Journal of Nonlinear Optical Physics & Materials

In this work, we report preliminary results obtained for methacrylic polymers incorporating azobenzene side-group as nonlinear optical (NLO) active molecule. The trans-cis isomerization properties are discussed. The third-order non-resonant nonlinear refractive index (n₂) and nonlinear absorption coefficient (β) are measured using the Z-scan technique at 1064 nm in the picosecond regime. The influence of different electron-acceptor groups in azobenzene moieties on the nonlinear properties is investigated.

We report on the design of a particular holographic grating to be exploited for the stability control of an active optical holographic setup. The low-cost transmission grating made of alternating slices of pure polymer slices and pure nematic liquid crystal is used as a reference grating for the active feedback system that enables the interference patterns stabilization. The stability test of the interference pattern confirms the effectiveness of the proposed technique.

The fluctuation effects in the ideal quasi-phase-matching have already been studied in detail from the point of view of periodicity and wavelength. In this paper, the length fluctuation on each segment of periodicity poled nonlinear crystals (PPNC) in the second harmonic generation has been studied. By adding the linear crystals in PPNC which is positive, zero, negative and zero (PZNZ) configuration, (+, 0, -, 0), random length errors affect its output efficiency. It has also been revealed that in disordered structures, the output efficiency of the nonlinear generation of light is increased in PZNZ and in these conditions, the efficiency in PZNZ is better than that of PPNC.

We present an analytical and numerical investigation of a spatial soliton propagating in a waveguide with ramp linear refractive index profile (ramp waveguide) and nonlocal nonlinearity. It is shown analytically by equivalent particle approach and numerically by implicit Crank-Nicolson scheme that in a ramp waveguide with local nonlinearity, the soliton experiences negative acceleration along the waveguide where its refractive index decreases linearly. On the other hand, if the soliton propagates in a uniform medium with nonlocal nonlinear response then it will experience a self-bending in the positive direction where the bending level depends on the soliton amplitude as well as on the strength of nonlocality. By combining these two effects, rich dynamics of soliton can be achieved. In this case, the soliton may oscillate inside the waveguide, move to the left or to the right part of the waveguide or even be trapped. Such soliton steering can be controlled by the soliton amplitude or by its initial position.

In order to develop an ultra fast all-optical switch, we have studied optical Kerr effect and two photon absorption in photonic crystal line defect waveguides. Based on these results, we have succeeded in all-optical Mach-Zehnder interferometer switching.

The precursor glasses in (mol%) 25.53Li₂O-21.53Ta₂O₅-35.29SiO₂-17.65Al₂O₃ (LTSA) and 25K₂O-25Nb₂O₅-50SiO₂ (KNS) glass systems were prepared by the melt-quench technique. Ferroelectric LiTaO₃ (LT) and KNbO₃ (KN) crystallites containing bulk nano glass-ceramics have been prepared by controlled crystallization of these precursor glasses respectively. Second harmonic generations (SHG) at 532 nm in both the glass-ceramics have been realized under fundamental beam of Nd³⁺:YAG laser source (1064 nm). The SHG power output has been found to increase up to 14 and 62.4 nJ with variation of rotation angle for LT and KN bulk nano glass-ceramics respectively due to orientation of ferroelectric domains under applied field.

A simple, sensitive SERS-based immunoassay realized in aqueous solution is demonstrated with a sandwich immune protocol. In such an immunoassay, antibodies-immobilized silica nanoparticles served as the immune substrate while 4MBA-labeled immuno-Au nanoparticles are used as the immune sensors. According to the TEM images, it is clear that the immune gold nanoparticles are embedded onto the surfaces of the silica nanoparticles specifically after the immunoreaction. As a result, the aggregations of gold nanoparticles have been formed with SERS-active "hot spots" on the dimers or multimers. The SERS results confirm that the method proposed in this paper is an effective way for SERS-based aqueous immunoassay and that the detection limit is as low as 0.1 ng/mL.

We have synthesized highly stable silver nanoparticles in aqueous solution at room temperature by standard reduction method using bovine serum albumin (BSA) as a stabilizing agent. The nonlinear optical properties of nanoparticles were investigated using Z-scan technique at 532 nm. The obtained nonlinear absorption coefficient and negative nonlinear refractive index is found to be 88.36 cm/GW and -5.1 × 10^-7 esu respectively. The real and imaginary part of third order susceptibility of silver nanoparticles is found to be 1.553 × 10^-7 esu and 0.7 × 10^-7 esu respectively. The silver nanoparticles in BSA template show good optical limiting property.

This paper proposes a new ring resonator device, in which a modified add/drop multiplexer incorporated with two nanoring resonators is modeled. Such a system is known as the PANDA ring resonator structure. By controlling the suitable input parameters and the control optical signals, the optical pulses are employed to form the gradient potentials, finally, the optical vortices (gradient optical fields/wells) are generated, which can be deployed in various applications.

The propagation of two beams of light with slightly different frequencies through a photorefractive media is investigated. In this process, the refractive index experienced by either wave is modified with the intensity of the wave. The coupled nonlinear Schrödinger equation that models the beam propagation is derived from wave equation and solved analytically. The existence of soliton like solutions for the photorefractive media is also verified.

In this paper, we have realized amplification without inversion (AWI) in quantum dot (QD). A Y-type four-level system of In_xGa_1-xN quantum dot has been obtained and investigated for AWI. It has been shown that, with proper setting of control fields' amplitude, we can obtain reasonable gain. With proper setting of phase difference of control fields and probe field, we can obtain considerable gain in resonant wavelength. We have designed this system by solving the Schrödinger–Poisson equations for In_xGa_1-xN quantum dot in GaN substrate, self-consistently.