this is for holding javascript data
Ning Zhu added Our_setup_consisted_of_a__.tex
over 8 years ago
Commit id: 633bba4966a42c1db46cd4b488568c2ab4769abf
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Our setup consisted of a HeNe laser, a solenoid, an adjustable polarizer, and a photodiode. Linearly polarized light was sent through the solenoid containing a glass tube but without any current flowing through it, passed through the polarizer, and detected by the photodiode. We rotated the polarizer around 360 degrees, using 15 degree steps, and recorded the voltage read by the photodetector. We then repeated the previous procedure, but with a current of -3.0 amps running through the solenoid, therefore producing a magnetic field. The current was controlled by a bipolar operational power supply. We then fit our data to a function of the form $V=V_{0}sin(\varphi)^2$. We could find $\frac{\Delta V}{\delta \phi}$ by taking the derivative and using φ=45 degrees, and we could find ΔV by taking the difference of the voltage read by the photodetector when the laser is on (at maximum voltage read) and off. We could then find Δφ by calculating how much the angle of maximum transmission through the polarizer shifter. With all of this information, we could find dB/dφand use the equation $\frac{\Delta B}{\delta \phi}=\frac{1}{L}\times\frac{1}{C_{v}}$ to find the Verdet constant of the glass tube.
The previous method mentioned allowed us to find the angle of greatest sensitivity of the polarizer, which is the point of inflection on the V vs φ graph. To verify the value of the Verdet constant, we used a second method where the polarized stayed at the angle of greatest sensitivity and we varied the current of the solenoid, going in 0.5A steps from -3A to 3A, thereby varying the magnetic field within the solenoid. We could then graph voltage vs magnetic field, which results in a linear graph. The slope of the graph is \frac{\Delta V}{\delta B}. We calculated $\frac{\delta V}{\delta \phi}$ previously, so we can find dB/dφ and therefore the Verdet constant.
A third method for finding the Verdet constant of a material involves using a lock-in amplifier to better read the signal from the photodiode. The lock-in we used was set at a frequency range was 100 Hz, the fine frequency range was 10 Hz. The lock-in amplifier had a gain of 10, the pre-amplifier a gain of 500, the bandpass filter a gain of 2, and the low pass filter a gain of 1.We used a function generator to sinusoidally drive the voltage going into the solenoid, using a frequency of 100 Hz. We varied the RMS value of the voltage driving the solenoid and recorded the RMS value of the corresponding photodiode voltage.
