The effects of excited state lifetime, optical intensity, and excited state quenchers on the photostability of zwitterionic chromophores

Abstract

Photoluminescence (PL) and photostability measurements have been made on thin films containing the 2nd order nonlinear optic chromophore, PYR-3, and amorphous polycarbonate (APC). We find that the PYR-3 singlet excited state PL lifetime systematically decreases with increasing PYR-3 concentration, which may be due to PYR-3 excited state energy transfer to non-radiative decay sites. There is no correlation between the PL lifetime and the photostability for low optical intensities, and we find that the photobleaching data cannot be modeled with a single photodegradation quantum efficiency. There is an increase in the photostability with increasing optical intensity, and this enhancement is larger for high PYR-3 concentrations. It can be explained by a reduction in the oxygen content by oxygen-mediated photodegradation for the 5% PYR-3/APC films. This also partly explains the enhancement in the 15% PYR-3/APC films, but there is an additional mechanism as well. The photostability can also be improved by adding beta-carotene, which leads to an enhancement factor of greater than 6.

Optically switchable diffraction grating in a photochromic/polymer thin film

“…The photodegradation 1∕e time at this intensity is ∼250 s. Photodegradation is oxygen-mediated and occurs in the open form. Hence, similar to measurements done on other organic dyes [25][26][27], it can be dramatically reduced by minimizing the oxygen content of the film by either placing it in a vacuum or by encapsulation as well as including oxygen singlet quenchers [26][27][28][29].…”

“…Thus, it may be possible to use CHM/APC films in practical applications (e.g., in a reconfigurable add/drop multiplexer) to completely reflect a certain wavelength. As mentioned above, oxygen-mediated photodegradation can be a problem that can be significantly reduced by encapsulation in a low oxygen content environment as well as by including singlet oxygen quenchers [26][27][28][29].…”

Electrically modulated diffraction gratings in organic chromophore thin films

“…The method used to make PYR-3/APC thin films is similar to that reported previously [10,11]. They were fabricated by spin-coating a solution containing PYR-3 and APC (glass temperature, T g 218°C) in 1,1,2-trichloroethane onto an indium tin oxide (ITO) coated glass substrate.…”

“…Diffraction gratings were made in the films in transmission mode and without the gold coated top plate electrode using a two-beam interference method and a 488 nm laser to periodically bleach the film in the charge transfer band that peaked at ∼614 nm [10,11]. The angle between one of the beams and the surface normal was 4.9°, which corresponds to a grating period of Λ 2850 nm.…”

“…They have a number of advantages over conventional solid state compounds (e.g., LiNbO 3 ) that include the ability to easily create arbitrary shapes (e.g., optical fibers, thin films) when compared with LiNbO 3 [1]. One disadvantage is that they are susceptible to photodegradation in the presence of oxygen [8][9][10][11]. However, the photostability can be significantly enhanced by reducing the oxygen content [8] or using an encapsulating barrier that reduces oxygen diffusion into chromophore/polymer films [12,13].…”