1. Two-photon absorption standards in the 550-1600 nm excitation range: establishing a correction curve for accurate cross section calibration Nikolay S. Makarov, Mikhail Drobizhev, Aleksander Rebane Department of Physics, Montana State University, Bozeman, MT

2. Outline Motivation Experimental setup Pulse duration Beam profile Correction curve 2PA standards, example Conclusions

3. Motivation Absolute 2PA cross section: Relative 2PA spectrum: Correction curve: If the 2PA reference standards were available: If there are no standards (establishing standards): Absolute 2PA cross section: Relative 2PA spectrum:

4. OPA wavelength control LN CCD sample L1 M1 600 l mm -1 laser system Coherent VERDI CW 532nm Coherent MIRA 900 Coherent LEGEND-HE regen. amplifier, 1kHz TOPAS-C FROG autocorrelator pulse characterization FW digital oscilloscope filter wheel control ref. detector spectrometer PH2 USB control serial control GPIB PC LabView /2 color filters pol. PH1 SHG crystal spectrometer & CCD control Experimental setup

5. Pulse duration SH signal SH idler Signal Measured with SHG autocorrelator Clark MXR AC-150 ~ 70 – 140 fs pulse duration range ~ 5% fixed wavelength measurement error ~ 3% step-to-step relative measurement error

6. Beam profile SH signal SH idler Signal Measured with CCD camera Xillix MicroImager PMI1400 ~ 0.03 – 0.10 cm diameter range ~ 4% fixed wavelength measurement error

7. Correction curve ~ 8% fixed wavelength measurement error ~ 3% step-to-step relative measurement error

8. 2PA standard: Rhodamine 6G

9. 2PA standard: Rhodamine B

10. 2PA standards: Full set

11. Conclusions 2PA of 15 commercially available dyes in 550–1600 nm  10% estimated accuracy of 2PA cross sections Values are in good agreement with literature data (fluorescence technique) Data can be used as reference for determining absolute 2PA cross sections and spectra This work is supported by AFOSR Grant No. FA9550-05-1-0357 Acknowledgement