29th Annual Report (2016-17)

137 FaradayRotationExperiment forCommunication The polarization of light is quite frequently observed in nature, and with other properties like amplitude, frequency and phase of an electromagnetic (EM) wave, it constitutes one of the most fundamental quantities, which completely describes it. In physics and optics, the polarization of light is studied through ”Faraday Rotation Effect” using optical materials like glass, crystals, chemicals, etc. Its analogue in radio waves is transmission of polarized wave in ferrites materials. The idea is to study the potential of fast polarization modulation for data communication, which is not much explored yet. The study of polarization of light through Faraday Rotation Effect, rotation of plane of polarized wave when traveling through crystals placed inside solenoid; subjected to a strong axial magnetic field, can be a novel approach in communication. Experiment shows conversion of polarization-modulated light into intensity-modulated light, and phase shifted demodulated wave form with respect to input modulating signal. Insertion of properly matched and tuned circuit before coil and amplifier after demodulation leads to better reception of signal. The laser will act as a carrier and the audio is given as a modulating signal to the solenoid, the audio signal modulated in the presence of Faraday material (TGG) and demodulated by converting polarization modulation into intensity modulation at the photo detector. The power requirement is very low as compared to the existing analog modulation techniques. The system is successfully working over the audio bandwidth. HornAntenna for 21 cmHydrogenLine The 21 cm Hydrogen line is a spectral line emitted by atomic Hydrogen. Since Hydrogen is the most abundant element in the universe, this makes the Hydrogen line a very important in radio astronomy. Ahorn antenna was designed for detecting this line from our galaxy. The horn has enabled us to study hydrogen line profiles from the galaxy. The spiral structure of the galaxy can be estimated. It is also possible to estimate the rotation curve of the galaxy.