Photon-number squeezing by two-photon absorption in an organic polymer

We report the generation of photon-number squeezed light by two-photon absorption in a thin film of the organic polymeric dye R-478 with intense femtosecond laser pulses at 800 nm. Photon-number noise measurements of the transmitted laser beam were carried out simultaneously with the measurement of the sample's nonlinear transmission. A two-photon absorption coefficient (beta) of 7 cm/GW was estimated for the organic polymer thin film. At the highest incident peak irradiance used we observed a reduction of the photon-number noise of 0.1 dB (4.6%) below the standard quantum Limit. By considering the detection losses we inferred 7.7% squeezing at the sample output. The experimental results were compared with the predictions of a theoretical model relating the Fano factor to the nonlinear transmission. The analysis of the experimental results indicates that sub-Poissonian photon statistics occurs when the Linear optical losses in the sample are overcome by the quantum noise reduction effect of multi-photon absorption. (C) 2000 Published by Elsevier Science B.V. All rights reserved.