Laser hyperacoustic spectroscopy of single crystal germanium

Chigarev, N. V.; Parashchuk, D. Yu.; Pan, Yu; Gusev, Vitalyi

doi:10.1134/1.1469160

Cited by 7 publications

(4 citation statements)

References 23 publications

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“…Values as large as 100 000 cm/s were found not to have a significant effect on the simulations. The ambipolar diffusivity is taken as D = 65 cm 2 /s . Modeling of hot carrier diffusion indicates that 50% of the carriers excited at t = 0 have diffused out of the region probed on the 3.5 ps time scale of the pump−probe experiment, Figure .…”

Section: Resultsmentioning

confidence: 99%

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Ultrafast Time-Evolution of the Nonlinear Susceptibility of Hot Carriers at the Ge(111)−GeO₂ Interface As Probed by SHG

2004

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Time-resolved second harmonic generation (SHG) was used to study hot carrier dynamics at the Ge(111)-GeO 2 interface on the femtosecond time scale. A linear dependence of the change in SHG on the pump power was observed for the carrier density range of 3 × 10 18 to 2.2 × 10 19 cm -3 . The ratio of the hot carrier to valence band nonlinear susceptibilities was determined to be 924 ( 40 in the Ge(111)-GeO 2 system, an order of magnitude greater than for Si(111)-SiO 2 . The dynamic SHG response is attributed to a change in the nonlinear susceptibility of the excited carriers and the diffusion of excited carriers away from the interface. The time to reach SHG steady-state response (410 ( 70 fs) appears independent of carrier density in the range explored. The time evolution of the hot carrier nonlinear susceptibilities for Ge(111)-GeO 2 at the 211 azimuth was extracted and shown to follow a double exponential evolution with time constants of 170 ( 50 fs and 3500 ( 1450 fs, similar to the literature values for bulk scattering times of electrons out of the Γ valley (∼100 fs) and into the L valley (∼3.7 ps).

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Section: Resultsmentioning

confidence: 99%

“…The ambipolar diffusivity is taken as D ) 65 cm 2 /s. 26 Modeling of hot carrier diffusion indicates that 50% of the carriers excited Fractional bleach vs pump power. χ /(2) /χ (2) ) 924 ( 40 in the Ge(111)-GeO2 system data was taken with a p-polarized pump and s-polarized probe.…”

Section: Methodsmentioning

confidence: 99%

Ultrafast Time-Evolution of the Nonlinear Susceptibility of Hot Carriers at the Ge(111)−GeO₂ Interface As Probed by SHG

2004

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“…The damping coefficient of FS is much lower, than that of the grease, but the initial pressure transients in the silica sample are much steeper ͑subnanosec-ond widths͒, resulting in much stronger damping of their high-frequency components. [20][21][22][23] Finally, geometric factors such as relative positions and effective sizes of the ultrasonic source and the transducer are important for diffraction effects. 24 In this particular ultrasonic far-field study we have paid attention to variations of the ultrasonic pulse amplitude, width, and waveform shape with the laser pulse energy in order to retrieve details such as EHP density and its spatiotemporal dynamics.…”

Section: Samples and Experimental Setupmentioning

confidence: 99%

Optical and ultrasonic signatures of femtosecond pulse filamentation in fused silica

Mizeikis

Juodkazis

Balčiūnas

et al. 2009

Journal of Applied Physics

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Millimeter-long filaments and accompanying luminous plasma and defect channels created in fused silica by single, moderately focused femtosecond laser pulses with supercritical powers were probed in situ using optical imaging and contact ultrasonic techniques. Above the threshold pulse energy Eopt=5 μJ corresponding to a few megawatt power, the pulses collapse due to self-focusing and the nonlinear focus moves upstream with increasing pulse energy. Behind the focus, elongated, gradually narrowing awl-shaped channels of electron-hole plasma and luminescent defects are produced. In the channels, whose dimensions generally depend on the pulse energy, supercontinuum emission propagating downstream the channels occurs, although its observation requires elevated pulse energies above 25 μJ in order to compensate energy dissipation in the channels. Ultrasonic side-view imaging of the channels, conducted from a few millimeters distance, reveals predominantly compressive pressure transients. The compressive signals are observed above the same threshold pulse energy Eopt, and their amplitude increases linearly with the laser pulse energy, simultaneously exhibiting significant temporal broadening of the corresponding pulsewidths, reflecting square root dependence of the channel length and sublinear (∝E3/4) dependence of the source pressure on the pulse energy. Altogether, these optical and ultrasonic studies demonstrate filamentary pulse propagation with considerable dissipation (∼10 cm−1) in the awl-shaped subcritical plasma channels rich with generated point defects and optical damage sites.

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“…Intense photoexcitation of semiconducting materials produces coherent acoustic phonons, the nature of which renders them amenable to study with ultrafast X-ray and electron scattering [1][2][3]. For example, coherent acoustic-phonon wavetrains manifest as traveling contrast bands in ultrafast electron microscopy (UEM) image series.…”

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Quantifying Transient Strain and Energy of Coherent Acoustic Phonons with UEM Imaging

Cremons

Flannigan

2020

Microsc Microanal

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Laser hyperacoustic spectroscopy of single crystal germanium

Cited by 7 publications

References 23 publications

Ultrafast Time-Evolution of the Nonlinear Susceptibility of Hot Carriers at the Ge(111)−GeO₂ Interface As Probed by SHG

Ultrafast Time-Evolution of the Nonlinear Susceptibility of Hot Carriers at the Ge(111)−GeO₂ Interface As Probed by SHG

Optical and ultrasonic signatures of femtosecond pulse filamentation in fused silica

Quantifying Transient Strain and Energy of Coherent Acoustic Phonons with UEM Imaging

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Laser hyperacoustic spectroscopy of single crystal germanium

Cited by 7 publications

References 23 publications

Ultrafast Time-Evolution of the Nonlinear Susceptibility of Hot Carriers at the Ge(111)−GeO2 Interface As Probed by SHG

Ultrafast Time-Evolution of the Nonlinear Susceptibility of Hot Carriers at the Ge(111)−GeO2 Interface As Probed by SHG

Optical and ultrasonic signatures of femtosecond pulse filamentation in fused silica

Quantifying Transient Strain and Energy of Coherent Acoustic Phonons with UEM Imaging

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Product

Resources

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Ultrafast Time-Evolution of the Nonlinear Susceptibility of Hot Carriers at the Ge(111)−GeO₂ Interface As Probed by SHG

Ultrafast Time-Evolution of the Nonlinear Susceptibility of Hot Carriers at the Ge(111)−GeO₂ Interface As Probed by SHG