Tamm plasmon polariton-based planar hot-electron photodetector for the near-infrared region.

Light-trapping devices have always been a topic of intense interest among researchers. One such device that has gained attention is the hot-electron photodetector with a tunable detection wavelength. Photodetectors based on plasmon nanostructures that provide excitation of surface plasmon polaritons are challenging to manufacture. To address this issue, a planar hot-electron photodetector based on a Tamm plasmon polariton localized in a metal-semiconductor-multilayer mirror structure has been proposed in this study. The parameters and materials of the structure were adjusted to ensure perfect absorption at the resonance wavelength. As a result, the photoresponsivity of the proposed device can reach 42.6 mA W-1 at 905 nm. For the first time, the photosensitivity was calculated analytically by solving the dispersion law for the Tamm plasmon polariton.

Wavelength- and Angle-Selective Photodetectors Enabled by Graphene Hot Electrons with Tamm Plasmon Polaritons.

Recently, two-dimensional materials have attracted attention owing to their special optical characteristics and miniaturization, with low thickness as well as extremely high responsivity. Additionally, Tamm plasmon polariton (TPP) resonance can be observed by combining a metal film and a one-dimensional (1D) photonic crystal (PC), where an electric field confinement is located at the metal-1D PC interface. In this study, a graphene layer combined with a TPP is proposed as a wavelength- and angle-selective photodetector. The graphene layer is located where the strong field confinement occurs, and the photocurrent response is significantly enhanced with increasing absorption by over four times (from 62.5 µA⋅W-1 to 271 µA⋅W-1 and undetected state to 330 µA⋅W-1 in two different samples). Moreover, the graphene-TPP photodetector has wavelength and angle selectivity, which can be applied in LiDAR detecting, sun sensors, laser beacon tracking, and navigational instruments in the future.

Nanostructured photosensitive layer for Tamm-plasmon-polariton-based organic solar cells.

The influence of the volume fraction of plasmonic nanoparticles on the efficiency of the Tamm-plasmon-polariton-based organic solar cell is investigated in the framework of temporal coupled mode theory and confirmed by the transfer matrix method. It is shown that, unlike a conventional plasmonic solar cell, in which the efficiency is directly proportional to the volume fraction of nanoparticles in the photosensitive layer, the efficiency of the proposed solar cell reaches the highest value at low volume fractions. This effect is explained by the fact that at these volume fractions, the critical coupling condition of the incident field with the Tamm plasmon polariton is fulfilled. Thus, for the incoming radiation range of 350 to 500 nm, a maximal cell efficiency of 28% is achieved with a volume fraction of nanoparticles equal to 10%. Additionally, the optical properties of the photosensitive layer are compared for the cases of determining its complex refractive index by effective medium theory and the S-parameter retrieval method. A good agreement between the results is demonstrated, which encourages the use of the effective medium theory for preliminary calculations.

Double-Resolved Beam Steering by Metagrating-Based Tamm Plasmon Polariton.

We consider Tamm plasmon polariton in a subwavelength grating patterned on top of a Bragg reflector. We demonstrate dynamic control of the phase and amplitude of a plane wave reflected from such metagrating due to resonant coupling with the Tamm plasmon polariton. The tunability of the phase and amplitude of the reflected wave arises from modulation of the refractive index of a transparent conductive oxide layer by applying the bias voltage. The electrical switching of diffracted beams of the ±1st order is shown. The possibility of doubling the angular resolution of beam steering by using asymmetric reflected phase distribution with integer and half-integer periods of the metagrating is demonstrated.

Broadband Tamm Plasmons in Chirped Photonic Crystals for Light-Induced Water Splitting.

An electrode of a light-induced cell for water splitting based on a broadband Tamm plasmon polariton localized at the interface between a thin TiN layer and a chirped photonic crystal has been developed. To facilitate the injection of hot electrons from the metal layer by decreasing the Schottky barrier, a thin n-Si film is embedded between the metal layer and multilayer mirror. The chipping of a multilayer mirror provides a large band gap and, as a result, leads to an increase in the integral absorption from 52 to 60 percent in the wavelength range from 700 to 1400 nm. It was shown that the photoresponsivity of the device is 32.1 mA/W, and solar to hydrogen efficiency is 3.95%.

Metal-Dielectric Polarization-Preserving Anisotropic Mirror for Chiral Optical Tamm State.

This numerical study demonstrates the possibility of exciting a chiral optical Tamm state localized at the interface between a cholesteric liquid crystal and a polarization-preserving anisotropic mirror conjugated to a metasurface. The difference of the proposed structure from a fully dielectric one is that the metasurface makes it possible to decrease the number of layers of a polarization-preserving anisotropic mirror by a factor of more than two at the retained Q-factor of the localized state. It is shown that the proposed structure can be used in a vertically emitting laser.

Chiral-Selective Tamm Plasmon Polaritons.

Chiral-selective Tamm plasmon polariton (TPP) has been investigated at the interface between a cholesteric liquid crystal and a metasurface. Different from conventional TPP that occurs with distributed Bragg reflectors and metals, the chiral-achiral TPP is successfully demonstrated. The design of the metasurface as a reflective half-wave plate provides phase and polarization matching. Accordingly, a strong localized electric field and sharp resonance are observed and proven to be widely tunable.

Photosensitivity and reflectivity of the active layer in a Tamm-plasmon-polariton-based organic solar cell.

We report on a model of an organic solar cell in which a photosensitive layer doped with plasmon nanoparticles acts as not only an absorbing element but also a mirror involved in the formation of the Tamm plasmon polariton. It is shown that such solar cells can be fabricated without metal contacts, thus avoiding undesired losses in the system. Methods for an additional increase in the integral absorption by applying metal or dielectric mirrors to the lower boundary of the photonic crystal are proposed. It has been found that the integral absorption in the active layer can be increased by 15% compared to classical optimized planar solar cells.

Strain Sensor via Wood Anomalies in 2D Dielectric Array.

Optical sensing is one of many promising applications for all-dielectric photonic materials. Herein, we present an analytical and numerical study on the strain-responsive spectral properties of a bioinspired sensor. The sensor structure contains a two-dimensional periodic array of dielectric nanodisks to mimic the optical behavior of grana lamellae inside chloroplasts. To accumulate a noticeable response, we exploit the collective optical mode in grana ensemble. In higher plants, such a mode appears as Wood's anomaly near the chlorophyll absorption line to control the photosynthesis rate. The resonance is shown persistent against moderate biological disorder and deformation. Under the stretching or compression of a symmetric structure, the mode splits into a couple of polarized modes. The frequency difference is accurately detected. It depends on the stretch coefficient almost linearly providing easy calibration of the strain-sensing device. The sensitivity of the considered structure remains at 5 nm/% in a wide range of strain. The influence of the stretching coefficient on the length of the reciprocal lattice vectors, as well as on the angle between them, is taken into account. This adaptive phenomenon is suggested for sensing applications in biomimetic optical nanomaterials.

Critical coupling vortex with grating-induced high Q-factor optical Tamm states.

We investigate optical Tamm states supported by a dielectric grating placed on top of a distributed Bragg reflector. It is found that under certain conditions the Tamm state may become a bound state in the continuum. The bound state, in its turn, induces the effect of critical coupling with the reflectance amplitude reaching an exact zero. We demonstrate that the critical coupling point is located in the core of a vortex of the reflection amplitude gradient in the space of the wavelength and angle of incidence. The emergence of the vortex is explained by the coupled mode theory.

Model of a tunable hybrid Tamm mode-liquid crystal device.

A concept of an easily tunable device based on hybrid Tamm modes is proposed. The device can be controlled using a high-sensitivity chiral liquid crystal serving as a mirror. The coupling of the chiral optical Tamm state with the Tamm plasmons is predicted. The Tamm plasmons are excited at different frequencies for the orthogonal linear polarizations, while the chiral Tamm state is excited at only one frequency. The properties of the proposed model are analytically and numerically calculated. The possibility of creating a two- and three-mode laser with tunable characteristics on the basis of the proposed model is discussed.

Chiral Optical Tamm States at the Interface between a Dye-Doped Cholesteric Liquid Crystal and an Anisotropic Mirror.

The resonant splitting of optical Tamm state numerically is demonstrated. The Tamm state is localized at the interface between a resonant chiral medium and a polarization-preserving anisotropic mirror. The chiral medium is considered as a cholesteric liquid crystal doped with resonant dye molecules. The article shows that the splitting occurs when dye resonance frequency coincides with the frequency of the Tamm state. In this case the reflectance, transmittance, and absorptance spectra show two distinct Tamm modes. For both modes, the field localization is at the interface between the media. The external field control of configurable optical and structural parameters paves the way for use in tunable chiral microlaser.

Electrically induced transformations of defects in cholesteric layer with tangential-conical boundary conditions.

Electric-field-induced changes of the orientational structures of cholesteric liquid crystal layer with the tangential-conical boundary conditions have been investigated. The samples with the ratio of the cholesteric layer thickness d to the helix pitch p equalled to 0.57 have been considered. The perpendicularly applied electric field causes a decrease of the azimuthal director angle at the substrate with the conical surface anchoring. In the cells with d = 22 µm, the defect loops having the under-twisted and over-twisted areas are formed. At the defect loop the pair of point peculiarities is observed where the 180° jump of azimuthal angle of the director occurs. Under the action of electric field the loops shrink and disappear. In the cells with d = 13 µm, the over-twisted and under-twisted defect lines are formed. Applied voltage results in the shortening of lines or/and their transformation into a defect of the third type. The director field distribution near defect lines of three types has been investigated by the polarising microscopy techniques. It has been revealed that the length ratio between the over-twisted and third-type defect lines can be controlled by the electric field.