We describe a quantitative and inexpensive method of demonstrating frustrated total internal reflection based on the attenuation of a laser beam through a wedge-shaped air gap between two glass prisms. An advantage of this method is that the thickness of the air gap can be determined by observing interference effects with only a slight modification of the setup. The experiment avoids the need to employ high-precision translation stages as is often the case in standard demonstrations of frustrated total internal reflection.

A simple demonstration of frustrated total internal reflection

We present a detailed study of the Gaussian laser propagation through a dielectric system composed by two right angle prisms. We investigate the transition between the spatial coherence limit, which exhibits wave-like properties and for which the resonance phenomenon can be seen, and the decoherence limit, which exhibits particle-like properties and for which the multiple diffusion occurs. We also analyze the tunneling at critical angles. In our numerical analysis, we shall use BK7 and Fused Silica prisms and a Gaussian He-Ne laser with a wavelength of 632.8 nm and beam waists of 2 mm and 200 μm.

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Resonance, multiple diffusion and critical tunneling for Gaussian lasers

A new surface plasmon resonance (SPR) configuration is proposed, which consists of a prism, a dielectric layer, a metal coating, and a matching liquid. The optical constants of each layer in the proposed prism-dielectric-metal-liquid (PDML) configuration have been optimized to match the SPR conditions and reach the strongest intensity. Combining the PDML configuration with spectroscopic ellipsometry, SPR spectroscopic ellipsometry (SPRSE) with a PDML configuration was developed. The SPR wavelength can be adjusted to the desired wavelength by varying the thickness of the dielectric layer. The amplitude and phase change, magnified by the SPR in the visible and near-infrared wavelengths, were obtained to determine the optical constants and thickness of ultrathin metal coatings. The extracted optical constants were found to be in good agreement with the results obtained using transmission electron microscopy (TEM) and X-ray reflectivity (XRR) techniques. These SPRSE measurements show great potential for characterizing the interface between a metal coating and a dielectric layer, and the surface uniformity of ultrathin metal coatings.

Measuring ultrathin metal coatings using SPR spectroscopic ellipsometry with a prism-dielectric-metal-liquid configuration.

Due to the recent interest in studying propagation of light through triangular air gaps, we calculate, by using the analogy between optics and quantum mechanics and the multiple step technique, the transmissivity through a triangular air gap surrounded by an homogeneous dielectric medium. The new formula is then compared with the formula used in literature. Starting from the qualitative and quantitative differences between these formulas, we propose optical experiments to test our theoretical results.

/pdf/light-transmission-through-a-triangular-air-gap-10hx2i5mc9.pdf

Light transmission through a triangular air gap

Due to the recent interest in studying propagation of light through triangular air gaps, we calculate, by using the analogy between optics and quantum mechanics and the multiple step technique, the transmissivity through a triangular air gap surrounded by an homogeneous dielectric medium. The new formula is then compared with the formula used in the literature. Starting from the qualitative and quantitative differences between these formulas, we propose optical experiments to test our theoretical results.

/pdf/light-transmission-through-a-triangular-air-gap-19bbgbywul.pdf

We describe a new method to demonstrate frustrated total internal reflection in the visible band using the 100nm thick air film near the center of Newton’s rings. Experimental measurements of the light intensity distribution validate the theoretical predictions.

A new method to demonstrate frustrated total internal reflection in the visible band

Plasmonic resonances are attractive and promising for biosensing applications benefiting from their strong nanoscale light confinement and sensitivity to the refractive index of surrounding medium. Here, we numerically and theoretically investigate a metal–insulator-metal (MIM) nanograting structure, where gold nanostrip arrays are placed on a thin dielectric layer with a sodium film underlay. The structure is obliquely excited by a transverse magnetic (TM) wave from a prism supporting the whole MIM structure. We found that the plasmonic surface lattice resonance (SLR) mode and gap plasmon resonance (GPR) mode can be efficiently excited in our structure at the near infrared wavelength. Remarkably, the SLR mode can achieve ultranarrow linewidth less than 3 nm (quality factor > 500), sensitivity over 1000 nm/RIU and the corresponding figure of merit (FOM) larger than 300 RIU−1. Our study may pay a way to achieve high-performance sensing in a simple plasmonic nanostructure that could be vastly used in biological and chemical circumstances. 

Near-Infrared Narrow Plasmonic Resonances for High-Performance Optical Sensing in a Sodium-Based Nanograting

A multicavity based quasi-parity-time (PT) symmetric structure is theoretically investigated for realizing highly sensitive gas detection. In the PT-symmetric broken phase, the singular pole effect can be achieved with much enhanced transmission, based on which low concentration of gas in the air can be efficiently sensed. In addition, the sensing signal is directly recorded by the change of the transmittance (T) of the sensor, real-time monitoring can be realized in our proposed structure. The sensitivities of -ΔT/ΔnD can reach 79437.2602 RIU−1 and 24753.7366 RIU−1 for benzene and methane, respectively. Such high sensitivity just occurs in the low concentration range. Our structures show great promise in constructing sensitive gas sensors to detect various harmful gases, such as volatile organic compounds (VOC) etc. 

Jin Zhou

Papers

A new method to demonstrate frustrated total internal reflection in the visible band

Near-Infrared Narrow Plasmonic Resonances for High-Performance Optical Sensing in a Sodium-Based Nanograting

Highly sensitive gas optical sensing in a multicavity based quasi-parity-time-symmetric structure

Ultrafast all-optical switching in a silicon-polymer compound slotted photonic crystal nanobeam cavity