
Journal of Quantum Informatio n Science, 2011, 1, 69-72
doi:10.4236/jqis.2011.12010 Published Online September 2011 (http://www.SciRP.org/journal/jqis)
Copyright © 2011 SciRes. JQIS
Third Order Optical Nonlinearities and Spectral
Characteristics of Methylene Blue
Velloli Sindhu Sukumaran1*, Alkondan Ramalingam2
1Central Institute of Plastics and Engineering Technology Guindy, Chennai, India
2Centre for Laser Technology, Department of Physics , Anna University, Chennai, India
E-mail: *sindhusukumaran@yahoo.co.in
Received May 24, 2011; revised July 6, 2011; accepted July 26, 2011
Abstract
We have investigated third order nonlinear optical properties and spectral characteristics of methylene blue
dye in both polymer and liquid mixtures. The spectral characteristics of the dye is studied by recording the
absorption and fluorescence spectra of the dye doped in poly(methylmethacrylate) modified with additive
n-butyl acetate(nBA) and the dye in MMA and nBA (liquid mixture). The spectral results of the dye doped
polymer rod are compared with dye in liquid Mixture. The nonlinear measurements of the dye in liquid and
polymer medium were performed using CW He-Ne laser of wavelength 632.8 nm by employing z-scan tech-
nique. The dye methylene blue showed a negative nonlinear refractive index.
Keywords: Methylene Blue, Polymer, Solid Dye Laser, nBA, MMA, Spectral Characteristics, Nonlinear
Refractive Index, Polymer Thin Film
1. Introduction
The protection of sensitive optical equipment has been
the focus of much attention in recent times. Of great im-
portance is the protection of human eye from potentially
harmful intense beams. A large number of compounds
have been synthesized to realize nonlinear susceptibili-
ties far larger than the inorganic optical material [1]. In
this paper we report the synthesis, characterization and
nonlinear optical properties of methylene blue dye doped
polymer and compare it with dye doped monomer.
Nonlinear optical properties of polymer solution was
studied by means of a z-scan set-up. Nonlinear optical
effects can be employed for the design and performance
of optical limiter. It has been showed that optical limiting
can be used for the protection of eyes and sensors from
intense lasers [2].
Solid matrix used as lasers get rid of many of the
common problems associated with static or flowing liq-
uid systems. The most frequently used polymeric mate-
rial is polymethylmethacrylate (PMMA) [3]. Review of
literature showed most of the work on dye-doped polymers
was done with rhodamine dyes [4] and pyromethane
dyes [5]. Some work was reported on coumarin dyes [3]
and on dye IR140 [6].
In this paper, the fabrication of dye methylene blue
doped polymer rods and films, its spectral parameters
and the study of nonlinear refractive index under the He-
Ne laser excitation are reported. The properties of the
dyes in liquid medium are compared with that in the
solid matrix.
2. Experimental Procedure
2.1. Synthesis of Dye-Doped Polymer Rods and
thin Films
Methylene blue, a phenothiazine dye, supplied by Exci-
ton, USA, is chosen for the study. The molecular struc-
ture of the dye is shown in Figure 1. Thin layer choro-
matography (TLC) test confirms the absence of any im-
purities in the dye. Methyl methacrylate (MMA) is used
as a monomer for synthesizing dye doped polymer film.
Initial MMA compositions are cleared of foreign inclu-
sions. Spectroscopic grade n-butyl acetate (nBA) is used
Figure 1. Molecular Structure of Methylene blue.