Generation and detection of optical vortex beam

doctoral thesis

• Title (english): Generiranje i detekcija optičkih vrtložnih snopova
• Author: Ali Mardan Dezfouli
• Mentor: Hrvoje Skenderović (mentor)
• Committee member: Mario Rakic (predsjednik povjerenstva)
• Committee member: Hrvoje Skenderović (član povjerenstva)
• Committee member: Hrvoje Buljan (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Physics); Zagreb
• Defense date and country: 2024-05-23, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Physics
• Universal decimal classification (UDC): 53 - Physics

Abstract

Light can have a special property called orbital angular momentum (OAM), which gives beams a twisted shape of the wavefront. Twisted beams carry a specific amount of angular momentum in the direction of propagation. This property opens possibilities for increasing amount of information we can send in both optical and quantum communication. It could also help us improve and expand the capabilities of some types of quantum technology. By changing a regular beam of light in a particular way, we can create beams with some unique features. In this work, emphasis is given on Laguerre-Gaussian (LG) modes, and their generation and detection. LG modes carry non-zero OAM and are characterized by two numbers: the radial mode index 𝑝 and the azimuthal mode index 𝑙, known as topological charge (TC).
This thesis delves into exploring the use of spatial light modulators (SLM) for the modal detection of Laguerre-Gaussian (LG) beams. A critical challenge in utilizing LG beams is to accurately determine indices of the unknown LG beam, which constitutes the main topic of this thesis.
As a major contribution, a new type of diffraction grating was designed, which offers effective modal detection of LG beams. Our approach showcases a robust method capable of simultaneously determining both mode indices of an LG mode. Theoretical and experimental results show a clear correlation of the radial and azimuthal mode indices with the intensity distribution in the far-field diffraction pattern.

Abstract (croatian)

Svjetlost može biti nositelj i kutne količine gibanja (OAM), što se ispoljava u valnoj fronti uvrnutog oblika, odnosno svjetlosnom vrtlogu. Vrtložne zrake nose određenu kutnu količinu gibanja u smjeru širenja. Ovo svojstvo otvara mogućnosti za povećanje količine informacija koje možemo poslati u redovnoj i kvantnoj komunikaciji. Također bi nam moglo pomoći da poboljšamo i proširimo mogućnosti nekih vrsta kvantne tehnologije. Promjenom regularne zrake svjetlosti na određeni način, možemo stvoriti zrake s jedinstvenim značajkama. U ovoj studiji ćemo staviti naglasak na Laguerre-Gaussovi (LG) modove, njihovo generiranje i detekciju. LG modovi nose OAM različit od nule i karakteriziraju ih dva broja: indeks radijalnog moda p i indeks azimutalnog moda l, poznat kao topološki naboj (TC).
Ovaj se doktorski rad bavi istraživanjem upotrebe prostornih modulatora svjetla (SLM) za modalnu detekciju Laguerre-Gaussovih (LG) zraka. Kritični izazov u korištenju LG snopa je točno određivanje indeksa nepoznatog LG snopa, što je i glavna tema ove disertacije.
Kao originalni doprinos, u doktoratu je dizajnirana nova vrsta difrakcijske rešetke kojom se postiže učinkova detekcija moda LG zrake. Naš pristup predstavlja robusnu metodu koja može istovremeno odrediti oba indeksa LG zrake. Teorijski i eksperimentalni rezultati pokazuju jasnu korelaciju između indeksa radijalnog i azimutalnog moda i distribucije intenziteta u difrakcijskom uzorku dalekog polja.

• Keywords: orbital angular momentum of light; spatial light modulator; diffraction
• Keywords (english): kutna količina gibanja svjetlosti; prostorni modulator svjetlosti; difrakcija
• Language: english
• URN:NBN: urn:nbn:hr:217:581255
• Promotion: 2024
• Project: Number: DOK-2020-01-8574; Title: Biological and bioinspired structures for multispectral surveillance; Title: Biological and bioinspired structures for multispectral surveillance; Leader: Hrvoje Skenderović; Jurisdiction: Croatia; Funder: Hrvatska zaklada za znanost; Funding stream: Young Researchers’ Career Development Project - Training New Doctoral Students
• Study programme: Title: Doctoral study; Study programme type: university; Study level: postgraduate; Academic / professional title: doktor/doktorica znanosti u području prirodnih znanosti (doktor/doktorica znanosti u području prirodnih znanosti)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access
• Created on: 2024-07-18 10:57:27