arXiv subjects

Daryoush Abdollahpour

Publications and source records attributed to Daryoush Abdollahpour.

4 recordsLinked to original sources

arXiv2026

Invertible mapping between structured light and vector terahertz emission

Terahertz (THz) radiation provides a powerful platform for ultrafast spectroscopy, imaging, and communication, yet deterministic control over its spatial and polarization structure remains challenging. Here we establish a unified framework for generating and synthesizing vectorial THz beams through coherent control of ultrafast photocurrents in semiconductors. By exploiting quantum interference between one- and two-photon excitation pathways driven by femtosecond vector beams, we demonstrate that the spatial phase and polarization structure of the optical fields can be directly mapped onto the magnitude and orientation of injected currents. This structured charge motion acts as a programmable THz antenna, enabling tailored far-field emission. Beyond forward modeling of THz generation from cylindrical vector beams and full Poincaré beams, we introduce an inverse-design methodology that reconstructs the required current distribution--and corresponding excitation beam profiles--from a desired THz field pattern. This invertible mapping transforms coherent photocurrent control into a systematic design strategy for THz beam shaping. Our results bridge structured light and THz photonics, providing a route toward compact, all-optical, and reconfigurable THz sources with engineered amplitude, phase, and polarization profiles.

physics.optics↗

arXiv2025

Formation of axially modulated plasma strings by filamentation of interfering femtosecond Bessel beams

We numerically investigate the formation of axially modulated plasma strings through the filamentation of two interfering femtosecond Bessel beams. The constituent Bessel beams have different central spot sizes and propagate collinearly. Our results show that filamentation of these beams in air leads to the formation of intense axially modulated light filaments, and corrugated plasma strings with high modulation depths and tunable modulation periods. We find that the modulation periods of the intensity and the plasma density are identical and comparable to the modulation period of the intensity in the linear propagation regime. Furthermore, we show that, in the nonlinear propagation regime, the modulation period is independent of the pulse energy and can be tuned by selecting appropriate central spot sizes for the interfering Bessel beams. Finally, we propose a simple interferometric arrangement using a single axicon to generate two interfering Bessel beams with adjustable spot sizes enabling the creation of axially-modulated plasma strings with tunable periodicity at high input powers.

physics.optics↗

arXiv2024

Filamentation of Femtosecond Vector Beams

We numerically study the filamentation of femtosecond vector beams with spatially varying polarization profiles in air. The vector beams include azimuthal, radial, and spiral cylindrical vector beams (CVBs), as well as low-order Full Poincaré beams (FPBs) with star and lemon polarization topologies. Comparing the filamentation of CVBs to that of a circularly polarized Laguerre-Gaussian (LG) beam, we found that CVBs undergo filamentation more easily due to their more effective nonlinear focusing, in contrast to the LG beam. In the case of low-order FPBs, we examined the role of the constituent orthogonally polarized spatial modes in their filamentation process. Our findings revealed that the Gaussian mode within these beams primarily contributes to their filamentation. Additionally, when compared to a linearly polarized Gaussian beam, star and lemon FPBs displayed greater resistance to filamentation. Furthermore, we investigated the evolution of polarization profiles of the beams during filamentation. We observed that the polarization profiles of CVBs remained largely unchanged. In contrast, the polarization profiles of the FPBs underwent significant non-uniform changes due to differences in accumulated nonlinear phase and Gouy phase among the constituent modes.

physics.optics↗

arXiv2023

Flying doughnut terahertz pulses generated from semiconductor currents

The ability to manipulate the space-time structure of light waves diversifies light-matter interaction and light-driven applications. Conventionally, metasurfaces are employed to locally control the amplitude and phase of light fields by the material response and structure of small meta-atoms. However, the fixed spatial structures of metasurfaces offer limited opportunities. Here, using quantum control we introduce a new approach that enables the amplitude, sign, and even configuration of the generated light fields to be manipulated in an all-optical manner. Following this approach, we demonstrate the generation of flying doughnut terahertz (THz) pulses. We show that the single-cycle THz pulse radiated from the dynamic semiconductor ring current has an electric field structure that is azimuthally polarized and that the space- and time-resolved magnetic field has a strong, isolated longitudinal component. As a first application, we detect absorption features from ambient water vapor on the spatiotemporal structure of the measured electric fields and the calculated magnetic fields. Quantum control is a powerful and flexible route to generating any structured light pulse in the THz range, while pulse compression of cylindrical vector beams is available for very high-power magnetic-pulse generation from the mid-infrared to near UV spectral region. Pulses such as these will serve as unique probes for spectroscopy, imaging, telecommunications, and magnetic materials.

physics.optics↗