DocumentCode :
1822592
Title :
Femtosecond time-resolved photodynamical study on Ag-O-Ba thin film
Author :
Danling Wang ; Xiucheng Feng ; Hong Yang ; Zongju Xia ; Qihuang Gong
Author_Institution :
Dept. of Phys., Peking Univ., Beijing, China
fYear :
2001
fDate :
11-11 May 2001
Firstpage :
212
Lastpage :
213
Abstract :
Summary form only given. The ultrafast relaxation of the Ag-O-Ba composite film was investigated by using a pump supercontinuum-probe technique (PSCP). The measurement was performed using a Ti:sapphire chirped-pulse amplification (CPA) laser system. Its output pulse was 800 nm, 120 fs, 10 mJ. The pulse was split into two beams. One beam, after passing a variable delay line, was used for optical pumping. The other beam was focused into distilled water to generate supercontinuum probe pulse wavelengths which ranged from 400 nm to 1000 nm. The Ag-O-Ba thin film consisted of silver nanoparticles embedded in a BaO semiconductor matrix which was considered as a new type of photoemissive material. When the Ag-O-Ba thin film was pumped by laser pulses of 800 nm wavelength, only free electron (intraband transition) absorption occurred through multiphoton absorption because the excitation wavelength is far from the surface plasma resonance (SPR) at 400 nm and the energy level of silver nanoparticles above the Fermi energy level is quasi-continuum. Meanwhile, the size of metal nanoparticles was around 40 nm in our experiment. It is convenient to describe the photodynamics in nanoparticles using a small solid approach. Thus the quantum confinement can not modify the band structure. So the maximal probability for electron transition should be the state gap energy between the occupied state density peak L/sub 2/ above the Fermi level and the unoccupied state density peak X/sub 4/ below the Fermi level according to Berglang´s (1994) energy structure of silver. The time-resolved transient transmissivity induced by multiphoton absorption were investigated at different probe wavelengths. The decay time of the Ag-O-Ba thin film changes from 0.67 ps to 4 ps. A typical result is shown at 700 nm probe wavelength. The transmission difference at zero delay caused by the pump was also measured. The maximal difference at 700 nm indicated that the unoccupied state density peak X/sub 4/ is 1- 47eV above the Fermi level.
Keywords :
Fermi level; barium compounds; infrared spectra; light transmission; multiphoton spectra; nanostructured materials; optical pumping; semiconductor materials; semiconductor thin films; silver; time resolved spectra; visible spectra; 0.67 to 4 ps; 10 mJ; 120 fs; 40 nm; 400 to 1000 nm; 700 nm; 800 nm; Ag-BaO; Ag-O-Ba; Ag-O-Ba composite film; Ag-O-Ba thin film; BaO semiconductor matrix; Fermi energy level; Ti:sapphire chirped-pulse amplification laser system; band structure; decay time; distilled water; electron transition; excitation wavelength; femtosecond time-resolved photodynamical study; free electron absorption; intraband transition; laser pulse pumping; maximal probability; metal nanoparticle size; multiphoton absorption; occupied state density peak; optical pumping; output pulse; photoemissive material; pump supercontinuum-probe technique; quantum confinement; quasicontinuum energy level; silver nanoparticles; small solid approach; state gap energy; supercontinuum probe pulse wavelengths; surface plasma resonance; time-resolved transient transmissivity; transmission difference; ultrafast relaxation; unoccupied state density peak; variable delay line; zero delay; Absorption; Free electron lasers; Laser beams; Laser excitation; Nanoparticles; Optical pulses; Probes; Pulse amplifiers; Silver; Transistors;
fLanguage :
English
Publisher :
ieee
Conference_Titel :
Quantum Electronics and Laser Science Conference, 2001. QELS '01. Technical Digest. Summaries of Papers Presented at the
Conference_Location :
Baltimore, MD, USA
Print_ISBN :
1-55752-663-X
Type :
conf
DOI :
10.1109/QELS.2001.962084
Filename :
962084
Link To Document :
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