Three-Photon Absorption Spectra and Bandgap Scaling In Direct-Gap Semiconductors

This paper presents three-photon absorption (3PA) measurement results for nine direct-gap semiconductors, including full 3PA spectra for ZnSe, ZnS, and GaAs. These results, along with our theory of 3PA using an eight-band Kane model (four bands with double spin degeneracy), help to explain the significant disagreements between experiments and theory in the literature to date. 3PA in the eight-band model exhibits quantum interference between the various possible pathways that is not observed in previous two-band theories. We present measurements of degenerate 3PA coefficients in InSb, GaAs, CdTe, CdSe, ZnTe, CdS, ZnSe, ZnO, and ZnS. We examine bandgap, Eg, scaling using -band tunneling and perturbation theories that show agreement with the predicted Eg−7 dependence; however, for those semiconductors for which we measured full 3PA spectra, we observe significant discrepancies with both two-band theories. On the other hand, our eight-band model shows excellent agreement with the spectral data. We then use our eight-band theory to predict the 3PA spectra for 15 different semiconductors in their zinc-blende form. These results allow prediction and interpretation of the 3PA coefficients for various narrow to wide bandgap semiconductors

Temporal And Spectral Nonlinear Absorption Characterization Of A Hybrid Porphyrin-Squaraine-Porphyrin Macromolecule

The nonlinear absorption mechanisms of a porphyrin-squaraine-porphyrin macromolecule have been studied with femto/pico/nanosecond pulsewidths. Two-photon absorption of the macromolecule is ̃10× larger than the constituents and is explained by intra-molecular charge transfer. © 2008 Optical Society of America

Three-Photon Absorption Of Gaas And Other Semiconductors

A 4-band Kane model gives good agreement for three-photon absorption spectra of GaAs and other semiconductors, showing quantum interference between pathways; however, 2- band scaling rules showing Eg-7 scaling with bandgap give useful estimates. © OSA 2013

Temporal and spectral nonlinear absorption characterization of a hybrid porphyrin-squaraine-porphyrin macromolecule

The nonlinear absorption mechanisms of a porphyrin-squaraine-porphyrin macromolecule have been studied with femto/pico/nanosecond pulsewidths. Two-photon absorption of the macromolecule is ̃10× larger than the constituents and is explained by intra-molecular charge transfer. © 2008 Optical Society of America

Temporal and spectral nonlinear absorption characterization of a hybrid porphyrin-squaraine-porphyrin macromolecule

The nonlinear absorption mechanisms of a porphyrin-squaraine-porphyrin macromolecule have been studied with femto/pico/nanosecond pulsewidths. Two-photon absorption of the macromolecule is ̃10× larger than the constituents and is explained by intra-molecular charge transfer. © 2008 Optical Society of America

Nonlinear absorption spectroscopy of a bis(Porphyrin)-substituted squaraine

The nonlinear absorption mechanisms of a bis(porphyrin)-substituted squaraine have been studied with femtosecond, picosecond, and nanosecond pulsewidths. The two-photon absorption is ~10× larger than those of the constituents and is explained by intra-molecular charge transfer. © 2009 Optical Society of America

Linear and nonlinear spectroscopy of a porphyrin-squaraine-porphyrin conjugated system.

The linear and nonlinear absorption properties of a squaraine-bridged porphyrin dimer (POR-SQU-POR) are investigated using femto-, pico-, and nanosecond pulses to understand intramolecular processes, obtain molecular optical parameters, and perform modeling of the excited-state dynamics. The optical behavior of POR-SQU-POR is compared with its separate porphyrin and squaraine constituent moieties. Linear spectroscopic studies include absorption, fluorescence, excitation and emission anisotropy, and quantum yield measurements. Nonlinear spectroscopic studies are performed across a wide range (approximately 150 fs, approximately 25 ps, and approximately 5 ns) of pulsewidths and include two-photon absorption (2PA), single and double pump-probe, and Z-scan measurements with detailed analysis of excited-state absorption induced by both one- and two-photon absorption processes. The 2PA from the constituent moieties shows relatively small 2PA cross sections; below 10 GM (1 GM = 1 x 10(-50) cm4 s/photon) for the porphyrin constituent and below 100 GM for the squaraine constituent except near their one-photon resonances. In stark contrast, the composite POR-SQU-POR molecule shows 2PA cross sections greater than 10(3) GM over most of the spectral range from 850 to 1600 nm (the minimum value being 780 GM at 1600 nm). The maximum value is approximately 11,000 GM near the Nd:YAG laser wavelength of 1064 nm. This broad spectral range of large 2PA cross sections is unprecedented in any other molecular system and can be explained by intramolecular charge transfer. A theoretical quantum-chemical analysis in combination with different experimental techniques allows insight into the energy-level structure and origin of the nonlinear absorption behavior of POR-SQU-POR

Nonlinear absorption spectroscopy of a bis(Porphyrin)-substituted squaraine

The nonlinear absorption mechanisms of a bis(porphyrin)-substituted squaraine have been studied with femtosecond, picosecond, and nanosecond pulsewidths. The two-photon absorption is ~10× larger than those of the constituents and is explained by intra-molecular charge transfer. © 2009 Optical Society of America

Synthesis and two-photon spectrum of a bis(porphyrin)-substituted squaraine.

A chromophore in which zinc porphyrin donors are linked through their meso positions by ethynyl bridges to a bis(indolinylidenemethyl) squaraine core has been synthesized using Sonogashira coupling. The chromophore exhibits a two-photon absorption spectrum characterized by a peak cross section of 11,000 GM and, more unusually, also exhibits a large cross section of >780 GM over a photon-wavelength window 750 nm in width