Pulse duration and wavelength stability measurements of a midinfrared free-electron laser

Qin, Yu; Zen, Heishun; Wang, Xiaolong; Kii, Toshiteru; Nakajima, Takashi; Ohgaki, Hideaki

doi:10.1364/ol.38.001068

Cited by 15 publications

(6 citation statements)

References 9 publications

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“…The pulse width of the micropulse of the was 0.6 ps and the pulse width of the probe light was 7.5 ps. 24,32,33) The pulse width of the FEL is ignored in the estimation of the phonon lifetime of the T 2g mode because the pulse width of the micropulse is much shorter than the lifetime of the phonon. It is difficult to make a strict estimation of the phonon lifetime because the time-width of the probe laser occupies a non-negligible part of the signal.…”

Section: Resultsmentioning

confidence: 99%

Mode-selective excitation of an infrared-inactive phonon mode in diamond using mid-infrared free electron laser

Akasegawa¹,

Zen²,

Hachiya³

et al. 2021

Jpn. J. Appl. Phys.

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The direct demonstration was achieved for the selective excitation of the infrared-inactive T 2g mode (1332 cm−1) in the single crystal diamond by two-photon excitation using a mid-infrared free electron laser (MIR-FEL) as pump light. Anti-Stokes Raman scattering light at around −1339 cm−1 was observed with cooling at 5 K only when MIR-FEL whose wavenumber was that of one-half of the T 2g mode, 666 cm−1, was irradiated. Update of the probe system, i.e. the introduction of the image intensified CCD, made it possible to probe the scattering signal with a lower laser power density compared to our previous study, and it relieved the surface damage on the sample accompanied by laser irradiations which induced a red-shift and a band broadening of the mode in the previous study.

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Section: Resultsmentioning

confidence: 99%

Mode-selective excitation of an infrared-inactive phonon mode in diamond using mid-infrared free electron laser

Akasegawa¹,

Zen²,

Hachiya³

et al. 2021

Jpn. J. Appl. Phys.

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“…LIPSS formation. We used Ti:Sapphire laser (wavelength λ: 800 nm, pulse duration: 100 fs, repetition frequency: 1 kHz) and MIR-FEL 42,43 (λ: 11.4 μm, micro-pulse duration: 500 fs, repetition frequency of micropulses: 2856 MHz, macro-pulse duration: 2 μs, repetition frequency of macro-pulses: 2 Hz) for the formation of LIPSS. Si (100) substrates were used as irradiated materials.…”

Section: Methodsmentioning

confidence: 99%

Crystallinity in periodic nanostructure surface on Si substrates induced by near- and mid-infrared femtosecond laser irradiation

Miyagawa

Kamibayashi

Nakamura

et al. 2022

Sci Rep

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Laser-induced periodic surface structure (LIPSS), which has a period smaller than the laser wavelength, is expected to become a potential technique for fine surface processing. We report the microscopic and macroscopic observations of the crystallinity of LIPSSs, where the characteristics such as defects generation and residual strain were analyzed, respectively. The LIPSSs were formed on a Si substrate using two different femtosecond pulses from Ti:Sapphire laser with near-infrared wavelength (0.8 μm) and free-electron laser (FEL) with mid-infrared wavelength (11.4 μm). The photon energies of the former and latter lasers used here are higher and lower than the Si bandgap energies, respectively. These LIPSSs exhibit different crystalline states, where LIPSS induced by Ti:Sapphire laser show residual strain while having a stable crystallinity; in contrast, FEL-LIPSS generates defects without residual strain. This multiple analysis (microscopic and macroscopic observations) provides such previously-unknown structural characteristics with high spatial resolution. To obtain LIPSS with suitable properties and characteristics based on each application it is paramount to identify the laser sources that can achieve such properties. Therefore, identifying the structural information of the LIPSS generated by each specific laser is of great importance.

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“…As explained in the previous report, 17) the pump laser, KU-FEL, has a specific pulse structure with two types of pulses: macro-and micropulses with durations of 2 µs (FWHM) and 0.6 ps (FWHM) at 12 µm, respectively. 31,32) The reported lifetimes of the phonons in GaN exceed 2 ps, 19) and the pulse width of the micropulse of KU-FEL is shorter than the phonon relaxation time. Therefore, the MIR-FEL irradiation induces modeselective phonon excitation via a photoexcitation effect.…”

Section: Introductionmentioning

confidence: 99%

Mode-selective phonon excitation in gallium nitride using mid-infrared free-electron laser

Kagaya

Yoshida

Zen

et al. 2017

Jpn. J. Appl. Phys.

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The single-phonon mode was selectively excited in a solid-state sample. A mid-infrared free-electron laser, which was tuned to the target phonon mode, was irradiated onto a crystal cooled to a cryogenic temperature, where modes other than the intended excitation were suppressed. An A 1 (LO) vibrational mode excitation on GaN(0001) face was demonstrated. Anti-Stokes Raman scattering was used to observe the excited vibrational mode, and the appearance and disappearance of the scattering band at the target wavenumber were confirmed to correspond to on and off switching of the pump free-electron laser and were fixed to the sample vibrational mode. The sum-frequency generation signals of the pump and probe lasers overlapped the Raman signals and followed the wavenumber shift of the pump laser.

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Pulse duration and wavelength stability measurements of a midinfrared free-electron laser

Cited by 15 publications

References 9 publications

Mode-selective excitation of an infrared-inactive phonon mode in diamond using mid-infrared free electron laser

Mode-selective excitation of an infrared-inactive phonon mode in diamond using mid-infrared free electron laser

Crystallinity in periodic nanostructure surface on Si substrates induced by near- and mid-infrared femtosecond laser irradiation

Mode-selective phonon excitation in gallium nitride using mid-infrared free-electron laser

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