Optical nonlinearity in lead sulfide microtowers

• Published in: Journal of physics. D, Applied physics Vol. 43; no. 38; p. 385402
• Main Authors: Tamilselvan, V, Sridharan, Kishore, Narasimha Rao, K, Philip, Reji
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 29.09.2010; Institute of Physics
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Excitation; Femtosecond; Lead sulfides; Materials science; Nanocomposites; Nanocrystalline materials; Nanoscale materials and structures: fabrication and characterization; Nanostructure; Nonlinearity; Optical constants: refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of bulk materials and thin films; Other topics in nanoscale materials and structures; Physics; Quantum confinement; Tungsten; Quantum confinement; Semiconductor materials; Lead sulfide; Aperture; Absorption coefficients; Physical properties; Z scan; Laser pulse; Optical properties; Apertures; Bulk properties; Two-photon processes; Non linear effect; Nanostructured materials; Nonlinear optics; Nanocrystal
• ISSN: 0022-3727; 1361-6463
• DOI: 10.1088/0022-3727/43/38/385402

Lead sulfide (PbS) microtowers on silicon substrates, having the physical properties of bulk PbS, have been synthesized. Optical nonlinearity studies using the open aperture z-scan technique employing 5 ns and 100 fs laser pulses reveal effective two-photon type absorption. For nanosecond excitation the nonlinear absorption coefficients (β eff ) are in the order of 10 −11  m W −1 , two orders of magnitude less than the values reported for quantum confined PbS nanocrystals. For femtosecond excitation β eff is of the order of 10 −14  m W −1 . These results obtained in bulk PbS experimentally confirm the importance of quantum confinement in the enhancement of optical nonlinearities in semiconductor materials.