Phase-dependent noise in femtosecond pump-probe experiments on Bi and GaAs

Misochko, O. V.; Sakai, Kiyomi; Nakashima, S.

doi:10.1103/physrevb.61.11225

Cited by 38 publications

(40 citation statements)

References 23 publications

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“…19 Furthermore, squeezed lattice fields are generally expected to be continuumlike rather than quasi-monochromatic. 10 The objective of the present study was to revisit some of the time-resolved reflectivity experiments of Misochko et al, 15 focusing on those on Bi and GaAs which typify the reported behavior, in an attempt to clarify the origin of their observations.…”

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confidence: 93%

“…In a very different and more controversial, type of alloptical experiment, Misochko et al [15][16][17][18] have reported the observation of a phase-dependent variance in the probe intensity in room temperature, time-domain reflectivity studies of phonons impulsively excited by relatively weak ͑few tens of microjoule per square centimeter͒ femtosecond laser pulses. These studies encompass a wide range of materials, including the semiconductor GaAs, 15 semimetals Sb 16 and Bi, 15 and the high-temperature superconductor YBa 2 Cu 3 O 7−␦ .…”

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confidence: 99%

“…These studies encompass a wide range of materials, including the semiconductor GaAs, 15 semimetals Sb 16 and Bi, 15 and the high-temperature superconductor YBa 2 Cu 3 O 7−␦ . 17,18 The variance in the time-domain reflectivity was found to have maxima at nodes in the phonon contribution and minima at antinodes.…”

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Absence of phase-dependent noise in time-domain reflectivity studies of impulsively excited phonons

Hussain

Andrews

2010

Phys. Rev. B

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There have been several reports of phase-dependent noise in time-domain reflectivity studies of optical phonons excited by femtosecond laser pulses in semiconductors, semimetals, and superconductors. It was suggested that such behavior is associated with the creation of squeezed phonon states although there is no theoretical model that directly supports such a proposal. We have experimentally re-examined the studies of phonons in bismuth and gallium arsenide, and find no evidence of any phase-dependent noise signature associated with the phonons. We place an upper limit on any such noise at least 40-50 dB lower than previously reported. DOI: 10.1103/PhysRevB.81.224304 PACS number͑s͒: 78.47.jg, 63.20.Ϫe, 42.50.Lc Coherent phonons in semiconductors, superconductors, metals, and insulators have been widely studied in the time domain since the first report of their excitation by femtosecond laser pulses in about 1990.1,2 The most general excitation mechanism is impulsive stimulated Raman scattering ͑ISRS͒.3 A special case of ISRS in opaque materials is sometimes referred to as the displacive mechanism 1 and is associated with electronic excitation from bonding to antibonding orbitals. Longitudinal optical phonons in semiconductors can also be driven by the transient polarization associated with the screening of surface space-charge fields following interband excitation. 2The amplitude of a phonon mode may be decomposed into two quadrature components with the time dependences cos t and sin t. In a coherent state, the closest quantum counterpart to a classical field, the fluctuations in the two quadratures have the same variance and are randomly distributed in phase. The product of the variances in each quadrature is the minimum allowed by the Heisenberg uncertainty principle. Minimum uncertainty states in which the fluctuations in one quadrature have a variance that falls below the zero-point quantum noise level are called squeezed states. 4 Squeezed electromagnetic fields were experimentally studied for the first time in the mid-1980s ͑Ref. 5͒ and nonclassical light is now an established area of research.6 A phasedependent nonlinear process is necessary to generate a squeezed state. For example, squeezed optical fields can be produced by parametric amplification or four-wave mixing. Recently, there has been interest in extending the study of nonclassical fields to lattice vibrations in condensed matter but except for a few studies of squeezing, 7-12 and amplitude collapse and revival, 13 there has been relatively little work on phonon fields. Squeezing of phonons generated by secondorder Raman scattering was predicted 7 and later reported 9,11 in low temperature, femtosecond pump-probe transmission measurements on KTaO 3 . In this case the mechanism is a three-phonon parametric process analogous to that used to produce coherent two-photon states. This type of experiment has been extended to the creation of coexcited coherent and squeezed vibrations 10 and to squeezed spin waves 14 in MnF 2 but in no case has the...

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Absence of phase-dependent noise in time-domain reflectivity studies of impulsively excited phonons

Hussain

Andrews

2010

Phys. Rev. B

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“…To date the coherent phonons have been observed in a great variety of solids [1][2][3][4][5] with increasing attention being turned towards not only observation but also understanding of physics which occurs at this short time scale. In analogy with photon states in quantum optics [6][7][8] the generation and manipulation of specific phonon states has become a major issue in condensed matter physics [9][10][11][12][13][14][15][16][17][18][19][20]. Yet, notwithstanding the recent experimental and theoretical advances, a clear relation between quantum mechanical coherent phonon state and the experimentally observed coherent phonons, typically described in classical terms, is still missing.…”

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confidence: 99%

Controlling phonon squeezing and correlation via one- and two-phonon interference

Misochko

Nakamura

2011

Physics Letters A

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When ultrafast laser pulse strikes the crystal with a van Hove singularity in the phonon density of states, it can create a pair of anti-correlated in wave-vector phonons. As a result, the atomic fluctuations in either position or momentum become squeezed in such a way that their size might fall below the vacuum level. The ultrafast pulses can also generate a biphonon state in which the constituent phonons are correlated and/or entangled. Here we show that via the interplay between one-and two-phonon interference the bound and squeezed two-phonon state in (110) oriented ZnTe single crystal can be manipulated.

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“…While in most cases coherent phonon amplitudes and nonequilibrium phonon occupations have been investigated, in recent years there has been a growing interest in the study of the fluctuation properties of the generated phonons. The generation of squeezed phonons by second-order Raman scattering has been predicted [4] and signatures of phonon squeezing have been observed by pump-probe spectroscopy in transmission [5] or reflection [6] geometry as well as recently in femtosecond X-ray diffraction [7].…”

Section: Introductionmentioning

confidence: 99%