Fabrication and Testing of Index Gradients in Fluoride Materials
Abstract
The feasibility of manufacturing and measuring gradient-index (GRIN) fluoride materials that transmit ultraviolet light is demonstrated. Conventional Czochralski crystal growing equipment is modified to allow controlled doping of the melt during the growth of a mixed crystal. This doping produces a composition that varies along the axis of the crystal in a predictable manner. Mixed barium fluoride and calcium fluoride crystals that transmit optical wavelengths to 210 nm are grown. The theory of crystal growth in conjunction with active doping is discussed and the appropriate equations governing the index profile as a function of growth parameters are derived. This method is of a general nature and is applicable to the production of controlled index gradients in a wide variety of materials whose phase properties include a solid solution. In order to measure the index profiles in the ultraviolet region of the spectrum an achromatic moire deflectometer is designed and built. To provide accurate phase information an automated phase retrieval scheme is implemented using a personal computer and the harmonic phase modulation method. The diffraction theory for the operation of the deflectometer is presented along with the theory of harmonic phase modulation that is used to extract phase information from the fringe pattern. An analysis of the effects of non-ideal phase modulation is also presented. Measurements of the index profiles of several GRIN materials are made at wavelengths from the visible to the UV and the results are presented with a discussion of possible sources of error and their removal or compensation.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 1990
- Accession Number
- ADA228894
Entities
People
- Michael T. Houk
Organizations
- University of Rochester