ultra-sensitive all-optical switches, integrated optical chips, stealth physics, and so on.

Optical anisotropy and refractive index dispersion of Zn2GeO4 microrods

Dielectric resonators with high light confinement offer low optical losses, which is essential for the development of high-performance optoelectronic devices. Among the different compounds, Zn2GeO4 has emerged as a promising wide band gap transparent conductive oxide with a low-dielectric constant. In order to control and optimize their optoelectronic properties, a good knowledge of their optical constants, such as the refractive index, is required. Here, we exploit the behaviour of Zn2GeO4 microrods as optical cavities to estimate experimentally for the first time, so far as we know, the refractive index dispersion of this compound. In addition, first principle calculations by density functional theory (DFT) of the dielectric function as a function of the light propagation direction have been performed, which have revealed a strong optical anisotropy. The results show that there is also an influence of native defects on the optical propagation properties. These physical aspects are crucial to tailor the optical features of Zn2GeO4 and exploit them in optoelectronic devices with bespoke properties.

Analysis of Methods for Determining Shallow Waterbody Depths Based on Images Taken by Unmanned Aerial Vehicles.

Hydrographic surveys enable the acquisition and processing of bathymetric data, which after being plotted onto nautical charts, can help to ensure safety of navigation, monitor changes in the coastal zone, and assess hydro-engineering structure conditions. This study involves the measurement of waterbody depth, identification of the seabed shape and geomorphology, the coastline course, and the location of underwater obstacles. Hydroacoustic systems mounted on vessels are commonly used in bathymetric measurements. However, there is also an increasing use of Unmanned Aerial Vehicles (UAV) that can employ sensors such as LiDAR (Light Detection And Ranging) or cameras previously not applied in hydrography. Current systems based on photogrammetric and remote sensing methods enable the determination of shallow waterbody depth with no human intervention and, thus, significantly reduce the duration of measurements, especially when surveying large waterbodies. The aim of this publication is to present and compare methods for determining shallow waterbody depths based on an analysis of images taken by UAVs. The perspective demonstrates that photogrammetric techniques based on the SfM (Structure-from-Motion) and MVS (Multi-View Stereo) method allow high accuracies of depth measurements to be obtained. Errors due to the phenomenon of water-wave refraction remain the main limitation of these techniques. It was also proven that image processing based on the SfM-MVS method can be effectively combined with other measurement methods that enable the experimental determination of the parameters of signal propagation in water. The publication also points out that the Lyzenga, Satellite-Derived Bathymetry (SDB), and Stumpf methods allow satisfactory depth measurement results to be obtained. However, they require further testing, as do methods using the optical wave propagation properties.

Nanoresonator Enhancement of Majorana-Fermion-Induced Slow Light in Superconducting Iron Chains.

We theoretically investigate Fano resonance in the absorption spectrum of a quantum dot (QD) based on a hybrid QD-nanomechanical resonator (QD–NR) system mediated by Majorana fermions (MFs) in superconducting iron (Fe) chains. The absorption spectra exhibit a series of asymmetric Fano line shapes, which are accompanied by the rapid normal phase dispersion and induce the optical propagation properties such as the slow light effect under suitable parametric regimes. The results indicated that the slow light induced by MFs can be obtained under different coupling regimes and different detuning regimes. Moreover, we also investigated the role of the NR, and the NR behaving as a phonon cavity enhances the slow light effect.

Semi-analytical model of the optical properties of a metasurface composed of nanofins

We propose a method to evaluate the optical propagation properties of a dielectric non-resonant metasurface composed of rectangular nanofins. Our approach is based on a semi-analytical assessment of the effective indices to perform guided vectorial propagation inside the nanostructure. The proposed model is an extension of the commonly used Pancharatnam–Berry model where the effect of the incidence angle can be satisfactorily accounted for. The model shows good agreement with numerical simulations, and it can be inverted to give the nanofin rotation angle for a given output phase function. We show that the far-field distribution of a metalens predicted by our model is in good agreement with data from a simulation code.

Temperature and curvature insensitive all-fiber sensor used for human breath monitoring.

In this paper, an all-fiber sensor based on hollow core Bragg fiber (HCBF) is proposed and successfully manufactured, which can be used for human breath monitoring. Benefiting from the identical outer diameters of HCBF and single mode fibers (SMFs), the sensor can be directly constructed by sandwiching a segment of HCBF between two SMFs. Based on optical propagation properties of HCBF, the transmission light is sensitive to specific environmental change induced by human breath. Thus, the breath signals can be explicitly recorded by measuring the intensity of the transmitted laser. The sensor presents a rapid response time of ∼0.15 s and recovery time of ∼0.65 s. In addition, the HCBF-based sensor shows good insensitivity to the variation of temperature and curvature, which enables its reliable sensing performance in the dynamic and changeful environment.

Integrated dynamic wet spinning of core-sheath hydrogel fibers for optical-to-brain/tissue communications.

Hydrogel optical light-guides have received substantial interest for applications such as deep-tissue biosensors, optogenetic stimulation and photomedicine due to their biocompatibility, (micro)structure control and tissue-like Young's modulus. However, despite recent developments, large-scale fabrication with a continuous synthetic methodology, which could produce core-sheath hydrogel fibers with the desired optical and mechanical properties suitable for deep-tissue applications, has yet to be achieved. In this study, we report a versatile concept of integrated light-triggered dynamic wet spinning capable of continuously producing core-sheath hydrogel optical fibers with tunable fiber diameters, and mechanical and optical propagation properties. Furthermore, this concept also exhibited versatility for various kinds of core-sheath functional fibers. The wet spinning synthetic procedure and fabrication process were optimized with the rational design of the core/sheath material interface compatibility [core = poly(ethylene glycol diacrylate-co-acrylamide); sheath = Ca-alginate], optical transparency, refractive index and spinning solution viscosity. The resulting hydrogel optical fibers exhibited desirable low optical attenuation (0.18 ± 0.01 dB cm−1 with 650 nm laser light), excellent biocompatibility and tissue-like Young's modulus (<2.60 MPa). The optical waveguide hydrogel fibers were successfully employed for deep-tissue cancer therapy and brain optogenetic stimulation, confirming that they could serve as an efficient versatile tool for diverse deep-tissue therapy and brain optogenetic applications.

Tunable fast to slow light and second-order sideband generation in an optomechanical system with phonon pump

We theoretically demonstrate optomechanically induced transparency (OMIT) and its related coherent optical propagation properties such as fast and slow light effects in a cavity optomechanical system driven by a weak coherent phonon pump for suitable parametric and detuning regimes. The probe transmission spectrum experiences different processes under different detuning regimes, and the numerical simulations indicating a tunable and controllable fast-to-slow light propagation can be achieved by controlling the driving amplitudes and phase of the phonon pump. Further, the second-order sideband (SOS) generation is also demonstrated in the system, and it is found that the efficiency of the SOS generation can be significantly enhanced with manipulating the phonon pump in the resonance regime with numerical simulations. More interestingly, the SOS generation is also sensitive to the detuning (the off-resonance regime), and a robust SOS can be induced and the efficiency of the SOS generation even presents mode splitting which is similar to the linear OMIT. These results lead to good tunability of SOS generation and may find applications in manipulation of light propagation.

Majorana fermions induced Fano resonance and fast-to-slow light in a hybrid semiconductor/superconductor ring device

We demonstrate theoretically the Fano resonance and the conversion from fast to slow light in a hybrid quantum dot (QD)–semiconductor/superconductor (S/S) ring device, where the QD is coupled to a pair of Majorana fermions (MFs) appearing in the hybrid QD–S/S ring device. The absorption spectra of the weak probe field can exhibit a series of asymmetric Fano line shapes, and their related optical propagation properties such as fast- and slow-light effects are investigated based on the hybrid system for suitable parametric regimes. The positions of the Fano resonances can be determined by the parameters, such as different detuning regimes and QD–MFs coupling strengths. Further, the transparency windows (i.e., the absorption dip approaches zero) in the probe absorption spectra are accompanied by the rapid steep dispersion of the Fano resonance profile, which promises the slow- or fast-light effect, and even tunable fast-to-slow light propagation (or vice versa) can be achieved by controlling different parameter regimes. Therefore, Fano resonance may indicate another means to investigate MFs and the investigation may open up promising applications in quantum information processing based on MFs in solid-state devices.

Auxiliary cavity enhanced dipole induced transparency and fast to slow light using cavity quantum electrodynamics in a photonic crystal nanocavity

We investigate the probe-field transmission in a hybrid cavity quantum electrodynamic (CQED) system, where one optical cavity containing a quantum dot (QD) with high cavity dissipation is coupled to another auxiliary cavity with a high quality factor. We also investigate the hybrid system operating in the weak coupling regime of the light-matter interaction via comparing the QD photon interaction with the dipole decay rate and the cavity field decay rate. It is shown that the dipole induced transparency (DIT) regime similar to electromagnetically induced transparency (EIT) can be achieved due to the destructive interference of the cavity field in the weak coupling regime, which is extremely significant for the field of semiconductor CQED. The auxiliary cavity plays a key role in the hybrid system, which affords a quantum channel to affect the probe transmission leading to enhanced DIT. Further, DIT induced coherent optical propagation properties such as fast and slow light effects are also investigated based on the hybrid system for suitable parametric regimes. By controlling the coupling strength J and the decay rate ratio δ of the two cavities, tunable and controllable fast-to-slow light propagation can be achieved. This study provides a promising platform for understanding the dynamics of QD-CQED systems and may open up promising on chip applications in quantum information processing.

Optical and recombination properties of dislocations in cast-mono silicon from short wave infrared luminescence imaging

We demonstrate the use of the D1/D2 defect luminescence spectral range (1400 nm &amp;lt; λ &amp;lt; 1700 nm) of dislocations in cast-mono silicon to access geometrical tilt and opto-electronic recombination properties in their vicinity. The angle between dislocation and surface was determined thanks to the spatial asymmetry of the PL intensity in the regions close to the dislocations. Our optical model relies on the classical recombination–diffusion continuity equation as well as simple optical absorption and light propagation properties. It takes advantage of the optical transparency of silicon for wavelengths above 1400 nm. Carrier transport properties such as nonradiative lifetime around that location are also investigated. The model is discussed with a parameter study and the unicity of the extracted parameter set has been confirmed. As an example, we find out an angle of a selected dislocation pattern of about 25.4° with respect to the surface and an effective lifetime of 0.8–0.9 μs.

Fano resonance induced fast to slow light in a hybrid semiconductor quantum dot and metal nanoparticle system

We theoretically demonstrate the Fano resonance and the conversion from fast to slow light in a hybrid semiconductor quantum dot (SQDs)-metal nanoparticle (MNPs) with cavity quantum electrodynamics treatment. The absorption spectra of the weak probe field exhibit a series of asymmetric Fano line shapes and their related optical propagation properties, such as fast and slow light effects, are investigated based on the hybrid system for suitable parametric regimes. Further, the transparency windows (i.e. the absorption dip approaches zero) in the probe absorption spectra are accompanied by the rapid steep dispersion of the Fano resonance profile, which promises the slow or fast light effect, and even tunable fast-to-slow light propagation (or vice versa) can be achieved by controlling different parameter regimes. Therefore the investigation may indicate promising applications in quantum information processing based on the hybrid SQD-MNP system.

复介质对光量子阱光传输特性的激活效应

复介质对光量子阱光传输特性的激活效应

Light transfer characteristics of MoS2/metal one-dimensional photonic crystals

We present a study of the optical propagation properties of one-dimensional (1D) MoS2/metal photonic crystals (PCs) formed by periodic stacking of alternating MoS2 and metal layers in ambient air atmosphere. The propagation properties of light moving in such a structure are solved using the transfer matrix method. The optical properties of the MoS2/metal PCs are obtained analytically as a function of the materials used, the thicknesses of the layers, and the number of units. Among Ag, Al, Ni, and Fe, Ag was the most suitable metal for constructing PCs in the visible light range. The transmission spectra of the MoS2/Ag PCs exhibited periodic oscillation, with 1, 2 photonic band gaps (PBGs) in the 400–800 nm range when the thickness of the Ag film was 1–2 nm, and the optimum number of periodic units, N, was 10-20. Beyond this range, the transmittance of the structures monotonically decreased with increasing wavelength. The periodic oscillation properties of transmittance in MoS2/Ag 1D PCs can be used in sensors and detectors and as real-time monitors for biological and medical technology fields.

Excitation Position Sensitive Upconversion Emission of Lanthanide Ions Doped β‐NaYF4 Single Microcrystals

AbstractThe information about optical propagation properties and the directionality of emission light of individual microcrystal is essential for the applications of lanthanide ions doped (Ln‐doped) upconversion (UC) materials. In this work, we focus on the optical property of UC Yb3+ and Er3+ or Tm3+ doped β‐NaYF4 single crystal microrods and microdisks. Their optical propagation properties and directionality of the UC emission are investigated by the UC photoluminescence (PL) spectra and microarea PL microscopy images. The emission colors, directionality and intensity to the edges of the microcrystals are evidently sensitive to the initial excitation laser position. The waveguide effect and the self‐absorption effect of the doping ions are responsible for such anisotropic emission and emission color changing. And the ray‐dynamical interpretation can give well explanation on the emission light distribution.

Clean waveguides in lithium niobate thin film formed by He ion implantation

We report on the fabrication of channel waveguides by He ion implantation in a single-crystal LiNbO3 film bonded to a SiO2/LiNbO3 substrate. The planar waveguides were also formed under the same conditions to show the refractive index changes and the thermal annealing properties of ion-implanted LiNbO3 thin film. Using a moderate implantation energy, the formed channel waveguides were clean because He ions passed through the LiNbO3 thin film and deposited into the SiO2 layer. The optical propagation properties of channel waveguides were measured using an end-face coupling method, and the theoretical results were simultaneously calculated for comparison. The mode sizes and end-face reflectivities of channel waveguides with different widths were numerically calculated. The propagation losses were also estimated at approximately 12.2 and 14.3 dB/cm for 7 μm- and 5 μm-wide waveguides, respectively, by the Fabry–Perot method.

The formation and optical properties of planar waveguide in laser crystal Nd:YGG by carbon ion implantation

As one kind of prominent laser crystal, Nd:Y3Ga5O12 (Nd:YGG) crystal has outstanding performance on laser excitation at multi-wavelength which have shown promising applications in optical communication field. In addition, Nd:YGG crystal has potential applications in medical field due to its ability of emit the laser at 1110nm. Optical waveguide structure with high quality could improve the efficiency of laser emission. In this work, we fabricated the optical planar waveguide on Nd:YGG crystal by medium mass ion implantation which was convinced an effective method to realize a waveguide structure with superior optical properties. The sample is implanted by C ions at energy of 5.0MeV with the fluence of 1×1015ions/cm2. We researched the optical propagation properties in the Nd:YGG waveguide by end-face coupling and prism coupling method. The Nd ions fluorescent properties are obtained by a confocal micro-luminescence measurement. The fluorescent properties of Nd ions obtained good reservation after C ion implantation. Our work has reference value for the application of Nd:YGG crystal in the field of optical communication.

金属纳米光栅表面等离子体共振光学传播特性

本文分析了几种典型沟槽形状的金属纳米光栅(MNG)的光波传播特性。利用多重多级子程序法(MMP)计算了光栅形状和入射光波长对反射率和透射率的影响。结果显示，金属纳米光栅存在表面等离子体共振(SPR)和局域化表面等离子体共振(LSPR)两种共振模式。LSPR共振波长强烈依赖于光栅的沟槽形状、槽深、槽宽等结构参数，呈现宽带光谱响应机制，而SPR更多的依赖于光栅周期大小，呈现窄带光谱响应机制。两种共振模式的不同特性拓展了我们对金属纳米光栅的光学传播特性的认识，这对根据需要合理设计金属纳米光栅有重要的指导意义。 Optical propagation properties of metallic nano-gratings (MNG) with several classic groove shapes are analyzed. Influences of grating shape parameters and incident wavelength on reflectivity and transmission are calculated by means of multiple multipole program (MMP). Our results demonstrate that there are two resonant modes on the surface of MNG, surface plasmon resonance (SPR) and localized surface plasmon resonance (LSPR), respectively. LSPR presents a kind of broad band spectral response machanism, whose resonant wavelength strongly depends on groove shapes, groove depth and groove width parameters. SPR presents a kind of narrow band spectral response machanism, and its resonant wavelength is more dependent on grating period parameters. The different characteristics of the two resonant modes increase our knowledge about optical propagation properties of MNG. This investigation can be used as a guideline in designing metallic nano-gratings for certain applications.

Coherent optical propagation and ultrahigh resolution mass sensor based on photonic molecules optomechanics

We theoretically demonstrate the coherent optical propagation properties based on a photonic molecules optomechanics. With choosing a suitable detuning of the pump field from optomechanical cavity resonance, both the slow- and fast-light effect of the probe field appear in the system. The coupling strength of the two cavities play a key role, which affords a quantum channel and influences the width of the transparency window. Based on the photonic molecules optomechanical system, a high resolution mass sensor is also proposed. The mass of external nanoparticles deposited onto the cavity can be measured straightforward via tracking the mechanical resonance frequency shifts due to mass changes in the probe transmission spectrum. Compared with the single-cavity optomechanics mass sensors, the mass resolution is improved significantly due to the cavity–cavity coupling. The photonic molecules optomechanics provide a new platform for on-chip applications in quantum information processing and ultrahigh resolution sensor devices.

An efficient optical biochemical sensor based on a polyatomic photonic crystal ring resonator

In this paper, we introduce and investigate a design concept for a polyatomic photonic crystal ring resonator (PCRR). In contrast to conventional sensors, this PCRR comprises two different branching waveguides (WG), which are all oriented in the same lattice direction, but with different optical propagation properties due to the binary nature of the diatomic square lattice. Based on this new scheme, an on-chip biochemical sensor is proposed. Electromagnetic analysis, PWE and FDTD numerical techniques, were used to investigate the sensing performance. Our results show that such a sensor can efficiently detect small changes in the refractive index within the sensing area.