Can graph reveal optical absorption? – Interrogation through thermal lensing

Abstract

The paper is the first report delineating the potential of the graph in displaying optical absorption exemplified through the interrogation of thermal lensing. The present study employs the single beam (SB) and dual beam (DB) thermal lens (TL) configurations. Having understood the optical absorption by acetone, ethylene glycol, chlorophyll extract and carbon nanoparticle incorporated chlorophyll extract from the absorption spectrum, the TL signals from the samples are recorded in a digital storage oscilloscope. Complex networks are constructed from the TL time-series signals of SB and DB configurations. The analysis of the graph features shows clear distinction with the increase of optical absorption in terms of number of edges, network density, transitivity, network diameter, average path length, number of components and graph entropy. The difference in the optical absorption information carried by DBTL and SBTL signals is also brought out through the topology of the graph and its features. The number of disconnected nodes or the absence of edges in the graph can also be regarded as a criterion for selecting a suitable probe for the DBTL setup. The study also suggests the application of graph features in trace detection, which is exemplified through the graph of carbon nanoparticle incorporated chlorophyll.