STUDY OF THE GENERATION AND DETECTION OF HIGH POWER LAGUERRE GAUSSIAN BEAM

Abstract

Orbital angular momentum beam has been recognized as a new applicable resource in classical and quantum information aspects. One of the examples of orbital angular momentum beam is a Laguerre Gaussian beam. We studied the Laguerre Gaussian beam both theoretically and experimentally. A Gyrotron is one of the millimeter wave generator which has properties of high power and frequency millimeter wave generation. Using the device, we generated a high power 95GHz Gaussian beam and the beam transformed as a Laguerre Gaussian beam after passing through an optical device. In this thesis, we use a spiral phase plate with ladder form to generate Laguerre Gaussian beam, and fabricated spiral phase plates can create the Laguerre Gaussian beams which has topological charge one or two. We analyzed that Laguerre Gaussian beams and detected the characteristics of the beam intensity and phase. In addition, we conducted Young’s double slit experiment to identify the phase of the beam in the high power condition. The generated interference patterns imply what beam’s phase is. The aim of this work is to study a high power orbital angular momentum beam for applications and a method for phase detection with optical technique. This thesis deals with the study of the orbital angular momentum in a high power beam observation, which give additional information about those already inferred from the analysis of the intensity, frequency, and polarization of the beam. Indeed, the primary purpose of this work is that study of orbital angular momentum at the millimeter. The first part of the thesis handles theoretical background of orbital angular momentum and characteristic of the electromagnetic wave. The second part deals with an experimental verification of orbital angular momentum beam and several techniques for detection the phase of orbital angular momentum beam. Finally, all conducted results of the experiment are presented, and we discuss it in third and fourth sections.