Abstract
SPIE PHOTONICS WEST 2023 Integrated Optics: Devices, Materials,
and Technologies XXVII A new light responsive arylazopyrazole (AAP) containing polymer matrix thin
film is fabricated by spin-coating of different concentrations of the AAP azo
dye into the polydimethylsiloxane (PDMS) polymer at 150C. The new AAP molecular
switch was also used to fabricate a solid-state PDMS-AAP waveguide by contact
lithography and soft replica modeling methods in the micrometer scale. The
refractive index of the spin-coated photoswitchable material can be modulated
via the reversible trans-to-cis photoisomerization behavior of the AAP unit
using different concentrations. When 0.01 M solution of the AAP unit was used,
the refractive of the composite was 2.32 in the trans state and dropped to 1.85
in the cis state in the operating wavelength of 340 nm. At higher
concentrations of 0.020 and 0.03 M, a wide refractive index tuning is achieved
under the same wavelength. In 0.030 M the refractive index was 2.65 for the
trans state and 2.0 for the cis state. The results suggest that the increase in
refractive index tuning is related to the concentration of the AAP unit of the
composite film. Theoretically, the spectral properties of the composite film
are also simulated with two methods: 1) the Maxwell Equations; and 2) the
frequency dependent finite element, showing excellent agreement for the
different propagation modes of the proposed waveguide for regulated signals of
365/525 nm wavelengths. Furthermore, the photoisomerization of the PDMS-AAP
thin film is analyzed with UV-vis spectroscopy to demonstrate the isomerization
responses of the AAP moiety in the solid state. Additionally, preliminary
photomechanical actuation properties of the composite film have been
investigated. The PDMS-AAP waveguide described in this study provides a new
approach for optically tunable photonics applications in the Visible-IR region.