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Register a new userOptical Curtain Effect: Extraordinary Optical Transmission Enhanced by Antireflection
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In this paper, we employ an antireflective coating which comprises of inverted pi shaped metallic grooves to manipulate the behaviour of a TM-polarized plane wave transmitted through a periodic nanoslit array. At normal incidence, such scheme can not only retain the optical curtain effect in the output region, but also generate the extraordinary transmission of light through the nanoslits with the total transmission efficiency as high as 90%. Besides, we show that the spatially invariant field distribution in the output region as well as the field distribution of resonant modes around the inverted pi shaped grooves can be reproduced immaculately when the system is excited by an array of point sources beneath the inverted pi shaped grooves. In further, we investigate the influence of center-groove and side-corners of the inverted pi shaped grooves on suppressing the reflection of light, respectively. Based on our work, it shows promising potential in applications of enhancing the extraction efficiency as well as controlling the beaming pattern of light emitting diodes.
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We show that, a metasurface composed of subwavelength metallic slit array embedded in an asymmetric environment can exhibit either extraordinary optical transmission (EOT) or extraordinary optical diffraction (EOD). By employing an analytical model expansion method and the diffraction order chart in k-vector space, we found that the resonance decaying pathway of the local slit cavity mode can be tuned to either 0th or -1st diffraction order by changing the parallel wavevector, which gives rise to enhanced 0th transmission (EOT) of the structure for small incident angles, and enhanced -1st diffraction (EOD) for large incident angles. Based on this appealing feature, a multifunctional metasurface that can switch its functionality between transmission filter, mirror and off-axis lens is demonstrated. Our findings provide a convenient way to construct multifunctional integrated optical devices on a single planar device.
In this paper, we will propose that magnetic-resonance nanostructures in a metal surface could be used to realize extraordinary optical transmission (EOT). Toward this goal, we designed and fabricated a one dimensional diatomic chain of slit-hole resonator (SHR). Due to the strong exchange current interaction, a type of magnetic plasmon (MP) propagation mode with a broad frequency bandwidth was established in this system. Apparent EOT peaks induced by the MP mode were observed in our measured spectra at infrared frequencies. The strongest EOT peak was obtained at 1.07 eV with an incident angle of 20 degree. The measured dependence of EOT peaks on the incident angle coincided with the theoretical results quite well. This proposed MP propagation mode in SHR structure has good potential applications in multifrequency nonlinear optical processes.
We present a fully three-dimensional theoretical study of the extraordinary transmission of light through subwavelength hole arrays in optically thick metal films. Good agreement is obtained with experimental data. An analytical minimal model is also developed, which conclusively shows that the enhancement of transmission is due to tunneling through surface plasmons formed on each metal-dielectric interfaces. Different regimes of tunneling (resonant through a surface plasmon molecule, or sequential through two isolated surface plasmons) are found depending on the geometrical parameters defining the system.
Presented here is the development and demonstration of a tunable cavity-enhanced terahertz frequency-domain optical Hall effect technique. The cavity consists of at least one fixed and one tunable Fabry-Perot resonator. The approach is suitable for enhancement of the optical signatures produced by the optical Hall effect in semi-transparent conductive layer structures with plane parallel interfaces. The physical principle is the constructive interference of electric field components that undergo multiple optical Hall effect induced polarization rotations upon multiple light passages through the conductive layer stack. Tuning one of the cavity parameters, such as the external cavity thickness, permits shifting of the frequencies of the constructive interference, and enhancement of the optical signatures produced by the optical Hall effect can be obtained over large spectral regions. A cavity-tuning optical stage and gas flow cell are used as examples of instruments that exploit tuning an external cavity to enhance polarization changes in a reflected terahertz beam. Permanent magnets are used to provide the necessary external magnetic field. Conveniently, the highly reflective surface of a permanent magnet can be used to create the tunable external cavity. The signal enhancement allows the extraction of the free charge carrier properties of thin films, and can eliminate the need for expensive super-conducting magnets. Furthermore, the thickness of the external cavity establishes an additional independent measurement condition, similar to, for example, the magnetic field strength, terahertz frequency, and angle of incidence. A high electron mobility transistor structure and epitaxial graphene are studied as examples. We discuss the theoretical background, instrument design, data acquisition, and data analysis procedures.
We present a procedure for reproducibly fabricating ultrahigh transmission optical nanofibers (530 nm diameter and 84 mm stretch) with single-mode transmissions of 99.95 $ pm$ 0.02%, which represents a loss from tapering of 2.6 $,times ,$ 10$^{-5}$ dB/mm when normalized to the entire stretch. When controllably launching the next family of higher-order modes on a fiber with 195 mm stretch, we achieve a transmission of 97.8 $pm$ 2.8%, which has a loss from tapering of 5.0 $,times ,$ 10$^{-4}$ dB/mm when normalized to the entire stretch. Our pulling and transfer procedures allow us to fabricate optical nanofibers that transmit more than 400 mW in high vacuum conditions. These results, published as parameters in our previous work, present an improvement of two orders of magnitude less loss for the fundamental mode and an increase in transmission of more than 300% for higher-order modes, when following the protocols detailed in this paper. We extract from the transmission during the pull, the only reported spectrogram of a fundamental mode launch that does not include excitation to asymmetric modes; in stark contrast to a pull in which our cleaning protocol is not followed. These results depend critically on the pre-pull cleanliness and when properly following our pulling protocols are in excellent agreement with simulations.
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