Optical gain in dye-doped polymer waveguides using oxidized porous silicon cladding

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 characterized 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 characterize 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.