Origin of light scattering in dye doped polymeric waveguides and the dependence of excitation geometry on coherent random lasing
- 16 March 2020
- journal article
- research article
- Published by IOP Publishing in Journal of Physics D: Applied Physics
- Vol. 53 (24), 245104
- https://doi.org/10.1088/1361-6463/ab8039
Abstract
We present an experimental investigation on the origin of coherent random laser (RL) emission from 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminos-tyryl)-4H-pyran (DCM) doped polyvinyl alcohol (PVA) thin film (DCM-PVA) planar waveguide using various characterization techniques. Absorption and fluorescence spectra of the DCM-PVA thin film confirm the presence of aggregates at dye concentrations greater than 0.08 wt. %. Time correlated single photon counting measurements were performed to confirm the presence of dye aggregates in the PVA matrix. X-ray diffraction studies reveal the semi-crystalline nature of the DCM-PVA thin film. The optical gain coefficient was determined by variable stripe length method under 532 nm pulsed laser excitation and was found to be 2.1 cm-1 using the one-dimensional amplifier model for the 0.08 wt. % thin film. The RL emission of the planar waveguide depends on the geometry of the excitation spot. The emission spectrum consists of randomly positioned narrow spectral lines under stripe excitation geometry whereas, a smooth spectrum lacking the narrow peaks is observed under circular spot excitation, both above the lasing thresholds. The origin of weak scattering in DCM-PVA waveguide is attributed to the formation of dye aggregates and inhomogeneities created by the semi-crystalline nature of the film. The RL threshold decreases with an increase of the stripe length due to weak waveguiding in the planar film under stripe excitation. The high optical gain and low lasing thresholds attainable in DCM-PVA waveguides make them a promising candidate for the fabrication of polymer waveguide based photonic devices.Keywords
Funding Information
- Science and Engineering Research Board (DST/TDT/AMT/2017/050)
This publication has 42 references indexed in Scilit:
- On the coherent modes of ultranarrowband random lasers with nonresonant feedbackApplied Optics, 2011
- On the characteristic lengths in the variable stripe length method for optical gain measurementsJournal of the Optical Society of America B, 2010
- Naturally occurring resonators in random lasing of π-conjugated polymer filmsNature Physics, 2010
- Studies of random laser action in π-conjugated polymersJournal of Optics, 2010
- Amplified spontaneous emission and optical gain measurements from pyrromethene 567 ?? doped polymer waveguides and quasi-waveguidesOptics Express, 2008
- Effect of dye doping in poly(vinyl alcohol) waveguidesJournal of Modern Optics, 2005
- m-lines technique: prism coupling measurement and discussion of accuracy for homogeneous waveguidesJournal of Optics A: Pure and Applied Optics, 2000
- Mirrorless Lasing from Mesostructured Waveguides Patterned by Soft LithographyScience, 2000
- Amplified spontaneous emission from photopumped films of a conjugated polymerPhysical Review B, 1998
- Low loss channel waveguides in polymersJournal of Lightwave Technology, 1989