Photonic crystal and structural properties of synthesized opal films filled with the iron oxides: hematite
(α-Fe2O3) and
magnetite (Fe3O4) were investigated by means of scanning electron microscopy, X-ray diffraction, and Fourier
transforme spectroscopy. Hematite was infiltrated into opal film pores without depositing the oxide onto the outer film
surface by the method of lateral infiltration under capillary forces from a liquid precursor. The synthesis of Fe3O4 was
performed in the opal pores using α→Fe2O3 as a precursor. The evolution of Bragg diffraction line from the (111) planes
of the f.c.c lattice of the opal-α-Fe2O3 film with a various filling degree was studied. The maximum filling degrees both
of opal- α-Fe2O3 and of opal-Fe3O4 films, estimated from the reflection spectra, appeared to be similar and equal to
~ 55% of the pore volume. The reversible chemical transformation of fillers in opal pores α-Fe2O3→Fe3O4→α-Fe2O3
changes only the filler dielectric constant but does not practically produce structural defects that could affect the
photonic crystal properties of the composite.
One dimensional periodic and non-periodic silicon photonic structures have been designed and fabricated on silicon-on-insulator
substrate for the investigation of the electro-tuning effect in composite system Photonic Crystal - Liquid
Crystal. The reflection spectra registered for non-periodic structures demonstrate the phase polarisation shift for bands
of high reflection, while for the periodic structure the shift of the photonic band gap edge was observed. Under an
applied electric field in the range from 2V to 10V, the shift of the polarised reflection spectra, caused by reorientation of
the LC director from planar to homeotropic alignment, has been obtained. A significant change in the refractive index
close to Δn=0.2, which is a characteristic feature for LC E7, has been achieved due to LC reorientation in all structures
just after LC infiltration. It was found that after switching-off the applied electric field the initial planar orientation of LC
molecules is not restored. This effect is related to weak anchoring of LC molecules to the silicon side-walls which
results in the transition of LC to the pseudo-isotropic alignment after the applied voltage is off. A relatively smaller (with
Δn=0.07), but highly reproducible electro-tuning effect was revealed during the LC reorientation from pseudo-isotropic
to homeotropic alignment. The shift of the edge of PBG by Δλ=0.16 or by Δλ/λ=1.6% in relative shift units was
observed in this case. The response time estimated under applied square shaped ac pulses of various frequencies was
found to be around 30 ms.
Transparent polycrystalline diamond films with grain size ranging from a few tens to hundreds of nanometres were prepared on fused silica substrate by Microwave Chemical Plasma Vapour Deposition method (MPCVD). The new technique, called alternating nanodiamonds injection, was applied for substrate pretreatment. It was demonstrated that nanodiamonds injected on fused silica substrate serve as nucleation centres and make possible an increase in nucleation density to 1010 cm-2. The influence of MPCVD parameters such as methane concentration, total pressure and substrate temperature on the crystalline structure and optical properties of diamond films were investigated by using micro-Raman spectroscopy and scanning electron microscopy, transmittance and reflectance measurements in the wavelength range of 400-1000 nm. Under appropriate MPCVD parameters, diamond films with optical transmission ~70% from 650 to 1000 nm and high content of diamond phase were fabricated.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.