In-plane anisotropic photoresponse in all-polymer planar microcavities

We report on the optical photomodulation properties of all-polymer planar microcavities in which the photochromic poly((4-pentyloxy-3’-methyl-4’-(6-methacryloxyhexyloxy))azobenzene) (PMA4) acts as photoresponsive cavity layer. We induce the trans-cis isomerization process of the azobenzene group by polarized 405 nm CW-laser irradiation, while the backward process is driven by unpolarized CW-laser irradiation at 442 nm. The all-optical photoisomerization process induces a remarkable in-plane anisotropic spectral shift of the cavity modes for the first and second order photonic band gaps. The spectral and intensity modulation effects for these flexible all-polymer microcavities are discussed with respect to those so far reported in literature for analogous systems. All-polymer flexible planar microcavities containing the photochromic poly((4-pentyloxy-3’-methyl-4’-(6-methacryloxyhexyloxy))azobenzene) have been prepared. The reversible photoisomerization of the azobenzene moiety under CW polarized and unpolarized irradiation induces a large, well-defined and anisotropic change of the spectral position of the microcavity mode. This proof-of-concept results may be exploited for all-optical switches or modulators. [Display omitted] •All-polymer planar microcavities doped with a photochromic azo-polymer are grown.•The trans-to-cis photoisomeization modulates the cavity mode spectral position.•Very strong in-plane anisotropic all-optical photomodulation is achieved.•Photomodulation occurs for both the first and second order photonic band gaps.