Optoelectronics and Photonics Engineering MS Thesis Defense by Mustafa Mert Bayer

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KOÇ UNIVERSITY

GRADUATE SCHOOL OF SCIENCES & ENGINEERING

OPTOELECTRONICS AND PHOTONICS ENGINEERING

MS THESIS DEFENSE BY MUSTAFA MERT BAYER

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Title: Elastic Light Scattering, Fluorescence, and Raman Spectroscopy of a Diamond Microsphere

Speaker: Mustafa Mert Bayer

Time: Aug. 21, 2017, 13:30

Place: ENG 120

Koç University

Rumeli Feneri Yolu

Sariyer, Istanbul

Thesis Committee Members:

Prof. Ali Serpengüzel (Advisor, Koc University)

Prof. Alper Kiraz (Koc University)

Asst. Prof. Onur Ferhanoğlu (Istanbul Technical University)

Abstract:

In this thesis, Raman and photoluminescence spectroscopy is performed with various diamond samples including a diamond microsphere. The measurement setups are presented for both spectroscopies. Nitrogen vacancy (NV) centers inside the diamond lattice exhibit 575 nm or 637 nm zero phonon lines along with their corresponding phonon side bands depending on the charge state of the point defect, NV⁰ and NV^–, respectively. A 572 nm inelastic Raman scattering (1332.25 cm^-1) is observed with 532 nm excitation laser due to the vibrational state of C-C bonds with sp3 configuration, whereas sp2 hybridization (1444.56 cm^-1) yields inelastically scattered photons with 576 nm wavelength. It is possible to identify the main impurities within the diamond lattice, and confirm the C-C bonds with spectroscopic techniques. In addition, the demonstration of a diamond microsphere whispering gallery mode resonator in the standard telecom wavelengths between 1426.10 nm and 1427.42 nm in the 90° elastic light scattering for both transverse magnetic and transverse electric polarizations is realized. The highest measured whispering gallery mode Q-factor is on the order of 10⁴, and the mode spacing 0.332 nm for both transverse polarizations. The coupling of the continuous wave tunable infrared excitation laser to the diamond microsphere is achieved by a single mode silica optical fiber half coupler. All in all, diamond is a unique material with particular optical properties. Utilizing such properties in a spherical morphology can give rise to distinctive applications. It is essential to observe the aspects of the whispering gallery modes created by the light circumnavigating a diamond microsphere such as mode spacing and Q-factor to classify the properties of a 1 mm synthetically grown spherical diamond microresonator. Such a diamond resonator can further be used as stable optical frequency comb generators or lasing microcavities by exploiting the nitrogen vacancy centers present within the lattice of the diamond.