scholarly journals Terahertz Circular Dichroism Spectroscopy of Biomaterials Enabled by Kirigami Polarization Modulators

2019 ◽  
Author(s):  
Won Jin Choi ◽  
Gong Cheng ◽  
Zhengyu Huang ◽  
Shuai Zhang ◽  
Theodore B. Norris ◽  
...  
Keyword(s):  
Circular Dichroism ◽  
Dynamic Range ◽  
Mechanical Strain ◽  
Thz Radiation ◽  
Polarization Modulation ◽  
Electromagnetic Spectrum ◽  
Polarization Rotation ◽  
Optical Elements ◽  
Out Of Plane ◽  
Circular Dichroïsm

ABSTRACTSTerahertz circular dichroism (TCD) offers spectroscopic capabilities for understanding mesoscale chiral architecture and low-energy vibrations of macromolecules in (bio)materials1–5. However, the lack of dynamic polarization modulators comparable to polarization optics for other parts of electromagnetic spectrum impedes proliferation of TCD spectroscopy6–10. Here we show that tunable optical elements fabricated from patterned plasmonic sheets with periodic kirigami cuts make possible polarization modulation of THz radiation under application of mechanical strain. A herringbone pattern of microscale metal stripes enables dynamic range of polarization rotation modulation exceeding 80° over thousands of cycles. Upon out-of-plane buckling, the plasmonic stripes function as reconfigurable semi-helices of variable pitch aligned along the THz propagation direction. Several biomaterials, exemplified by elytrons of Chrysina gloriosa beetles, revealed distinct TCD fingerprints associated with the helical substructure in the biocomposite. Analogous kirigami modulators will also enable other applications in THz optics, such as polarization-based terahertz imaging and phase-encrypted telecommunication.

Remote Biodetection Method Using Circular Dichroism

1993 ◽  
Vol 47 (11) ◽  
pp. 1887-1891 ◽  
Author(s):  
David L. Rosen
Keyword(s):  
Circular Dichroism ◽  
Circular Polarization ◽  
Laser Light ◽  
New Method ◽  
Optical Elements ◽  
Biological Aerosols ◽  
Optical Table ◽  
Circular Dichroïsm ◽  
Aerosol Plume

This paper proposes a new method for remote biodetection and simulates it with a laboratory optical table experiment. The new method, called circular polarization transmissometry, uses laser light scattered from the ground to measure the circular dichroism in an aerosol plume. In the optical table experiment, a scatter plate simulated the ground, and solutions of camphoroquinone simulated the biological aerosols. The experiment showed that this biodetection method could work even in daylight. Optical elements with inherent birefringence caused an optical artifact background that was subtracted from the signal.

Circular extinction of plasmonic silver nanocaps and gas sensing

2016 ◽  
Vol 186 ◽  
pp. 345-352 ◽  
Author(s):  
Jun Li ◽  
Nicholas. A. Kotov
Keyword(s):  
Circular Dichroism ◽  
Structural Control ◽  
Gas Sensing ◽  
Metallic Silver ◽  
Subwavelength Structures ◽  
Plasmonic Nanostructures ◽  
Electromagnetic Spectrum ◽  
Silver Deposition ◽  
Plasmonic Materials ◽  
Circular Dichroïsm

Chiral plasmonic nanostructures exhibit strong rotatory optical activity and are expected to enrich the field of metaoptical materials. Potential applications of chiroplasmonic nanostructures include circular polarizers, optical polarization detectors, asymmetric catalysts, and sensors. However, chiral plasmonic materials require subwavelength structural control and involve laborious chemical or lithographic procedures for their manufacturing. Moreover, strong rotatory activity of subwavelength structures whose chirality was imparted by microfabrication, has been obtained for the red and infrared parts of the spectrum but faces new challenges for the blue and violet spectral ranges even with plasmonic materials with plasmonic bands in the 200–400 nm window. In this study, we address this problem by preparing chiral subwavelength nanostructures by glancing angle sputtering of metallic silver on ZnO nanopillar arrays. Silver deposition in two different planes is a convenient method for preparation of silver chiroplasmonic nanocaps (Ag CPNCs) with controlled asymmetry. Circular dichroism spectroscopy was used to examine the circular extinction for the left-handed nanocaps (L-CPNCs) with understanding that not only circular dichroism but also many other optical effects contribute to the amplitude of these bands. The pillared silver films exhibit circular extinction in the violet area of the electromagnetic spectrum. Partial oxidation of Ag to AgxO causes the absorption and corresponding circular extinction band obtained using a conventional CD spectrometer at 400–525 nm to increase and shift. This optical material may be used to detect oxygen and extends the spectrum of application of chiroplasmonic materials to gas sensing.

scholarly journals X-Ray Magnetic Circular Dichroism Spectroscopy and Microscopy

MRS Bulletin ◽  
1995 ◽  
Vol 20 (10) ◽  
pp. 41-44 ◽  
Author(s):  
N.V. Smith ◽  
H.A. Padmore
Keyword(s):  
Circular Dichroism ◽  
Magnetic Circular Dichroism ◽  
X Rays ◽  
Circularly Polarized ◽  
X Ray ◽  
Insertion Device ◽  
Magnetic Circular Dichroism Spectroscopy ◽  
Out Of Plane ◽  
X Ray Absorption ◽  
Circular Dichroïsm

The advent of electron accelerators dedicated to the production of high-intensity x-rays has revitalized experimental techniques based on x-ray absorption. A recent variant is to use circularly polarized x-rays generated either by use of out-of-plane radiation from a bending magnet or from a specially designed “insertion device.” This new field of x-ray magnetic circular dichroism (XMCD) shows considerable promise in spectroscopy and microscopy of magnetic materials. In this article, we describe the nature of XMCD, offer a few examples of recent progress, and review the prospects for future development using the newly constructed Advanced Light Source (ALS).

scholarly journals Optical planar chiral metamaterial designs for strong circular dichroism and polarization rotation

2008 ◽  
Vol 16 (16) ◽  
pp. 11802 ◽  
Author(s):  
Do-Hoon Kwon ◽  
Pingjuan L. Werner ◽  
Douglas H. Werner
Keyword(s):  
Circular Dichroism ◽  
Polarization Rotation ◽  
Circular Dichroïsm ◽  
Chiral Metamaterial

Polarization Modulation Fourier Transform Infrared Spectroscopy with Digital Signal Processing: Comparison of Vibrational Circular Dichroism Methods

2001 ◽  
Vol 55 (11) ◽  
pp. 1435-1447 ◽  
Author(s):  
Jovencio Hilario ◽  
David Drapcho ◽  
Raul Curbelo ◽  
Timothy A. Keiderling
Keyword(s):  
Signal Processing ◽  
Circular Dichroism ◽  
Digital Signal Processing ◽  
Digital Signal ◽  
Vibrational Circular Dichroism ◽  
Polarization Modulation ◽  
Rapid Scan ◽  
Ft Ir ◽  
Lock In ◽  
Circular Dichroïsm

Digital signal processing (DSP) has been implemented in a step-scan FT-IR spectrometer in a modification that enables processing of high-frequency polarization modulation signals. In this work, direct comparison is made between vibrational circular dichroism (VCD) spectra measured on the same instrument, with the same samples, under the same conditions, using this new DSP method and a conventional rapid-scan technique (employing a lock-in amplifier for demodulation). In this initial test, both techniques generated high-quality VCD for solution phase, rigid chiral molecules such α-pinene and camphor. Noise and reproducibility of known spectral features, as well as enhancing signal measurability and discrimination, were used as criteria for the selection of optimal DSP measurement parameters. Both DSP and rapid-scan VCD methods produced qualitatively reasonable spectra for biologically related molecules such as poly-γ-benzyl-L-glutamate, poly-L-proline, and duplex RNA homopolymer. In most cases, the DSP method had a slight signal-to-noise advantage based on standard deviations of the noise trace data over the rapid-scan measurement, but the final results did depend on the details of the data collection and the phase correction methods inherent in both methods.

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