Efficiency estimates and practical aspects of an optical Kerr gate for time-resolved luminescence spectroscopy.

We report experience of assembling an optical Kerr gate setup at the Femtosecond Laser Center for collective use at the Institute of Physics of the National Academy of Sciences of Ukraine. This offers an inexpensive solution to the problem of time-resolved luminescence spectroscopy. Practical aspects of its design and alignment are discussed and its main characteristics are evaluated. Theoretical analysis and numerical estimates are performed to evaluate the efficiency and the response time of an optical Kerr gate setup for fluorescence spectroscopy with subpicosecond time resolution. The theoretically calculated efficiency is compared with the experimentally measured one of ~12% for Crown 5 glass and ~2% for fused silica. Other characteristics of the Kerr gate are analyzed and ways to improve them are discussed. A method of compensation for the refractive index dispersion in a Kerr gate medium is suggested. Examples of the application of the optical Kerr gate setup for measurements of the time-resolved luminescence of Astra Phloxine and Coumarin 30 dyes and both linear and nonlinear chirp parameters of a supercontinuum are presented.

Synthesis of 1D regular arrays of gold nanoparticles and modeling of their optical properties.

Self-organized formation of uniform coating of semiconductor substrate by metal nanoparticles offers a convenient and efficient access to large-scale arrays of uniform metal-semiconductor nanostructures. We used a cheap and facile method of photoinduced chemical gold deposition from an aqueous or alcohol gold salt solution onto semiconductor surface (GaAs, InP). By controlling of both the solution composition and the deposition conditions, gold particles of 10-50 nm in diameter were obtained and the gold covering degree of the semiconductor surface was varied in a wide range. Morphology of the nano/micro structures formed was characterized by atomic force microscopy and scanned electron microscopy with local element analysis. The investigations show that the semiconductor surface patterning can be used for the selective deposition of gold nanoparticles, because they are located predominantly at the tops of the microrelief. We have used specially textured by the anisotropic chemical etching microrelief surfaces of semiconductor single crystal as templates and have obtained nanoparticle arrays in the shape of 1D systems of near parallel quasiperiodical wires. For the periodic 1D array of metal nanowires built into the air-semiconductor interface the spectral and angular dependencies of the transmittance/reflectance of the polarized light have been obtained theoretically using differential formalism. These dependencies demonstrate non-monotonic behaviour at surface plasmon polariton excitation conditions and show possibility of designing functional subwavelength devices.