Polarization-Division Interferometry: Far-Infrared Dichroism

1994 ◽  
Vol 48 (11) ◽  
pp. 1410-1418 ◽  
Author(s):  
Prasad L. Polavarapu ◽  
Gang-Chi Chen
Keyword(s):  
Circular Dichroism ◽  
Far Infrared ◽  
Linear Dichroism ◽  
Infrared Region ◽  
Input Beam ◽  
Free Standing ◽  
Reflecting Surfaces ◽  
Infrared Dichroism ◽  
Linear Polarizer ◽  
Circular Dichroïsm

We report the first far-infrared dichroism measurements using a polarization-division interferometer (PDI) developed in our laboratory. This interferometer uses a free-standing wire-grid beamsplitter made of tungsten wires. In conjunction with a linear polarizer in front of the source and two roof-top mirrors (one in each arm of the interferometer), the PDI divides the input beam into two orthogonal linear polarization components, recombines them for interference at the beamsplitter, and directs the output beam at 90° to the direction of the input beam. Light exiting the interferometer is manipulated with far-infrared lenses, to avoid polarization distortions that are inherent to the reflecting surfaces of the mirrors. The performance of the PDI is evaluated by measuring the linear dichroism of oriented PVF2 [poly(vinylidenefluoride) and circular dichroism of α-pinene, camphor, and 3-methylcyclohexanone. The dichroic multiplex advantage (ability to measure dichroism in the entire far-infrared region from a single measurement) and throughput advantage are demonstrated. These measurements establish the utility of the PDI in measuring transmission and linear dichroism spectra simultaneously without the need for any additional components. Additional developments appear necessary to establish the circular dichroism measurements when the magnitudes are less than one part in one thousand.

Development, Justification, and Applications of a Mid-Infrared Polarization-Division Interferometer

1994 ◽  
Vol 48 (10) ◽  
pp. 1224-1235 ◽  
Author(s):  
Prasad L. Polavarapu ◽  
Gang-Chi Chen ◽  
Stephen Weibel
Keyword(s):  
Circular Dichroism ◽  
Linear Dichroism ◽  
Infrared Region ◽  
Input Beam ◽  
Output Beam ◽  
Mid Infrared ◽  
Oriented Polypropylene ◽  
Reflecting Surfaces ◽  
Linear Polarizer ◽  
Circular Dichroïsm

We report the development of a polarization-division interferometer (PDI) for the mid-infrared region. This interferometer uses a self-designed beamsplitter constructed in-house from a BaF2 polarizer and a matching substrate. In conjunction with a linear polarizer in front of the source and two roof-top mirrors, one in each arm of the interferometer, the PDI divides the input beam into two orthogonal linear polarization components, recombines them for interference at the beamsplitter, and directs the output beam at 90° to the direction of the input beam. Light exiting the interferometer is manipulated entirely with lenses, to avoid polarization distortions that are inherent to the reflecting surfaces of the mirrors. Details of the instrumental design for this mid-infrared PDI are presented. The performance of the PDI is evaluated by measuring the circular dichroism of α-pinene and camphor and the linear dichroism of oriented polypropylene and polystyrene. These measurements establish the utility of the PDI to measure transmission, circular dichroism, and linear dichroism spectra simultaneously without need for any additional components. The dichroic multiplex advantage (ability to measure dichroism in the entire mid-infrared region from a single measurement) and throughput advantage are demonstrated.

Measurement of Vibrational Circular Dichroism below ∼600 cm−1: Progress towards Meeting the Challenge

1996 ◽  
Vol 50 (5) ◽  
pp. 686-692 ◽  
Author(s):  
Prasad L. Polavarapu ◽  
Zhengyu Deng
Keyword(s):  
Circular Dichroism ◽  
Far Infrared ◽  
Vibrational Circular Dichroism ◽  
Current Status ◽  
Free Standing ◽  
Future Developments ◽  
Crucial Component ◽  
Incoming Beam ◽  
Metal Wires ◽  
Circular Dichroïsm

The measurement of vibrational circular dichroism (VCD) below ∼600 cm−1 is one of the experimental challenges of the current times. Polarization-division interferometry is considered to be the most efficient approach for realizing these measurements. A crucial component for successful applications of this interferometry is the beamsplitter, which divides the incoming beam according to polarization. Free-standing metal wires and the metal wires deposited on a mylar substrate have been employed as beamsplitters, and their performance has been evaluated for the ∼700–10 cm−1 region. VCD measurements obtained for the enantiomers of α-pinene in the 400–250 cm−1 region are presented. The current status and future developments needed for routine far-infrared VCD measurements are summarized.

Polarization-Division Interferometry: Time-Resolved Infrared Vibrational Dichroism Spectroscopy

1995 ◽  
Vol 49 (2) ◽  
pp. 229-236 ◽  
Author(s):  
Prasad L. Polavarapu ◽  
Zhengyu Deng ◽  
Gang-Chi Chen
Keyword(s):  
Circular Dichroism ◽  
Fourier Transforms ◽  
External Perturbation ◽  
Linear Dichroism ◽  
Central Component ◽  
Input Beam ◽  
Time Resolved ◽  
Direct Measurements ◽  
Ft Ir ◽  
Circular Dichroïsm

We report the first direct measurements of time-resolved Fourier transform infrared vibrational dichroism (TR/FT-IR/VD). The central component for these measurements is a polarization-division interferometer (PDI). This interferometer uses an in-house-designed beamsplitter constructed in-house from a BaF2 polarizer and a matching substrate. In conjunction with a linear polarizer in front of the source and two rooftop mirrors, one in each arm of the interferometer, the PDI divides the input beam into two orthogonal linear polarization components, recombines them for interference at the beamsplitter, and directs the output beam at 90° to the direction of input beam. The signals measured as a function of the moving mirror position in the PDI represent the linear/circular dichroism interferograms, whose cosine/sine Fourier transforms yield linear/circular dichroism spectra. Time-resolved dichroism interferograms were measured with the use of this PDI with the asynchronous external perturbation method. Microsecond time-resolved linear dichroism spectra of a nematic liquid crystal, under the influence of bipolar electric field oscillating at 2 kHz, were measured and presented as the first examples.

Conformation of membrane-bound proteins revealed by vacuum-ultraviolet circular-dichroism and linear-dichroism spectroscopy

2016 ◽  
Vol 84 (3) ◽  
pp. 349-359 ◽  
Author(s):  
Koichi Matsuo ◽  
Yasuyuki Maki ◽  
Hirofumi Namatame ◽  
Masaki Taniguchi ◽  
Kunihiko Gekko
Keyword(s):  
Circular Dichroism ◽  
Vacuum Ultraviolet ◽  
Linear Dichroism ◽  
Membrane Bound ◽  
Circular Dichroïsm

Chiral carbazole-based porphyrins showing absorption and circular dichroism in the near-infrared region

2020 ◽  
Vol 24 (01n03) ◽  
pp. 247-251
Author(s):  
Chihiro Maeda ◽  
Tadashi Ema
Keyword(s):  
Circular Dichroism ◽  
Near Infrared ◽  
Infrared Region ◽  
Nir Absorption ◽  
Near Infrared Region ◽  
Induced Aggregation ◽  
First Time ◽  
Circular Dichroïsm

Chiral carbazole-based porphyrins were synthesized for the first time via the incorporation of hydrobenzoin units at the thiophene moieties. They showed absorption and circular dichroism in the near-infrared (NIR) region. The NIR absorption was further red-shifted by solvent-induced aggregation.

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