Wavelength Tunable Random Lasers

Vasil P. Yashchuk 1,3Eugen O. Tikhonov 2Olga A. Prygodjuk 1Volodymyr I. Bezrodny 2

1. Department of Physics, Taras Shevchenko Kyiv University, 6 Gloushkov avenue, Kyiv 252022, Ukraine
2. Institute of Physics, National Academy of Sciences, Prospekt Nauki 46, Kyiv 03650, Ukraine
3. Institute of Physics NASU (IP), Prospect Nauki 46, Kyiv 03028, Ukraine

Abstract

Random lasers are principally new sources of stimulated emission where positive feedback realized by multiple light scattering. The laser is active the scattering medium itself without any cavity as well as the other optical elements. Hereupon the lasers distinctions are small gain volume and arbitrary shape.
In this work we investigated lasing parameters of random lasers made of dye polymer solution with embedded scattering particles. The continuous lasing wavelength tuning method was realized in this laser. The method is based on the dye lasing wavelength dependence on the luminescence reabsorption within active medium [1]. Since the reabsorption is dependent on the active region depth it can be continuously changed by wedge-like sample displacing relatively to the focused pump beam.
We realized the continuous lasing wavelength tune within 8nm spectral range in the R6G random laser with silica scattering particles. The active medium was wedge-like shaped of ~0.5cm length with thickness difference Δ d=0.05-0.5mm.
The tune range depends on wedge thickness difference Δ d and light penetration depth into the sample, which could be changed by scattering efficiency varying. The outside tune range is limited by luminescence and absorption spectra overlapping. The accuracy of lasing wavelength tune increases with pump beam cross section σ decreasing. Both lasing threshold and lasing intensity depend on σ and thickness of active medium excited. It is conditioned by two following reasons: effective gain coefficient dependence on the excited region size, and effect of reflection from the sample surfaces on the feedback formation.
[1] E.Tikhonov; Vasil P.Yashchuk, O.Prygodjuk, V.Bezrodny, Yu.Filatov, Functional Materials, v.11,p.142-145,(2003).

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Presentation: oral at E-MRS Fall Meeting 2004, Symposium G, by Vasil P. Yashchuk
See On-line Journal of E-MRS Fall Meeting 2004

Submitted: 2004-04-30 17:24
Revised:   2009-06-08 12:55