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The acousto-optic modulation over a broad near-infrared (NIR) spectrum with high speed, excellent integrability, and relatively simple scheme is crucial for the application of next-generation opto-electronic and photonic devices. This study aims to experimentally demonstrate ultrafast acousto-optic phenomena in the broad NIR spectral range of 0.77–1.1 eV (1130–1610 nm). Hundreds of GHz of light modulation are revealed in an all-optical configuration by combining ultrafast optical spectroscopy and light–sound conversion in 10–20 nm-thick bismuth selenide (Bi2Se3) van der Waals thin films. The modified optical transition energy and the line shape in the NIR band indicate phonon–photon interactions, resulting in a modulation of optical characteristics by the photoexcited interlayer vibrations in Bi2Se3. This all-optical, ultrafast acousto-optic modulation approach may open avenues for next-generation nanophotonic applications, including optical communications and processing, due to the synergistic combination of large-area capability, high photo-responsivity, and frequency tunability in the NIR spectral range.

We carried out the development and study of methods for changing the sensitivity of Fiber Bragg Gratings (FBG) to temperature and strain by applying various low-melting metals. Investigation of sensitive elements based on SMF-28 single-mode optical fibers with formed FBG and various metal coatings applied over the fiber have been made. The influence of FBG coating with low-melting metals on its sensitivity to temperature and deformation has been studied. Various fiber-optic sensitive elements have been developed, which are fibers with fiber Bragg gratings formed in them, while coatings of various thicknesses of tin or solder in the form of an alloy of tin and lead (Sn63Pb37) were deposited on the area with such diffraction structures. The presented experimental data are in good agreement with the calculated ones. The temperature sensitivity of the Bragg grating resonance with a solder or tin coatings is 4 times higher than the sensitivity of an uncoated grating. In turn, the analysis of the sensitivity to stretching allows us to conclude that, in comparison with the standard FBG, the sensitivity of the grating in the coating decreases and is about 0.017 pm/(μm/m) compared to 1.2 pm/(μm/m) (for the wavelength of the Bragg resonance 1530 nm) for a standard FBG without coating. The results obtained can be used to control and change the FBG sensitivity to temperature and/or defor

Based on potassium tantalate niobate (KTN) as a platform, a Lamb wave-generated tunable photonic structure is proposed. A half-micrometer-thick KTN film is perturbed by a GHz Lamb wave disturbance to produce alternate contraction and rarefaction. Considering the elasticity of the plate, the strength of the disturbance is optimized, and the induced strain is calculated. Following the photoelastic relations, the strain-modified optical properties of the medium along the film length are assessed. The spatial optical index distribution over a space of a few micrometers, as induced by elastic disturbance, may open forbidden electromagnetic band gaps. Utilizing the transfer matrix method, the dispersion curves and transmittance of electromagnetic waves are evaluated and analyzed. As a consequence of Lamb disturbance, a photonic band gap lying in the mid-wavelength infrared range is achieved from the KTN slab. To establish the band gap tunability, the effect of Lamb frequency on the range of photonic band gaps is analyzed. The accomplished acoustic-optical phenomenon on the KTN slab may be utilized for mid-wavelength infrared-ranged tunable optical applications. [ABSTRACT FROM AUTHOR]

We introduce a spectral analysis method in picosecond ultrasonics to derive strain pulse shapes in an opaque sample with known optical properties. The method makes use of both the amplitude and phase of optical transient relative reflectance changes obtained, for example, by interferometry. We demonstrate this method through numerical simulation and by analysis of experimental results for a chromium film.

As a new type of semiconductor fiber, silicon-core fibers have a higher non-linear effect compared with silica fibers. Forward-stimulated Brillouin scattering as a typical optical non-linear effect holds strong promise for applications in, for example, fiber-optic sensing. The study of the FSBS effect in silicon-core fibers facilitates further theoretical exploitation of the potential of FSBS in fiber-optic sensing. In this paper, the FSBS in the silicon-core fiber is studied using the finite element method. The model is based on a silicon-core fiber, whose silicon-core diameter is 4 μm and silica cladding diameter is 33.4 μm, and the optical field modes are classified by the vector method to obtain the acoustic field modes excited by FSBS—radial mode (R0m) and torsional radial mode (TR2m). The FSBS gain of the fiber shows that R0m has the best coupling with TM and TE optical modes, and TR2m has the best coupling with HE optical modes. It is concluded that the sound field frequency shift of R0m is more sensitive to the change in the effective refractive index of the optical field than that of TR2m. The factors affecting the gain are refined into photoelastic effects and moving boundary perturbations, and their contributions to the total gain are summarized. Finally, it was confirmed that a strong FSBS gain similar to 365.57 (1/mw) can be obtained with silicon-core fibers without the need to reduce the size to the usual dimensions of silicon waveguides, paving the way for further research studies in areas such as frequency-tunable laser emission, mode-locked pulsed lasers, low-noise oscillators, and optical gyroscopes.

The sense of touch is fundamental for a one-to-one mapping between the environment and a robot that physically interacts with the environment. Herein, we describe a tactile fingertip design that can robustly detect interaction forces given data collected from a camera. This design is based on the photoelastic effect observed in silicone matter. Under the force applied to the silicone rubber, owing to the stress-induced birefringence, the light propagating within the silicone rubber is subjected to the angular phase shift, where the latter is proportional to the increase in the image brightness in the camera frames. We present the calibration and test results of the photoelastic sensor design on a bench using a robot arm and with a certified industrial force torque sensor. We also discuss the applications of this sensor design and its potential relationship with human mechano-transduction receptors. We achieved a force sensing range of up to 8 N with a force resolution of around 0.5 N. The photoelastic tactile fingertip is suitable for robot grasping and might lead to further progress in robust tactile sensing. [ABSTRACT FROM AUTHOR]

Defect inspection methods are basic steps in electronic chip manufacturing and power device production processes in the semiconductor industry. Based on stress induced photoelastic anisotropy, in-line polarized stress imaging (PSI) and quantitative determination of the local shear stress component are possible in single crystalline silicon wafers. Hereafter, such polarization stress images are compared and validated quantitatively with results of finite element simulations based on different 3D elastic models. Uniquely, high resolution at high throughputs is achieved for 300 mm wafer size in the present quantitative stress imaging study. [Display omitted] [ABSTRACT FROM AUTHOR]

The sense of touch is fundamental for a one-to-one mapping between the environment and a robot that physically interacts with the environment. Herein, we describe a tactile fingertip design that can robustly detect interaction forces given data collected from a camera. This design is based on the photoelastic effect observed in silicone matter. Under the force applied to the silicone rubber, owing to the stress-induced birefringence, the light propagating within the silicone rubber is subjected to the angular phase shift, where the latter is proportional to the increase in the image brightness in the camera frames. We present the calibration and test results of the photoelastic sensor design on a bench using a robot arm and with a certified industrial force torque sensor. We also discuss the applications of this sensor design and its potential relationship with human mechano-transduction receptors. We achieved a force sensing range of up to 8 N with a force resolution of around 0.5 N. The photoelastic tactile fingertip is suitable for robot grasping and might lead to further progress in robust tactile sensing.

The surface of the normal component of the inverse tensor of the dielectric permittivity of a cubic photorefractive piezoelectric Bi12SiO20 crystal was constructed. A volume phase holographic grating with a wave vector along the 1 1 ¯ 1 crystallographic axis was recorded in this crystal. It is established that the combined action of the photoelastic and piezoelectric effects leads to an increasing normal component of the inverse tensor of the dielectric permittivity along the 1 1 ¯ 1 direction and a decreasing normal component of the inverse tensor of the dielectric permittivity in the perpendicular direction. It is revealed that the anisotropy of the contribution of the photoelastic and piezoelectric effects causes an increase in the output energetic characteristics (optimized in the azimuth of polarization of light waves) for the transmission hologram and their decrease for the reflection hologram. [ABSTRACT FROM AUTHOR]

A hybrid plasmonic–phononic cavity design which enables high vacuum coupling rate has been proposed in lithium niobate (LN) phononic crystals (Phncs) that have been perforated by air holes and coated with thin silver film. By tailoring the geometry, optomechanical interaction between the plasmonic modes (produced by the metal/insulator) and the phononic modes (confined by the phononic bandgap effect) is greatly enhanced. Numerical results based on finite-element method (FEM) reveal that in this hybrid plasmonic–phononic design, high vacuum coupling rate that predominantly contributed by moving boundary effect is on the order of 106 Hz, which is about one to two orders higher than that contributed by photoelastic effect shown in conventional phoxonic crystal designs. Results evidence how the vacuum coupling rate depends on geometrical parameters like the radius of the defect air hole, the thickness of silver layer, and LN layer. The simultaneous confinement and strong coupling, combined with other advantages as lack of constraint to the refractive index, and integration of piezoelectric material and metal in a chip, this hybrid design may be suitable for non-invasive biological sensing, optomechanically tunable plasmonic heater for drug release and lab-on-chip devices. [ABSTRACT FROM AUTHOR]

While the narrow bezel technology has gradually become one of the necessary technologies for LCD splicing screen products to improve their competitiveness, it also brings the problem of peripheral light leakage to the LCD splicing screen in the dark state. In order to quantify the level of peripheral light leakage in the dark state and propose corresponding improvement measures, this paper proposes a characterization method and test plan for light leakage sensitivity. The experimental results show that the characterization method can correctly reflect the light leakage level of the LCD splicing screen in the dark state. [ABSTRACT FROM AUTHOR]

We introduce a spectral analysis method in picosecond ultrasonics to derive strain pulse shapes in a opaque sample with known optical properties. The method makes use of both the amplitude and phase of optical transient relative reflectance changes obtained, for example, by interferometry. We demonstrate this method through numerical simulation and by analysis of experimental results for a chromium film., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Author(s).)

The experimental data on the mass transfer in condensed media under the action of mechanical stress and light pressure are presented. In both cases, the observed formation of periodic structures is interpreted from the point of view of the dynamical principle of minimum entropy production. The prospects of using the discovered self-organizing processes for the formation of photonic crystals and optical metamaterials are discussed. [ABSTRACT FROM AUTHOR]

The peculiarities of photoelastic and acousto-optic effects are first tested in chalcohalide 65GeS 2 -25Ga 2 S 3 -10CsCl glass exploring the interferometry method. The determined piezo-optic coefficients occur to be (in Br) π 11 = 2.8 ± 0.6, π 12 = 6.0 ± 0.9 and π 44 = − 3.2 ± 1.1. In respect to maximal acousto-optic figure of merit М 2 = 55.6 · 10 − 15 s 3 /kg proper for longitudinal acoustic wave propagation and polarization along X 2 ( і = 2) direction, this glass seems more perspective for photoelastic and acousto-optic modulation in visible and near IR ranges, than many alternative candidates, such as crystalline quartz, LiNbO 3 , CaWO 4 , PbMoO 4 , β -BaB 2 O 4, etc. For the first time it has been shown that piezo-optic effect of isotropic solids is anisotropic, and the degree of anisotropy is the difference of π 11 – π 12 coefficients. [ABSTRACT FROM AUTHOR]

Correct use of the photoelastic effect for the description of thermally induced refractive index change is discussed and the analytical relations between thermo-optic coefficients at zero stresses and zero strains are found for all classes of cubic crystals. These relations may be useful for the investigation of thermal effects in very promising sesquioxide class m3 laser crystals. An accepted set of elasto-optical coefficients of the YAG crystal and an alternative one found in the literature were used in numerical simulations. Significant differences in the calculated thermo-optic coefficients and induced birefringence are found using different sets of these coefficients. Misunderstandings related with the so-called photoelastic coefficients are resolved and new expressions for these coefficients are found. It is shown that the incorrect use of these coefficients for different pump beam distributions can lead to significant discrepancies for thermally induced birefringence. It is also shown that common use of the generalized thermo-optic coefficients significantly overestimates the values of optical power of thermal lenses when they are applied to the laser rods with lengths several times longer than their diameter. [ABSTRACT FROM AUTHOR]

A new method for calculating thermally induced phase distortions in laser ceramics is proposed. The depolarization degree as well as mean and dispersion of the phase incursion of a laser beam after passing through one ceramic element and at the output of the scheme with compensation of birefringence have been calculated. The specificity of photoelastic properties of 23 and m3 crystal classes has been taken into consideration. The results of the computations will be used for calculating parameters of beam quality in Part II of this paper. [ABSTRACT FROM AUTHOR]

Residual stresses within the veneer are linked to the high prevalence of veneer chipping observed in clinical trials of zirconia prostheses. We hypothesized that the thermal mismatch between the zirconia infrastructure and the veneer porcelain, as well as the rate used for cooling zirconia-veneer crowns, would be directly proportional to the magnitude of residual stresses built within the veneer layer. Two porcelains with different coefficients of thermal expansion were used to veneer zirconia copings, to create high or low thermal mismatches. The crowns were cooled according to a fast- or a slow-cooling protocol. The retardation of polarized light waves was used to calculate the residual stress magnitude and distribution across the veneer, according to the photoelasticity principle, in 1.0-mm-thick crown sections. While thermal mismatch was an important factor influencing the maximum stress development in the veneer, cooling rate had a minor role. Curved surfaces were preferential sites for stress concentration regardless of thermal mismatch or cooling rate. [ABSTRACT FROM PUBLISHER]

Halite crystal growth was conducted within a polydimethylsiloxane (PDMS) microfluidic device to understand the mineral deposition behavior in a confined environment as well as the properties and evolution of the crystallization pressure. Supersaturation was induced by cooling a NaCl solution from 35 to 25 °C, and time-lapse images of halite crystal growth in the PDMS channel were collected. Halite crystal growth caused the PDMS to deform when the crystal faces reached the PDMS channel walls. The interface between the halite crystal and the channel wall changed over time and showed non-equilibrium behavior. Deformation of the PDMS wall was evident from the photoelastic effect within the PDMS material. The crystallization pressure in the laboratory experiments was quantitatively evaluated through numerical models of microscopic PDMS deformation due to halite crystal growth. Halite indentation observed in the laboratory experiments was reproduced in the model based on the retardance observed by the photoelastic effects of the PDMS. The crystallization pressure, defined as the normal stress acting to the PDMS wall surface from the halite crystal, was inhomogeneously distributed along the interface, with a maximum value of 2.0 MPa at the crystal corner. PDMS microfluidic devices are useful for understanding the behavior of mineral precipitation in confined environments. Deformation analysis of the photoelastic stress, along with numerical modeling, may be used to examine the nature of the crystallization pressure and to shed light on the mechanism of deformation due to the crystallization pressure. [ABSTRACT FROM AUTHOR]

Abstract: In order to enhance the accuracy of three-component seismic acceleration detection, a novel three-component micro-optoelectronic mechanical systems (MOEMS) accelerometer based on photoelastic effect has been designed. The mechanical properties of sensitive unit under three-component acceleration are analyzed theoretically and a Finite Element Analysis (FEM) simulation is performed simultaneously. Meanwhile, a Mach-Zehnder (M–Z) interferometer which is based on photoelastic effect had been designed and a Beam Propagation Method (BPM) simulation has been processed as well, experimental results indicated that the sensor had a high sensitivity, wide frequency response range and a good linearity in the range of seismic band. [Copyright &y& Elsevier]

Abstract: We present a new method to calculate the indicative surfaces of the photoelastic effect in biaxial crystals. The corresponding equations are derived and applied to the calculations of the indicative surfaces of the longitudinal and transverse photoelastic effects in orthorhombic Cs2HgCl4 crystals. By means of the indicative surfaces the spatial anisotropy of photoelastic interaction in Cs2HgCl4 crystals is evaluated. [Copyright &y& Elsevier]

A theory of a novel optical filter of drawing the fiber Bragg grating by the heated elastic sheet is advanced. Based on the heat conduction equation, a set of functions of temperature and thermal expansion on the heated elastic sheet are calculated. And the most displacement of the heated elastic sheet is also described. Finally the expression of the reflected Bragg wavelength deviation in terms of the thermal power density of heat-source is deduced. The physics feasibility of these conclusions mentioned above is proved. It is a potential value for the novel optical filter to research. [ABSTRACT FROM AUTHOR]

We systematically analyze the mode-coupling effects of stress-induced long-period gratings (LPGs) using photonic crystal fiber (PCF). Two Mach–Zehnder interferometers based on this grating are demonstrated. These devices offer the unique advantages of being tunable and reconfigurable. Their good interfering efficiency makes them promising for wavelength-selective filters in WDM communication systems. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 1379–1383, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21647 [ABSTRACT FROM AUTHOR]

Abstract: In this paper, coupled-mode theory is applied to a two-core microstructured optical fiber for the first time to calculate the coupling coefficients for different fiber structures by employing a simple effective index model approach. The dependence of the mode coupling properties upon the geometrical parameters of the two-core structures (air-hole arrangement, hole size, and pitch size) and wavelength are evaluated systematically. The effective index coupled-mode theory is compared with the finite-element method based super-mode theory in details and the results show good agreement. The coupling characteristics are proven to be insensitive to the longitudinal strain by considering the photoelastic effects. [Copyright &y& Elsevier]

Abstract: We present a novel variable optical attenuator (VOA) using a new micro-optical waveguide (MOW) on micro-actuating platform (MAP) structure. The device consists of a fused biconical taper (FBT) coupler mounted on an electromechanical system where the axial stress over the waist of FBT coupler is precisely controlled. Its operation is based on change of coupling constant by compressive stress induced photoelastic effects on the waist zone. Three different types of devices operating near 1450 nm were fabricated with different cross-sectional morphologies at the FBT waists. The device with a circular cross section showed the highest stress sensitivity, where π phase shifts in the coupling constant were observed at an axial displacement of 9.5 μm. The proposed device showed a monotonic and continuous attenuation control up to 34.45 dB, with a very low PDL of 0.06 dB and a relatively low operating voltage of 15.3 V. [Copyright &y& Elsevier]

A new technology has been developed for optically visualizing the intensity distribution of the acoustic wave within a surface acoustic wave (SAW) device. In this technique, the strain generated by the SH (Shear Horizontal) wave in a LiTaO3 crystal is detected via the photoelastic effect as a change of polarization state of the light passing through the device. By detecting the SH component, which is the main component of the SAW on a 42°YX LiTaO3, the method provides for more direct observation of the behavior of the acoustic wave in a device than in the conventional technique that detects the SV (Shear Vertical) component, a secondary component. Based on the present technique, an acoustic wave observation setup is developed and a simple resonator is evaluated. It is found that the acoustic-wave distributions within an IDT depend on the driving frequencies and that acoustic wave energy is leaked outside the resonator at specific frequencies. Further, a more accurate visualization of the acoustic wave component is made possible by correcting for the influence of the electro-optical effect on the observation results. Another setup has been developed in which a probe light beam is incident from the back side of the substrate and the light reflected from the device surface is used in order to determine the distribution under an electrode. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 2, 87(6): 10–17, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjb.20066 [ABSTRACT FROM AUTHOR]

Presents a novel technique for studying the dynamics of hydrogen diffusion in optical fiber. It shows that the hydrogen contributes directly to the effective refractive index of the fiber by its dielectric susceptibility. It provides a simple theory that relates the refractive index change to the total hydrogen concentration in the fiber core. It also deduces that there is a small contribution of less than 5% to the refractive index through the photoelastic effect. A low-finesse fiber Bragg grating Fabry-Perot interferometer allows the determination of the evolution of the hydrogen concentration in situ. The experimental results obtained for isothermal and isobaric diffusion between 45°C and 90°C yielded values for the parameters of Arrhenius-type expressions for the diffusivity, permeability, and solubility of hydrogen in germanium/boron codoped single-mode fiber. In addition, least squares curve-fits for outdiffusion yielded the gas-phase mass-transfer coefficient as a function of temperature. [ABSTRACT FROM PUBLISHER]

The contact angle of ball and screw affects the ballscrew''s life. A novel method for measurement of the contact angle of ballscrew is developed by using the photoelastic effect and digital image processing techniques. Substituting the steel ball by a photoelastic disk, the contact angles of the disk at contact with a 90° groove and a real screw are measured by processing the digitized photoelastic disk images. Acceptable results have been achieved for consideration of the accuracy and reliability of the measurement. The method is cost-effective and is able to substitute the commonly used profiler for practical inspection of the screw. [Copyright &y& Elsevier]

A novel corrugated structure on an optical fiber is proposed and demonstrated to produce tunable long-period index modulation based on photoelastic effect. The corrugated structure is a periodic variation made by chemical etching on the cladding radius of an optical fiber. By imposing this corrugated structure upon a built-in fiber Bragg grating (FBG), a superstructure grating with tunable reflectance is formed. In addition, couplings between the fundamental core mode and cladding modes take place under such a corrugated structure when the phase-matching condition is satisfied. Thus, the device can also act effectively as a long-period fiber grating (LPFG) with tunable coupling strength. We also develop the coupled-mode theory based on Fourier series expansion to describe such a corrugated sampled Bragg grating. The phase-matching condition for various sampling orders can be derived, and the calculated spectra are compared with those based on the fundamental matrix method. Optical measurements demonstrate some unique characteristics of these devices, and good qualitative agreements between simulation and measurement verify the viewpoint that long periodic index modulation is indeed induced by such a corrugated structure through the photoelastic effect when a tensile force is applied [ABSTRACT FROM PUBLISHER]

Characteristics of guided acoustic wave Brillouin scattering in polarization maintaining fibers are investigated theoretically and experimentally. Spectra of polarized and depolarized scattering are measured for two different types of polarization maintaining fibers: the PANDA (polarization maintaining and absorption reducing) fibers and the elliptical-jacket fibers. Calculated results are in agreement with the experimental ones in the low frequency region. [ABSTRACT FROM AUTHOR]

Understanding the optoelectronic properties of semiconducting polymers under external strain is essential for their applications in flexible devices. Although prior studies have highlighted the impact of static and macroscopic strains, assessing the effect of a local transient deformation before structural relaxation occurs remains challenging. Here, we employ scanning ultrafast electron microscopy (SUEM) to image the dynamics of a photoinduced transient strain in the semiconducting polymer poly(3-hexylthiophene) (P3HT). We observe that the photoinduced SUEM contrast, corresponding to the local change of secondary electron emission, exhibits an unusual ring-shaped profile. We attribute the observation to the electronic structure modulation of P3HT caused by a photoinduced strain field owing to its low modulus and strong electron-lattice coupling, supported by a finite-element analysis. Our work provides insights into tailoring optoelectronic properties using transient mechanical deformation in semiconducting polymers and demonstrates the versatility of SUEM to study photophysical processes in diverse materials.

• Comprehensive and systematic review of the biomechanical assessment of cornea. • Reviews the structure and birefringent property of the cornea. • Reviews the stress analysis of the cornea using various photoelastic techniques. • Presents the important aspects of digital photoelasticity pertaining to optomechanical characterization of the cornea. The cornea is a transparent and refractive tissue. It has an intricate microstructure that determines its optical function. The cornea's geometry and microstructure creates a compounding effect on the biomechanical assessment and makes it difficult. The current study is a comprehensive review of the structure-property relationship of the cornea. Various methods and techniques have been highlighted that characterize the mechanical and optical properties of the cornea. The photoelastic effect observed in the cornea is the derivative of its structure-property relationship. This review thematically discusses various notions on the birefringent property of the cornea. It is suggested that digital photoelasticity is a promising technique for the in-vivo optomechanical characterization. The applicability of digital photoelasticity that involves techniques such as phase shifting, integrated photoelasticity, and hybrid methodologies is emphasized for their development as clinical tools and devices in clinical ophthalmology. [ABSTRACT FROM AUTHOR]

The article presents a study on the capability of four-wave mixing (FWM) microscopy to visualize photoelastic effect with depth resolution. It notes that the change in the intensity of FWM signal is proportional to the curvature of the fiber, and its signs are different for the orthogonal linear polarizations. The result shows that there is an anisotropic change detected in the FWM signal which was generated inside the bent optical fiber.

Abstract: Main results of acousto-optic investigations in physical acoustics of solids obtained in Ioffe Physico-Technical Institute during recent yeas are presented. Both monocrystals, and glass alloys of different compositions were used as objects of researches. The studies were fulfilled in wide ranges of optical wavelengths (0.63–10.6mkm), temperatures (77–400K) and frequencies (10–1800MHz) of bulk and surface acoustic waves. [Copyright &y& Elsevier]