Resonant Nonlinear Optical Properties Research Articles

Nonlinear photoresponse in II-VI-based nanocomposite thin films: a semiquantitative four-level model

We have measured the one-photon, resonant nonlinear optical properties of sputter-deposited nanocomposite CdS:ZnO thin films with a characteristic grain size of about 3 nm. These films show a completely reversible photodarkening at low fluences as well as fast recovery, making them useful for optical limiting applications. The observed photoresponse can be ascribed to excited-state absorption and is in good agreement with a semiquantitative, four-level model proposed by us.

Microstructural and nonlinear optical properties of silica–titania sol-gel film doped with PbS quantum dots

Thin silica–titania films doped with different concentration of PbS quantum dots (PbS/oxide molar ratios ranging from 5% to 25%) were fabricated via a sol-gel route. The structural properties were studied by x-ray diffraction, high-resolution transmission electron microscopy, and Rutherford backscattering spectrometry. The PbS crystals were found to have a mean diameter in the range 2.3–3.5 nm with narrow size distribution. The resonant nonlinear optical properties were studied by the nonlinear m-line technique and degenerate four-wave mixing. High negative nonlinear refractive indices (n2) were measured at 1.064 μm. Different n2 values were obtained for nanosecond excitation (n2=10−7–10−8 cm2/kW) and for picosecond excitation (n2=10−9–10−10 cm2/kW). The differences can be explained by saturation effects. Measurements at 532 nm showed n2 values ten times higher than at 1.064 μm. The response time of the nonlinearity for both wavelengths was below 35 ps.

Resonant nonlinear optical properties of PbS nanocrystals under nano- and picosecond pulsed laser excitation

Using the sol-gel technique we have investigated PbS-doped thin films. The resonant nonlinear refractive index of these samples was measured, using two different techniques: nonlinear m-lines and degenerate four-wave mixing (DFWM). The measured values of the nonlinear refractive index are and for the m-lines and DFWM, respectively. We explain this difference as being due to the different durations of the laser pulses used (7 ns for m-lines and 30 ps for DFWM).

Resonant nonlinear optical properties and excited-state dynamics of pristine, oxygen-doped, and photopolymerized C60 in the solid state.

Resonant nonlinear optical properties and excited-state dynamics of pristine, oxygen-doped, and photopolymerized C60 in the solid state.

Resonant nonlinear optical properties of spin-cast films of soluble oligomeric bridged (phthalocyaninato)ruthenium(II) complexes

Spin-cast films of the oligomeric bridged (phthalocyaninato)ruthenium(II)complex [t-Bu 4 PcRu(dib)] n , which is axially linked by a p-diisocyanobenzene (dib) bridging ligand, were investigated by degenerate four wave mixing with laser wavelenghts varied over the complete range of the Q-band absorption and by third harmonic generation at 1064 nm. The magnitudes of χ (3) (-3ω;ω,ω,ω) and χ (3) (-ω;ω,ω,-ω) and characteristic dependence on the absorption coefficient α(ω) were determined

Resonant third-order nonlinear optical properties of poly(3-dodecylthiophene)

We have investigated the resonant nonlinear optical properties of both chemically prepared and electrochemically prepared poly(3-dodecylthiophene) samples using femtosecond degenerate four-wave mixing. The measured χ(3) values for the two polymers are 3×10−10 and 5×10−10 esu at 602 nm. The value of χ(3) at 705 nm is an order of magnitude less. The nonlinearity shows a subpicosecond response. The power dependence of the conjugate reflectivity shows saturation at high input powers. The origin of this saturation is discussed in terms of the saturable absorber behavior. It is concluded that the saturation is consistent with the predictions of simple kinetic models. The origin of the phase conjugate response is discussed in terms of two models: (i) phase space filling model involving unrelaxed excitons and (ii) rapid conformational deformation leading to shift of oscillator strength to photogenerated polaronic states. The analysis of our results favors the mechanism involving unrelaxed excitons as the source of the observed third-order optical nonlinearity.

Anisotropy of the Third Order Nonlinear Optical Susceptibility in a Degenerate Ground State Conjugated Polymer;Trans-(CH)x

Abstract The promise of conducting polymers as fast response nonlinear optical materials has been recently ernphaized1-3. Polymers such as polyacetylene, polythiophene and the soluble (and processible) poly(3alkylthienylenes) contain a high density of welectrons, and they are known to exhibit photoinduced absorption and photoinduced bleaching, indicating major shifts of oscillator strength upon photoexcitation2-4. For polyacetylene, these nonlinear effects have been studied in detail in the picosecond5a-b and subpicosecond5c time regime and correlated with the photoproduction of charge carriers through fast photoconductivity measuremenkm6. The data have demonstrated ul-tra-fast response with nonlinear shifts in oscillator strength occurring at times of the order of 10−13 seconds. These resonant nonlinear optical properties are intrinsic; they originate from the nonlinearity of the self-localized photoexcitations7 which characterize this class of polymers: solitons, polarons and bipolarons4.

Third Order Nonlinear Optical Susceptibility of Trans-(CH)x: A Degenerate Ground State Conjugated Polymer

ABSTRACTThe promise of conducting polymers as fast response nonlinear optical materials has been recently emphasized [1,3]. Polymers such as polyacetylene, polythiophene and the soluble (and processible) poly(3-alkylthienylenes) contain a high density of x-electrons, and they are known to exhibit photoinduced absorption and photoinduced bleaching, indicating major shifts of oscillator strength upon photoexcitation [2,4]. For polyacetylene, these nonlinear effects have been studied in detail in the picosecond [5a,b] and sub-picosecond [5c] time regime and correlated with the photoproduction of charge carriers through fast photoconductivity measurements [6]. The data have demonstrated ultra-fast response with nonlinear shifts in oscillator strength occurring at times of the order of 10-13 seconds. These resonant nonlinear optical properties are intrinsic; they originate from the nonlinearity of the self-localized photoexcitations [7] which characterize this class of polymers: solitons, polarons and bipolarons [4].

Observation d'états excitoniques à température ambiante dans les semiconducteurs à puits quantiques de type InGaAs/InP (Applications)

Semiconductor quantum wells and their band gap resonant nonlinear optical properties have been shown to be important because of their potential for applications in optical switching and signal processing. The near band gap optical properties of quantum well structures are dominated by strong excitonic effects due to quantum confinement. There is much interest in the use of optical devices as MQW for performing all optical switching or by using electrostatic field to change the absorption directly by driving electrons in the QW structure. Such effects are able to produce a family of optical logic elements. In this paper, we present the linear and nonlinear optical properties seen in III-V (GaInAs/InP) multi quantum well structures. The nonlinear properties associated to the absorption saturation of the heavy hole excitons are demonstrated. We review the applications of these nonlinear processes in the field of the 2D and integrated optics (intrinsic bistability and nonlinear coupler) Etude des caracteristiques de transmission optique et mise en evidence d'effets non lineaires associes a la saturation d'absorption excitonique; applications (bistabilite intrinseque, coupleur optique)