Showing papers on "Total internal reflection published in 2015"

Wavelength conversion element, light source device, and projector

Abstract: A wavelength conversion element includes a substrate, a reflecting section disposed on one surface side of the substrate, a wavelength conversion layer disposed on an opposite side of the reflecting section to the substrate, and emitting fluorescence in response to irradiation with excitation light, and a reflecting surface disposed between a surface of the wavelength conversion layer on an opposite side to the reflecting section and the reflecting section, and adapted to totally reflect light having been input at an angle no smaller than a critical angle out of the fluorescence.

Universal spin-momentum locking of evanescent waves

Abstract: We show the existence of an inherent property of evanescent electromagnetic waves: spin-momentum locking, where the direction of momentum fundamentally locks the polarization of the wave. We trace the ultimate origin of this phenomenon to complex dispersion and causality requirements on evanescent waves. We demonstrate that every case of evanescent waves in total internal reflection, surface states and optical fibers/waveguides possesses this intrinsic spin-momentum locking. We also introduce a universal right-handed triplet consisting of momentum, decay and spin for evanescent waves. We derive the Stokes parameters for evanescent waves which reveal an intriguing result - every fast decaying evanescent wave is inherently circularly polarized with its handedness tied to the direction of propagation. We also show the existence of a fundamental angle associated with total internal reflection (TIR) such that propagating waves locally inherit perfect circular polarized characteristics from the evanescent wave. This circular TIR condition occurs if and only if the ratio of permittivities of the two dielectric media exceeds the golden ratio. Our work leads to a unified understanding of this spin-momentum locking in various nanophotonic experiments and sheds light on the electromagnetic analogy with the quantum spin hall state for electrons.

Direct optical nanoscopy with axially localized detection

Abstract: Evanescent light excitation is widely used in super-resolution fluorescence microscopy to confine light and reduce background noise. Here, we propose a method of exploiting evanescent light in the context of emission. When a fluorophore is located in close proximity to a medium with a higher refractive index, its near-field component is converted into light that propagates beyond the critical angle. This so-called supercritical-angle fluorescence can be captured using a high-numerical-aperture objective and used to determine the axial position of the fluorophore with nanometre precision. We introduce a new technique for three-dimensional nanoscopy that combines direct stochastic optical reconstruction microscopy (dSTORM) with dedicated detection of supercritical-angle fluorescence emission. We demonstrate that our approach of direct optical nanoscopy with axially localized detection (DONALD) typically yields an isotropic three-dimensional localization precision of 20 nm within an axial range of ∼150 nm above the coverslip. Researchers exploit direct stochastic optical reconstruction microscopy and dedicated detection of super-critical-angle fluorescence emission to enable direct optical nanoscopy with axially localized detection.

What is the Temporal Analog of Reflection and Refraction of Optical Beams

Abstract: It is shown numerically and analytically that when an optical pulse approaches a moving temporal boundary across which the refractive index changes, it undergoes a temporal equivalent of reflection and refraction of optical beams at a spatial boundary. The main difference is that the role of angles is played by changes in the frequency. The frequency dependence of the dispersion of the material in which the pulse is propagating plays a fundamental role in determining the frequency shifts experienced by the reflected and refracted pulses. Our analytic expressions for these frequency shifts allow us to find the condition under which an analog of total internal reflection may occur at the temporal boundary.

Enhanced spin Hall effect of transmitted light through a thin epsilon-near-zero slab

Abstract: Spin Hall effect (SHE) of transmitted light is small even near the Brewster angle in general case, e.g., at the air-glass interface. However, we find that the SHE can be enhanced when a linearly polarized Gaussian beam transmits through a thin epsilon-near-zero slab due to the difference between the Fresnel transmission coefficients t(p) and t(s). For a vertically polarized incident beam, the spin-dependent transverse displacement of transmitted beam is enhanced near the Brewster angle, while it takes large value over a large angle scale for a horizontally polarized incident beam.

Trapping of microwave radiation in hollow polypyrrole microsphere through enhanced internal reflection: a novel approach.

Abstract: In present work, spherical core (polystyrene, PS)/shell (polypyrrole, PPy) has been synthesized via in situ chemical oxidative copolymerization of pyrrole (Py) on the surface of sulfonated PS microsphere followed by the formation of hollow polypyrrole (HPPy) shell by dissolving PS inner core in THF. Thereafter, we first time established that such fabricated novel art of morphology acts as a conducting trap in absorbing electromagnetic (EM) wave by internal reflection. Further studies have been extended on the formation of its silver nanocomposites HPPy/Ag to strengthen our contention on this novel approach. Our investigations showed that electromagnetic interference (EMI) shielding efficiency (SE) of HPPy (34.5-6 dB) is significantly higher compared to PPy (20-5 dB) in the frequency range of 0.5-8 GHz due to the trapping of EM wave by internal reflection. We also observed that EMI shielding is further enhanced to 59–23 in 10 wt% Ag loaded HPPy/Ag-10. This is attributed to the simultaneous contribution of internal reflection as well as reflection from outer surface. Such high EMI shielding capacity using conducting polymers are rarely reported.

Refractive index sensing with hyperbolic metamaterials: strategies for biosensing and nonlinearity enhancement.

Abstract: Metamaterials with hyperbolic dispersion based on metallic nanorod arrays provide a flexible platform for the design of bio- and chemical sensors and nonlinear devices, allowing the incorporation of functional materials into and onto the plasmonic metamaterial. Here, we have investigated, both analytically and numerically, the dependence of the optical response of these metamaterials on refractive index variations in commonly used experimental sensing configurations, including transmission, reflection, and total internal reflection. The strategy for maximising refractive index sensitivity for different configurations has been considered, taking into account contributions from the superstrate, embedding matrix, and the metal itself. It is shown that the sensitivity to the refractive index variations of the host medium is at least 2 orders of magnitude higher than to the ones originating from the superstrate. It is also shown that the refractive index sensitivity increases for higher-order unbound and leaky modes of the metamaterial sensor. The impact of the transducer’s thickness was also analysed showing significant increase of the sensitivity for the thinner metamaterial layers (down to few 0.01 fraction of wavelength and, thus, requiring less analyte) as long as modes are supported by the structure. In certain configurations, both TE and TM-modes of the metamaterial transducer have comparable sensitivities. The results provide the basis for the design of new ultrasensitive chemical and biosensors outperforming both surface plasmon polaritons and localised surface plasmons based transducers.

Self-assembled conjugated polymer spheres as fluorescent microresonators

Abstract: Confinement of light inside an active medium cavity can amplify emission. Whispering gallery mode (WGM) is one of mechanisms that amplifies light effectively by confining it inside high-refractive-index microstructures, where light propagates along the circumference of a sphere via total internal reflection. Here we show that isolated single microspheres of 2–10 μm diameter, formed from self-assembly of π-conjugated alternating copolymers, display WGM photoemission induced by laser pumping. The wavelengths of the emission peaks depend sensitively on the sphere size, position of the excitation spot and refractive index of each polymer. The Q-factor increases with increasing sphere diameter and displays a linear correlation with the reciprocal radius, indicating that the small curvature increases the efficacy of the total internal reflection. WGM photoemission from π-conjugated polymer microspheres is unprecedented and may be of high technological impact since the microspheres fulfill the role of fluorophores, high-refractive-index media and resonators simultaneously, in addition to their simple fabrication process.

High sensitivity refractive index sensor based on adiabatic tapered optical fiber deposited with nanofilm by ALD.

Abstract: Atomic layer deposition (ALD) technology is introduced to fabricate a high sensitivity refractive index sensor based on an adiabatic tapered optical fiber. Different thickness of Al2O3 nanofilm is coated around fiber taper precisely and uniformly under different deposition cycles. Attributed to the high refractive index of the Al2O3 nanofilm, an asymmetry Fabry-Perot like interferometer is constructed along the fiber taper. Based on the ray-optic analysis, total internal reflection happens on the nanofilm-surrounding interface. With the ambient refractive index changing, the phase delay induced by the Goos-Hanchen shift is changed. Correspondingly, the transmission resonant spectrum shifts, which can be utilized for realizing high sensitivity sensor. The high sensitivity sensor with 6008 nm/RIU is demonstrated by depositing 3000 layers Al2O3 nanofilm as the ambient refractive index is close to 1.33. This high sensitivity refractive index sensor is expected to have wide applications in biochemical sensors.

Experimental Demonstration of Effective Medium Approximation Breakdown in Deeply Subwavelength All-Dielectric Multilayers.

Abstract: We report the first experimental demonstration of anomalous breakdown of the effective medium approximation in all-dielectric deeply subwavelength thickness (d∼λ/160-λ/30) multilayers, as recently predicted theoretically [H. H. Sheinfux et al., Phys. Rev. Lett. 113, 243901 (2014)]. Multilayer stacks are composed of alternating alumina and titania layers fabricated using atomic layer deposition. For light incident on such multilayers at angles near the total internal reflection, we observe pronounced differences in the reflectance spectra for structures with 10- vs 20-nm thick layers, as well as for structures with different layers ordering, contrary to the predictions of the effective medium approximation. The reflectance difference can reach values up to 0.5, owing to the chosen geometrical configuration with an additional resonator layer employed for the enhancement of the effect. Our results are important for the development of new high-precision multilayer ellipsometry methods and schemes, as well as in a broad range of sensing applications.

Surface light source device and liquid crystal display device

Abstract: An angular intensity distribution shaping member includes a first surface for receiving a light beam emitted from a light source, the first surface having a length in a width direction that is longer than that in a thickness direction; second surfaces forming a plate-shaped light path on which the light beam incident from the first surface propagates by total reflection, the second surfaces including at least one adjustment surface for spreading a full angle of an angular intensity distribution, in the width direction, of the light beam incident from the first surface so that the full angle becomes wider than that of the angular intensity distribution of the light beam just after emission from the light source; and a third surface through which the light beam exits, the full angle of its angular intensity distribution in the width direction having been widened by the at least one adjustment surface.

Visco-thermal effects in acoustic metamaterials: from total transmission to total reflection and high absorption

Abstract: We theoretically and experimentally investigate visco-thermal effects on the acoustic propagation through metamaterials consisting of rigid slabs with subwavelength slits embedded in air. We demonstrate that this unavoidable loss mechanism is not merely a refinement, but it plays a dominant role in the actual acoustic response of the structure. Specifically, in the case of very narrow slits, the visco-thermal losses avoid completely the excitation of Fabry-Perot resonances, leading to 100% reflection. This is exactly opposite to the perfect transmission predicted in the idealised lossless case. Moreover, for a wide range of geometrical parameters, there exists an optimum slit width at which the energy dissipated in the structure can be as high as 50%. This work provides a clear evidence that visco-thermal effects are necessary to describe realistically the acoustic response of locally resonant metamaterials.

Enhanced light extraction of scintillator using large-area photonic crystal structures fabricated by soft-X-ray interference lithography

Abstract: Soft-X-ray interference lithography is utilized in combination with atomic layer deposition to prepare photonic crystal structures on the surface of Bi4Ge3O12 (BGO) scintillator in order to extract the light otherwise trapped in the internal of scintillator due to total internal reflection. An enhancement with wavelength- and emergence angle-integration by 95.1% has been achieved. This method is advantageous to fabricate photonic crystal structures with large-area and high-index-contrast which enable a high-efficient coupling of evanescent field and the photonic crystal structures. Generally, the method demonstrated in this work is also suitable for many other light emitting devices where a large-area is required in the practical applications.

Planar immersion lens with metasurfaces

Abstract: A planar immersion lens can include any number of features. A planar immersion lens can be configured to control a phase profile of an incident wave by modulating the incident wave with sub-wavelength structures of varying impedances. The planar immersion lens can also be directly excited, with electronics or other subwavelength sources coupled to the planar immersion lens, to generate a wave with the desired phase profile. The planar immersion lens can include a plurality of metallic elements and passive elements disposed over a substrate. The passive elements can be selected, based on both the intrinsic and mutual impedances of the elements, to shape the spatial phase profile of the incident wave within this phase range. The phase gradient can be introduced along the incident material/refractive material interface to focus the incident wave into the refractive material having wave components at or beyond the critical angle. Methods are also provided.

A reusable evanescent wave immunosensor for highly sensitive detection of bisphenol A in water samples

Abstract: This paper proposed a compact and portable planar waveguide evanescent wave immunosensor (EWI) for highly sensitive detection of BPA. The incident light is coupled into the planar waveguide chip via a beveled angle through undergoing total internal reflection, where the evanescent wave field forms and excites the binding fluorophore-tagged antibodies on the chip surface. Typical calibration curves obtained for BPA has detection limits of 0.03 μg/L. Linear response for BPA ranged from 0.124 μg/L–9.60 μg/L with 50% inhibition concentration for BPA of 1.09 ± 0.25 μg/L. The regeneration of the planar optical waveguide chip allows the performance of more than 300 assay cycles within an analysis time of about 20 min for each assay cycle. By application of effective pretreatment procedure, the recoveries of BPA in real water samples gave values from 88.3% ± 8.5% to 103.7% ± 3.5%, confirming its application potential in the measurement of BPA in reality.

Optical system and method for transmitting a source image

Abstract: An optical system for transmitting a source image is provided. Light having a field angle spectrum emanates from the source image. The optical system includes an optical waveguide arrangement, in which light can propagate by total internal reflection. The optical system also includes a diffractive optical input coupling arrangement for coupling the light emanating from the source image into the optical waveguide arrangement. The optical system further includes a diffractive optical output coupling arrangement for coupling the light that has propagated in the optical waveguide arrangement out from the optical waveguide arrangement. The disclosure also provides related methods.

Direct measurements of forces induced by Bloch surface waves in a one-dimensional photonic crystal.

Abstract: An experimental study of the interaction between a single dielectric microparticle and the evanescent field of the Bloch surface wave in a one-dimensional (1D) photonic crystal is reported. The Bloch surface wave-induced forces on a 1 μm polystyrene sphere were measured by photonic force microscopy. The results demonstrate the potential of 1D photonic crystals for the optical manipulation of microparticles and suggest a novel approach for utilizing light in lab-on-a-chip devices.

Anomalous effective medium approximation breakdown in deeply subwavelength all-dielectric photonic multilayers

Abstract: We present a comprehensive analysis of the applicability of the effective medium approximation to deeply subwavelength (period ≤λ/50 all-dielectric multilayer structures. We demonstrate that even though the dispersion relations for such multilayers differ from the effective medium prediction only slightly, there can be regimes when an actual multilayer stack exhibits significantly different properties compared to its homogenized model. In particular, reflection near the critical angle is shown to strongly depend on even very small period variations, as well as on the choice of the multilayer termination. We identify the geometries for which the influence of the subwavelength features is maximized and demonstrate that the difference between the reflectance from the actual multilayer and the effective medium prediction can be as great as 0.98. The results of this analysis can be useful for high-precision multilayer ellipsometry and in sensing applications.

Photonic skin-depth engineering

Abstract: Recently, we proposed a paradigm shift in light confinement strategy showing how relaxed total internal reflection and photonic skin-depth engineering can lead to sub-diffraction waveguides without metal [Optica1, 96 (2014)10.1364/OPTICA.1.000096OPTIC82334-2536]. Here, we show that such extreme-skin-depth (e-skid) waveguides can counterintuitively confine light better than the best-case all-dielectric design of high index silicon waveguides surrounded by vacuum. We also establish analytically that figures of merit related to light confinement in dielectric waveguides are fundamentally tied to the skin depth of waves in the cladding, a quantity surprisingly overlooked in dielectric photonics. We contrast the propagation characteristics of the fundamental mode of e-skid waveguides and conventional waveguides to show that the decay constant in the cladding is dramatically larger in e-skid waveguides, which is the origin of sub-diffraction confinement. We also propose an approach to verify the reduced photonic skin depth in experiment using the decrease in the Goos–Hanschen phase shift. Finally, we provide a generalization of our work using concepts of transformation optics where the photonic skin-depth engineering can be interpreted as a transformation on the momentum of evanescent waves.

Coalescence and break-up of nearly inviscid conical droplets

Abstract: In the presence of electric fields, pairs of liquid drops can be rapidly drawn together such that, at contact, the deformed interface resembles a double-cone. Following contact, these drop pairs are observed to either coalesce or recoil. Experimental and theoretical results suggest that the transition between coalescence and recoil is due to the conical drop topology rather than charge effects. However, even with this assumption, existing models disagree on how the transition develops, leading to different predictions of the critical cone angle and bridge morphology. Here we use high-resolution numerical simulations to highlight the impact of the initial double-cone angle on drop coalescence and reconcile the differences in the previous models. The results demonstrate a self-similar behaviour at intermediate scales for both coalescence and recoil that is independent of the other length scales in the problem. We calculate a critical polar angle of rad ( ), or a complementary angle of . This calculated critical angle for morphological transition is in agreement with previous experimental observations of .

Determination of the refractive index of glucose-ethanol-water mixtures using spectroscopic refractometry near the critical angle.

Abstract: A spectroscopic refractometer was used to investigate the dispersion curves of ethanol and D-glucose solutions in water near the critical angle; here, the reflectivity was measured using a white source. Dispersion curves were obtained in the 320-1000 nm wavelength range with a resolution better than 10(-4) for the refractive index, n. The differential refractive index is measured as a function of wavelength, and a simple expression is proposed to obtain the refractive index of the glucose-ethanol-water ternary system. Using this expression, combined with the experimental differential refractive index values, the concentrations of individual components can be calculated.

Diffractive optical element using polarization rotation grating for in-coupling

Abstract: In an optical display system that includes a waveguide with multiple diffractive optical elements (DOEs), an in-coupling DOE couples light into the waveguide, an intermediate DOE provides exit pupil expansion in a first direction, and an out-coupling DOE provides exit pupil expansion in a second direction and couples light out of the waveguide. The in-coupling DOE is configured with two portions—a first portion includes a grating to rotate a polarization state of in-coupled light while a second portion couples light into the waveguide without modulation of the polarization state. The in-coupled light beams with different polarization states are combined in the waveguide after undergoing total internal reflection. However, as the difference in optical path lengths of the constituent light beams exceeds the coherence length, the combined light has random polarization (i.e., a degree of polarization equal to zero).

The use of the stationary phase method as a mathematical tool to determine the path of optical beams

Abstract: We use the stationary phase method to determine the paths of optical beams that propagate through a dielectric block. In the presence of partial internal reflection, we recover the geometrical result obtained by using Snell's law. For total internal reflection, the stationary phase method overreaches Snell's law, predicting the Goos-Hanchen shift.

Depth-Resolved Structure Analysis of Cylindrical Microdomain in Block Copolymer Thin Film by Grazing-Incidence Small-Angle X-ray Scattering Utilizing Low-Energy X-rays

Abstract: Depth-resolved structure analysis of a polystyrene-b-poly(2-vinylpyridine) (S2VP) thin film (420 nm thick) was achieved by grazing-incidence small-angle X-ray scattering (GISAXS) utilizing low-energy X-rays (“tender” X-rays). In contrast to techniques utilizing hard X-rays, a gradual change of the penetration depth of soft X-rays around the critical angle of total reflection of a polymer surface is anticipated. In this research, X-ray energy of 2.4 keV was chosen to control the penetration depth and achieve depth-sensitive GISAXS measurement. Microphase-separated structure of the annealed S2VP in the thin film was confirmed to be hexagonally packed cylinders (HEX) aligned parallel to the substrate surface. Significant elongation of the Bragg spots in the qz direction was observed for an incidence angle close to the critical angle. The experimental full width at half-maximum (fwhm) values of the (11) HEX diffraction spot was interpreted using the theoretical fwhm values estimated using the Laue function co...

Dynamical measurement of refractive index distribution using digital holographic interferometry based on total internal reflection

Abstract: We present a method for dynamically measuring the refractive index distribution in a large range based on the combination of digital holographic interferometry and total internal reflection. A series of holograms, carrying the index information of mixed liquids adhered on a total reflection prism surface, are recorded with CCD during the diffusion process. Phase shift differences of the reflected light are reconstructed exploiting the principle of double-exposure holographic interferometry. According to the relationship between the reflection phase shift difference and the liquid index, two dimensional index distributions can be directly figured out, assuming that the index of air near the prism surface is constant. The proposed method can also be applied to measure the index of solid media and monitor the index variation during some chemical reaction processes.

Extended field of view in near-eye display using wide-spectrum imager

Abstract: In a near-eye optical display system comprising a waveguide and diffractive optical elements (DOEs) configured for in-coupling, exit pupil expansion, and out-coupling, a wide-spectrum imager generates imaging light that is in-coupled to the system with an input pupil having an extended field of view (FOV). Wide-spectrum imaging light impinges on the in-coupling DOE over a range of incidence angles. As chromatic dispersion in the in-coupling DOE causes different wavelengths to propagate with different angles, for a given input pupil incidence angle, at least a portion of the imaging light spectrum meets a critical angle condition that enables propagation with total internal reflection (TIR) in the waveguide without leakage to the outside. Thus, different parts of the imaging light spectrum can be used for different regions of the FOV.

Electromagnetic inhomogeneous waves at planar boundaries: tutorial.

Abstract: In this review paper, we summarize the fundamental properties of inhomogeneous waves at the planar interface between two media. We point out the main differences between the wave types: lateral waves, surface waves, and leaky waves. We analyze each kind of inhomogeneous wave, giving a quasi-optical description and explaining the physical origin of some of their properties.

Refraction and reflection of sound at the boundary of a bubbly liquid

Abstract: Reflection and refraction of acoustic waves at the interface between pure water and bubbly water are investigated for the case of oblique incidence. From an analysis of analytic solutions, it is concluded that, for a wave incident on the interface from the side of a bubbly liquid, a critical angle of incidence, which depends on the frequency and the parameters of the disperse system, exists, so that, at angles of incidence exceeding the critical one, the wave is totally reflected from the interface.