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Theoretical analysis on two-photon absorption spectroscopy in a confined four-level atomic system

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Chinese Optics Letters 2009年第7期7卷 640-642页

作者：李院院白晋涛李莉张彦鹏侯洵 Institute of Photonics and Photonic Technology Key Laboratory of Photoelectronic Technology of Sha~nxi Province Northwest University Xi'an 710069 China Department of Physics Xi'an University of Arts and Science Xi'an 710065 China Key Laboratory for Physical Electronics and Devices of the Ministry of Education Xi'an Jiaotong University Xi'an 710049 China State Key Laboratory of Transient Optics and Technology Xi'an Institute of Optics and Precision Mechanics Chinese Academy of Sciences Xi'an 710068 China

We investigate theoretically two-photon absorption spectroscopy modified by a control field in a confined Y-type four-level system. Dicke-narrowing effect occurs both in two-photon absorption lines and the dips of transparency against two-photon absorption due to enhanced contribution of slow atoms. We also find that the suppression and the enhancement of two-photon absorption can be modified by changing the strength of the control field and the detuning of three laser fields. This control of two-photon absorption may have some applications in information processing and optical devices.

关键词： Absorption Atomic spectroscopy Data processing Light absorption luminescence of organic solids Multiphoton processes Optical instruments Optical materials Photons

Investigation of transient two-photon excited fluorescence in biological tissue

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Chinese Optics Letters 2012年第5期10卷 44-46页

作者：邱怡申陈恩果李高明李晖 Key Laboratory of OptoElectronic Science and Technology for Medicine Ministry of Education Fujian Provincial Key Laboratory for Photonics TechnologyFujian Normal University Department of Optical Engineering Zhejiang University

The fluorescence power from biological tissue excited by a femtosecond laser pulse compared with excitation power does not appear to obey a simple quadratic relationship given by the steady non-linear theory. A more reliable analysis is developed based on transient two-photon absorption because the response time of two-photon absorption is longer than the width of a femtosecond pulse. Good agreement is obtained between the theoretical analysis and the experimental results of fluorescence power versus excitation power. This letter offers potential value to non-linear optics in biological tissues.

关键词： Electromagnetic pulse Fluorescence Light absorption luminescence of organic solids Two photon processes Ultrafast lasers Ultrashort pulses

Nonlinear two-photon absorption properties induced by femtosecond laser with the films of two novel anthracene derivatives

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Chinese Optics Letters 2012年第10期10卷 49-52页

作者：李亮吴谊群王阳 Shanghai Institute of Optics and Fine Mechanics Chinese Academy of Sciences Key Lab of Functional Inorganic Material Chemistry(Heilongjiang University) Ministry of Education

Two novel anthracene derivatives containing 4-vinylpyridine （FPEA） and 2-vinylpyridine （TPEA） poly（methyl methacrylate） films are prepared on quartz glass substrates. Their nonlinear absorption properties are investigated by using a 120-fs, 800-nm Ti：sapphire femtosecond pulsed laser operating at a 1-kHz repetition rate. The unique nonlinear absorption properties of these new compounds are observed by utilizing a Z-scan system. These two-photon absorption （TPA） properties are proven by the two-photon fluorescence excited at 800 nm. The FPEA and TPEA films have nonlinear TPA coefficients of 0.164 and 0.148 cm/GW and the TPA cross sections of 3.345 × 10^-48 and 3.081 × 10^-48 cm4 ·s/photon, respectively. The influence of the chemical structures on the nonlinear TPA properties of the compounds is also discussed. The highly nonlinear TPA activities of the films implied that the new anthracene derivatives are suitable materials with promising applications in super-high-density three-dimensional data storage and nano- or microstructure fabrication.

关键词： Anthracene Esters Lasers Light absorption luminescence of organic solids Quartz Sapphire Substrates Two photon processes

Coherent control of two-photon absorption of Pr^(3+) ion by shaped ultrashort laser pulses

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Chinese Optics Letters 2013年第4期11卷 73-76页

作者：程文静张诗按贾天卿马婧冯东海孙真荣 State Key Laboratory of Precision Spectroscopy Department of Physics East China Normal University

Enhancing the photoluminescence and depressing the background emission are important problems in rare earth ion-doped materials. In this letter, the two-photon absorption （TPA） probability in a Pr3＋ ion system is enhanced by a factor of 12.3 by a π-phase step scanning of ultrashort laser pulses. This level is significantly higher than that achieved by a transform-limit pulse. However, the laser intensity of shaped pulse is reduced to 37% of the initial transform-limited pulse. In this method, the TPA probability can also be reduced to 58%. Furthermore, the el＇feet of the shift of the intermediate energy level and the bandwidth of final states on TPA probability is discussed.

关键词： Light absorption luminescence of organic solids Metal ions Probability Two photon processes