M. Trejo-Valdez

Inhibition of the two-photon absorption response exhibited by a bilayer TiO2 film with embedded Au nanoparticles

We use two different synthesis approaches for the preparation of TiO(2) films in order to study their resulting third order optical nonlinearity, and its modification by the inclusion of Au nanoparticles in one of the samples. An ultrasonic spray pyrolysis method was used for preparing a TiO(2) film in which we found two-photon absorption as a dominant nonlinear effect for 532 nm and 26 ps pulses; and a purely electronic nonlinearity at 830 nm for 80 fs pulses. A strong optical Kerr effect and the inhibition of the nonlinear optical absorption in 532 nm can be obtained for the first sample if Au nanoparticles embedded in a second TiO(2) film prepared by a sol-gel technique are added to it. We used an optical Kerr gate, z-scan, a multi-wave mixing experiment and an input-output transmittance experiment for measuring the optical nonlinearities.

Identification of inhomogenous optical absorptive response by chaotic photonic signals in Au nanoparticles

A chaotic circuit allows us to identify with a high sensitivity the optical absorption associated with a highly transparent sample with Au nanoparticles embedded in a TiO2?thin film prepared by a sol?gel method. The measurements are based on a comparison of the correlation between a controlled optical irradiance that propagates through different zones of the sample. Nanosecond nonlinear optical measurements were obtained by monitoring the transmittance and the amplitude modification for the vectorial components of the electric fields in a two-wave mixing interaction. In addition, we theoretically study chaotic physical behavior exhibited by optical signals under nonlinear optical absorption. Our numerical results point out that small intensity fluctuations related to excitations of the absorptive nonlinearity can be described using a simple fractal model. Potential applications for developing sensors and instrumentation of the optical response of advanced materials are contemplated.

Mechano-optical modulation and optical limiting by multiwall carbon nanotubes

An optical limiting effect in multiwall carbon nanotubes was modulated by using a two-wave mixing experiment assisted with a mechanical actuator. We employed a 532 nm wavelength and 1 ns pulse duration for exciting the nonlinear optical absorption. The nanotubes were prepared by an aerosol pyrolysis method. The resulting samples were deposited on a pure silica substrate as an inhomogeneous thin film. The mechano-optical modulation was obtained by the orthogonal rotation of the sample with respect to the probe beam. In addition, low-irradiance patterns provided by a Michelson optical interferometer allowed us to comparatively corroborate the mechano-optical effect induced by the rotation of the film.

Bidirectional optical Kerr transmittance in a bilayer nanocomposite with Au nanoparticles and carbon nanotubes

Experimental and numerical results about the propagation of optical signals in a bidirectional two-wave mixing system with Au nanocomposites and carbon nanotubes are presented. Au nanoparticles embedded in a TiO2 thin solid film were prepared by a sol–gel processing route; while carbon nanotubes were obtained by a thermal decomposition approach. A thin film conformed by carbon nanotubes was put on top of the Au nanocomposites for the nonlinear optical measurements. A two-wave mixing experiment was conducted to distinguish the direction of propagation of a probe-beam through the exploration of an induced birefringence and two-photon absorption. The third-order nonlinear optical response of the sample was evaluated by considering discrete groups of energy numerically modeled by the beam propagation method. Remarkable differences exhibited by the propagation and counter-propagation of a polarized probe beam were identified by nanosecond pulses at 532 nm wavelength. By employing a 405 nm wavelength as a probe beam, we were able to change the behavior of the direction of maximum Kerr transmittance in a particular geometry of a non-degenerated multi-wave system. It can be contemplated that the influence of distinctive near- and off-resonant excitations of the samples seems to be useful to control a selective one-way transmittance with potential applications for developing all-optical systems.

Magneto-conductivity and magnetically-controlled nonlinear optical transmittance in multi-wall carbon nanotubes.

The impact of vectorial magnetic field effects on electrical conductivity and nonlinear optical transmittance exhibited by multi-wall carbon nanotubes was studied. The samples were synthetized by an aerosol pyrolysis processing route in a thin film form. Optical signals in a two-wave mixing configuration allowed us to identify two orthogonal directions of propagation for a magnetic field travelling through the nanomaterials studied. A selective modification in optical absorption was considered to be induced by magnetic perturbations in the sample. Standard optical Kerr gate measurements were carried out for exploring the third order nonlinear optical behavior of the film. A capacitive effect influenced by optical and magnetic excitations was distinguished to be characteristic of the sample. Magneto-quantum conductivity sensitive to the direction of an external magnetic field interacting with the tubes was analyzed. Magnetically-induced changes in electronic band parameters seem to be the main responsible for the optical and electrical modulation observed in the nanostructures. Immediate applications for developing magneto-optical and magneto-electrical functions can be contemplated.

Mechano-optic logic gate controlled by third-order nonlinear optical properties in a rotating ZnO:Au thin film

Measurements of the third-order nonlinear optical properties exhibited by a ZnO thin solid film deposited on a SnO2 substrate are presented. The samples were prepared by a spray pyrolysis processing route. Scanning electron microscopy analysis and UV–Vis spectroscopy studies were carried out. The picosecond response at 1064 nm was explored by the z-scan technique. A large optical Kerr effect with two-photon absorption was obtained. The inhibition of the nonlinear optical absorption together with a noticeable enhancement in the optical Kerr effect in the sample was achieved by the incorporation of Au nanoparticles into the ZnO film. Additionally, a two-wave mixing configuration at 532 nm was performed and an optical Kerr effect was identified as the main cause of the nanosecond third-order optical nonlinearity. The relaxation time of the photothermal response of the sample was estimated to be about 1 s when the sample was excited by nanosecond single-shots. The rotation of the sample during the nanosecond two-wave mixing experiments was analyzed. It was stated that a non-monotonic relation between rotating frequency and pulse repetition rate governs the thermal contribution to the nonlinear refractive index exhibited by a rotating film. Potential applications for switching photothermal interactions in rotating samples can be contemplated. A rotary logic system dependent on Kerr transmittance in a two-wave mixing experiment was proposed.

Optoelectronic switching in a microstructure containing Au nanoparticles

Photoconduction and nonlinear optical refraction effects exhibited by an array of separated Au microchannels are reported. The samples were constituted by Au thin solid films containing Au nanoparticles prepared by an evaporation method. The photoconductivity of the sample was measured with continuous illumination at 532 nm wavelength with 1 W average power. A vectorial two-wave interaction allowed us to explore the optical Kerr effect exhibited at 532 nm wavelength and 1 ns pulse duration. Z-scan experiments performed in a comparative Au thin solid film pointed out a saturated optical absorption as a dominant physical mechanism that originates the optical nonlinearity at 1064 nm wavelength with 150 ps pulses. The third-order optical nonlinearities measured in the studied cases with ps and ns pulses were estimated to be about  = 10−10 esu. Microscopy observations were carried out to describe the morphology that is responsible for the noticeable optical Kerr effect. The optoelectronic switching behavior exhibited by the studied array was analyzed.

Participation of the third order optical nonlinearities in nanostructured silver doped zinc oxide thin solid films

We report the transmittance modulation of optical signals in a nanocomposite integrated by two different silver doped zinc oxide thin solid films. An ultrasonic spray pyrolysis approach was employed for the preparation of the samples. Measurements of the third-order nonlinear optical response at a nonresonant 532nm wavelength of excitation were performed using a vectorial twowave mixing. It seems that the separated contribution of the optical nonlinearity associated with each film noticeable differs in the resulting nonlinear effects with respect to the additive response exhibited by the bilayer system. An enhancement of the optical Kerr nonlinearity is predicted for prime number arrays of the studied nanoclusters in a two-wave interaction. We consider that the nanostructured morphology of the thin solid films originates a strong modification of the third-order optical phenomena exhibited by multilayer films based on zinc oxide.

Nonlinear mechano-optical effects and speckle fringe patterns exhibited by Gold-Platinum nanoparticles in cells

Speckle fringe patterns modulated by the third-order nonlinear optical behavior of Gold-Platinum nanoparticles in rotation were analyzed by a two-wave mixing configuration. Random interference patterns derived by speckles were obtained by employing a Nd:YAG laser system featuring nanosecond pulses at 532 nm wavelength for the measurements. The nanostructured samples were prepared by a sol-gel method and contained in a water suspension. Transmission electronic microscopy, UV-vis spectroscopy and Energy-dispersive X-ray spectroscopy studies were undertaken in order to characterize the samples. The bimetallic nature of the nanoparticles gave origin to an optically anisotropic response related to nonlinear optics enhanced by plasmonic excitations. The orientation of the samples produced important changes in the ratio between the real and imaginary parts of the third-order nonlinear optical susceptibility. Gyroscopic properties of the samples confirmed the possibility to identify mechanical motion of the system through the evaluation of induced birefringence and multi-photonic absorption. Vectorial self-diffraction signals generated by two-wave mixing experiments were explored to reveal the mechanisms responsible for the nonlinearities observed. The nanoparticles were incorporated in randomly distributed cells in order to monitor their mechanical activity by recording speckle fringe patterns. A self-focusing effect resulting from a positive nonlinear refractive index in the nanoparticles allowed us manipulating the location of the speckle fringe pattern; and then, a focusing system dependent on irradiation was proposed for the observation of mechano-optical processes. Nonlinear optical interactions for performing ultrafast all-optical instrumentation functions can be contemplated.

XOR Logic Gate by Carbon/Metal Nanoinks Based on a Double-Stage Optical Kerr Gate Configuration

Two-input binary exclusive-or logic operations were presented by the assistance of multiwall carbon nanotubes in a double-stage optical Kerr gate scheme with two control beams. The samples were prepared by the aerosol pyrolysis method and decorated by platinum nanoparticles using a chemical vapor deposition technique. The nanostructures were suspended in ethanol to obtain carbon/metal nanoinks with different concentrations and then randomly distributed networks integrated in thin film form were fabricated. Polarization-selectable functions were obtained in the double-stage scheme by using nanosecond third-order nonlinear optical effects at 532 nm wavelength exhibited by the samples. Potential applications for ultrafast identification and encryption of nonlinear optical signals were discussed.