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Influence of the cumulative effect on the excited state absorption spectra obtained with white-light continuum Z-scan

N. Neto, Samuel L. Oliveira, L. Misoguti, Cléber Renato Mendonça, Sérgio Carlos Zílio, Pablo José Gonçalves, Iouri E. Borissevitch

Published Jan 1, 2006• 1 citation
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Abstract

This work reports on the observation of excited state absorption (ESA) cumulative effect of a resonant nonlinear absorber when ESA spectra are obtained through the white-light continuum Z- scan technique. Besides, from the nonlinear transmittance achieved and simulation procedure, assuming a singlet three level system, the ESA cross-section spectrum can obtain if chirp rate and ground state absorption cross-sections are known.

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Two-step four-photon absorption

Bing Gu, Wei Ji

We report a theoretical investigation of effective four-photon absorption (4PA) process and propose a two-step 4PA model of three-photon- induced excited-state absorption (ESA). Based on three-level rate-equation theory, we find an analytical result for the effective 4PA coefficient that depends on the three-photon absorption (3PA) cross-section, excited-state photophysical properties, and laser pulse duration. We present the analytical theory of the z-dependent nonlinear transmission for straightforwardly yet unambiguously evaluating the 3PA and effective 4PA coefficients simultaneously.

Optics Express•Jun 24, 2008•22 citations

Excited-state nonlinear absorption and its application in photonic technology

Li Chun-Fei, Jinhai Si, Yang Miao +1 more

The main achievements in our research on the physical phenomena of the excited-state nonlinear absorption in a molecular system and its applications in photonic technology are described. In the first part of this paper, some energy-level models and rate-equations are used to explain various mechanisms of the excited-state nonlinear absorption under different conditions, such as reverse saturable absorption caused by the triplet and/or the singlet excited-state absorption; saturable absorption due to the first and/or the second singlet excited-state absorption; and the excited-state nonlinear absorption induced by two-photon absorption. The experimental results for metal-organic and C 60 materials irradiated by ps and ns laser pulses are consistent with the simulated curves of the transmittance versus fluences. In the second part, the applications of excited-state nonlinear absorption in photonic techniques including optical bistability, optical switching, optical limiting, optical modulation, optical logic and optical storage are introduced. The working principles of the photonic devices based on the excited-state nonlinear absorption are presented. The experimental characteristic curves are found in good agreement with the theoretical simulations for these devices.

Acta Physica Sinica (Overseas Edition)•Aug 1, 1995•5 citations

Excited-state nonlinear absorption in multi-energy-level molecular systems

Chunfei Li, Jinhai Si, Yang Miao +2 more

Three typical excited-state nonlinear absorption effects in molecular systems with weak ground-state absorption (at 532 nm) are experimentally demonstrated: (a) reverse saturable absorption (RSA) caused by strong triplet first-to-second excited-state absorption in a copper phthalocyanine solution with 15-ns laser pulses; (b) RSA caused by strong singlet first-to-second excited-state absorption in a ${\mathrm{C}}_{60}$ solution with 21-ps laser pulses; (c) the RSA-SA turnover caused by strong singlet first-to-second excited-state absorption and weak singlet second-to-third excited-state absorption in a metallo-porphyrin-like solution with 21-ps laser pulses. To simulate these excited-state nonlinear absorption behaviors we propose a general ten-level density-matrix model and its simplified models for the three cases. All simulations are in good agreement with the experimental results.

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Roman L. Kolesov, Elena Kuznetsova, Olga A. Kocharovskaya

Propagation of a short pulse in an amplifier with excited-state absorption (ESA) is considered. As is shown both analytically and numerically, if the stimulated emission cross section exceeds the ESA cross section, a steady-state pulse of a dissipative soliton type can exist. The parameters of the soliton, i.e., its width, amplitude, and velocity, are calculated. In the opposite case, amplification is inhibited unless ESA is suppressed using an additional control field applied to a transition adjacent to the ESA one [Phys. Rev. A 70, 043801 (2004)]. Propagation and amplification dynamics of a probe pulse in the presence of a strong control field is analyzed. In the limit of a continuous wave control field, a dissipative soliton solution forms, which is a pair of pulses similar to adiabatons. In the case of a pulsed control field, amplification of the probe pulse is transient. Conditions for optimal amplification are derived. Estimates of soliton parameters are made for rare-earth and transition-metal ion-activated laser crystals.

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Excited-state absorption of Tm3+-doped single crystals at photon-avalanche wavelengths

N. Garnier, R. Moncorgé, H. Manaa +3 more

Excited-state absorption (ESA) spectra calibrated in units of cross sections are reported in the case of Tm3+-doped YAG, YAP, and Y2O3 single crystals around wavelengths at which photon-avalanche absorptions were observed recently. The peak ESA cross sections are compared with those obtained theoretically by using the Judd–Ofelt approach.

Journal of Applied Physics•Apr 15, 1996•21 citations

Dynamics of two-photon-induced three-photon absorption in nanosecond, picosecond, and femtosecond regimes

Bing Gu, Kai Lou, Hui‐Tian Wang +1 more

Based on five-level rate-equation theory, we develop the laser-pulse-duration dependence of two-photon-absorption-induced singlet and triplet excited-state absorptions (ESAs). We present analytical expressions for the effective three-photon absorption coefficients caused by both singlet and triplet ESAs under the pulsed excitation on time scales from femtoseconds to microseconds. We demonstrate that the triplet ESA is predominant with longer laser pulses (microseconds to tens of nanoseconds) and that the resultant nonlinear absorption (NLA) can be adequately interpreted by a simplified four-level model. Under the excitation of picosecond laser pulses, generally speaking, the competition between singlet and triplet ESAs is observable. In this instance, the photodynamics of the system can be understood by a five-level model. In the femtosecond regime, however, a three-level model is validated in the prediction of NLA, because the triplet ESA becomes negligible.

Optics Letters•Jan 28, 2010•30 citations
This work reports on the observation of excited state absorption (ESA) cumulative effect of a resonant nonlinear absorber when ESA spectra are obtained through the white-light continuum Z- scan technique. Besides, from the nonlinear transmittance achieved and simulation procedure, assuming a singlet three level system, the ESA cross-section spectrum can obtain if chirp rate and ground state absorption cross-sections are known.
We report a theoretical investigation of effective four-photon absorption (4PA) process and propose a two-step 4PA model of three-photon- induced excited-state absorption (ESA). Based on three-level rate-equation theory, we find an analytical result for the effective 4PA coefficient that depends on the three-photon absorption (3PA) cross-section, excited-state photophysical properties, and laser pulse duration. We present the analytical theory of the z-dependent nonlinear transmission for straightforwardly yet unambiguously evaluating the 3PA and effective 4PA coefficients simultaneously.
The main achievements in our research on the physical phenomena of the excited-state nonlinear absorption in a molecular system and its applications in photonic technology are described. In the first part of this paper, some energy-level models and rate-equations are used to explain various mechanisms of the excited-state nonlinear absorption under different conditions, such as reverse saturable absorption caused by the triplet and/or the singlet excited-state absorption; saturable absorption due to the first and/or the second singlet excited-state absorption; and the excited-state nonlinear absorption induced by two-photon absorption. The experimental results for metal-organic and C 60 materials irradiated by ps and ns laser pulses are consistent with the simulated curves of the transmittance versus fluences. In the second part, the applications of excited-state nonlinear absorption in photonic techniques including optical bistability, optical switching, optical limiting, optical modulation, optical logic and optical storage are introduced. The working principles of the photonic devices based on the excited-state nonlinear absorption are presented. The experimental characteristic curves are found in good agreement with the theoretical simulations for these devices.
Three typical excited-state nonlinear absorption effects in molecular systems with weak ground-state absorption (at 532 nm) are experimentally demonstrated: (a) reverse saturable absorption (RSA) caused by strong triplet first-to-second excited-state absorption in a copper phthalocyanine solution with 15-ns laser pulses; (b) RSA caused by strong singlet first-to-second excited-state absorption in a C60{\mathrm{C}}_{60}C60​ solution with 21-ps laser pulses; (c) the RSA-SA turnover caused by strong singlet first-to-second excited-state absorption and weak singlet second-to-third excited-state absorption in a metallo-porphyrin-like solution with 21-ps laser pulses. To simulate these excited-state nonlinear absorption behaviors we propose a general ten-level density-matrix model and its simplified models for the three cases. All simulations are in good agreement with the experimental results.
Propagation of a short pulse in an amplifier with excited-state absorption (ESA) is considered. As is shown both analytically and numerically, if the stimulated emission cross section exceeds the ESA cross section, a steady-state pulse of a dissipative soliton type can exist. The parameters of the soliton, i.e., its width, amplitude, and velocity, are calculated. In the opposite case, amplification is inhibited unless ESA is suppressed using an additional control field applied to a transition adjacent to the ESA one [Phys. Rev. A 70, 043801 (2004)]. Propagation and amplification dynamics of a probe pulse in the presence of a strong control field is analyzed. In the limit of a continuous wave control field, a dissipative soliton solution forms, which is a pair of pulses similar to adiabatons. In the case of a pulsed control field, amplification of the probe pulse is transient. Conditions for optimal amplification are derived. Estimates of soliton parameters are made for rare-earth and transition-metal ion-activated laser crystals.
Based on five-level rate-equation theory, we develop the laser-pulse-duration dependence of two-photon-absorption-induced singlet and triplet excited-state absorptions (ESAs). We present analytical expressions for the effective three-photon absorption coefficients caused by both singlet and triplet ESAs under the pulsed excitation on time scales from femtoseconds to microseconds. We demonstrate that the triplet ESA is predominant with longer laser pulses (microseconds to tens of nanoseconds) and that the resultant nonlinear absorption (NLA) can be adequately interpreted by a simplified four-level model. Under the excitation of picosecond laser pulses, generally speaking, the competition between singlet and triplet ESAs is observable. In this instance, the photodynamics of the system can be understood by a five-level model. In the femtosecond regime, however, a three-level model is validated in the prediction of NLA, because the triplet ESA becomes negligible.