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Strained silicon is a versatile new type of material, which has found application in microelectronics and integrated optics in the last years. Unlike ordinary silicon, it does not possess a centrosymmetric lattice structure. This allows for stimulation of nonlinear optical processes that involve second-order nonlinear susceptibility. Here, the dependence of the nonlinear susceptibility on the applied strain by means of reflected second-harmonic generation is investigated. This surface-sensitive technique is suitable for the investigation of bulk silicon strained by a layer of thermal oxide. The obtained relation between applied stress and susceptibility enhancement is compared to theoretical prediction based on an analytical model for the deformed silicon orbital. The knowledge of the stress-susceptibility dependence can be used to develop suitable photonic devices that benefit from second-order nonlinear processes in silicon.

A review of recent progress in the field of strained silicon photonics is presented. The application of strain to waveguide and photonic crystal structures can be used to alter the linear and nonlinear optical properties of these devices. Here, methods for the fabrication of strained devices are summarized and recent examples of linear and nonlinear optical devices are discussed. Furthermore, the relation between strain and the enhancement of the second order nonlinear susceptibility is investigated, which may enable the construction of optically active photonic devices made of silicon.

Nd3+-doped fluorozirconate glasses, which were additionally doped with chlorine ions, were investigated for their photoluminescence (PL) properties. Upon heat treatment of the asmade glass, hexagonal phase BaCl 2 nanocrystals are formed within the material, which undergo a phase transformation to orthorhombic BaCl2 upon annealing at a higher temperature. The glasses with hexagonal phase BaCl2 nanocrystals show an enhanced Nd3+PL in the visible spectral range. Time-resolved spectroscopy on the 4G5/2 / 2G7/2 4I9/2 transition shows that the existence of hexagonal BaCl2 nanocrystals results in a significantly longer decay time. The temperature dependence of the lifetime yielded that the enhanced PL is due to a reduced multi-phonon relaxation rate

The interactions of the drugs 2,7-bis[(diethylamino)-ethoxy]-fluoren-9-one dihydrochloride (Tilorone), 2,7-bis[(dipropylamino)-acetamido]-fluoren-9-one dihydrochloride (FA-2), 2'-(4-hydroxyphenyl)-5-(4-methyl-1-piperazinyl)-2,5'-bi-1H-benzimidazole trihydrochloride (Hoechst 33258), and hematoporphyrin IX derivative (HPD) with synthetic self-complementary DNA (36-b.p.; 5'-biotin-spacer-[d(CGCTATATAGCG)]3-3') were studied by SPR (Surface Plasmon Resonance). Monolayers of biotinylated DNA were immobilized on a streptavidin-dextran-gold triple-layer. Small portions of the drugs (approximately 30 pmol/ml) were injected in continuous flow. The mass corresponded to the amount of the bound molecules. Injections of 50 mM sodium hydroxide pulses separated the DNA double strands, releasing the effector molecules. Subsequent treatments with the effectors gave reproducible results. The maximum interaction between drug and DNA was observed in the case of Tilorone. 41 molecules could bind to the 36-b.p. DNA duplex. To investigate the microscopic behavior in condensed nucleic acid phases, SFM (Scanning Force Microscopy)-imaging and polarizing microscopic observations of DNA-effector complexes were carried out. Supplementary UV-absorption thermal denaturation curves of DNA with the above-mentioned effectors in dilute solutions were measured. As an additional aid to understand the geometries of DNA-drug interactions, computer simulations were performed and compared with the experimental data.