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Author: Morales, Felipe × Publisher: Washington, DC : Soc. ×

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Now showing 1 - 3 of 3
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    Propagator operator for pulse propagation in resonant media
    (Washington, DC : Soc., 2021) Morales, Felipe; Richter, Maria; Olvo, Vlad; Husakou, Anton
    We show that, for the case of resonant media, the available models for unidirectional propagation of short pulses can face serious challenges with respect to numerical efficiency, accuracy, or numerical artifacts. We propose an alternative approach based on a propagator operator defined in the time domain. This approach enables precise simulations using short time windows even for resonant media and facilitates coupling of the propagation equation with first-principle methods such as the time-dependent Schödinger equation. Additionally, we develop a numerically efficient recipe to construct and apply such a propagator operator.
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    Cross-polarized common-path temporal interferometry for high-sensitivity strong-field ionization measurements
    (Washington, DC : Soc., 2022) Nie, Zan; Nambu, Noa; Marsh, Kenneth A.; Welch, Eric; Matteo, Daniel; Zhang, Chaojie; Wu, Yipeng; Patchkovskii, Serguei; Morales, Felipe; Smirnova, Olga; Joshi, Chan
    Absolute density measurements of low-ionization-degree or low-density plasmas ionized by lasers are very important for understanding strong-field physics, atmospheric propagation of intense laser pulses, Lidar etc. A cross-polarized common-path temporal interferometer using balanced detection was developed for measuring plasma density with a sensitivity of ∼0.6 mrad, equivalent to a plasma density-length product of ∼2.6 × 1013 cm-2 if using an 800 nm probe laser. By using this interferometer, we have investigated strong-field ionization yield versus intensity for various noble gases (Ar, Kr, and Xe) using 800 nm, 55 fs laser pulses with both linear (LP) and circular (CP) polarization. The experimental results were compared to the theoretical models of Ammosov-Delone-Krainov (ADK) and Perelomov-Popov-Terent'ev (PPT). We find that the measured phase change induced by plasma formation can be explained by the ADK theory in the adiabatic tunneling ionization regime, while PPT model can be applied to all different regimes. We have also measured the photoionization and fractional photodissociation of molecular (MO) hydrogen. By comparing our experimental results with PPT and MO-PPT models, we have determined the likely ionization pathways when using three different pump laser wavelengths of 800 nm, 400 nm, and 267 nm.
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    Non-instantaneous third-order optical response of gases in low-frequency fields
    (Washington, DC : Soc., 2022) Morales, Felipe; Richter, Maria; Ivanov, Misha; Husakou, Anton
    It is commonly assumed that for low-intensity short optical pulses far from resonance, the third-order optical nonlinear response is instantaneous. We solve the three-dimensional time-dependent Schrödinger equation for the hydrogen atom and show that this is not the case: the polarization is not simply proportional to the cube of the electric field even at low intensities. We analyze the fundamental-frequency and third-harmonic nonlinear susceptibilities of hydrogen, investigate their dependence on intensity, and find that the delays in the Kerr response rapidly approach the femtosecond time-scale at higher intensities, while the delays in the third harmonic generation remain much lower. We also propose an experimental scheme to detect and characterize the above effects.