We report on the design of a stable optical limiter in the low laser power regime based on the thermal variation of refractive index in a novel nanocomposite material. The optical material, chloroaluminium-phthalocyanine (ClAlPc), is embedded in SiO2-Nafion nanocomposite membrane (ClSNf) and its thermally induced nonlinear refractive index is characterized by the Z-scan technique with a low power cw He-Ne laser as the source. The value of nonlinear refractive index coefficient, n2, is found to be about 1.11 × 10-11 m2 W-1. The experiment is repeated with the dye doped in pure Nafion membrane (ClNf) and the results are compared with those of ClAlPc doped SiO2-Nafion nanocomposite membrane. The value of n2 is found to be 1.36 × 10 -11 m2 W-1 and is larger than that of the ClAlPc embedded SiO2-Nafion nanocomposite membrane. The photostability of the dye-embedded membrane is studied by exposing the sample to cw He-Ne laser and monitoring its fluorescence emission intensity continuously. The samples are found to show large thermal lens effect and demonstrated to be good optical limiters in the low power regime. Whereas the optical properties of dye-doped Nafion appear to be slightly better than those of the dye embedded in silica and incorporated in Nafion, the latter is found to offer excellent photostability. © 2007 IOP Publishing Ltd.

C. Vijayan

Department Of Physics

K Sathiyamoorthy

Mahendra Prasad Kothiyal

Alumina

Dyes

Nanocomposites

Optical design

Optical materials

Refractive index

silica

Nafion

Optical limiters

PHOTOSTABILITY

PHTHALOCYANINE

Limiters

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Design of a low power optical limiter based on a new nanocomposite material incorporating silica-encapsulated phthalocyanine in Nafion

Journal of Physics D: Applied Physics

We demonstrate the use of stable films containing PbS nanocrystals as media for self-adaptive phase filtering in phase contrast imaging of transparent objects by a cost-effective exploitation of nonlinear optical refraction in a simple, all-optical, and self-adjusting 4f imaging system. The optical nonlinearity is characterized by z-scan technique using a continuous wave He-Ne laser as the excitation source. The mechanism of nonlinearity in this case is mainly due to the nonlocal thermo-optical interaction between the laser beam and the sample. The value of nonlinear refractive index coefficient is found to be -3:5 × 10-7 cm2=W. The nanocomposite material shows a thermal lens effect and is a potential candidate for phase contrast imaging. © 2009 Optical Society of America.

Applied Optics

Spatial phase filtering based on the intensity-dependent refractive index of PbS nanocomposite film

We report for the first time on the synthesis of core-shell particles containing chloroaluminiumphthalocyanine (ClAlPc) prepared using a sol-gel technique. These particles have die dye molecules at the core, encapsulated by silica shell. The mean size of the particle is determined from HRTEM studies and is found to be approximately 0.08 μm. The surface and bulk compositions of the core-shell particles are studied by XPS and EDAX measurements, respectively. Time-resolved fluorescent measurements indicate a decrease in fluorescence lifetime for the core-shell particles as compared to that of bare dye dissolved in ethanol. This is analyzed on the basis of available theoretical models. Third-order nonlinear optical effects are investigated by the Z-scan technique using 8 ns pulses at a wavelength of 532 nm from a frequency-doubled Nd:YAG laser. The analysis indicates that both singlet and triplet excited-state absorption contribute to nonlinear absorption. © 2008 American Chemical Society.

Langmuir

Nonlinear optical response of chloroaluminiumphthalocyanine encapsulated by silica core-shell particles

Nonlinear optical behavior of a novel nanocomposite material based on chloroaluminum phthalocyanine (ClAlPc) embedded in silica and incorporated in the structural nanopores of a Nation membrane is investigated using the Z-scan technique. The experiments are performed at 532 nm using 8 ns pulses at a pulse repetition rate of 10 Hz from a frequency-doubled Nd:YAG laser. The nonlinearity in the hybrid membranes is characterized by obtaining the nonlinear refractive index and nonlinear absorption coefficient. Fluorescence lifetimes are measured using a time-correlated single photon counting technique. The effects of dynamic and static quenching on photostability are studied. Incorporating phthalocynanine molecules in the stable hybrid membrane renders them stable against photobleaching and provides a convenient solid matrix. © 2008 American Chemical Society.

Journal of Physical Chemistry C

Nonlinear refraction and absorption phenomena in a novel nanocomposite based on a dye stabilized in a solid hybrid matrix

Journal of Materials Science: Materials in Electronics

Studies on linear and nonlinear optical properties of 4-N,N-dimethylamino-4′-N′-methyl-stilbazolium 2,4,6-trimethylbenzenesulfonate crystal

Estimation of thermodynamic and third-order nonlinear optical properties of a series of organic liquids based on ethylenediaminium divalent cation, [C2H10N2]X2 (where X = 2-nitrophenol, 4-nitrophenol, 2,4-dinitrophenol and 2,4,6-trinitrophenol respectively) was made. Increase in nitro groups of ethylenediaminium nitrophenolates has predominantly increased the point of decomposition (145–243 °C). Various thermodynamic properties as a function of temperature were estimated theoretically from the DSC curves. Thermal conductivity and specific heat capacity was increasing while thermal diffusivity was decreasing with rise in temperature. Ethylenediaminium trinitrophenolate (EDA246TNP) showed maximum thermal conductivity (30.3 W m− 1 K− 1) and specific heat capacity (2684 J kg− 1 K− 1), while thermal diffusivity (9.6 × 10− 6 m2 S− 1) was higher for ethylenediaminium 2-nitrophenolate (EDA2NP). Z-scan experiment showed that all samples exhibit saturable absorption and self-defocusing behaviour under CW laser (532 nm, 50 mW) excitation. The observed nonlinearity was found to be thermal in origin with order of nonlinearity as ED246TNP &gt; EDA24DNP &gt; EDA4NP &gt; EDA2NP. EDA246TNP possess maximum nonlinear absorption coefficient (8.37 × 10− 3 cm/W), nonlinear refractive index (8.41 × 10− 8 cm2/W), third-order nonlinear optical susceptibility (5.21 × 10− 6 esu), second-order hyperpolarizability (9.81 × 10− 25 esu) and thermo-optic coefficient (− 0.21 × 10− 6 K− 1) than other phenol-ammonium salts. All samples exhibit optical limiting action with optical limiting onset values of 35–38 mW having limiting amplitude of 6.7–9.3 mW. The influence of number and position of nitro groups in tuning the thermodynamic and nonlinearity of ethylenediaminium nitrophenolate was discussed in detail. © 2017 Elsevier B.V.

Journal of Molecular Liquids

Influence of number and position of nitro groups in tuning the thermodynamic and nonlinear optical properties of ethylenediaminium nitrophenolates

Self-organization and other processes of aggregation in metalloporphyrins are of recent interest in view of their scope for several new applications. The technique of photoacoustic spectroscopy is used in the present work to investigate the optical properties of FeTPPCl aggregates on glass substrate. The observed features in the photoacoustic spectrum of the aggregates are compared with those of the porphyrin in solution and powder forms. Spectral shifts and broadening of the bands indicating aggregation as well as well-resolved features of hyper spectra are observed clearly in the photoacoustic spectra. © 2007 Elsevier B.V. All rights reserved.

Materials Letters

Photoacoustic investigations on self-organization effects in metalloporphyrins on glass substrates

The increasing use of low power cw lasers in various applications calls for the design of optical limiters with low thresholds. To this end, the optical nonlinearity exhibited by zinc tetraphenyl porphyrin at low laser powers is utilized to design an optical limiter for low threshold operation. The basic parameter responsible for limiting action, the nonlinear refractive index of the medium, is measured using the Z-scan technique and found to have a value of -1.4×10-7cm2/W at the helium-neon laser wavelength of 632.8 nm. The origin of nonlinearity is explained on the basis of the thermal lens model. It is shown that effective optical limiting at desired threshold values can be achieved by the optimal choice of aperture size and experimental geometry. © 2005 Elsevier Ltd. All rights reserved.

Optics and Laser Technology

Low-threshold optical power limiting of cw laser illumination based on nonlinear refraction in zinc tetraphenyl porphyrin

A solid state nonlinear optical medium is obtained by the incorporation of the metalloporphyrin, Zinc Tetra Phenyl Porphyrin (ZnTPP) in Nafion polymer membrane. The nonlinear refractive index of this membrane is measured at 632.8 nm by the z-scan technique and found to be on par with that exhibited by ZnTPP in the solution form. Photodegradation effects seen in the porphyrin solution appear to be inhibited due to its incorporation in the membrane. The material is found to exhibit optical limiting effects based on nonlinear refraction and its behaviour is investigated in comparison with that of ZnTPP in solution form. The nonlinearity appears to be of thermal origin. © 2004 Elsevier B.V. All rights reserved.

Optical Materials

Nonlinear optical properties of a porphyrin derivative incorporated in Nafion polymer

Optical nonlinearities of CdS quantum dots in the strongly confined regime are probed through degenerate four-wave-mixing experiments in an attempt to study the size dependence of the third order optical susceptibility χ(3). The results indicate that χ(3) is strongly dependent on the diameter of the dots and that there is a large increase in χ(3) values as the diameter decreases below 2 nm. Polarization discrimination studies point to nonthermal contributions to the mechanism of optical nonlinearity.

Journal	Journal of Physics D: Applied Physics
Publisher	Institute of Physics Publishing
ISSN	00223727
Open Access	No