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Design, Preparation and Characterization of Optical Coatings in Visible and Infrared Band

Asghar, Muhammad Hammad (2008) Design, Preparation and Characterization of Optical Coatings in Visible and Infrared Band. PhD thesis, University of the Punjab, Lahore.

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Abstract

Design, preparation and characterization of multilayer thin film structures have been carried, which are to act as antireflection coatings in visible, near infrared and mid infrared spectral ranges. TiO2, Ta2O5 and SiO2 have been used as optical thin film materials to form these structures. Optimization of these materials is carried out by varying deposition parameters and characterizing individual layers to acquire optimized optical constants and structural properties suitable for multilayer applications. All these materials are optimized at comparatively low substrate temperature using electron beam evaporation technique. Multilayer structures with 4-6 layers have been designed in visible and near infrared spectral bands to give wide and high transmission bands with T>99% in the desired spectral ranges. The prepared samples are compared with the designed values and an excellent agreement has been found between the two, with smooth and dens film layers highly desirable for optical applications. For the first time ever, antireflection coatings in mid infrared spectral band have been produced with the given materials. These coatings have been characterized and their results are reported in this thesis. Post deposition annealing of the samples has been carried out to enhance the performance of these coatings in the temperature range of 150-450° C. Average transmission >90% has been achieved with post deposition annealing of the samples, showing strong dependence of such films on post deposition annealing. The results of annealing are also studied and discussed in this work. The research work has been extended to develop optical filters with the same materials to meet very tough design requirements. Bandpass filters, edge filters and bandstop filters for practical applications have been designed and prepared to meet the design requirements practically. The filter samples prepared in this work range from 29 layer configuration to 44 layer structure. Optical spectroscopy, ellipsometery, atomic force microscopy, x-ray diffraction and scanning electron microscopy have been used to characterize the samples optically and structurally prepared during this research work. The research work has established that the used materials have shown enormous potential to be used as thin film structures with applications in visible, near infrared and mid infrared spectral bands. This work also opens the avenues for further study on these materials in infrared wavelength range for producing optical coatings and spectral filters.

Item Type:Thesis (PhD)
Uncontrolled Keywords:Design, Preparation, Characterization, Optical Coatings, Multilayer, Visible, Infrared, spectral, Band
Subjects:Physical Sciences (f)
ID Code:6709
Deposited By:Mr. Javed Memon
Deposited On:20 Jul 2011 11:09
Last Modified:20 Jul 2011 11:09

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