Fast-type high-accuracy universal polarimeter using charge-coupled device spectrometer

• Main Authors: Akifumi Takanabe, Hideko Koshima, Toru Asahi
• Format: Article
• Language: English
• Published: AIP Publishing LLC 2017-02-01
• Series: AIP Advances
• Online Access: http://dx.doi.org/10.1063/1.4977440

A fast, high-accuracy universal polarimeter was developed using a charge-coupled device (CCD) spectrometer (CCD-HAUP), to carry out simultaneous optical anisotropic (linear birefringence, LB; linear dichroism, LD) and chiroptical (circular birefringence, CB; circular dichroism, CD) measurements on single crystals without any pretreatment, in the visible region between 400–680 nm. The principle of the HAUP method is to measure the intensities of emergent light passing through a polarizer, a crystal sample, and then an analyzer, as the azimuth angles of the polarizer and analyzer are independently altered. The CCD-HAUP has the unique feature that white transmitted light intensity can be measured using a CCD spectrometer, compared with the generalized HAUP (G-HAUP) system in which monochromatic transmitted light is measured using a photomultiplier. The CCD-HAUP measurements across the entire wavelength region are completed within the G-HAUP measurement time for a single wavelength. The CCD-HAUP drastically reduces the measurement time for a dataset to only 1.5 h, from the 24 h required for the G-HAUP system. LB, LD, CB, and CD measurements of single crystals of α-quartz and enantiomeric photomechanical salicylidenephenylethylamines before, during, and after ultraviolet light irradiation show results comparable to those obtained using the G-HAUP system. The newly developed system is very effective for samples susceptible to degradation induced by external stimuli, such as light and heat.