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Integration of glass microspheres and planar waveguides for microsphere lasers

Integration of glass microspheres and planar waveguides for microsphere lasers
Integration of glass microspheres and planar waveguides for microsphere lasers
Microsphere resonators with sizes in the micrometer range are reported to support very high Q’s of more than 109 for a fused silica microsphere. This high Q value represents many promising characteristics such as low cavity loss, long cavity life time, and narrow band width. With their remarkable characteristics, microsphere resonators can be used in various applications such as the narrow band filter, add-drop multiplexer, microlasers, and etc. In this work, the integration of microspheres with planar waveguides is the main focus. High quality neodymium-doped BK7 microspheres are fabricated and characterised to observe laser oscillation at 1.06 µm from the 4F3/2 - 4I11/2 transition.

Theoretical calculation of the microsphere mode and field and the characteristic equation which describes the relation of the sphere mode numbers l, m, n to the wavelength, are obtained. The theoretical expressions of the microsphere WGM can be described with the sphere mode numbers based on spherical Bessel and Hankel functions. Coupling and quality factors of the waveguide-coupled system are obtained by integrating the overlapped fields of the microsphere and waveguide, and the study of Q factors as a function of sphere/waveguide separation are elaborated. Theoretical models to calculate the total loss and gain of the microsphere lasers and the Q which is required for lasing action, are developed. The expressions for power threshold in the microsphere and in the input waveguide are derived, and the threshold pump power as a function of sphere/waveguide separation is obtained.

Experimental work to observe the WGM propagation of a passive microsphere has been carried out, and results obtained at wavelengths in the 800 nm and 1550 nm regions, and modal assignment including the evaluation of Q for each system are carried out. The experiments to observe the fluorescence and the lasing oscillation of the neodymium-doped BK7 microspheres are demonstrated. The measurement of the fluorescence lifetime of a neodymium-doped BK7 microsphere, is obtained. A laser oscillation is demonstrated with the free-space pump excitation, with the threshold pump power of 8 mW at lambda = 808nm.
Panitchob, Yuwapat
4f0a194f-e533-4dda-88c2-6837a473c12e
Panitchob, Yuwapat
4f0a194f-e533-4dda-88c2-6837a473c12e
Wilkinson, James
73483cf3-d9f2-4688-9b09-1c84257884ca

Panitchob, Yuwapat (2008) Integration of glass microspheres and planar waveguides for microsphere lasers. University of Southampton, Optoelectronics Research Centre, Doctoral Thesis, 212pp.

Record type: Thesis (Doctoral)

Abstract

Microsphere resonators with sizes in the micrometer range are reported to support very high Q’s of more than 109 for a fused silica microsphere. This high Q value represents many promising characteristics such as low cavity loss, long cavity life time, and narrow band width. With their remarkable characteristics, microsphere resonators can be used in various applications such as the narrow band filter, add-drop multiplexer, microlasers, and etc. In this work, the integration of microspheres with planar waveguides is the main focus. High quality neodymium-doped BK7 microspheres are fabricated and characterised to observe laser oscillation at 1.06 µm from the 4F3/2 - 4I11/2 transition.

Theoretical calculation of the microsphere mode and field and the characteristic equation which describes the relation of the sphere mode numbers l, m, n to the wavelength, are obtained. The theoretical expressions of the microsphere WGM can be described with the sphere mode numbers based on spherical Bessel and Hankel functions. Coupling and quality factors of the waveguide-coupled system are obtained by integrating the overlapped fields of the microsphere and waveguide, and the study of Q factors as a function of sphere/waveguide separation are elaborated. Theoretical models to calculate the total loss and gain of the microsphere lasers and the Q which is required for lasing action, are developed. The expressions for power threshold in the microsphere and in the input waveguide are derived, and the threshold pump power as a function of sphere/waveguide separation is obtained.

Experimental work to observe the WGM propagation of a passive microsphere has been carried out, and results obtained at wavelengths in the 800 nm and 1550 nm regions, and modal assignment including the evaluation of Q for each system are carried out. The experiments to observe the fluorescence and the lasing oscillation of the neodymium-doped BK7 microspheres are demonstrated. The measurement of the fluorescence lifetime of a neodymium-doped BK7 microsphere, is obtained. A laser oscillation is demonstrated with the free-space pump excitation, with the threshold pump power of 8 mW at lambda = 808nm.

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Published date: November 2008
Organisations: University of Southampton, Optoelectronics Research Centre

Identifiers

Local EPrints ID: 69881
URI: http://eprints.soton.ac.uk/id/eprint/69881
PURE UUID: eaf53acc-bd3d-4266-82f4-a011a778c7b8
ORCID for James Wilkinson: ORCID iD orcid.org/0000-0003-4712-1697

Catalogue record

Date deposited: 08 Dec 2009
Last modified: 11 Dec 2021 02:35

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Contributors

Author: Yuwapat Panitchob
Thesis advisor: James Wilkinson ORCID iD

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