IISER MOHALI

Abstract:
The generation and control of currents on an ultrafast timescale hold promise for numerous scientific and practical applications. Utilizing femtosecond laser pulses to drive ultrafast currents in matter presents a novel route for generating terahertz bandwidth, intense, and rapid magnetic impulses [1]. The amplitude and polarity of these currents can be precisely controlled by manipulating the relative phase between a fundamental beam and its second harmonic pulse, a technique known as coherent control. In semiconductors, the coherence-induced current injection is explained by quantum interference between two pathways leading to the same initial and final state [2]. In this presentation, I will delve into current generation and manipulation using spatially structured laser pulses. We have demonstrated the versatility of this approach, showing that nearly any transient current structure can be engineered by combining a circularly polarized near-infrared (NIR) pulse with a phase-structured linearly polarized visible light pulse [2]. These reconfigurable transient current structures serve as a source of spatially tailored magnetic fields, optoelectronic circuitry, and structured terahertz pulses [3]. Furthermore, I will discuss our investigations into the terahertz radiation emitted by coherent-controlled dynamic currents excited by two-color cylindrical vector beams, known as 'flying electromagnetic doughnut' pulses. Our measurements capture the space-time structure of the electric field and enable the calculation of the space-time structure of the corresponding magnetic field [4,5]. I
will conclude with a brief overview of my future research direction.

References:
1. S. Sederberg et al. Phys. Rev. X 10, 011063 (2020).
2. K. Jana et al. Nature Photonics 15, 622(2021).
3. K. Jana et al. Nanophotonics 11, 787 (2022).
4. K. Jana et al. Science Advances 10, eadl1803 (2024).
5. K. Jana et al. arXiv:2411.04943 (Under Review).