Phonons induced by laser pulses for Brillouin scattering measurements

Perino, Alessandro; Shibagaki, Yoshiaki; Hayashi, Yutaka; Matsukawa, Mami

doi:10.7567/jjap.57.07lb19

Cited by 3 publications

(3 citation statements)

References 27 publications

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“…a polymer film has to be spin-coated on top). For this transducer material, spot-size should be < 5 μm 36 , rendering the traditional goniometer approach impractical.…”

Section: Methodsmentioning

confidence: 99%

“…by analyzing the frequency-shift of continuous-wave (CW) probe light scattered from phonons transmitted by the PnC. Previous proof-of-principle experiments have already combined pulsed 35 , 36 and even harmonic 37 phonon pumps with BLS, where the samples were rectangular prisms that had one facet coated with a metallic transducer film. Conceptually, it is then straightforward to place the PnC between transducer and detection prism, and scan different frequencies by changing scattering angle by means of a goniometer.…”

Section: Introductionmentioning

confidence: 99%

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Lifting restrictions on coherence loss when characterizing non-transparent hypersonic phononic crystals

Rolle

Yaremkevich

Scherbakov

et al. 2021

Sci Rep

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Hypersonic phononic bandgap structures confine acoustic vibrations whose wavelength is commensurate with that of light, and have been studied using either time- or frequency-domain optical spectroscopy. Pulsed pump-probe lasers are the preferred instruments for characterizing periodic multilayer stacks from common vacuum deposition techniques, but the detection mechanism requires the injected sound wave to maintain coherence during propagation. Beyond acoustic Bragg mirrors, frequency-domain studies using a tandem Fabry–Perot interferometer (TFPI) find dispersions of two- and three-dimensional phononic crystals (PnCs) even for highly disordered samples, but with the caveat that PnCs must be transparent. Here, we demonstrate a hybrid technique for overcoming the limitations that time- and frequency-domain approaches exhibit separately. Accordingly, we inject coherent phonons into a non-transparent PnC using a pulsed laser and acquire the acoustic transmission spectrum on a TFPI, where pumped appear alongside spontaneously excited (i.e. incoherent) phonons. Choosing a metallic Bragg mirror for illustration, we determine the bandgap and compare with conventional time-domain spectroscopy, finding resolution of the hybrid approach to match that of a state-of-the-art asynchronous optical sampling setup. Thus, the hybrid pump–probe technique retains key performance features of the established one and going forward will likely be preferred for disordered samples.

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“…a polymer film has to be spin-coated on top). For this transducer material, spot-size should be < 5 μm 36 , rendering the traditional goniometer approach impractical.…”

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Lifting restrictions on coherence loss when characterizing non-transparent hypersonic phononic crystals

Rolle

Yaremkevich

Scherbakov

et al. 2021

Sci Rep

View full text Add to dashboard Cite

show abstract

“…Previously, micro-Brillouin light spectroscopy (BLS) has been combined with laser pumping and metallic transducers to generate acoustic waves, but this method was limited to bulk waves in insulating materials ( 15 , 16 ). An alternative optical approach for the excitation of hypersonic phonons is through optomechanical coupling in low-dimensional structures ( 17 ) harnessing the interaction of standing, acoustic waves with electromagnetic cavity modes ( 18 ).…”

Section: Introductionmentioning

confidence: 99%

Frequency-domain study of nonthermal gigahertz phonons reveals Fano coupling to charge carriers

et al. 2020

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Telecommunication devices exploit hypersonic gigahertz acoustic phonons to mediate signal processing with microwave radiation, and charge carriers to operate various microelectronic components. Potential interactions of hypersound with charge carriers can be revealed through frequency- and momentum-resolved studies of acoustic phonons in photoexcited semiconductors. Here, we present an all-optical method for excitation and frequency-, momentum-, and space-resolved detection of gigahertz acoustic waves in a spatially confined model semiconductor. Lamb waves are excited in a bare silicon membrane using femtosecond optical pulses and detected with frequency-domain micro-Brillouin light spectroscopy. The population of photoexcited gigahertz phonons displays a hundredfold enhancement as compared with thermal equilibrium. The phonon spectra reveal Stokes–anti-Stokes asymmetry due to propagation, and strongly asymmetric Fano resonances due to coupling between the electron-hole plasma and the photoexcited phonons. This work lays the foundation for studying hypersonic signals in nonequilibrium conditions and, more generally, phonon-dependent phenomena in photoexcited nanostructures.

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Frequency comb enhanced Brillouin microscopy

et al. 2020

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Brillouin light scattering (BLS) microscopy is a well established and powerful technique to study acoustic and magnetic excitations in the frequency domain with sub-micron spatial resolution. Many other spectroscopic techniques have benefited from the introduction of femtosecond laser sources to optically pump and stimulate the sample under investigation. In BLS microscopy, the use of femtosecond lasers as the excitation source introduces several challenges, primarily since the measured frequency shift is small and the signal levels are weak due to the low duty cycle of typical femtosecond lasers. Here we present a method to evade these challenges. A strong enhancement of the weak scattering amplitude on selected modes is observed by pumping the sample with a high repetition rate frequency comb laser source. The laser beam can be focused to the diffraction limit, providing a micron pumping area. We can thus preserve the innate high frequency and spatial resolution of BLS microscopy. Furthermore, we are able to induce a point-like source of mode-selected elementary excitations which propagate away from the pumping spot. We conclude that we have demonstrated frequency comb pumped BLS microscopy as an attractive tool for studies of ultrafast induced laser dynamics directly in the frequency domain.

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Phonons induced by laser pulses for Brillouin scattering measurements

Cited by 3 publications

References 27 publications

Lifting restrictions on coherence loss when characterizing non-transparent hypersonic phononic crystals

Lifting restrictions on coherence loss when characterizing non-transparent hypersonic phononic crystals

Frequency-domain study of nonthermal gigahertz phonons reveals Fano coupling to charge carriers

Frequency comb enhanced Brillouin microscopy

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