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Controlling Ultrafast Excitations in Germanium: The Role of Pump-Pulse Parameters and Multi-Photon Resonances.

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Title: Controlling Ultrafast Excitations in Germanium: The Role of Pump-Pulse Parameters and Multi-Photon Resonances.
Authors: Eskandari-asl, Amir1 (AUTHOR), Avella, Adolfo1,2,3 (AUTHOR) a.avella@unisa.it
Source: Materials (1996-1944). Jan2026, Vol. 19 Issue 2, p408. 10p.
Subjects: Germanium, Multiphoton processes, Semiconductors, Optical pulse generation, Optical control, Quantum optics, Picosecond pulses
Abstract: We employ the Dynamical Projective Operatorial Approach (DPOA) to investigate the ultrafast optical excitations of germanium under intense, ultrashort pump pulses. The method has very low resource demand relative to many other available approaches and enables detailed calculation of the residual electron and hole populations induced by the pump pulse. It provides direct access to the energy distribution of excited carriers and to the total energy transferred to the system. By decomposing the response into contributions from different multi-photon resonant processes, we systematically study the dependence of excited-carrier density and absorbed energy on key pump-pulse parameters: duration, amplitude, and photon energy. Our results reveal a complex interplay between these parameters, governed by resonant Rabi-like dynamics and competition between different multi-photon absorption channels. For the studied germanium setup, we find that two-photon processes are generally dominant, while one- and three-photon channels become significant under specific conditions of pump-pulse frequency, duration, and intensity. This comprehensive analysis offers practical insights for optimizing ultrafast optical control in semiconductors by targeting specific multi-photon pathways. [ABSTRACT FROM AUTHOR]
Copyright of Materials (1996-1944) is the property of MDPI and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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  Data: Controlling Ultrafast Excitations in Germanium: The Role of Pump-Pulse Parameters and Multi-Photon Resonances.
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  Data: <searchLink fieldCode="AR" term="%22Eskandari-asl%2C+Amir%22">Eskandari-asl, Amir</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Avella%2C+Adolfo%22">Avella, Adolfo</searchLink><relatesTo>1,2,3</relatesTo> (AUTHOR)<i> a.avella@unisa.it</i>
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  Data: <searchLink fieldCode="JN" term="%22Materials+%281996-1944%29%22">Materials (1996-1944)</searchLink>. Jan2026, Vol. 19 Issue 2, p408. 10p.
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  Data: <searchLink fieldCode="DE" term="%22Germanium%22">Germanium</searchLink><br /><searchLink fieldCode="DE" term="%22Multiphoton+processes%22">Multiphoton processes</searchLink><br /><searchLink fieldCode="DE" term="%22Semiconductors%22">Semiconductors</searchLink><br /><searchLink fieldCode="DE" term="%22Optical+pulse+generation%22">Optical pulse generation</searchLink><br /><searchLink fieldCode="DE" term="%22Optical+control%22">Optical control</searchLink><br /><searchLink fieldCode="DE" term="%22Quantum+optics%22">Quantum optics</searchLink><br /><searchLink fieldCode="DE" term="%22Picosecond+pulses%22">Picosecond pulses</searchLink>
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: We employ the Dynamical Projective Operatorial Approach (DPOA) to investigate the ultrafast optical excitations of germanium under intense, ultrashort pump pulses. The method has very low resource demand relative to many other available approaches and enables detailed calculation of the residual electron and hole populations induced by the pump pulse. It provides direct access to the energy distribution of excited carriers and to the total energy transferred to the system. By decomposing the response into contributions from different multi-photon resonant processes, we systematically study the dependence of excited-carrier density and absorbed energy on key pump-pulse parameters: duration, amplitude, and photon energy. Our results reveal a complex interplay between these parameters, governed by resonant Rabi-like dynamics and competition between different multi-photon absorption channels. For the studied germanium setup, we find that two-photon processes are generally dominant, while one- and three-photon channels become significant under specific conditions of pump-pulse frequency, duration, and intensity. This comprehensive analysis offers practical insights for optimizing ultrafast optical control in semiconductors by targeting specific multi-photon pathways. [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of Materials (1996-1944) is the property of MDPI and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
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        Value: 10.3390/ma19020408
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      – Code: eng
        Text: English
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        PageCount: 10
        StartPage: 408
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      – SubjectFull: Germanium
        Type: general
      – SubjectFull: Multiphoton processes
        Type: general
      – SubjectFull: Semiconductors
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      – SubjectFull: Optical pulse generation
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      – SubjectFull: Optical control
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      – SubjectFull: Quantum optics
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      – SubjectFull: Picosecond pulses
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      – TitleFull: Controlling Ultrafast Excitations in Germanium: The Role of Pump-Pulse Parameters and Multi-Photon Resonances.
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              M: 01
              Text: Jan2026
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              Y: 2026
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