Font Size: a A A

Lasing characteristics of non-spherical cavities

Posted on:2002-01-13Degree:Ph.DType:Dissertation
University:Chinese University of Hong Kong (People's Republic of China)Candidate:Pu, Xiao-YunFull Text:PDF
GTID:1468390011995013Subject:Physics
Abstract/Summary:
Lasing characteristics of a dye-doped pendant drop as a non-spherical optical cavity were investigated.; Spatial resolved spectral measurements show that the lasing wavelength varies along a vertical rim of the drop. Time resolved measurements indicate that lasing precession occurs within the drop. Various lasing patterns due to lasing precession are explained. Results of computer simulation of light rays travelling inside a model pendant drop are in agreement with those of our experiment. The measured precession periods are compared with the calculated values based on a theory of whispering-gallery-modes.; A method for measuring the lasing intensity distributions inside a circular resonator formed within the equatorial plane of a dye-doped pendant drop has been demonstrated. Polymer particles were added to the dye solution to enhance elastic scattered lasing light inside the pendant drop. The elastic scattered light was exploited to deduce the internal lasing intensity distribution. A theory that connects wave and ray pictures in treating the cavity resonance was used to calculate the internal intensity distribution. The experimental and theoretical results are in good agreement for large enough scattering particle densities so that the cavity mode efficiency is ∼1 for all resonant modes.; Selected optical properties of an oval-shaped resonant cavity with continuously variable geometric parameters, namely, a dye-doped pendant drop deformed by an applied electric field, have been investigated. When pumped by nitrogen laser pulses within the equatorial plane of the pendant drop, lasing arcs were observed on the rim of the pendant drop. Three lasing features of an oval-shaped resonant cavity have been found: (1) Lasing threshold decreases with the increase of the degree of the shape deformation. (2) Lasing intensity along a direction perpendicular to that of the applied electric field increases with the degree of shape deformation. (3) Angular lasing intensity distribution is anisotropic, the anisotropy increases with the degree of shape deformation.; Feature (1) is due to the reduction of the number of modes that support lasing. Based on a multimode escape picture, feature (2) has been explained. Poincaré surface of section, together with a theory of photo tunneling have been used to explain feature (3).
Keywords/Search Tags:Lasing, Pendant drop, Cavity
Related items