Anti-Stokes femtosecond photon echo in a polymer film

An anti-Stokes model is proposed which explains the room-temperature blue shift of the echo-signal spectrum compared to the spectrum of exciting femtosecond pulses in a polymer film doped with dye molecules. The possibility of realising the anti-Stokes regime of coherent laser cooling of such films is analysed. © 2007 Kvantovaya Elektronika and Turpion Ltd.