Příprava, měření a manipulace polarizace světla pomocí kapalných krystalů

Bc. et Bc. Martin BIELAK

Master's thesis

Polarization state generation, measurement and control using liquid-crystal modulators

Abstract:

The polarization degree of freedom of light is frequently used in optical communication and metrology as well as in quantum information processing. Rotating polarization retarders, such as half wave plate and quarter wave plate, are commonly used in many experiments for polarization analysis. The liquid crystals represent one of the technologies which do not require major interventions in already assembled experimental setups and can enhance the measurements. Particularly, devices made of liquid crystals can be used to speed up polarization preparation and analysis. This thesis deals with the characterization of device made from liquid crystals cells and its application in polarization preparation and analysis. We discuss an extraction of the liquid crystal cell from a liquid crystal display and the process of its calibration to a reference polarimeter. Also, the theoretical description by means of analytical model and machine learning model is discussed. We present basic imperfections and problems that can be observed in the real-world use of liquid crystal cells and that are not commonly covered by the theoretical models. These phenomena can be included in the machine learning model as it learns and extrapolates from actual measured data. It outperforms significantly the analytical model, which is verified on a large measured data set. Furthermore, we report on the use of the developed device for various types of polarization tomographic schemes, such as minimum tomography (for states), eigenstates of Pauli operators (three bases or six states), and covariant measurement. We perform a calibration and the tomographic procedure for the first two schemes mentioned. Also, we carried out numerical simulations of an overcomplete tomographic scheme, which converges to the covariant measurement. The overcomplete measurements are used to demonstrate the reduction of uncertainty in the case of a large number of projections used for analysis and benefits of liquid crystals for this type of measurement. The results which are presented in this thesis show the possibility of using the device made from commercially available liquid crystal displays in polarization preparation, analysis, and polarization encoding of information in general.

Abstract:

Elektrooptická modulace světla pomocí prvků s kapalnými krystaly je využita pro přípravu a měření libovolného polarizačního stavu světla a také pro transformaci mezi různými stavy polarizace klasických i jednofotonových optických signálů. Součástí práce je návrh a realizace vhodných kombinací modulátorů pro dosažení požadovaných polarizačních operací, jejich kalibrace a demonstrace využití ve vybraných experimentech.

Keywords

polarizace, tekuté krystaly, modely tekutých krystalů, zařízení s tekutými krystaly, displej z tekutých krystalů, minimální analýza, analýza polarizace, příprava polarizace, metody tomografického měření, genetický algoritmus, strojové učení

Language used: English

Date on which the thesis was submitted / produced: 2. 5. 2019

Thesis defence

• Supervisor: RNDr. Miroslav Ježek, Ph.D.

Palacký University Olomouc

Faculty of Science

Master programme / field:
Physics / Optics and Optoelectronics