Nonlinear optical studies in tetraphenyl-porphyrin-doped boric acid glass using picosecond pulses |
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Authors: | K Divakara Rao S Anantha Ramakrishna PK Gupta |
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Institution: | (1) Biomedical Applications Section, Centre for Advanced Technology, Indore 452 013, India (Fax: +91-731/488-430, E-mail: kdivakar@cat.ernet.in; sar@rri.res.in; pkgupta@cat.ernet.in), IN |
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Abstract: | We report the results of our studies on the nonlinear optical response of thin films of tetraphenyl porphyrin doped in boric
acid glass for picosecond-duration pulses. The fluence-dependent transmission measurements show that the sample exhibits reverse
saturation behavior at 532 nm and saturable absorber action at 683 nm. By fitting the nonlinear transmission data at these
wavelengths to a rate equation model, values for σS
e and σL the excited singlet and ground state cross sections were obtained. The large value (≈8) for σS
e/σL makes it a potential material for optical limiting at 532 nm, whereas at 683 nm the ratio σL/σS
e≈4.3. Intensity dependence of degenerate forward four-wave mixing at 683 nm was also investigated to establish the order and
magnitude of the nonlinearity. The forward four-wave mixing signal at 683 nm showed a cubic dependence on the input intensity,
establishing the third-order nonlinearity. A value of 4×10-12 esu for the third-order susceptibility |χ(3)| was estimated from the measured efficiency. The time response of the nonlinearity was measured by the pump-probe transmission
experiment, resulting in a decay constant of about 1.8 ns for the repopulation of the ground singlet state at 683 nm.
Received: 13 April 2000 / Published online: 20 September 2000 |
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Keywords: | PACS: 42 65 42 70 |
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