Total Internal Reflection Condition Research Articles

In Situ Measurement of Individual W/O Microemulsions of Aerosol OT in Dodecane/Water Extraction System by Total Internal Reflection Laser Light Scattering Microscopy

Abstract The laser light scattering microscopy under the total internal reflection condition allowed one to do in situ measurements of individual W/O microemulsions of aerosol OT (AOT) formed spontaneously at a dodecane/water interface in a thin-layer two-phase microcell. The instrument can detect the AOT microemulsions being larger than 50 nm in hydrodynamic radius at the interface and in the dodecane phase without any probe molecules.

Mode-area scaling of helical-core, dual-clad fiber lasers and amplifiers using an improved bend-loss model

For small-bend radii, the waveguide condition for total internal reflection is violated in a large angular spread of incident angles at the interface of the fiber core. To account for this, we derived an improved semianalytic bend-loss model that allows for the propagation of radiated fields outside the plane of the fiber bend. This new model is applied to large-mode-area helical-core fibers (which require small-bend radii) for use as high-power fiber lasers and amplifiers. In particular, the limits of scaling the mode area while maintaining good beam quality are explored. Single-mode operation is expected for a 40 μm core with a 0.10 numerical aperture, and scaling to a 100 μm core diameter is shown to be possible. Additionally, helical fibers are shown to readily perform where conventional coiled fibers are not appropriate to operate long term.

Diffraction under total internal reflection for micro-fluidic analysis

This work presents the principles of a novel micro-optical system for micro- and nano-fluidic analysis. It is based on diffraction, occurring in total internal reflection conditions. The developed detector is integrated in an autonomous micro-fluidic device, produced by a unique combination of different techniques for micro- and nano-structuring and micro-machining. The micro-fluidic sensor is examined both experimentally and theoretically with respect to the parameters of the light and the diffraction grating. The most beneficial configurations with respect to maximum sensitivity towards the fluidic optical constants are discussed. Optical experiments show sensitivity of 5×10-4 to the fluidic refractive index and of 3.5×106 m-1 to the absorption coefficient. Envisioned applications of the integrated micro-sensor are concentration and composition analysis, environmental protection control, medical, biological and chemical diagnostics, and so on.

Control of reflection at an optical interface in the absence of total internal reflection for a retroreflective display application

Reflection at an interface between two materials can be modulated by means of varying the optical properties at the interface. We have studied this modulation of the reflected light with an aim to develop a flashing retroreflector for roadside conspicuity applications. Reflectance modulation has previously been studied under the conditions of total internal reflection (TIR), where a light-absorbing material placed in the associated evanescent wave region can be used to attenuate the intensity of the reflected light. If instead the light rays strike the interface at an angle that is slightly smaller than the critical angle required for TIR, they instead undergo a substantial, but partial, reflection. We have demonstrated that an analogous attenuation effect to the TIR situation is observed, even though there is no evanescent wave present under these circumstances. We have studied this behavior and have developed a model to describe the motion of the absorbing material and the related interference effects that occur.

Evanescent wave holographic recording in nanosize thick chalcogenide glass films

The results of holographic gratings recording in 29, 15 and 8nm thick As2S3 films are presented in the paper. The method is based on the interference of surface-propagating evanescent waves, created by total internal reflection. The condition for successful recording is the penetration depth of these inhomogeneous waves to be greater than the films thickness. In this case, the film’s refractive index does not affect the total internal reflection (TIR) condition and could be greater than the input glass prism. The experimentally obtained low diffraction efficiencies by this holographic recording technique is due to the very low refractive index modulation, but the good signal-to-noise ratio – better than 50:1 and Bragg-type diffraction are a base for future applications of this grating formation method in nanotechnology.

Micro-fluidic analysis based on total internal light reflection

The work presents a novel micro-optical sensor for micro and nano-fluidic analysis. It is based on diffraction, occurred in total internal reflection conditions. The detector is integrated on an autonomous micro-fluidic device and produced by a unique combination of different techniques for micro- and nano-structuring and micromachining. The preliminary optical investigation shows sensitivity to the fluidic refractive index of 2 × 10 −3 and to the absorption coefficient of 6 × 10 6 m −1. Envisioned applications of the integrated micro-sensor are medical, biological and chemical diagnostic of liquid substances and dispersions of drugs, serums, proteins, peptides, DNA, RNA, etc.

Topography characterization of a deep grating using near-field imaging

Using near-field optical microscopy at the wavelength of 633 nm, we image light intensity distributions at several distances above an approximately 2-microm-deep and a 1-microm-period glass grating illuminated from below under the condition of total internal reflection. The intensity distributions are numerically modeled, and an inversion procedure based on a least-squares-fit optimization is employed to extract the grating geometry from the optical images.

Tunneling of X-ray photons through a thin film under total internal reflection conditions

Tunneling of 0.154-and 0.139-nm x-ray photons through a thin film under total internal reflection conditions has been experimentally demonstrated. The NiSi2 film 13 nm thick is deposited by magnetron sputtering on a polished Si substrate. A beam with an angular spread of 20″ is directed to the Si/NiSi2 interface from the inside through the lateral surface of a sample. A peak associated with tunneling of photons from Si to air through the NiSi2 film is observed at grazing angles of θ1 > 0.4θc, where θc is the critical angle of total internal reflection at the Si/NiSi2 interface. The integral intensity of tunneling peaks that is measured for various θ1 angles agrees with the calculations.

Optical lifting force under focused evanescent wave illumination: A ray optics model

We propose a ray optics model to calculate the trapping force on a dielectric particle located on the interface between two media and illuminated by a focused evanescent field beam. Such a focused evanescent beam is produced by a high numerical aperture objective with a central obstruction whose size satisfies the total internal reflection condition on the interface. The dependence of the lifting force on the obstruction size, the particle size, and the distance of the particle from the interface is revealed.

InGaAsP annular Bragg lasers: theory, applications, and modal properties

A novel class of circular resonators, based on a radial defect surrounded by Bragg reflectors, is studied in detail. Simple rules for the design and analysis of such structures are derived using a transfer matrix formalism. Unlike conventional ring resonators, annular Bragg resonators (ABR) are not limited by the total internal reflection condition and can exhibit both large free spectral ranges and low bend losses. The Bragg reflection mechanism enables the confinement of light within a defect consisting of a low refractive index medium (such as air). Strong atom-photon interaction can be achieved in such a structure, making it a promising candidate for sensing and cavity quantum electrodynamics applications. For sensing applications, we show that the ABR structure can possess significantly higher sensitivity when compared to a conventional ring resonator sensor. Lasing action and low threshold levels are demonstrated in ABR lasers at telecommunication wavelengths under pulsed optical pumping at room temperatures. The impact of the intensity and dimensions of the pump spot on the emitted spectrum is studied in detail.

Total internal reflection second-harmonic generation spectrometer system optimized for the liquid/liquid interface

An apparatus for optical second-harmonic generation (SHG) spectroscopy at the liquid/liquid interface has been constructed. The fundamental laser beam of 780–920nm was irradiated to the interface under the total internal reflection condition, and the interfacial second-harmonic spectrum was obtained during 390–460nm. An automatically wavelength-tuned Ti:Sapphire laser was employed in this study, and it was simultaneously controlled with other peripheral instruments, such as monochromator. The acquisition time per spectrum with 2nm interval was less than 30min. The measurement of SHG spectrum of water-soluble porphyrin adsorbed at the heptane/water interface was demonstrated. The solvatochromic shift of the SHG maximum of the adsorbed porphyrin was ascribed to the less polar environment around the porphyrin molecule at the interface in comparison with the aqueous phase.

Time-resolved total internal reflection fluorescence spectroscopy : Part I. Photophysics of Coumarin 343 at liquid/liquid interface

Pico-second time-resolved time-correlated single photon counting (TCSPC) technique under the total internal reflection (TIR) condition has been used to study the photophysical properties of Coumarin 343 (C343) dye molecules adsorbed at the water/1,2-dichloroethane (DCE) interface. The fluorescence decay profile of C343 under TIR condition at the water/DCE interface was non-exponential and fitted to the double exponential decay function with the fluorescence lifetimes 0.3 and 3.6 ns, which proved the existence of two different forms of C343 species having largely different lifetimes at the interface. The longer fluorescence lifetime component of C343 at the interface is attributed to the emission from the monomeric form of the dye molecules and the shorter lifetime component is due to the aggregation of dye molecules. The penetration depth dependence of decay curves indicated no change in the fluorescence lifetime components, however, the amplitude corresponding to the lifetime of aggregate increased and the amplitude corresponding to the lifetime of monomer decreased with the decrease in penetration depth of the aqueous phase from the interface. Aggregation is significant in the interfacial layer. The decrease in monomer lifetime at the interface compared to that in the bulk solution is interpreted in terms of excitation energy migration between the dye molecules.

High Sensitive Optical Detection of Bio-Chemicals onto a Silicon Oxide Surface Based on Waveguide Mode

ABSTRACTThis work presents high sensitive detection of specific adsorption of proteins onto a silicon oxide (SiOx) surface modified by molecules with a biotinyl-end group. We fabricated a SiOx waveguide by sputtering onto a thin gold film and measured the incident angle-dependence of reflectivity using a polarized He-Ne laser under total internal reflection condition. When the s-polarized light was irradiated to the SiOx waveguide (760 nm) coupled with a prism, the incident angle-dependence of reflectivity showed narrow dips due to excitation of the waveguide mode. The waveguide surface was modified by the molecules with the biotinyl-end group as a protein probe. Specific adsorption of streptavidin in a PBS buffer solution was monitored through time course of the reflectivity change at a constant incident angle, where the waveguide mode was excited. As compared with conventional SPR system using a gold surface, high sensitive detection of the specific adsorption was achieved. Additionally, we fabricated micro-patterned arrays of biotinyl-end layers onto the SiOx waveguide surface by micro-contact printing. Then we observed the specific adsorption behavior on the micro-patterned arrays by the imaging based on the waveguide mode using a CCD camera.

Anomalous phenomenon of a focused evanescent Laguerre-Gaussian beam

We demonstrate theoretically and experimentally an anomaly in the intensity distribution at the focal region of a Laguerre-Gaussian beam, when such a beam is focused by a high numerical aperture objective lens through an index-mismatched interface satisfying the total internal reflection condition. An asymmetric rotation of the focal field arising from the interplay of the phase shift induced by the total internal reflection and the helical phase of the Laguerre-Gaussian beam has been experimentally observed by a scanning near-field optical microscope. A cross-section analysis shows that the experimental results match well with the theoretical predictions.

Collection-mode near-field scanning infrared microscope based on silver halide probes

We developed a collection-mode scanning near field microscope for the midinfrared spectral range, employing probes fabricated from tapered silver halide fibers. The system was tested in the photon scanning tunneling regime, where a sample was illuminated under total internal reflection conditions. The experimental results agreed with the results obtained by an analytical theoretical model.

Control of laser pulse parameters in a cavity with a thermal-nonlinearity shutter

The light pulse generation by a laser controlled by shutter from a finite-thickness absorbing layer with thermal nonlinearity has been studied theoretically. The layer placed in the cavity is oriented with respect to the mirror so that conditions for nonlinear total internal reflection of generated radiation are created. In the plane-wave approximation, a self-consistent system of nonlinear truncated equations for the field amplitudes together with constitutive equations has been obtained. Numerical simulation with the use of the obtained system has shown that it is possible to control the form and duration of the generated pulse by varying the absorption coefficient of the nonlinear medium and the angle of incidence on the absorbing layer, as well as the layer thickness.

Continuously tunable fibre attenuator operating in the wavelength range near 1.5 μm

A fibre attenuator is fabricated for the telecommunication wavelength range near 1.5 μm in which a single-mode silica fibre with side polishing is used. The fibre surface is covered by a layer of fluorine-containing polymer with a large thermooptic coefficient. The principle of attenuator operation is based on a change in the conditions of total internal reflection for a guided mode in the polished region due to thermally induced variation in the refractive index of the fluoropolymer layer. The attenuator is insensitive to light polarisation, it has a continuously variable attenuation coefficient in the range 0.2–27 dB, and can be easily incorporated into fibreoptic links.

Surface-enhanced Raman scattering from oleate-stabilized silver colloids at a liquid/liquid interface.

Oleate-stabilized silver colloids of 5-nm-diameter were adsorbed to a toluene/water interface, and surface enhanced Raman scattering (SERS) spectra from these colloids were measured under the total internal reflection (TIR) condition. From the observed spectra, we examined the states of oleate ions and toluene molecules on silver colloids at the liquid/liquid interfacial region. The TIR-SERS spectra of oleate ions showed stronger peaks of the carboxylate group and the ethylene group than those of alkyl chains. From these results, it was found that the oleate ions were adsorbed on the silver surface in two different ways at the liquid/liquid interface; the carboxylate group adsorbed in the organic phase side, while the ethylene group adsorbed in the aqueous phase side. The shifts of the toluene in the interfacial SERS spectra were identical to those of bulk toluene, though the relative intensities among the peaks were not same. This result suggested that the toluene was adsorbed with a weak interaction, but was significantly enhanced by the local electromagnetic field at the colloid surface.

Transformation of Nanosecond Laser Pulses under the Conditions of Total Internal Reflection from a Layer with Thermal Nonlinearity

The nonlinear, total internal reflection of a laser pulse from an absorbing layer of finite thickness in the presence of a retrodirective mirror has been considered in the framework of the plane-wave approximation. The dynamics of reflection of a pulse from a nonlinear layer has been investigated on the basis of the solution of Maxwell equations for a refracted wave and constitutive equations for a medium with thermal nonlinearity. The numerical solution of the unsteady equations obtained allows one to determine the evolution of the reflectance of a layer. The time evolution of the energy parameters and the shape of the reflected and transmitted pulses has been numerically simulated.

Total internal reflection ellipsometry: principles and applications.

A concept for a measurement technique based on ellipsometry in conditions of total internal reflection is presented. When combined with surface plasmon resonance (SPR) effects, this technique becomes powerful for monitoring and analyzing adsorption and desorption on thin semitransparent metal films as well as for analyzing the semitransparent films themselves. We call this technique total internal reflection ellipsometry (TIRE). The theory of ellipsometry under total internal reflection combined with SPR is discussed for some simple cases. For more advanced cases and to prove the concept, simulations are performed with the Fresnel formalism. The use of TIRE is exemplified by applications in protein adsorption, corrosion monitoring, and adsorption from opaque liquids on metal surfaces. Simulations and experiments show greatly enhanced thin-film sensitivity compared with ordinary ellipsometry.