Second harmonic generation (SHG) has been obtained in a rich in sodium niobium orophosphate glass by a thermal poling treatment. The thermally poled glass SHG signal has been studied through an original analysis of both transmitted and reflected polarized Maker-fringe patterns. Therefore, the second order nonlinear optical (NLO) efficiency was estimated from the simulation of the Maker-fringe patterns with a stepwise decreasing profile from the anode surface. A reproducible chi(2) susceptibility value as high as 5.0 +/-0.3 pm/V was achieved at the anode side. The nonlinear layer, found to be sodium-depleted up to 5 microm deep inside the anode side, identical to the simulated nonlinear zone thickness, indicates a complex space-charge-migration/ nonlinear glass matrix response process.

In this paper, acido- and phototriggered enhancement of the nonlinear optical (NLO) properties are achieved by combining the 10-(2-arylethenyl)indolino[2,1-b]oxazolidine unit with various styrylic residues. The synthetic pathway allows the preparation of phenyl, naphthyl, anthryl, and phenanthryl derivatives, which have been shown to display photochromic and acidochromic behavior at ambient temperature. The multiaddressable molecular switches are characterized by a large contrast of the NLO response along the reversible transformations. Hyper-Rayleigh scattering (HRS) experiments clearly indicate the strong influence of the electrodonating substituent borne by the aromatic system. Theoretical calculations have been performed for representative molecules showing a good agreement with the experimental hyperpolarizabilities. This enables a better understanding of the NLO responses in terms of structural and electronic parameters for both closed and protonated open forms.

Molecular switches: Highly efficient acido- and photoswitchable frequency doublers (see scheme) based on the indolinooxazolidine core are studied by means of hyper-Rayleigh experiments and quantum-chemical calculations.To optimize the nonlinear optical (NLO) contrast, a series of indolinooxazolidine derivatives with electron-withdrawing substituents in the para position on the indolinic residue have been synthesized. Their linear and nonlinear optical properties have been characterized by UV-visible absorption and hyper-Rayleigh scattering measurements, as well as by ab initio calculations. The two-way photo- or pH-triggered switching mechanism has been demonstrated by comparing the absorption spectra of the zwitterionic and protonated open forms (POF). Hyper-Rayleigh measurements have revealed that the second-order NLO contrast between the closed indolinooxazolidine and the open pi-conjugated colored forms remain very large upon substitution. Theory and measurements show that for the POFs the amplitude of the first hyperpolarizability follows the Hammett parameters of the withdrawing groups. However, because the measurements are performed in resonance, to recover this behavior, elaborate procedures including homogeneous and inhomogeneous broadenings, as well as single-mode vibronic structures are necessary to extrapolate to the static limit.