Non-Linear Optical Properties of Nano Particle C60 Fullerene Using Lasers
Received Date: Apr 06, 2018 / Accepted Date: Apr 18, 2018 / Published Date: Apr 25, 2018
The third order non-linear optical properties of Buckminster fullerene (C60) molecule has been studied using a Nd:YAG laser, in the visible and in the infrared region. The solvent using toluene was specifically used because of low threshold intensity for an optical limiter application. Closed aperture Z-scan technique was adopted to characterize the material due to its simplicity and high sensitivity in measuring the third-order optical nonlinearity. This allows computing the contributions of nonlinear absorption and nonlinear refraction towards nonlinearity. Saturable Absorption (SA) for C60 nano particles is also established. RSA is not established. FT-IR studies is also carried out to characterize the sample and to correlate the NLO studies.
Keywords: Buckminster fullerene; Non-linear properties; Visible and infrared regions; Nd: YAG laser; Third order NLO property; Optical limiter; Non-linear refraction
Nanotechnology plays an important role in finding new nano scale materials for the benefit of renewable energies. Nano structured materials are mainly used in applications such as hydrogen and methane storage, fuel cells, solar cells, bio-fuel cells, rechargeable batteries, super capacitors, electrodes, catalysts, gas sensors and other applications. For developing new or novel materials, it is required to synthesize, fabricate, characterize and process these nano materials for any specific application. One such study is the non-linear optical property (NLO) of this C60, Buckminsterfullerene nano particles. The C60 molecule was discovered by Zhou et al.  during conduction of an experiment involving graphite under an inert atmosphere of helium. C60 and other such similar structures are considered as promising nonlinear optical materials due to its non-linear refraction and scattering process which is a necessary property for optical limitation.
An optical limiter is a device that will have high transmission of low input signal and for large input signal there will be constant output signal. For example, an intense laser or a light beam can damage the eye. So by using properly designed lenses, one can protect the eye. The other application of NLO property is in shaping of short laser pulses. Simplicity and a fast response time is the main reason for choosing NLO property of C60 material. Saturable absorption, also known as SA is the well-known mechanism for optical limiting devices.SA is applicable for molecular systems because the excited state cross-sectionex is larger than the ground state cross-sectiong which is an ideal situation for an optical limiter application. There are a several characterization techniques available for measuring the third-order optical nonlinearities these includes degenerate four-wave mixing, nearly degenerate three-wave mixing, optical Kerr effect, ellipse rotation, interferometric methods, two beam coupling, beam self-bending and third harmonic generation . Among the available techniques z-scan technique offers simplicity as well as very high sensitivity in measuring the third-order optical nonlinearity and also allows computing the contributions of nonlinear absorption and nonlinear refraction towards the nonlinearity. Z-scan technique is based on the principle of spatial beam distortion. It was originally proposed by Sheik-Bahae, has been since then implemented and applied to the study of third-order optical nonlinearity. Using z-scan technique, the magnitude of nonlinear absorption and the sign and magnitude of nonlinear refraction can be determined simultaneously. When a high intensity laser beam propagates through a material, induced refractive index changes leads to self-focusing or defocusing of the laser beam. This enables to determine the third-order nonlinear optical properties of various materials in liquid, thin film or crystal forms. In this technique, the sample under investigation is moved along the tightly focused Gaussian laser beam. The intensity of the laser beam changes as the sample is moved. This is because the sample experiences different intensities, depending on the position of the sample relative to focus (z=0). The power transmitted through the sample is measured by translating the sample along the z-direction through the beam waist of a focused beam and hence the name z-scan.
We obtained a pure research grade 99.999% pure M/s.Merck Co.Ltd. for the analysis of C60 nanoparticles.Initially we tried to record the second order optical non-linearity of the C60 fullerene molecule with the help of a Nd: YAG pulsed laser with wavelength equal to 1.064 micrometre. But the sample did not show any absorption as the IR beam did not pass through it. The IR light was reflected back from the sample without any absorption and so it is reported that there is no second order optical non-linearity for this sample. Thereafter, we proceeded to do the Z-scan experiment to study the third order optical non-linearity using a Nd: YAG laser with a second harmonic output wavelength of 532 nm .
Since fullerene molecule shows high volatility it is dissolved in solution to perform NLO studies and so, the C60 nano particles were dissolved in a solvent toluene with a transmittance of 64%. The reason to choose toluene is that it gives a low threshold intensity, to be used as an optical limiter, than any other solution like carbon-black, chloronapthalene etc .The sample cell was kept in front of a Nd:YAG laser using 532 nm second-harmonic generated beam in the visible region, for the study of third order NLO properties. The experimental set-up is shown here below in Figure 1 and the schematic of the z-scan experimental set up is shown in Figure 2 below.
The characterization of the sample was also done using the FT-IR for percentage of transmission of the C60 molecule and it was found that the sample showed highest transmission (reference is 4000 cm-1 at 100%), (97.8%) at 450 cm-1 (0.002222 cm wavelength) and the lowest transmission percentage (5%) at 1426 cm-1 (0.00070126 cm wavelength), indicating that at the lower wavelength, the sample has low percentage of transmittance and at higher wavelength it has high percentage of transmittance. Thus the third order nonlinear refractive index property can be observed at higher wavelengths due to high transmittance of light in the visible region . The FT-IR spectrum recorded is shown below in Figure 3, (Table 1).
Table 1: below gives data related to minimum and maximum percentage transmission of a FT-IR spectrum recorded for C60 molecule.
The recorded parameters for the C60 fullerene molecules during our experiment are, namely, Kerr nonlinearity is found to be (n2)=5.38 x 10-8 cm2/W,
Two-photon absorption coefficient TPA (β)=0.04 × 10-4 cm/W,
Linear refractive index (n0)=1.13, third order electric susceptibility Re (χ3)=1.73 × 10-6 esu,
Imaginary part of the third order electric susceptibility Im (χ3)=0.42 × 10-6 esu, third order electric susceptibility (χ3)=1.79 × 10-6 esu. The Table 2 gives the details as shown below.
|n2 x 10-8 cm2/W||β x 10-4 cm/W||n0||Re χ(3) x 10-6 esu||Im χ(3) x 10-6 esu||χ(3) x 10-6 esu|
Table 2: C60 fullerene molecule- recorded parameters during z-scan experiment
It is seen from the Table 2 above that the contributions of nonlinear absorption (β) and nonlinear refraction (n2) towards nonlinearity is established [5-10]. The laser intensity dependent refractive index in the third order, namely, (χ3) has been prominent, showing negative signs for the absorptive nonlinearities. We attribute this negativity to saturable absorption [11,12]. This shows that C60 Fullerene nano particle is suitable for an optical limiting device, plasmon waveguide, sensor protection, medicine, and nano probes.
A graphical plot and a comparison between closed aperture and open aperture experiment and also the ratio between the two types is shown below.
From the graph seen in Figures 4 and 5, it is seen that linear absorption coefficient has been steadily increasing from the centre on both sides, with the distance of z scan from the centre of the cell in which the solvent is kept. From the Figure 6, we can infer that the solubility in toluene is complete and the sample has shown more transmittance towards the centre of the cell and hence this non-linear refractive index property will be suitable to act as an optical limiter for C60 nano particles. The data from which the graph has been plotted is shown in Table 3 below.
|Linear Abs. Co.||Closed||Open||Ratio|
Table 3: Data on linear absorption coefficient, closed, open apertures and their ratio.
Result and Discussion
For the C60 nano particles, closed aperture Z-scan technique was adopted to characterize the material due to its simplicity and high sensitivity in measuring the third-order optical nonlinearity. This allows computing the contributions of nonlinear absorption and nonlinear refraction towards nonlinearity. The characterization of the sample was also done using the FT-IR for percentage of transmission of the C60 molecule and it was found that the sample showed highest transmission (reference is 4000 cm-1 at 100%), (97.8%) at 450 cm-1 (0.002222 cm wavelength) and the lowest transmission percentage (5%) at 1426 cm-1 (0.00070126 cm wavelength), indicating that at the lower wavelength, the sample has low percentage of transmittance and at higher wavelength it has high percentage of transmittance. It is seen from the experimentally recorded data above, that the contributions of nonlinear absorption (β) and nonlinear refraction (n2) towards nonlinearity is established. The laser intensity dependent refractive index in the third order, namely, (χ3) has been prominent, showing negative signs for the absorptive nonlinearities. The non-linear refractive index property of C60 nano particles is thus suitable to act as an optical limiter, plasmon waveguide, sensor protection, medicine, and nano probes.
The authors wish to acknowledge with thanks, Dr.Vinitha, Assoc. Professor, Department of Physics, VIT, Chennai, India for doing the Z-scan experimental part at their laboratory, Dr. Vijayaraghavan, Asst. Professor, Department of Physics, Crescent Engineering College, Chennai, India for checking the second order NLO property for C60, DST, Govt. of India for carrying out FT-IR studies at the SAIF-IITM, Chennai, India and also would like to thank the Principal and the management of Sri Sairam Engineering College for encouraging us to present such type of work in international conferences.
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Citation: Subramaniam TK, Vinitha G, Jayakumar CV, Premanand R (2018) Non- Linear Optical Properties of Nano Particle C60 Fullerene Using Lasers. J Laser Opt Photonics 5: 182. DOI: 10.4172/2469-410X.1000182
Copyright: © 2018 Subramaniam TK, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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