Nonlinear effects in optics offer the possibility of generating or manipulating light in almost any manner. The laser itself, producing light not available in nature, is the most obvious example. Therefore nonlinear interactions are the basis of photonics.

Nonlinear Interactions of Light and Matter Without Absorption

Four-wave mixing by gain saturation in a laser-pumped Ti:sapphire (Ti3+:Al2O3) amplifier is demonstrated for the first time to our knowledge. Small-signal gain in excess of 250 has been obtained by intense laser pumping at 532 nm, resulting in observed four-wave mixing energy reflectivity as high as 360% for nanosecond pulses at 780 nm.

Tunable phase conjugation in a Ti:sapphire amplifier

We report on the optical performances of laccaic acid dye in solution at different concentrations and dye–poly(methyl methacrylate) composite thin films. The linear spectral characteristics including optical constants, i.e. refractive index (n) and extinction coefficient (k), were carried out in a comprehensive way through absorbance, fluorescence and ellipsometric studies. The nonlinear optical parameters such as nonlinear absorption coefficient β
 eff (or β
 2), the imaginary third-order susceptibility (Im[χ
 (3)]) and the imaginary part of second-order hyperpolarizability (γ) of the samples were evaluated using the open-aperture Z-scan technique with a laser pulse duration of 10 ns at 532 nm wavelength. The corresponding numerical values of these parameters were of 10−10, 10−11 and 10−32 order, respectively. Two-photon absorption was revealed to be the main driving physical mechanism in the nonlinear response. This suggests that laccaic acid dye can be a potential candidate for NLO materials application.

Linear and nonlinear optical absorption characterization of natural laccaic acid dye

We demonstrate the use of highly efficient degenerate four-wave mixing for phase conjugation with multipass geometries in a polymer laser dye saturable amplifier. Phase-conjugate energy reflectivity of as much as 20,000% with a four-pass geometry in the longitudinally pumped polymer dye was obtained at 564 nm.

Highly efficient degenerate four-wave mixing with multipass geometries in a polymer laser dye saturable amplifier.

Studies on the nonlinear optical properties of rf plasma polymerized aniline thin films by open aperture z-scan technique

We present the first report to the best of our knowledge of highly efficient phase conjugation in a laser-pumped polymer-dye saturable amplifier. Phase-conjugate reflectivity of as much as 210% at 560 nm has been obtained. Moreover, efficient reflectivity has been obtained in the broad wavelength region from 556 to 567 nm.

Naoyuki Hayashi

Papers

Tunable, visible phase conjugator with a saturable-amplifier polymer laser dye.