Pitchfork Bifurcation and Zharov Splitting in Nonlinear Mid-infrared Photothermal Spectroscopy in a liquid crystal using a Quantum Cascade Laser

• DOI: 10.48550/arxiv.1310.0123
• Publication Date: 2013-01-01
• Authors: Alket Mërtiri; Hatice Altug; Mineui Hong; P. Mehta; Jerome Mertz; L. D. Ziegler; Shyamsunder Erram...
• Keywords: Pitchfork bifurcation; Quantum cascade laser; Photothermal spectroscopy

We report on the mid-infrared nonlinear photothermal spectrum of neat liquid crystal 4-Octyl-4'-Cyanobiphenyl (8CB) using a tunable Quantum Cascade Laser (QCL). The nonequilibrium steady state characterized by infrared response undergoes supercritical pitchfork bifurcation. bifurcation, observed in heterodyne two-color pump-probe detection, leads to ultrasharp spectra similar those reported visible region. A systematic study peak splitting as function absorbed power shows bifurcation has critical exponent 0.5. surprising observation an apparently universal is explained simple model reminiscent mean field theory. Apart from intrinsic interest for studies, methods lead dramatic narrowing spectral lines, giving rise potential new contrast mechanism rapidly emerging microspectroscopy QCLs.