We report on a novel organic/inorganic hybrid waveguide approach, which is composed of a cladding of extremely low
refractive index oxidized porous silicon formed on a bulk silicon substrate and of it, a polymeric
(polymethylmethacrylate) core doped with a visible laser dye (Nile-Blue) was deposited by spin coating.
The waveguiding properties of the structures have been characterised by means of the m-line technique, demonstrating
that the use of oxidized porous silicon as a cladding can considerably improve the mode confinement factor of single-mode
waveguides. The low refractive index achievable in the cladding (n=1.16) allows forming waveguides with a low
index polymer cores.
Variable stripe length (VSL) measurements have been also performed in order to characterise the amplification
properties of the waveguides. We demonstrate a clear transition from losses to gain at 694nm with a pump threshold of
28mJ/cm2. Values of net optical gain up to 104dB/cm have been measured at this wavelength.
We present an experimental work on porous silicon-based optical devices. Notch filters and planar waveguides are fabricated and characterized. Three different types of filters are shown, the first one is a stop band filter in the 1.5 micron region, where improvements have been performed (smoothing of the index profile, apodization and index matching). The second is a double Notch filter in the IR range, which blocks two different frequencies. Finally Notch filters in the visible range are shown, where porous silicon has been completely oxidized. Double layer waveguides are fabricated and characterized by atomic force microscopy, luminescence and prism coupling techniques. All the results shown are compared with numerical calculations. The photoluminescence changes and the refractive index variations for different annealing times are modeled in terms of oxidation of silicon and slow condensation of the porous structure.
Laser-excited site selective spectroscopy of the Eu3+ ions has been used in malonate crystals to detect a structural phase transition. From room temperature (RT) to 236 K a unique crystal-field site around the Eu3+ ions is observed. However, two different sites are clearly identified below this temperature indicating a structural phase transition.
Room temperature intense green upconversion emission under excitation at 749 nm in a fluoroindate glass doped with 2.5 mol% of Ho3+ has been observed. Analysis of spectral measurements suggest a photon avalanche mechanism with emissions from the 5S2 and 5F4 levels of Ho3+ ions.