Prism Coupling Research Articles

The Application of Surface Plasmon Resonance with As2S3 Waveguide for Alcohols Identification

AbstractIn a composite structure, which contains dielectric‐metal interface, waves of electric charge densities can be initiated. The wave intensity decreases exponentially in adjacent media meaning that the wave closely localized at the interface does exist. Label‐free chemical sensors are realized as the propagation constant of the wave is highly sensitive to the refractive index. Surface plasmons can be excited by incident light flow directed at some specific angle (surface plasmon resonance) with a very sharp shape. In the present paper the possibility of identification of several most common alcohols such as methanol, ethanol, propanol, butanol, or pentanol, which have different refractive indices, has been studied. The structure is composed of a coupling prism made of rutile (TiO2), a thin gold film, and an amorphous arsenic sulfide (As2S3) thin film.

Prism coupling technique investigation of optical and thermo-optical properties of polyvinyl alcohol and polyvinyl alcohol/silica nanocomposite films

In this paper, the optical and thermo-optical properties of polyvinyl alcohol (PVA) and polyvinyl alcohol/silica (PVA/SiO 2) nanocomposite films were characterized by using the prism coupler technique. The polymer films were deposited by solution casting method at room temperature. The refractive indices of TE polarization mode, nTE, of all samples were measured at 444 nm, 633 nm, 829 nm, and 1308 nm, respectively. The wavelength dependence of the refractive index is well described by Cauchy’s equation. The effect of polymer molecular weights and the concentration of silica nanoparticles on the optical properties of PVA films was also investigated and discussed. The refractive index of the PVA films was found to increase with molecular weight, whereas it decreases with the concentration of SiO 2 in PVA matrix. The variation of the refractive index of neat PVA and PVA/SiO 2 nanocomposite films with temperature in the range of 30 to 70 °C was determined. Both PVA and PVA/SiO 2 nanocomposites show negative thermo-optic coefficients (dn∕dT) of the order of 10−4 °C−1. Moreover, it was found that the addition of silica in the PVA affect thermo-optic coefficients of the films. The obtained results suggest that PVA is a material with tunable refractive indices and it is suitable for use in optical devices such as optical temperature sensors.

Investigation of novel optical and waveguide characteristics for an air–graphene–LiNbO3 system

The optical characteristics of a planar thin film waveguide system composed of air–graphene–LiNbO3 have been investigated. Monolayer or bilayer graphene of high quality are characterized by Raman spectroscopy, scanning electron microscopy and atomic force microscopy. The refractivity and reflectivity of the air–graphene–LiNbO3 system are measured experimentally and compared with those of a LiNbO3 waveguide by the prism coupling method. The reflectivity shows an overall decrease due to the lower transmittance for graphene on the LiNbO3 substrate. The refractivity increases significantly at the wavelength of 1540 nm, which may be attributed to the generation of graphene surface plasmons excited by infrared radiation. A shaped air–graphene–LiNbO3 waveguide is designed and simulated by Mode Solutions. The distribution of an optical field is performed and analyzed. The preparation of the proposed air–graphene–LiNbO3 structure incorporates the commonly used chemical vapor deposition and thin film transfer techniques, and is compatible with existing optoelectronic integration processes, which can be employed for building various optical integrated devices.

Low-Temperature and Low-Pressure Silicon Nitride Deposition by ECR-PECVD for Optical Waveguides

We report on low-temperature and low-pressure deposition conditions of 140 °C and 1.5 mTorr, respectively, to achieve high-optical quality silicon nitride thin films. We deposit the silicon nitride films using an electron cyclotron resonance plasma-enhanced chemical vapour deposition (ECR-PECVD) chamber with Ar-diluted SiH4, and N2 gas. Variable-angle spectroscopic ellipsometry was used to determine the thickness and refractive index of the silicon nitride films, which ranged from 300 to 650 nm and 1.8 to 2.1 at 638 nm, respectively. We used Rutherford backscattering spectrometry to determine the chemical composition of the films, including oxygen contamination, and elastic recoil detection to characterize the removal of hydrogen after annealing. The as-deposited films are found to have variable relative silicon and nitrogen compositions with significant oxygen content and hydrogen incorporation of 10–20 and 17–21%, respectively. Atomic force microscopy measurements show a decrease in root mean square roughness after annealing for a variety of films. Prism coupling measurements show losses as low as 1.3, 0.3 and 1.5 ± 0.1 dB/cm at 638, 980 and 1550 nm, respectively, without the need for post-process annealing. Based on this study, we find that the as-deposited ECR-PECVD SiOxNy:Hz films have a suitable thickness, refractive index and optical loss for their use in visible and near-infrared integrated photonic devices.

Optical properties and annealing effects of planar waveguides on fluoride lead silicate glass formed by proton and helium-ion implantation

The optical planar waveguides were fabricated by proton implantation with an energy of 400 keV and a dose of 8 × 1016 ions / cm2 or 400-keV helium-ion implantation with a fluence of 6 × 1016 ions / cm2 in the fluoride lead silicate glass. The morphologies were studied by a Zeiss microscope to estimate the thickness of the waveguides. The annealing effects on the fluoride lead silicate glass waveguides were investigated by 60 min annealing cycles at different temperatures ranging from 260°C to 310°C in air atmosphere. The dark-mode spectra and corresponding effective refractive indices before and after the thermal treatments were measured by the prism coupling system. The Stopping and Range of Ions in Matter 2013 code was used to simulate the irradiation process and calculate the energy losses. The refractive index distributions were reconstructed by the reflectivity calculation method. The near-field light intensity profiles of the proton and helium-ion implanted fluoride lead silicate glass waveguides were measured by the end-face coupling system. The comparison of optical properties between the proton-implanted waveguide and helium-ion implanted one was carried out. The experimental results show that the helium-ion implantation is more suitable for the fabrication of the fluoride lead silicate glass optical waveguides and the He + -implanted waveguide has better optical propagation performances.

Sodium-Based Surface Plasmon Resonances for High-Performance Optical Sensing in the Near Infrared

Surface plasmon resonance (SPR) owing to its extreme sensitivity to the refractive index of surrounding medium has been widely applied to chemical and biological sensing. However, it is difficult to realize SPR sensing simultaneously with large sensitivity and figure of merit (FOM) in a conventional prism coupling structure. In this paper, we numerically study the SPRs in a polymer-protected sodium thin film and sinusoidal nanograting based on a prism Kretschmann configuration using finite element method (FEM). In the near-infrared wavelengths, both angular and wavelength interrogation are investigated and high sensitivity (14.9 μm/RIU and 750 deg/RIU for the thin film and nanograting, respectively) and FOM (480.6 /RIU and 255.6 /RIU for the thin film and nanograting, respectively) can be achieved simultaneously. It should be noticed that the large FOM mainly originates from the narrow resonant linewidth. Additionally, our nanograting structure can support a self-reference sensing scheme, which is beneficial to realize accurate sensing. Our FEM simulations are in good agreement with the calculation by the transfer matrix method (TMM) and rigorous coupled wave analysis (RCWA). Our proposed sodium-based SPR structures do not require complex plasmonic nanostructures and are compatible with a thermo-assisted spin-coating process, which shows great potential in realizing high-performance optical sensing beyond noble metals and expands the application scope of sodium-based plasmonic devices.

Lithium niobate planar and ridge waveguides fabricated by 3 MeV oxygen ion implantation and precise diamond dicing

We report on the fabrication and optimization of lithium niobate planar and ridge waveguides at the wavelength of 633 nm. To obtain a planar waveguide, oxygen ions with an energy of 3.0 MeV and a fluence of 1.5×1015 ions/cm2 are implanted in the polished face of LiNbO3 crystals. For planar waveguides, a loss of 0.5 dB/cm is obtained after annealing at 300°C for 30 min. The ridge waveguide is fabricated by the diamond blade dicing method on optimized planar waveguides. The guiding properties are investigated by prism coupling and end-face coupling methods.

Enhanced Raman intensity in ZnS planar and channel waveguide structures via carbon ion implantation

Planar and channel waveguides in ZnS single crystal are fabricated by 6.0 MeV C ion implantation with fluences of 5 × 1014 and 1 × 1015 ion/cm2 at room temperature. The optical modes for the planar waveguides are measured by using a prism coupler by the well-known m-line method. The near-field light intensity profiles for the planar and channel waveguides are measured by the end-face coupling setup at 633 nm and 1539 nm. The reflectivity calculation method and the finite difference beam propagation method are used to reconstruct the refractive index profile of the planar waveguides and near-field intensity distribution of planar and channel waveguides. Raman images obtained with a 532-nm laser are collected to evaluate the damage to the ZnS crystal and waveguide layers.

Peculiarities of prismatic input of narrow-band radiation into Ag-ion diffusion waveguide

The peculiarities of prism coupling elements input and output of narrow-band radiation into ion diffusion waveguide are researched. Gradient waveguide with a thickness of 1.67 μm was formed by ion exchange in K8 glass. The output signal intensity dependence on the input and output angles of incidence radiation was measured by developed automatic hardware-software system based on synchronous detection method to improve the signal-to-noise ratio. It was shown the maximum of output signal is reached at equal input and output angles.

Systematic study of the structure-property relationship of a series of near-infrared absorbing push-pull heptamethine chromophores for electro-optics

This study reports the facile synthesis, characterization and quantitative structure-property relationship analysis of molecular and material properties of tricyanofuran-based (TCF) dipolar heptamethines with different electron donors of indoline ( F1 ), benzo[ e ]- indoline ( F2 ), benz[ cd ]indoline ( F3 ), and Michler’s base derivatives ( M1 and M2 ). The linear and nonlinear optical (NLO) properties of these chromophores have been thoroughly investigated, and the relationship between molecular and bulk response has been analyzed and compared with dipolar tetraene AJLZ53 as one of the best chromophores for electro-optic (EO) devices. In particular, we provide responsible data collection and analysis of optical and EO properties for poled thin films using a widely-recognized and accredited methodology of prism coupling system with the help of rigid oriented gas model. We found that these push-pull heptamethines with synthetic efficacy exhibit high near-infrared absorption, excellent chemical stability and large hyperpolarizabilities ( β ) varied from 1,023×10−30 esu for F1 , 3,047×10−30 esu for M1 , and 3,547×10−30 esu for F3 at 1,304 nm in poled films, respectively. The β values of these molecules are among the highest ones for TCF-based dipolar chromophores, and also agree well with reported analytical results in the solutions. In poled polymers with a modest chromophoric loading density of 1.3× 1020 cm−3, M1 and M2 give a high poled-induced noncentrosymmetric order and relatively large r 33 values around 40 pm V−1 at 1,304 nm, indicative of large μβ values and suitable structural modification for high poling efficiency. Furthermore, a binary EO polymer based on the co-loading of M1 and AJLZ53 achieve a large r 33 value of 143.3 pm V−1 at 1,304 nm. Our studies suggest that concise synthesis and molecular design of push-pull polymethines can be well guided by the tabulation of their linear and NLO properties in bulk materials, and streamline future development of high performance organic EO materials for photonic applications.

The effect of gamma-ray irradiation on bulk optical plastic materials

We present our study of the effect of gamma-ray irradiation on bulk optical plastic materials as follows: three types of sheets commonly used for eyeglass lenses (CR-39, MR-8 and Trivex), cyclo olefin polymer ZEONEX E48R, styrene methyl methacrylate NAS21, polymethyl methacrylate PLEXIGLAS®7N, polyphenylsulfone EUROPLEX® PPSU, and poly(n-methyl methacrylimide PLEXIMID®8813. We used the panoramic gamma-radiation facility with 60Co source with applied doses 14.6 kGy and 54.2 kGy. For the thought properties, we measured the transmission spectra from 200 to 1800 nm and refractive indices using the prism coupling technique at six wavelengths 532.0, 654.2, 846.4, 1308.2, 1549.1, and 1652.1 nm. We also studied the possibility of using several approximation methods for evaluating the refractive indices including Cauchy, Cauchy–Schott, Herzberger, Sellmeier, Sellmeier-2, and Sellmeier with an infrared correction. The measurements showed that the most precise determination model of the refractive indices was obtained by the Sellmeier approximation with an infrared correction. The transmission spectra measurement showed that the CR-39 and EUROPLEX® PPSU polymers did not change significantly after the irradiation and the refractive indices measurement showed that ZEONEX E48R and EUROPLEX® PPSU did not change the refractive indices values.

Plasmonic infrared-laser attenuator

We describe two designs for a variable attenuator of infrared laser radiation. The principle is based on the excitation of surface plasmon polaritons with prism couplers on suitable conductors. Practical considerations dictate the use of conductors with infrared plasma frequency. An intensity variation of more than nine-orders is theoretically demonstrated. Both designs involve mechanical displacements of optical elements by less than several microns, which in principle might be much faster than current art for variable attenuators of IR laser beams. One design provides fine control at high attenuation. Experimental demonstrations support the predicted function.

Growth of 1, 3, 5 - Triphenylbenzene single crystal by modified vertical Bridgman method and its characterization for scintillation application

1, 3, 5-triphenylbenzene (TPB) single crystal (length 100 mm and diameter 10 mm) has been successfully grown for the first time by the modified vertical Bridgman technique (VBT). This method is developed for the growth of crystals (changing the translation system using gear setup), with enhanced quality. Physical, optical and scintillation properties such as crystalline nature, thermal stability, transmittance, radioluminescence and lifetime were investigated. The polished TPB sample has a good transmission (80%) in the wavelength range between 300 and 1500 nm. The thermal properties of the grown crystal were analyzed by thermogravimetric and differential thermal analyses. Measurements of the refractive index of TPB crystal were made using the prism coupling method at five different wavelengths in the range between 407 and 1551 nm. Birefringence study reveals that the grown crystal has good optical homogeneity. Scintillation properties such as radioluminescence using Sr-90 as a source and decay time were also investigated.

Uniaxial ɛ -near-zero metamaterials for giant enhancement of the transverse magneto-optical Kerr effect

We demonstrate a giant enhancement of the transverse magneto-optical Kerr effect. In contrast to conventional magnetoplasmonic structures, we exploit surface plasmon resonances (SPRs) excited along the surface of a ferromagnetic substrate on which a uniaxial $\ensuremath{\varepsilon}$-near-zero (ENZ) metamaterial is grown. In this design, bulky prism couplers are not required and SPR sensors can be produced in integrated, miniaturized systems. We also obtained the analytical expression for the ENZ-SPR phase-matching condition, which can be used for the straightforward design of plasmonic and magnetoplasmonic devices.

Investigation on the growth rate, crystalline perfection, refractive index, Z-scan and electrical characteristics of Z- cut imidazolium l-tartrate single crystal

Abstract Single crystal of imidazolium l -tartrate (IMLT) was grown by the Sankaranarayanan-Ramasamy method. The IMLT crystal system and space group were confirmed by single crystal X-ray diffraction (XRD) studies. X-ray Laue back reflection has been used to find out the orientations of the grown crystals. HRXRD studies revealed that the grown crystal shows good crystalline perfection with full-width-at-half-maximum ~23 arc-s. The UV–Vis–NIR studies show that the grown crystal has good transmission in the entire visible region. The refractive index (RI) and relative birefringence were measured for the first time to the best of our knowledge. Refractive index measurement was done by the prism coupling method. The observed variation of RI and birefringence (Δn) along principal directions depict IMLT belongs to a biaxial crystal system. Birefringence interferometry shows that the grown crystal has good refractive index homogeneity. The temperature dependent pyroelectric coefficients of IMLT have been determined. The nonlinear optical (NLO) properties of the IMLT crystal such as absorption coefficient (β), refractive index (n2) and the third order NLO susceptibility (χ(3)) have been analyzed by Z-scan measurement at 632.8 nm wavelength. Laser damage threshold (LDT) value of the SR method grown crystal has been determined at 532 nm by using a nanosecond second harmonic of Nd:YAG laser. Dislocation density of the SR method grown IMLT crystal was calculated by chemical etching studies. The IMLT crystal grown from the SR method has been found to have high laser damage stability, high piezoelectric coefficient and low dislocation density.

High-Sensitivity Biosensor-Based Enhanced SPR by ZnO/MoS2 Nanowires Array Layer with Graphene Oxide Nanosheet

A novel SPR biosensor that can achieve a high sensitivity is proposed; therefore, a new prism coupling structure based on metal nanowires array layer is designed in this paper. The thickness of each medium layer for the structure is analyzed to obtain the optimal SPR spectrum, by the finite element method, so that the sensitivity is able to be enhanced greatly. The optimal thicknesses of each medium layer are given, and the sensitivity of the SPR biosensor can reach as high as 210.75°/RIU for the refractive index of the sensing medium, from 1.30 to 1.38.

Surface plasmon resonance prism coupler for enhanced circular birefringence sensing and application to non-invasive glucose detection.

A surface plasmon resonance (SPR) prism coupler is proposed for the high-resolution non-invasive (NI) measurement of the circular birefringence (CB) properties of turbid media. The feasibility of the proposed device is demonstrated by means of numerical simulations. It is shown that the SPR sensor enables the CB properties to be detected with a resolution of up to 8.9 × 10-7 RIU (refractive index units) for refractive indices in the range of 1.3∼1.4. Moreover, for tissue phantom solutions containing 2% lipofundin, the device has a detection limit of 3.72 mg/dL. This resolution performance satisfies the detection limit of 10 mg/dL stipulated by the U.S FDA for point-of-care glucose monitoring devices. Thus, the proposed SPR sensor has significant potential for NI glucose sensing in such applications as diabetes detection and management.

An integrated, optofluidic system with aligned optical waveguides, microlenses, and coupling prisms for fluorescence sensing.

An improved, laser-induced fluorescence-based micro-optical biosensor was designed and fabricated, with cyclic olefin copolymer (COC) optical waveguides, a poly(methyl methacrylate) (PMMA) fluidic substrate with an array of microlenses, and a COC coupling prism integrated with the waveguide substrate or cover plate. The double-sided hot embossed fluidic substrate had sampling zone microchannels on the bottom and microlenses on the top. Dissolved COC injected into polydimethylsiloxane (PDMS) lost molds embedded the waveguides in the PMMA cover plate and formed the integrated coupling prism. The embedded COC waveguide was flycut down to 50 μm. The cover plate and shallow, 1:20 aspect ratio, microchannels were thermal fusion bonded using a pressure-assisted boiling point control system, without sagging. The large COC prism coupled better to the waveguide. The highest intensity evanescent excitation of the waveguide was obtained near the critical angle. The maximum signal-to-noise ratio (SNR) was 119 and the lowest detection limit was 7.34 × 10-20 mol at a SNR of 2 for a 100 μm wide by 50 μm deep waveguide. The microlenses highly focused the fluorescent radiation in the sampling zone. The microfabricated waveguide enables rapid, low-cost detection of fluorescent samples with high SNR, a low detection limit, and high sampling efficiency.

Fast-response halogenated 4-alkyl-4′′-cyano-p-terphenyls as dual frequency addressing nematics

Twenty-two compounds belonging to halogenated 4-alkyl-4′′-cyano-p-terphenyls have been synthesized and mesomorphic properties using polarizing optical microscope and differential scanning calorimetry have been determined. The birefringence of the compounds using prism coupling technique was determinated. The multicomponent eutectic mixture consisted of synthesised compounds was prepared and investigated. The prepared mixture exhibits very broad nematic phase range, over 140 °C, with the melting point below 0 °C. Dielectric studies revealed that prepared mixture is very useful for dual frequency adressing system, because it posses large positive dielectric anisotropy (above 22) and becomes negative above the relatively low cross-over frequency (14 kHz). The total response time of the prepared mixture measured at room temperature at low operating voltage (24 V) is short (6.5 ms) which is suitable for fast switching optical applications.

Experimental evidence for preservation of electro-optic property in titanium-diffused lithium niobate waveguide

Abstract Electro-optic (EO) property of titanium-diffused LiNbO3 optical waveguide was studied using prism coupling technique. The EO-effect-induced increment ΔN of effective refractive index (at the wavelength 1311 nm) was measured as a function of externally applied electric field E for TM0 and TM1 modes guided in the titanium-diffused LiNbO3 planar waveguide. By using the linearity between ΔN and E, the EO coefficient r33 is determined. For reference, the measurement was also performed on a bulk material of congruent LiNbO3, yielding r33 = 24.9 ± 0.8 p.m./V, which is in qualitative agreement with that obtained by extrapolating previously reported result to the 1311 nm wavelength, ~24 p.m./V, confirming the feasibility of the measurement method. Measurements on the titanium-diffused planar waveguide give r33 = 25.7 ± 0.6 p.m./V for the TM0 mode and 25.7 ± 0.4 p.m./V for the TM1 mode. Both values can be considered as identical within the error, and are the same as that of the bulk material, indicating that the EO property is well preserved in the titanium-diffused LiNbO3 waveguide. The main reason is that the LiNbO3 crystalline phase is well preserved in the titanium-diffused waveguide layer.