arXiv subjects

Ignas Astrauskas

Publications and source records attributed to Ignas Astrauskas.

3 recordsLinked to original sources

arXiv2023

Analysis of High-Contrast All-Optical Dual Wavelength Switching in Asymmetric Dual-Core Fibers

We systematically present experimental and theoretical results for the dual-wavelength switching of 1560 nm, 75 fs signal pulses (SPs) driven by 1030 nm, 270 fs control pulses (CPs) in a dual-core fiber (DCF). We demonstrate a switching contrast of 31.9 dB, corresponding to a propagation distance of 14 mm, achieved by launching temporally synchronized SP-CP pairs into the fast core of the DCF with moderate inter-core asymmetry. Our analysis employs a system of three coupled propagation equations to identify the compensation of the asymmetry by nonlinearity as the physical mechanism behind the efficient switching performance.

physics.optics↗

arXiv2021

High contrast all-optical spectrally distributed switching of femtosecond pulses in soft glass dual-core optical fiber

All-optical switching of 77 fs pulses centered at 1560 nm, driven by 270 fs, 1030 nm pulses in a dual-core optical fiber exhibiting high index contrast is presented. The fiber is made of a thermally matched pair of lead silicate and borosilicate glasses used as core and cladding material, respectively. The novel switching approach is based on nonlinear balancing of dual-core asymmetry, by control pulse intensity induced group velocity reduction of the fast fiber channel. Due to the fiber core made of soft glass with high nonlinearity high switching contrast exceeding 20 dB is attained under application of control pulses of only few nanojoule energy. The optimization of the fiber length brought the best results at 14 mm, which is in good correspondence with the calculated coupling length at the signal wavelength. The results express significant progress in comparison to similar studies based on self-switching of solitonic pulses in dual-core fibers and represent high application potential.

physics.optics↗

arXiv2020

Sub-surface modifications in silicon with ultrashort pulsed lasers above 2 microns

Nonlinear optical phenomena in silicon such as self-focusing and multi-photon absorption are strongly dependent on the wavelength, energy and duration of the exciting pulse. Thus, a pronounced wavelength dependence of the sub-surface modifications with ultra-short pulsed lasers exists, especially for wavelengths > 2 $μ$m. This wavelength dependence is investigated for wavelengths in the range of 1950-2400 nm, at a pulse duration between 0.5-10 ps and the pulse energy varying from 1 $μ$J to 1 mJ. Numerical and experimental analyses have been performed on both the surface and sub-surface of Si wafers processed with fibre-based lasers built in-house that operate in this wavelength range. The results have been compared to the literature data at 1550 nm. The analysis carried out has shown that due to a dip in the nonlinear absorption spectrum and a peak in the spectrum of the third-order non-linearity, the wavelengths between 2000 - 2200 nm are more favourable for creating sub-surface modifications in silicon. This is the case even though those wavelengths do not allow as tight a focusing as those at 1550 nm in the linear regime. This problem is compensated by an increased self-focusing due to the nonlinear Kerr-effect around 2100 nm at high light intensities, characteristic for ultra-short pulses.

physics.optics↗