Ultrafast Laser Energy Density and Retinal Absorption Cross-Section Determination by Saturable Absorption Measurements

Alfons Penzkofer, Meike Luck, Tilo Mathes, Peter Hegemann

Department of Exact Sciences/Biophysics, Vrije Universiteit, Amsterdam, The Netherlands.
Faculty of Physics, University of Regensburg, Regensburg, Germany.
Institute of Biology/Experimental Biophysics, Humboldt University to Berlin, Berlin, Germany.

DOI: 10.4236/jasmi.2014.41003                

Abstract

Laser pulse nonlinear transmission measurements through saturable absorbers of known absorption parameters allow the measurement of their energy density. On the other hand, nonlinear transmission measurements of laser pulses of known energy density through absorbing media allow their absorption parameter determination. The peak energy density w_0P of second harmonic pulses of a mode-locked titanium sapphire laser at wavelength λ_P = 400 nm is determined by nonlinear energy transmission measurement T_E through the dye ADS084BE (1,4-bis(9-ethyl-3-car-bazovinylene)-2-methoxy-5-(2’-ethyl-hexyloxy)-benzene) in tetrahydrofuran. T_E(w_0P) calibration curves are calculated for laser pulse peak energy density reading w_0P from measured pulse energy transmissions T_E. The ground-state absorption cross-section σ_P and the excited-state absorption cross-section σ_ex at λ_P, and the number density N₀ of the retinal Schiff base isoform RetA in pH 7.4 buffer of the blue-light adapted recombinant rhodopsin fragment of the histidine kinase rhodopsin HKR1 from Chlamydomonas reinhardtii were determined by picosecond titanium sapphire second harmonic laser pulse energy transmission measurement T_E through RetA as a function of laser input peak energy density w_0P. The complete absorption cross-section spectrum σ

Keywords

Laser Pulse Peak Energy Density Determination; Ground-State Absorption Cross-Section Determination; Excited-State Absorption Cross-Section Determination; Saturable Absorption; ADS084BE Dye; Histidine Kinase Rhodopsin HKR1; Retinal Schiff Base RetA Cofactor; Number Density Determination

Conflicts of Interest

The authors declare no conflicts of interest.

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