Faraday modulator

Fig. 2. Schematic representation of an experimental set-up for measuring the polar Kerr rotation. (After van Engen 1983). The light passes a fixed polarizer P and, after being reflected by the magnetized sample S, passes respectively through a linear phase retarder R, a Faraday modulator M and an electrically adjustable analyser A before reaching the detector D.

A Faraday modulator is a glass or fused silica cyliuder mouuted axially iu au electrical coil powered by au electrical (AC or DC) curreut. 

So far then what we have described is the normal (off-resonance) Faraday effect and this describes the principle of operation of the Faraday modulator used in the laser polarimeter I will describe in a later section. 

To extract the optical rotation signal with optimum signal to noise ratio, a square-wave modulation pattern is applied to the solenoid of the Faraday modulator as shown in figure 17(a). To cope with rapid changes in the current, the solenoid is wound to have low inductance... 

The Faraday modulator used in the polarimeter has another important function other than providing an easy way of optimising the signal to noise ratio it allows the real and imaginary parts of the refractive indices to be separated. This stems from the fact that in the... 

Figure 18. Experimental arrangement for Faraday modulated polarisation spectroscopy.

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