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EASUREMENT OFRADIATIVE LIFETIME AND ABSORPTION COEFFICIENTS

OF RUBY CRYSTAL AND RHODAMINE 6G SOLUTION AS GAIN MEDIA

DARKO POPOVIC
11 Drenovacka St., 11060 Belgrade, Serbia

INTRODUCTION

Inversely populated energy levels are a prerequisite for
laser radiation to be emitted. Supplied with energy, valence
electrons absorb it and move to higher energy levels,
becoming unstable and thereby effectingnonradiative
transmission to lower energy levels. They will maintain this Fig. 1.Alinechartofrubycrystal (left)
state until incident photons stimulate them to perform a andrhodamine 6Gsolution (right) absorptions
laser transfer and emit another photon.

METHODOLOGY

For the purpose of measuring the absorption coefficient, the
gain medium is excited by a 532 nm laser diode, provided
with the power of 250mA. In front of the gain medium, a
mobile optical cable was placed, conducting light to the Fig. 2.Alinechartofrubycrystal (left)
spectrometer. Using a USB cable, the obtained data were andrhodamine 6Gsolution (right) radiative lifetimes
transferred to the computer to be processed.
While measuring theradiactivelifetime, the gain medium is CONCLUSION
excited with the same pulsed mode laser diode that was
connected to the oscilloscope reading the voltage. A
photodiode with a filter was placed in front of the gain Onthebasisofthisexperiment,
ithasbeenconcludedthattheabsorptioncoefficientofrubycryst
medium, to detect light form the gain medium; it was alhasbeenconstant, whereasinaliquidlaseritincreaseswiththe
connected to an oscilloscope, to serve as another voltmeter.
increase of rhodamine 6G concentrationin the ethanol
solution.On the other hand, unlike the absorption
INVESTIGATION RESULTS coefficient, changes in the concentration of rhodamine 6G
in ethanol do not significantly affect the upper-state
radiative lifetime of the laser line, given the concentrations
Absorption Radiative measured.
Gainmedium coefficient lifetime This investigation confirms our theoretical expectations,
[1/mm] [ms] and the obtained values are characteristic of the gain media.
Ruby crystal 0.042±0.008 3.640±0.006
-6
0.61 0.0374±0.0008 (9.87±0.03)10
Rhodamine 1.23 0.0759±0.0006 (9.87±0.04)10 REFERENCES
-6
6G solution -6
C [mg/l] 1.75 0.0948±0.0008 (9.84±0.04)10 [1] N. Konjevic, Introductiontoquantumelectronics :lasers,
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2.26 0.1303±0.0009 (9.84±0.05)10
Naucnaknjiga, Belgrade 1981.
Table 1. The results of experimental measurements of
absorption coefficients and radiative lifetime [2] А. Penzkofer andW.Leupacher, Fluorescencebehaviour
of highly concentrated rhodamine 6G solutions,Journal of
Luminescence, vol. 37(1987), 61-72