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Unformatted text preview: Nonlinear optical effects and carbon nanotubes Chiyat Ben Yau Department of Physics, University of Cincinnati, OH 45221, USA (December 3, 2001) Abstract Materials with large second or third order optical nonlinearities are of great interest for data processing in photonic computing. Since the invention of laser in 1960 by Maiman and the first discovery of nonlinear optical (NLO) effect of quartz crystals, there has been a great deal of research directed at finding new materials with higher order NLO properties. Only noncentrosymmetric or polar materials could possess second order NLO susceptibility (2) . For most third order NLO materials, their (3) s are generally too low for prac- tical applications. Since the discovery of carbon nanotubes, which possess optimal properties (like highest thermal conductivity, Young modulus 100 times higher than steel, zero bandgap metal, ballistic conductance, simple structure, nanometer-size and ultra-light weight) by a NEC scientist Sumio Iijima in 1991, a heat of studying and engineering the properties of carbon nanotubes has been raised worldwide. Experimentalists recently discovered that carbon nanotube is also a NLO material with amazingly high third or- der NLO susceptibilities. And, up to now, there is no publication about the experimental proof of the second order NLO properties of carbon nanotubes. In this paper, we will review the basic physics of NLO properties of mate- rials, and state the reasons of high (3) and practically zero (2) of carbon nanotubes. 1 Before the invention of laser, the intensity of light is approximately 1 V/cm and nearly all materials exhibit linear relationship between the polarization of the materials and the incoming optical electric field E . When the high intensity (10 6-10 9 V/cm) coherence light was first provided by the first laser, which was invented by Maiman in 1960 , the nonlinear relationship between the averaged electric field inside material D and the incoming optical E field, as shown in Fig. 1, implying nonlinear polarization was discovered. When a red laser light enters a quartz crystal, as shown in Fig. 2, the outcoming light is blue, and this indicates that the frequency of outcoming light is doubled. This is a nonlinear optical (NLO) effect called Second Harmonic Generation (SHG). Since then, there has been a great deal of research directed at finding new materials with higher order nonlinear optical properties....
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This note was uploaded on 01/08/2012 for the course PHYSICS 707 taught by Professor Electrodynamics during the Fall '11 term at LSU.
- Fall '11