Study of Optical Limiting and Optical Phase Conjugation in DASPB Dye-doped Polymer Films

Abstract

Nonlinear optical properties, optical limiting
and Optical phase conjugation through degenerate fourwave
mixing is observed in 4-[4-(Dimethylamino)styryl]-1-
docosyl pyridinium bromide (DASPB) dye-doped in
Polymethyl methacrylate – metacrylic acid (PMMA-MA)
polymer films under low-power, continuous-wave laser
irradiation. A maximum phase conjugate efficiency of
0.42% has been obtained for probe beam intensity at 2.5
W/cm2. Phase conjugation is observed for both paralleland
orthogonally-polarized probe and pump beams. The
maximum PC reflectivity is achieved when the angle
between probe beam and forward pump beam is 8
degrees. The effects of dye concentration, inter beam
angle between probe and forward pump beam on phase
conjugation reflectivity are also studied. PC signal
strength first increases and then decreases with time. PC
reflectivity is also increased by increasing the intensity of
the backward and forward pump beam. The polarization
and intensity profile are verified to be preserved in the
conjugate signal. The predominant phase conjugation
signal is attributed due to the saturable absorption and
two photon induced florescence property of the dye
molecules.