Relevant Parameters for an Efficient All Optical Poling

After encoding of the we observe two regimes of relaxation an initial, very rapid decay, occurring just after stopping of the seeding process, and the second, much slower, multiexponential decay, comparable to the decay observed in polymers poled by the corona poling method. Orientation losses vary from 10% to 20% after 15 hours in the dark at ambient temperature. 

After several tests, it is possible to estimate approximately the optimal relative intensities needed to obtain large photoinduced nonlinearities within relatively short preparation periods. The dependence of the generated SH signal is a function of the phase difference A between the writing beams at 0) and 2t0 frequencies. The relative phase difference A can be varied by tilting a BK7 plate of known thickness and refractive index disper.sion.  

9 Real-time growth and decay of the SHG signal (in arbitrary units)/ Negative times correspond to the seeding step. At time zero, the seeding is stopped. Positive times are associated with the study of the temporal stability of the induced susceptibility.The sample is a spin-coated thin film of the DRI-MMA 35/65 copolymer,0.5 pm-thick, OD = 1.5 at 532 nm.The peak intensity of the 0) beam was a few GW/cm, the SH seeding beam was much weaker between 10 and 100 MW/cm.  

Within the limit of small angles of incidence, the phase difference between the writing beams is derived from the incidence angle 0 of the waves onto the 

ALEKSANDRA APOSTOLUK, CgUNE FIORINI.AND JEAN-MICHEL NUNZi 

ALEKSANDRA APOSTOLUK, CELINE FIORINI,AND JEAN-MtCHEL NUNZt 

IO Intensity of the generated SH signal (in arbitrary units) after 20 minutes of seeding time, in function of the relative phase difference A I between the writing beams at frequencies co and 2(o/The reference (i.e. A l = 0) is arbitrarily taken at normal incidence of the writing beams onto the BK7 plate.The solid line represents a theoretical fit to Equation 11.6. The curve shown in the insert shows 

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