Nonlinear Optical Properties of Two Different Nanoassemblies of Polydiacetylene (PDA): PDA Nanovesicles and PDA Nanocrystals

B Bhushan,T Kundu,B P Singh

doi:10.4236/opj.2013.34042

Abstract

We have synthesized and characterized two different nanoassemblies of polydiacetylene (PDA), PDA nanovesicles and PDA nanocrystals, in order to study the influence of chain packing geometry of the two nanoassemblies on their third order nonlinear optical properties. The second molecular hyperpolarizability γ(-ω,ω,-ω,ω）of the two samples was investigated by antiresonant ring interferometric nonlinear spectroscopic (ARINS) technique using femtosecond modelocked Ti:sapphire laser in the spectral range of 720 nm - 820 nm. The observed spectral dispersion of γ has been explained in the framework of three-essential states model involving the ground state, a one-photon excited state and a two-photon excited state. The observed optical nonlinearity has been correlated with the electronic structure of the two samples. The energy of two-photon state, transition dipole moments and line width of the transitions have been estimated. Our studies show that the arrangement of polymer chains in polydiacetylene nanocrystals is more favorable for higher nonlinearity.

Highlights

There has been considerable scientific research on the development of efficient nonlinear optical materials with large third-order nonlinear susceptibility for photonic devices such as ultrafast optical switching, optical data storage, optical limiting etc
We have synthesized and characterized two different nanoassemblies of polydiacetylene (PDA), PDA nanovesicles and PDA nanocrystals, in order to study the influence of chain packing geometry of the two nanoassemblies on their third order nonlinear optical properties
The second molecular hyperpolarizability ;, of the two samples was investigated by antiresonant ring interferometric nonlinear spectroscopic (ARINS) technique using femtosecond modelocked Ti:sapphire laser in the spectral range of 720 nm - 820 nm

Summary

Introduction

There has been considerable scientific research on the development of efficient nonlinear optical materials with large third-order nonlinear susceptibility for photonic devices such as ultrafast optical switching, optical data storage, optical limiting etc. In this direction, conjugated polymers have been investigated extensively due to their inherently large ultrafast nonresonant nonlinearity and scope for the improvement by way of molecular engineering. The quasi-infinite conjugated bonding in PDA is responsible for many unique properties, such as charge transport [1], electronic absorp-. The bond alternation implies a periodic modulation of the electron charge density that produces an energy gap between a filled valence band and an empty conduction band. PDAs are considered to be quasi 1-D semiconductors

Methods

Results

Conclusion