Two-photon-induced birefringence in azo-dye bearing polyimide; the birefringence changes versus the writing power

Abstract

Ultra-short high-intensity light pulses were utilized to induce the optical birefringence in a polyimide material possessing the azo-dye covalently bonded to the main chain. The obtained results showed that a two-photon absorption process was involved in a creation of the sample birefringence which, to the best of our knowledge, was not previously reported for polyimide materials. The growths and decays of birefringence were examined as functions of the pulse intensities. No damage to the material during the illumination process was detected in a wide range of optical powers applied. High birefringence level of the order of 0.005 was measured.A. Kozanecka-Szmigiel ( ) ·

Six-dimensional optical storage utilizing wavelength selective, polarization sensitive, and reflectivity graded Bragg reflectors

“…The induced birefringence value T n n n − = Δ // depends on writing light intensity and exposure time, and can be erased to zero by circular polarized light when the writing light intensity is below a destructive threshold value (over which the remained birefringence can't be removed). The required average writing power and exposure time are 50 mW and 425 s for inducing two-photon birefringence change, which corresponds to the peak writing intensity of 7.1 GW/cm² and effective illumination period of 42.5 ns since using 100 fs pulses at 1 kHz repetition rate, and when the average writing power and exposure time are 400 mW and 425 s, the induced erasable birefringence change is 0.005 15 . The average destructive writing power is 700 mW.…”

“…This type of polymer shows that two orthogonal axes of polyimide molecule can be reoriented by linearly polarized light with high intensity, resulting in two-photo induced and writing power dependent birefringence change of bulk medium 15 . That is, through polarized light illumination, if the refractive index in the polarization direction (named // n ) decrease, the in-plane index perpendicular to this direction ( T n ) will accordingly increase.…”

“…Because two-photon absorption wavelength range, such as in the azo-dye bearing polyimide film, is from 550 nm to beyond 240 nm (the corresponding single-photon absorption wavelength range is from 1100 nm to 480 nm) 15 , the wavelength λ may be taken from 250 nm to 460 nm at intervals of 10 nm, then when taking D = 8 µm, n = 1.7 or 1.9, the available smallest beam diameters d may be calculated, which are shown in Table B.…”

Isomerization and optical bistability of DR1 doped organic–inorganic sol–gel thin film

“…The polymer, such as PMMA and PPV, was widely used as a matrix material [6][7][8], but the low stability under UV irradiation limits its application [9], hence, during the last two decades, many research works on the stability of the azo-doped materials have been reported [10,11]. For examples, the polymers with high T g and derived by new synthetic method were employed to achieve a more stable material system [12,13]. However, the unadjustable component makes them difficult have the flexible properties including tunable rigidity and refractive index.…”

Investigation of Photoelastic Property and Stress Analysis for Optical Polyimide Membrane through Stress Birefringence Method

“…It is important to notice that the birefringence value is proportional to the primary stress difference and, thus, the birefringence value corresponds to the anisotropy of inner stress. Stress birefringence measurement is an effective method to reflect the inner stress of a transparent isotropic material, and many researchers have investigated stress distribution based on the method [17][18][19][20]. Birefringence can be observed and measured in many ways.…”