Abstract
Based on the finite-difference time-domain method, we study temporal variations of focal spot parameters when focusing a plane TE wave by use of a dielectric microcylinder with refractive index 1.59. It is shown that as a picosecond (ps) pulse travels through the microcylinder, the focal spot gets tighter, whereas its intensity and the mode energy stored in the microcylinder grow. As a result of the ps-pulse passage, in the cylinder a whispering gallery mode is excited, which is coincident with the mode in a circular wire with zero propagation constant. With time, the mode energy is leaking out. By solving the Helmholtz equation using a finite-element technique we show that in the stationary case, the best focal spot parameters are achieved in a cylinder of radius ( is wavelength): the focal spot size is , whereas the maximal intensity in the focus is 60 times the incident light intensity.
© 2015 Optical Society of America
Full Article | PDF ArticleMore Like This
I. Mahariq and H. Kurt
J. Opt. Soc. Am. B 32(6) 1022-1030 (2015)
Ibrahim Mahariq and Hamza Kurt
J. Opt. Soc. Am. B 33(4) 656-662 (2016)
L. Chantada, N. I. Nikolaev, A. L. Ivanov, P. Borri, and W. Langbein
J. Opt. Soc. Am. B 25(8) 1312-1321 (2008)