Authors:	B. De Geyter, P. Geiregat, Y. Gao, S. ten Cate, A.J. Houtepen, J. M. Schins, D. Van Thourhout, L. D.A. Siebbeles, Z. Hens
Title:	Broadband and picosecond intraband absorption in lead based colloidal quantum dots
Format:	International Conference Proceedings
Publication date:	7/2012
Journal/Conference/Book:	14th International Conference on Transparant Optical Networks (ICTON 2012) (invited)
Volume(Issue):	p.paper Th.A5.4
Location:	Coventry, United Kingdom
DOI:	10.1109/icton.2012.6254469
Citations:	Look up on Google Scholar
Download:	(372KB)

Abstract

Using femtosecond transient absorption spectroscopy we demonstrate that lead chalcogenide nanocrystals show
efficient, photoinduced absorption (PA) in a broad wavelength range starting just below the bandgap.
The time-dependent decay of the PA signal correlates well with the recovery of the band gap absorption.
Therefore, the same carriers are involved, which decay with the typical Auger recombination rate in these
nanocrystals. Based on this, we assign this PA signal to intraband absorption, i.e., the excitation of photogenerated
carriers from the bottom of the conduction band or the top of the valence band to higher energy levels in the
conduction and valence band continuum. This broadband response in the commercially interesting near to
mid-infrared range is very relevant for ultra-high speed all optical signal processing.