Refractive Index Of Prism Research Articles

Refractive Index Sensor Using Long-Range Surface Plasmon Resonance with Prism Coupler

Long-range surface plasmon resonance (LRSPR)-based sensors exhibit high sensitivity as compared to the conventional SPR sensors due to low losses. A high refractive index prism and low refractive index dielectrics are required to excite long-range surface plasmon (LRSP) mode. In this work, a symmetrical structure consisting of metal (Au) layer sandwiched between the two similar refractive index dielectrics has been utilized to excite LRSPR modes. Two dielectrics, i.e., LiF and MgF2 thin films have been chosen for glucose sensing. Theoretical simulations for optimizing the thickness of two dielectrics have been carried out. Highly sensitive refractive index sensors based on LRSPR have been developed using the two dielectric thin films and their sensitivities have been compared.

Numerical modelling of light propagation in surface plasmon resonance sensor with liquid crystal

The five-layer nanorod-mediated surface plasmon sensor with inhomogeneous liquid crystal layer was theoretically investigated. The reflectance as the function of the incident angle was calculated at different voltages applied to the liquid crystal (LC) for different analyte refractive indices. By changing the LC director orientation one can control the position of the reflective dips and choose the one that is the most sensitive to the analyte refractive index. At the chosen angle of incidence, the analyte refractive index can be found from the reflectance value. The director reorientation effect is stronger when the prism refractive index is between ordinary and extraordinary refractive indices of the LC. In this case, the voltage increase and the prism refractive index decrease have a similar effect on the reflectance features.

Establishment and correction of an Echelle cross-prism spectrogram reduction model

The accuracy of an echelle cross-prism spectrometer depends on the matching degree between the spectrum reduction model and the actual state of the spectrometer. However, the error of adjustment can change the actual state of the spectrometer and result in a reduction model that does not match. This produces an inaccurate wavelength calibration. Therefore, the calibration of a spectrogram reduction model is important for the analysis of any echelle cross-prism spectrometer. In this study, the spectrogram reduction model of an echelle cross-prism spectrometer was established. The image position laws of a spectrometer that varies with the system parameters were simulated to the influence of the changes in prism refractive index, focal length and so on, on the calculation results. The model was divided into different wavebands. The iterative method, least squares principle and element lamps with known characteristic wavelength were used to calibrate the spectral model in different wavebands to obtain the actual values of the system parameters. After correction, the deviation of actual x- and y-coordinates and the coordinates calculated by the model are less than one pixel. The model corrected by this method thus reflects the system parameters in the current spectrometer state and can assist in accurate wavelength extraction. The instrument installation and adjustment would be guided in model-repeated correction, reducing difficulty of equipment, respectively.

Brewster-angle 50%-50% beam splitter for p-polarized infrared light using a high-index quarter-wave layer deposited on a low-index prism.

A quarter-wave layer (QWL) of high refractive index, which is deposited on a transparent prism of low refractive index, can be designed to split an incident p-polarized light beam at the Brewster angle (BA) of the air-substrate interface into p-polarized reflected and transmitted beams of equal intensity (50% each) that travel in orthogonal directions. For reflection of p-polarized light at the BA, the supported QWL functions as a free-standing (unsupported) pellicle. An exemplary design is presented that uses SixGe1-x QWL deposited on an IRTRAN1 prism for applications (such as Michelson and Mach-Zehnder interferometry) with a variable compositional fraction x in the 2-6 μm mid-IR spectral range.

The lattice expansion, damage effect and propagation loss of KTiOPO4 waveguides formed by ion implantation

We investigated the damage effect on the refractive index as well as the lattice expansion induced by C3+ ion implantation into KTiOPO4 crystals. A KTiOPO4 channel waveguide was formed by area-selective 6.0 MeV C3+ ion implantation at a fluence of 5 × 1013 ions/cm2 using photoresist masking, and planar waveguides were formed by ion implantation with 6.0 MeV C3+ ions at fluences from 8 × 1012 ions/cm2 to 6 × 1014 ions/cm2. The propagation loss of the KTiOPO4 planar waveguides at 633 nm fabricated at fluences of 2 × 1013 ions/cm2 and 5 × 1013 ions/cm2 after annealing is as low as 0.38 and 0.54 dB/cm, respectively. Prism coupling and refractive index profile reconstruction using the reflectivity calculation method were used to investigate the anisotropy of the refractive indices in the KTiOPO4 waveguides region before and after annealing. The lattice expansion induced by ion implantation was investigated by combining X-ray rocking curves with atomic force microscopy. Rutherford backscattering spectrometry and channeling was applied for damage analysis, and the relationship between effective refractive index and relative defect concentration was studied.

Continuous Viewing Angle Distribution Control of Liquid Crystal Displays Using Polarization-Dependent Prism Array Film Stacked on Directional Backlight Unit

We present a polarization-dependent prism array film for controlling the viewing angle distribution of liquid crystal (LC) display panels without loss of light efficiency. On a directional backlight unit, our polarization-dependent prism array film, made into a stacked bilayer with a well-aligned liquid crystalline reactive mesogen (RM) layer on the UV-imprinted prism structure, can continuously control the light refraction function of the prism array by electrically switching incident polarization states of a polarization-controlling layer prepared by a twisted nematic LC mode. The viewing angle control properties of the polarization-dependent prism array film are analyzed under different prism angle and refractive index conditions of the RM layer. A simple analytic model is also presented to describe the intermediate viewing angle distributions with continuously varying applied voltages and incident polarization states.

Sensitivity Improved SPR Biosensor Based on the MoS2/Graphene–Aluminum Hybrid Structure

MoS2-graphene-based hybrid structures are biocompatible and useful in the field of biosensors. Herein, we propose a heterostructured MoS2/aluminum (Al) film/MoS2/graphene as a highly sensitive surface plasmon resonance (SPR) biosensor based on the Otto configuration. The sensitivity of the proposed biosensor is enhanced by using three methods. First, prisms of different refractive index have been discussed and it is found that sensitivity can be enhanced by using a low refractive index prism. Second, the influence of the thickness of the air layer on the sensitivity is analyzed and the optimal thickness of air is obtained. Finally, the sensitivity improvement and mechanism by using molybdenum disulfide (MoS2)–graphene hybrid structure is revealed. The maximum sensitivity ∼ 190.83°/RIU is obtained with six layers of MoS2 coating on both surfaces of Al thin film.

High-Speed Surface Plasmon Resonance (SPR) Reflectance Imaging of Drop Coalescence during Condensation and Evaporation

Drop condensation and coalescence is visualized using high-speed Surface Plasmon Resonance (SPR) reflectance microscopy. SPR microscopy is a label-free technique that can characterize thin films (less than 1µm) by detecting the changes in the refractive index of the test medium. The sensing surface is a 50 nm thick gold film on a 2.5 nm thick Ti layer is deposited on a borosilicate substrate. P-polarized monochromatic light (632 nm) is incident on the gold film in a total internal reflection mode. Free electrons in the gold film are excited by the incident light when a resonance condition is met. The result is a decrease in the reflected intensity. Resonance depends upon wavelength, incident angle, and refractive index of prism and test medium. To induce condensation, a water bridge is created between the SPR gold film and an ITO coated glass slide. When the ITO coated slide is heated water evaporates from the bridge and condenses on the gold film. The sequence of images on the process of droplet deposition and drop coalescence are captured at 1500 frames per second. Experiments were conducted at an SPR angle of 44o, which is slightly above the minimum intensity angle for air at 43.8o. Therefore, the brightest and darkest regions correspond to the areas on the gold film covered with bulk water and a very thin film of water, respectively. The thickness of the film is proportional to the intensity of reflected light.

Sufficient conditions for the avoidance of spectral dispersion in optical prisms.

Prisms are common optical elements consisting of only flat boundary surfaces. Two conditions need to be fulfilled to avoid chromatic aberration for a prism, namely, no mutual image tilt and no mutual image shift for different wavelengths. Mutual image tilt occurs when the unit directional vector of the exit ray varies as a function of the prism's refractive index, resulting in spectral dispersion. In a previous study by the present group [Appl. Opt.45, 3951 (2006)APOPAI0003-693510.1364/AO.45.003951], it was shown that when the rays enter and exit a prism perpendicularly, image reorientation is achieved without spectral dispersion. The present study derives a further sufficient condition to avoid spectral dispersion caused by refraction. The condition explains the ability of Dove prisms and solid glass corner cubes to produce the required image orientation even when the entrance and exit rays are not normal to the respective boundary surfaces. In general, the proposed condition provides a useful analytical guideline for avoiding spectral dispersion in a wide variety of optical systems.

Angularly symmetric splitting of a light beam upon reflection and refraction at an air–dielectric plane boundary: comment

In a recent paper, conditions for achieving equal and opposite angular deflections of a light beam by reflection and refraction at an interface between air and a dielectric were determined [J. Opt. Soc. Am. A32, 2436 (2015)JOAOD60740-323210.1364/JOSAA.32.002436]. The paper gives plots of angles of incidence and refraction as a function of the prism refractive index as well as plots of reflectances and incident linear-polarization azimuth angles as functions of the refractive index. We show here that it is possible to express these quantities as simple algebraic functions of the refractive index.

A comparative study of different metal and prism in the surface plasmon resonance biosensor having MoS2-graphene

In the present study, the optimum range of prism refractive index and better surface plasmons active metals for biosensing application are obtained on the basis of performance of the proposed SPR sensor. Proposed sensor utilizes the properties of graphene and MoS2 such as; mechanically strong, atomically thin and chemically inert coating for the protection against oxidation of SPs active metal. It is observed that the prism having moderate refractive index should be preferred and sensor having silver (Ag) has minimum full width at half maximum whereas copper (Cu) has maximum shift in resonance angle. Hence, Ag can be used for high quality and resolution whereas Cu for good sensitivity, which are protected from oxidation with the help of two dimensional MoS2 or graphene, or graphene over MoS2.

Goos-Hänchen effect in Kretschmann configuration with hyperbolic metamaterials

We study the Goos-Hänchen (GH) effect in a Kretschmann configuration with hyperbolic metamaterial (HMM) of ZnGaO/ZnO multilayer. Calculation method in anisotropic waveguides is developed based on stationary method and physical mechanism of enhanced GH effect is analyzed. Simulation results show the GH shift peaks are significantly influenced by the dispersion of material and the refractive index of prism and substrate. As the GH shift in the proposed Kretschmann configuration is rather sensitive to waveguide parameters, we discuss the possible applications in wavelength de-multiplexing and tiny refractive index detection with high resolution.

Theoretical investigation of adjustable period sub-wavelength grating inscribed by TE0 waveguide modes interference lithography

Sub-wavelength grating is a critical element in micro and nano-photonics. So its fabrication and application have attracted a great deal of research attention. While the existing lithography technologies of sub-wavelength grating fabrication have some insufficient points, such as high cost, low output, technical complexity, or difficult to change the period of the sub-wavelength grating. In this paper, an adjustable period and large area sub-wavelength grating with low cost and maskless is proposed and theoretically realized. The sub-wavelength grating is inscribed by the interference between two TE0 waveguide modes, where the TE0 waveguide mode is existent in an asymmetric metal-cladding dielectric waveguide structure excited by the prism coupling method. The dispersion curve of TE0 waveguide mode, the relationship between the period of the sub-wavelength grating and the exciting light source, the refractive index of the prism and the photoresist, especially the thickness of the photoresist are theoretically analyzed in detail. The distribution of the interference optical field of TE0 waveguide mode in the multilayer structure including metal film, photoresist and air layer is numerically simulated using the finite element method. The shorter the exciting light wavelength with the identical photoresist condition, the smaller the period of sub-wavelength grating inscribed by TE0 waveguide modes interference lithography is. For further studying the influences of refractive index and thickness of photoresist and the refractive index of the prism on the period of sub-wavelength grating, the exciting light with 442 nm wavelength and the Ag matel film are used. The period of sub-wavelength grating is smaller with thicker photoresist film, when the refractive indexes of photoresist and prism are the same. The larger refractive index of photoresist is beneficial to inscribing the sub-wavelength grating with smaller period when the refractive index of prism and the thickness of photoresist are identical. The prism with higher refractive index can provide wave vector-matching condition with lager propagation constant, and can inscribe sub-wavelength grating with smaller period. Compared with surface plasmons interference lithography which needs the thicker photoresist film due to the finite penetration depth of SPs, TE0 waveguide modes interference can realize adjustableperiod sub-wavelength grating writing for thicker photoresist condition by changing exciting light source, the refractive index of prism, the refractive index of photoresist and especially the thickness of photoresist. The realization of adjustable period sub-wavelength grating inscribed by TE0 waveguide modes interference lithography will provide important theoretical support for reducing the fabrication cost of sub-wavelength gratings and broadening the application scope of sub-wavelength grating.

Measurement of refractive indices of GdTaO4 crystal by the auto-collimation method

In this paper, the refractive index of GdTaO4 crystal is measured by the auto-collimation method. GdTaO4 crystal is processed into three rectangular prisms, their planes with longer right angle side are planes a, b and c of the crystal, respectively, and their normal directions are the directions of crystal plane axes a, b and c, respectively. with a side by angle . Plane enclosed by hypotenuse and the longer right angle side is subjected to fine polishing, while the surface plating for the latter is subjected to Al reflectance coating, so that the light is incident along the hypotenuse plane with minimum angle of deviation (), reflects on the plane with longer right angle and returns along the original path. The rectangular prisms processed by GdTaO4 crystal are placed on the platform of 32 J goniometer with an accuracy of arc seconds. The 473, 532 nm YAG double frequency laser, 633 nm He-Ne laser and 1064 nm YAG laser with stable light intensity are used as a measuring light source, light will refract into the light perpendicular to the longer right angle side when the laser of measuring light source shoots towards the bevel of a prism with a minimum angle of deviation (). The refractive indexes nx, ny, and nz of a crystallographic axis directions can be measured by , and the relationship between refractive index ellipsoid section and prism refraction of light. The constants Ai, Bi, Ci, and Di (i=x, y, z) are given in Sellmeier's equation ni2 =Ai+Bi/(2-Ci)-Di2, and the values of angle Vz included between light axis and refractive index at wavelengths of 473, 532, 632.8 and 1064 nm are calculated to be 22.5, 22.5, 21.9 and 22.0, respectively. It is proved that GdTaO4 crystal is optically positive biaxial crystal.

Angularly symmetric splitting of a light beam upon reflection and refraction at an air-dielectric plane boundary.

Conditions for achieving equal and opposite angular deflections of a light beam by reflection and refraction at an air-dielectric boundary are determined. Such angularly symmetric beam splitting (ASBS) is possible only if the angle of incidence is >60° by exactly one third of the angle of refraction. This simple law, plus Snell's law, leads to several analytical results that clarify all aspects of this phenomenon. In particular, it is shown that the intensities of the two symmetrically deflected beams can be equalized by proper choice of the prism refractive index and the azimuth of incident linearly polarized light. ASBS enables a geometrically attractive layout of optical systems that employ multiple prism beam splitters.

RANCANG BANGUN LASER UNTUK PEMBELAJARAN OPTIKA DALAM MENENTUKAN INDEKS BIAS DAN DIFRAKSI KISI

This research is executed as a mean to make laser with energy from ex- materials ( DVD) to be used to determine refractive index and difraction. For that, have been made laser diode appliance network used to determine \Kprism refractive index and laser wavelength [pass/through] difraction. This research is used by analysis with refractive index characteristic and difraction. Obtained result of that level of prism refractive index at variation of i1 (30o, 45o dan 60o) equal to (1.53 ± 0.07), (1.45 ± 0.08) and ( 1.53 ± 0.08). Green Laser wavelength at variation of N (100, 300 and 600 line / mm)successively equal to (500 ± 0.03),  (525 ± 0.02) and (541 ± 0.07). Pursuant to prism refractive index theory of[is level of 1.5 and green colour laser wavelength range from (500 – 570) nm. So that can be concluded that result of research have as according to this appliance and theory have earned to be told good to used in study of optics

Full-wave simulation of a three-dimensional metamaterial prism

In this article, a negative-index metamaterial prism based on a composite unit cell containing a split-ring resonator and a z-dipole is designed and simulated. The design approach combines simulations of a single unit cell to identify the appropriate cell design (yielding the desired negative-index behavior) together with subcell modeling (which simplifies the mesh representation of the resonator geometry and allows for a larger number of resonator cells to be handled). In addition to describing the methodology used to design a n = −1 refractive index prism, results including the effective-medium parameters, the far-field scattered patterns, and the near-zone field distributions corresponding to a normally incident plane-wave excitation of the prism are presented. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:537–540, 2015

Study on compensation method of beam deviation in division of time imaging polarimetry

In the division of time imaging polarimetry, polarization information of field under measurement (I, Q, U), is obtained by rotating the analyzer. In the process of measurement, the beam deviation caused by the wedge of the analyzer reduces the spatial resolution and polarization accuracy of imaging polarimetry. In this paper we present that the beam deviation above can be reduced or even compensated for by adjusting the tilt angle of analyzer with respect to the incident optical axis. Taking Glan prism as the analyzer, we establish the first-order approximate compensation model of beam deviation based on the theory of geometric optics, acquiring the function relation between the tilt angle and wedge of Glan prism, and verify the feasibility and effectiveness of the compensation method by simulation. The study shows that the first-order approximation error of beam deviation can be compensated for by adjusting the tilt angle of Glan prism if only Glan prism is placed in a convergent beam; the tilt angle is proportional to Glan prism wedge angle, refractive index, and distance to CCD, but inversely proportional to Glan prism thickness. The results provide a theoretical basis for developing the time division imaging polarimetry with high spatial resolution and polarization accuracy.

Surface plasmon resonance structures in spectral interrogation using high refractive index prism materials for sensing of different amino acids

A prism coupler-based nano-plasmonic sensor consisting of a high refractive index (RI) prism (2S2G-prism, LASF9-prism), gold (Au) metal film, and different amino acids as the dielectric sample is used for sensing in attenuated total internal reflection mode. An additional semiconductor (silicon) nano-layer over the gold surface has been used for increasing the stability and sensitivity of the surface plasmon resonance sensor. A comparative analysis of performance of the nano-plasmonic sensors in the spectral regime using these two high RI prism materials with an additional semiconductor nano-layer has been presented. The sensing performance of the proposed nano-plasmonic sensors in terms of evanescent field enhancement, spectral sensitivity, detection accuracy, figure of merit, and Q-factor with different amino acid samples has been discussed along with supporting theoretical simulations in a MATLAB® environment.

Dynamically generating a large-area confined optical field with subwavelength feature size.

By using a prism of high refractive index, free-space cylindrical vector beams can be selectively converted into confined optical fields with large area, such as surface plasmon polaritons or waveguide modes, whose interference will produce optical features at the nanometer scale. Due to the polarization sensitivity of these modes, the macroscopic distribution of the confined field can be dynamically manipulated through an electronically driven liquid crystal. Based on these phenomena, a promising maskless interference nanolithography is proposed and experimentally demonstrated.