Development of computer controlled characterization of volume Bragg gratings in photo-thermo-refractive glass

Keywords

Diffraction gratings

Abstract

Volume diffractive optical elements recorded in a photo-thermo-refractive glass (PTRG) are new robust components for optical communications, high power lasers, and optical data storage and processing. Those components work as angular and spectral filters, deflectors, attenuators, etc. in both transmitting and reflecting modes. Precise characterization of transmitting volume holographic gratings (Bragg gratings) recorded in PTRG is the main goal of this study. Measurement of angular selectivity of Bragg gratings was chosen as a main method of characterization. Computer controlled experimental setup and software for the measurement of dependence of intensities of transmitted and diffracted beams versus incident angle with accuracy better than 1 mrad was developed for samples in air and in a cuvette filled with a liquid having a matched refractive index. This setup was assembled, tested and calibrated. Numerous PTRG samples with different grating parameters were studied. The results of measurements are compared to the theoretical modeling using Kogelnik's coupled wave theory. It was found that diffraction patterns are close to the theoretical ones for uniform gratings with sinusoidal refractive index profile. This means that the current technology of PTRG Bragg gratings provides no detectable deformations occurring in the hologram fabrication process. Dependence of diffraction efficiency on thickness of a Bragg grating was used for calculation of distribution of refractive index modulation along the direction of beam propagation in PTR glass. Those data show uniformity of holographic PTRG gratings having thickness up to several millimeters. Mapping of large aperture Bragg gratings was used for development of a recording setup with uniform intensity distribution. Mathematical treatment of diffraction and interference patterns measurements was used for refractive index calculation. Those results were compared with precise measurements produced by conventional refractometry. Unlike conventional refractometry, this new method could be used for measuring refractive index, without the necessity of special sample preparation.

Notes

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Graduation Date

2003

Advisor

Glebov, Leon

Degree

Master of Science (M.S.)

College

College of Engineering

Department

Electrical Engineering and Computer Science

Degree Program

Electrical Engineering

Format

PDF

Pages

86 p.

Language

English

Length of Campus-only Access

None

Access Status

Masters Thesis (Open Access)

Identifier

DP0029124

Subjects

Dissertations, Academic -- Engineering; Engineering -- Dissertations, Academic

Accessibility Status

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