Faraday geometry

A convenient experimental scheme for the selective observations of different-order atomic coherences is the F = 2 —> F = 1 transition in 87Rb atoms with Faraday geometry setup (Fig. 1) that uses a single linearly polarized laser beam. In order to better understand the connection between the light-induced atomic coherences and atomic PM, consider first the atomic coherence picture, where the quantization axis is chosen parallel to the light propagation direction and coincides with the orientation of magnetic field B. In this case, the linearly polarized held E can be represented as a superposition of circularly polarized components A+ and E-, so that on the transition F — 2 —> F = 1 both A-(dashed) and M-systems (solid) are formed (Fig. 2). 

Further measurements were performed by these authors in the Faraday geometry for fields up to 30 T. The most notable result was the observation, above 25 T, of a line above the one-phonon band, whose energy increased linearly with the field. It was speculated that this feature was related to the first Landau level of the VB. 

The first application of the SNOM for the MO studies happened in 1992 [62], when it was demonstrated that near-field MO observation can be obtained in the same manner as conventional far-field observation— that is, by using two cross-polarizers. Betzig et al. [62] visualized 100-nm magnetic domains and claimed spatial resolution of 30-50 nm. The possibility of MO domain imaging was confirmed in both the transmission regime (Faraday geometry) [63,64] and the reflection regime (Kerr microscopy) [65-67]. 

Fig. 25. Amplitude modulation for Faraday geometry and Voigt-Cotton-Mouton geometry in CeAlj (Liithi and Lingner 1979).

Fig. 26. Phase differences

One can expect, in analogy to sound waves, similar effects for optical phonons. The splitting of the Eg optical phonons in Ce Laj F3 using Raman scattering has indeed been observed for the Cotton-Mouton, Voigt and the Faraday geometries (Ahrens and Schaack 1980). 

MR (magnetic field-modulated reflection) a magnetic field Is modulated with AH 140 Oe at 210 Hz In the Faraday geometry, Mitani, Koda [53], and with AH 120Oe In the Voigt geometry, Silberstein etal. [54]. 

Amperometric gas sensors are - electrochemical cells that produce a - current signal directly related to the concentration of the - analyte by - Faraday s law and the laws of - mass transport. The schematic structure of an amperometric gas sensor is shown in Fig. 1. The earliest example of this kind of sensor is the - Clark sensor for oxygen. Since that time, many different geometries, membranes, and electrodes have been proposed for the quantification of a broad range of analytes, such as CO, nitrogen oxides, H2S, O2, hydrazine, and other vapors. 

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