Download Varghese Abstract Talk in Graz

Optical Gain in Single Crystals of Organic
π-Conjugated Materials
Shinto Varghese
Madrid Institute for Advanced Studies (IMDEA) Nanoscience, Madrid, Spain
In quest of new materials for photonic applications, single crystals gained considerable
attention due to multitude of optical phenomenon observed as light interact and/or confine in the
crystalline environment. Understanding and ingenious utilization of these anisotropic optical
properties of inorganic crystals revolutionized the field of non-linear optics, especially in the field
of lasers. In recent years, the focus is shifted to crystalline organic materials as they offer the
possibility of tuning their intrinsic as well as macroscopic properties by modification of the
molecular backbone and by introducing substituents, which can modify the molecular packing and
thereby the habit. The high anisotropic refractive indices which leads to the preferential
propagation of electromagnetic radiation, resulting in excellent wave guiding and polarization
effects makes them potential candidates for organic solid state lasers.
b)
1.0
PL
ASE
0.8
3 nm
Emission Intensity (a. u.)
a)
LE
SRRS
0.6
0.4
c)
0.2
0.0
550
600
650
700
Wavelength (nm)
Figure 1. a) Optical gain narrowing, b) molecular packing diagram projected along the
crystallographic a-axis and c) three dimensional AFM topography image of DBADCS crystals.
Considerable progress has been made in the field of optically pumped lasers, however the lack
of understanding the state of aggregation and its effect on optical gain narrowing is still an open
question to be addressed. In this context we explored the optical gain narrowing in the single
crystals of few distyrylbenzene derivatives and correlate them to the intermolecular interactions
and the orientation of the molecules using different optical, XRD and AFM techniques. A typical
example of substituted dicyanodistyrylbenzene is shown in figure 1. Low temperature
measurements (1.3K), Raman experiments and theoretical calculations were also carried out to
have a deeper insight to the vibronic levels and the effect of intermolecular electronic interactions
in the molecular crystals. These factors of a few selected distyrylbenzene derivatives will be
discussed in the talk.
References.
(1) Stimulated Resonance Raman Scattering and Laser Oscillation in Distyrylbenzene Based Molecular
Crystals, Shinto Varghese, S.-J. Yoon, S. Casado, E. M. Calzado, P. G. Boj, M. A. Díaz-García, R. Resel, R.
Fischer, B. M. Milian, R. Wannemacher, S. Y. Park, J. Gierschner, Adv. Mater. 2012 (In Press).