Single layer lattice graphene deposited on the metal substrate can hardly be imaged by the optical microscope. In this Letter, a large field-of-view imaging ellipsometer is introduced to image single layer graphene which is deposited on a metal substrate. By adjusting the polarizer and the analyzer of imaging ellipsometer, the light reflected from surfaces of either single layer graphene or a Au film substrate can be extinguished, respectively. Thus, single layer graphene can be imaged correspondingly under brightfield or darkfield imaging modes. The method can be applied to imaging large-area graphene on a metal substrate.

In this work, we show how fiber-based terahertz systems can be robustly configured for accurate terahertz ellipsometry. To this end, we explain how our algorithms can be successfully applied to achieve accurate spectroscopic ellipsometry with a high tolerance on the imperfect polarizer extinction ratio and pulse shift errors. Highly accurate characterization of transparent, absorptive, and conductive samples comprehensively demonstrates the versatility of our algorithms. The improved accuracy we achieve is a fundamental breakthrough for reflection-based measurements and overcomes the hurdle of phase uncertainty.

The polarization state of transmitted light is linked to liquid crystal (LC) molecular distribution. The dynamic behavior of a twisted nematic LC molecule is measured with a home-built 10 kHz snapshot polarimeter. Only the transient molecule rotations are observed when the external voltage changes, and the molecules return to their original orientations quickly even when high voltage is applied. Our observations cannot be attributed to the traditional electro-optic effect. The invalidation of the static external field indicates the shielding effect of redistributing impurity ions in an LC cell.

The optical constants, photoluminescence properties, and resistivity of Al-Alq3 thin films prepared by the thermal co-evaporation method on a silicon substrate are studied with various Al fractions. A variable angle spectroscopic ellipsometry is employed to determine the optical constants in the wavelength from 300 to 1200 nm at incidence angles of 65°, 70°, and 75°, respectively. Both the refractive indices and extinction coefficient apparently increase with increasing Al fractions. The intensity of photoluminescence spectra gradually increases with decreasing Al fractions due to intrinsic energy level transition of Alq3 organic semiconductor in the ultraviolet wave band. The resistivity decreases from 42.1 to 3.36 Ω·cm with increasing Al fraction from 40% to 70%, resulting in a larger emission intensity in photoluminescence spectra for the 40% Al fraction sample.

Intramolecular vibrations of large macromolecules reside in the terahertz range. In particular, protein vibrations are closely spaced in frequency, resulting in a nearly continuous vibrational density of states. This density of vibrations interferes with the identification of specific absorption lines and their subsequent association with specific functional motions. This challenge is compounded with the absorption being dominated by the solvent and local relaxational motions. A strategy for removing the isotropic relaxational loss and isolating specific vibrations is to use aligned samples and polarization-sensitive measurements. Here, we demonstrate a technique to rapidlyattain the anisotropic resonant absorbance using terahertz time domain spectroscopy and a spinning sample. The technique, modulated orientation-sensitive terahertz spectroscopy (MOSTS), has a nonzero signal only for anisotropic samples, as demonstrated by a comparison between a silicon wafer and a wire grid polarizer. For sucroseand oxalic acid molecular crystals, the MOSTS response is in agreement with modeled results for the intermolecular vibrations. Further, we demonstrate that, even in the presence of a large relaxational background, MOSTS isolates underlying vibrational resonances.

We propose and experimentally demonstrate a novel type of polarization rotator that is capable of rotating the polarization plane of a linearly polarized light at any desired angle in either broad or narrow spectral bandwidth. The rotator comprises an array of standard half-wave plates rotated at specific angles with respect to their fast-polarization axes. The performance of the rotator depends on the number of individual half-wave plates, and in this paper we experimentally investigate the performance of two composite rotators comprising 6 and 10 half-wave plates.

We propose an ultra-simple dual-channel configuration for simultaneously evaluating two branches of a multifunctional integrated optic chip (MFIOC). In the configuration, the MFIOC is employed as a beam splitter to construct the demodulation interferometer together with a 2 × 2 fiber coupler. Interference happens between polarization modes traveling through different channels of the MFIOC. The cross-couplings of each channel are respectively characterized by the interference peaks which distribute on opposite sides of the central interference peak. Temperature responses of the MFIOC are experimentally measured from ?40°C to 80°C. Results show that the proposed configuration can achieve simultaneous dual-channel transient measurements with resolution of ?90 dB and dynamic range of 90 dB. In addition, the two channels of the configuration have consistent measuring performance, and the two branches of the MFIOC have different responses to temperature variation.