Terahertz Radar Cross Section Characterization using Laser Feedback Interferometry with a Quantum Cascade Laser

Radar cross section (RCS) measurements of complex, large objects are usually performed on scale models so that the measurement is carried out in a well-controlled environment. This letter explores the feasibility of RCS measurement using a terahertz quantum cascade laser via laser feedback interferometry. Numerical simulations show that the RCS information embedded in the non-linear interferometric signals obtained from simple targets can be retrieved through numerical fitting of the well-known excess phase equation. The method is validated experimentally using a terahertz quantum cascade laser and the results are well matched with those obtained from numerical simulations

Dependence of the emission from tris(8-hydroxyquinoline) aluminum based microcavity on device thickness and the emission layer position

In this work, we present a systematic study of the emission from bilayer organic microcavity light emitting diodes with two metal mirrors. The devices consisting of two organic layers, N,NV-di(naphthalene-1-yl)-N,NV-diphenylbenzidine as the hole transport layer and tris (8-hydroxyquinoline) aluminum as the emitting layer, and two metal mirrors were fabricated and characterized by transmittance, reflectance, photoluminescence, and electroluminescence measurements. The effects of layer thickness, interface position, and the choice of anode(bottom mirror) were investigated. The transmittance and reflectance spectra were modeled using a transfer matrix model, and the optical functions for all the materials used were determined by spectroscopic ellipsometry. The dependence of the photoluminescence and electroluminescence spectra on the device thickness and interface position is discussed

Optical guided dispersions and subwavelength transmissions in dispersive plasmonic circular holes

The light transmission through a dispersive plasmonic circular hole is numerically investigated with an emphasis on its subwavelength guidance. For a better understanding of the effect of the hole diameter on the guided dispersion characteristics, the guided modes, including both the surface plasmon polariton mode and the circular waveguide mode, are studied for several hole diameters, especially when the metal cladding has a plasmonic frequency dependency. A brief comparison is also made with the guided dispersion characteristics of a dispersive plasmonic gap [K. Y. Kim, et al., Opt. Express 14, 320-330 (2006)], which is a planar version of the present structure, and a circular waveguide with perfect electric conductor cladding. Finally, the modal behavior of the first three TM-like principal modes with varied hole diameters is examined for the same operating mode.Comment: 20 pages, 5 figures, 1 tabl

Detecting Genetic Variation in Plants by Mapping Cell Water Dynamics with Terahertz Laser Feedback Interferometry

This study investigated the use of terahertz (THz) imaging as a rapid, high-fidelity technique for discriminating between genetic variants of the Allium genus based on cellular water dynamics. It has been demonstrated earlier that plant genetic variations can be related to the biochemical and bio-mechanical alterations of the cell and that in turn they affect the water dynamics within the cell. In this article we show that the water dynamics, when considered in the form of the temporal evolution of the trajectory of the plant's response to terahertz radiation probe, and measured by a coherent terahertz transceiver, provides unique signature of the genetic makeup of the plant. Therefore by exploring these trajectories, we discriminate between closely related variants of the same genus. The technique used for THz probing was the laser feedback interferometry with THz quantum cascade lasers which enabled fast acquisition of high-resolution THz amplitude and phase images, which were processed into evaporation profiles describing the time-dependent dehydration of the samples. The trajectory of this profile in amplitude-phase reflectivity domain discriminates between different members of the Allium genus. This enables real-time genetic discrimination in agricultural and genome conservation applications

Terahertz in vivo imaging of human skin: Toward detection of abnormal skin pathologies

Terahertz (THz) imaging has long held promise for skin cancer detection but has been hampered by the lack of practical technological implementation. In this article, we introduce a technique for discriminating several skin pathologies using a coherent THz confocal system based on a THz quantum cascade laser. High resolution in vivo THz images (with diffraction limited to the order of 100 μm) of several different lesion types were acquired and compared against one another using the amplitude and phase values. Our system successfully separated pathologies using a combination of phase and amplitude information and their respective surface textures. The large scan field (50 × 40 mm) of the system allows macroscopic visualization of several skin lesions in a single frame. Utilizing THz imaging for dermatological assessment of skin lesions offers substantial additional diagnostic value for clinicians. THz images contain information complementary to the information contained in the conventional digital images