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Light optical techniques
Published in D. Campbell, R.A. Pethrick, J.R. White, Polymer Characterization, 2017
D. Campbell, R.A. Pethrick, J.R. White
The methods described above can be augmented by the use of quarter waveplates. A quarter waveplate is a birefringent filter that has the effect of retarding the component which has its plane of polarization parallel to the waveplate axis by a quarter of a wavelength more than the component with its polarization direction transverse to it (a property that is only exactly observed at one particular wavelength). If the quarter waveplate is placed at 45° to the plane of polarization of a plane polarized beam the effect is to produce circularly polarized light in which the electric vector rotates about the direction of propagation, maintaining the same amplitude. If a second quarter waveplate is placed between the first one and the analyser, and at 90° to the first one (i.e. at –45 ° to the original plane of polarization) no light will pass through the analyser if it is crossed with reference to the polarizer (‘dark field’). If a birefringent sample is placed between the two quarter waveplates, fringes are obtained which, if the birefringence is caused by stress, are loci of equal principal stress difference or maximum shear stress. If white light is used the fringes are coloured (‘isochromatics’). These are usually observed in a circular polariscope which has a large field of view, suitable for observing macroscopic samples, typically 200 mm in diameter.
Electromagnetic Waves in Anisotropic and Optically Active Media
Published in Vladimir V. Mitin, Dmitry I. Sementsov, An Introduction to Applied Electromagnetics and Optics, 2016
Vladimir V. Mitin, Dmitry I. Sementsov
A quartz plate has a thickness d1 = 1.00 mm and has the optical axis perpendicular to the surface of the plate. The plate rotates the plane of polarization of monochromatic linearly polarized light by an angle φ1 = 20°. What should be the thickness of the quartz plate d so that when it is placed between two polarizers with parallel axes the transmitted light is completely extinguished?Calculate the length l of a tube filled with a sugar solution of concentration of C = 0.4 g/cm3 to be placed between the two polarizers to obtain the same effect (the specific rotation of the sugar solution is α = 0.6657m⋅kg⋅m−3). (Answer: (a) d = 4.50 mm and (b) l = 0.34 m.)
Introduction to Optics
Published in Rajpal S. Sirohi, Introduction to OPTICAL METROLOGY, 2017
Depending on the magnitudes of the components and their phase difference, we also get linearly and circularly polarized light. When either of the components E0x or E0y is zero, or the phase difference ϕ is 0 or π, we have linearly polarized light. In the former case, it is polarized along either y-direction or x-direction, and in the latter case, it is linearly polarized in an arbitrary direction depending on the magnitudes of the components. The direction of the electric field and the direction of propagation determine the plane of polarization. When both the components, E0x and E0y, are equal and their phase difference is either π/2 or 3π/2, we obtain circularly polarized light.
Faraday rotation in cesium nano-layers in strong magnetic fields
Published in Journal of Modern Optics, 2019
Arevik Amiryan, Armen Sargsyan, Yevgenya Pashayan-Leroy, Claude Leroy, David Sarkisyan
When laser radiation with a frequency close to that of an atomic transition propagates through a vapour of alkali metal atoms in the presence of a longitudinal magnetic field (applied in the direction of the radiation propagation), a rotation of the polarization plane (Faraday rotation, FR) occurs. Detailed explanations of the FR effect are given in [1] that we briefly summarize hereafter. The rotation angle ϕ of the plane of polarization is given by , where and are the refractive indices for left () and right () circularly polarized radiations, respectively, L is the medium length and λ is the laser wavelength resonant with the media. As a rule, circularly polarized and radiations have different refractive indices in a magnetic field (they have also different absorption) and therefore, propagate with different velocities, leading to a rotation of the radiation plane of polarization. The FR effect is used, in particular, in magnetometry to determine weak magnetic fields less than μG [2]. Also, narrow-band atomic optical filters (AOF) based on the FR effect have been used where only useful background-free signal is transmitted when using crossed polarizers [3–5]. In addition, the linewidth of AOF transmission spectrum can be about three orders of magnitude smaller than that for available interference filters. A light compact optical isolator using the FR effect in Rb atomic vapour in the hyperfine Paschen–Back (HPB) regime is presented in [6]. In [7], the FR effect is studied in strong magnetic fields for 87Rb atomic vapour with the use of a millimetre-long cell, which nevertheless does not provide sub-Doppler resolution. It was shown in [8] that using thin garnet films doped with iron and applying the FR effect allows one to obtain an image of the domains of magnetic strips of credit cards.