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Subcycle-resolved probe retardation in strong-field pumped dielectrics.

Pati AP, Wahyutama IS, Pfeiffer AN - Nat Commun (2015)

Bottom Line: The response of a bulk dielectric to an intense few-cycle laser pulse is not solely determined by the pulse envelope, but also by ultrafast processes occurring during each optical cycle.Comparisons to model calculations show that the measurement is sensitive to the timing of the electronic Kerr response.When conduction band states are transiently populated at the crests of the laser field, the measurement is also sensitive to the interband dephasing time.

View Article: PubMed Central - PubMed

Affiliation: Institute for Optics and Quantum Electronics, Abbe Center of Photonics, Friedrich Schiller University, Max-Wien-Platz 1, 07743 Jena, Germany.

ABSTRACT
The response of a bulk dielectric to an intense few-cycle laser pulse is not solely determined by the pulse envelope, but also by ultrafast processes occurring during each optical cycle. Here, a method is presented for measuring the retardation of a probe pulse in a strong-field pumped, bulk dielectric with subcycle resolution in the pump-probe delay. Comparisons to model calculations show that the measurement is sensitive to the timing of the electronic Kerr response. When conduction band states are transiently populated at the crests of the laser field, the measurement is also sensitive to the interband dephasing time.

No MeSH data available.


Related in: MedlinePlus

The experimental setup for subcycle-resolved probe-retardation measurements.(a) Femtosecond pump and probe pulses are focused into a bulk dielectric sample with a variable delay in a close-to-collinear alignment. The probe retardation is determined by imaging the fluorescence from a head-on collision of the probe pulse with a reference pulse inside a cuvette filled with Fluorescein. In front of the sample, a beamsplitter steers a fraction of the pump and probe pulses to a camera, which measures the intensity I (b) to give an absolute time reference for the subcycle-resolved probe-retardation measurement (c).
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f2: The experimental setup for subcycle-resolved probe-retardation measurements.(a) Femtosecond pump and probe pulses are focused into a bulk dielectric sample with a variable delay in a close-to-collinear alignment. The probe retardation is determined by imaging the fluorescence from a head-on collision of the probe pulse with a reference pulse inside a cuvette filled with Fluorescein. In front of the sample, a beamsplitter steers a fraction of the pump and probe pulses to a camera, which measures the intensity I (b) to give an absolute time reference for the subcycle-resolved probe-retardation measurement (c).

Mentions: A 7-fs pulse with a peak wavelength at 820 nm is generated by a commercial femtosecond laser system and split into three collinearly polarized copies for pump, probe and reference pulses (Fig. 2). The pulses are focused into a bulk sample of borosilicate glass (Schott D 263 M, thickness 0.145 mm), where the pump pulse reaches a peak intensity of 2.3 TW cm−2, probe and reference pulses reach a peak intensity of 0.05 TW cm−2. Pump and probe pulses have a variable delay and overlap in the focus, and D-shaped mirrors are used to achieve a very small crossing angle of about 0.3° between them. No permanent modifications of the optical properties of the sample are observed, signalling that the pump intensity is well below the damage threshold through generation of an electron-hole plasma or an electron-ion plasma22. This is affirmed by the fact that the transmission of the pump beam alone without the presence of the probe pulse did not measurably depend on the pump intensity22, showing no significant nonlinear absorption. Simulations (see Methods section) show that the phase evolution of the pump pulse as it propagates through the sample does depend nonlinearly on the pump intensity, but this effect is smaller than the induced phase shift in the probe pulse, as it is expected in cross-phase modulation20.


Subcycle-resolved probe retardation in strong-field pumped dielectrics.

Pati AP, Wahyutama IS, Pfeiffer AN - Nat Commun (2015)

The experimental setup for subcycle-resolved probe-retardation measurements.(a) Femtosecond pump and probe pulses are focused into a bulk dielectric sample with a variable delay in a close-to-collinear alignment. The probe retardation is determined by imaging the fluorescence from a head-on collision of the probe pulse with a reference pulse inside a cuvette filled with Fluorescein. In front of the sample, a beamsplitter steers a fraction of the pump and probe pulses to a camera, which measures the intensity I (b) to give an absolute time reference for the subcycle-resolved probe-retardation measurement (c).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4510967&req=5

f2: The experimental setup for subcycle-resolved probe-retardation measurements.(a) Femtosecond pump and probe pulses are focused into a bulk dielectric sample with a variable delay in a close-to-collinear alignment. The probe retardation is determined by imaging the fluorescence from a head-on collision of the probe pulse with a reference pulse inside a cuvette filled with Fluorescein. In front of the sample, a beamsplitter steers a fraction of the pump and probe pulses to a camera, which measures the intensity I (b) to give an absolute time reference for the subcycle-resolved probe-retardation measurement (c).
Mentions: A 7-fs pulse with a peak wavelength at 820 nm is generated by a commercial femtosecond laser system and split into three collinearly polarized copies for pump, probe and reference pulses (Fig. 2). The pulses are focused into a bulk sample of borosilicate glass (Schott D 263 M, thickness 0.145 mm), where the pump pulse reaches a peak intensity of 2.3 TW cm−2, probe and reference pulses reach a peak intensity of 0.05 TW cm−2. Pump and probe pulses have a variable delay and overlap in the focus, and D-shaped mirrors are used to achieve a very small crossing angle of about 0.3° between them. No permanent modifications of the optical properties of the sample are observed, signalling that the pump intensity is well below the damage threshold through generation of an electron-hole plasma or an electron-ion plasma22. This is affirmed by the fact that the transmission of the pump beam alone without the presence of the probe pulse did not measurably depend on the pump intensity22, showing no significant nonlinear absorption. Simulations (see Methods section) show that the phase evolution of the pump pulse as it propagates through the sample does depend nonlinearly on the pump intensity, but this effect is smaller than the induced phase shift in the probe pulse, as it is expected in cross-phase modulation20.

Bottom Line: The response of a bulk dielectric to an intense few-cycle laser pulse is not solely determined by the pulse envelope, but also by ultrafast processes occurring during each optical cycle.Comparisons to model calculations show that the measurement is sensitive to the timing of the electronic Kerr response.When conduction band states are transiently populated at the crests of the laser field, the measurement is also sensitive to the interband dephasing time.

View Article: PubMed Central - PubMed

Affiliation: Institute for Optics and Quantum Electronics, Abbe Center of Photonics, Friedrich Schiller University, Max-Wien-Platz 1, 07743 Jena, Germany.

ABSTRACT
The response of a bulk dielectric to an intense few-cycle laser pulse is not solely determined by the pulse envelope, but also by ultrafast processes occurring during each optical cycle. Here, a method is presented for measuring the retardation of a probe pulse in a strong-field pumped, bulk dielectric with subcycle resolution in the pump-probe delay. Comparisons to model calculations show that the measurement is sensitive to the timing of the electronic Kerr response. When conduction band states are transiently populated at the crests of the laser field, the measurement is also sensitive to the interband dephasing time.

No MeSH data available.


Related in: MedlinePlus