Random Laser with Increased Efficiency
|Vasil P. Yashchuk 1, Eugen O. Tikhonov 2, Olga A. Prygodiuk 1, Volodymyr I. Bezrodny 2|
1. Department of Physics, Taras Shevchenko Kyiv University, 6 Gloushkov avenue, Kyiv 252022, Ukraine
The random laser is the strongly scattering active medium itself where the inter particle distance is about of light wavelength. The lasers do not demand any cavity use so they are of great interest due to the construction simplicity being useful for their producing and operation. But the random lasers have not been adopted yet because of low efficiency and high threshold of the pump intensity. In this work the method of these parameters refinement is proposed.
Lasing in the random laser is supplied by two non-resonant methods of the feedback formation: multiple scattering within the sample volume and diffusive reflection from the sample surfaces. The second feedback type is more effective and can be attained by sample thinning down to the excited region size and covering of the back sample surface with highly refracted powder. When the first condition is accomplished the sample is through depth excited and essential part of the radiated light achieves the back sample surface. Then highly refracting coating of the back sample side completely returns the radiated light to the excited region that is equal to the excited region extension. We produced and investigated the random laser on solid polymer solution of R6G with embedded particles of SiO2 (the mean diameter of the particles is ~0.5-1mm) in concentration 1011cm-3. The back side of the sample was covered with fine dispersed powder CeO2.
The energetic characteristics of the produced random laser were obtained to be higher that ones of the usual random laser and to depend on the laser effective thickness. The highest possible laser efficiency is at the sample thickness conforming to the excited region depth dact.The steady lasing is at any thickness but the least lasing threshold was achieved at the thickness ~3*dact. Further improving of lasing parameters can be achieved by use of micro lenses conjugated with the active medium.
Presentation: oral at E-MRS Fall Meeting 2005, Symposium E, by Vasil P. Yashchuk
See On-line Journal of E-MRS Fall Meeting 2005
Submitted: 2005-05-19 08:12 Revised: 2009-06-07 00:44