arXiv subjects

Karol Tarnowski

Publications and source records attributed to Karol Tarnowski.

7 recordsLinked to original sources

arXiv2025

Spectrally indistinguishable intermodal-vectorial four-wave-mixing in birefringent few-mode fibers for spatial-polarization-frequency hybrid-entangled photon-pairs generation

In this paper, we use a birefringent few-mode fiber to demonstrate an intermodal-vectorial four-wave mixing process that generates two pairs of spectrally overlapping signal-idler bands. Using phase-matching conditions, we show that the pairs of bands become spectrally indistinguishable when the group refractive indices of the signal and idler modes intersect at the pump wavelength. Our theoretical predictions are confirmed through experimental observations corroborated by numerical simulations. Furthermore, we introduce the two-photon state associated with the overlapping bands, which exhibits hybrid entanglement in spatial-polarization-frequency degrees of freedom. We explain that its degree of entanglement can be manipulated by tailoring the spectral position of the overlapping pairs of bands with respect to the Raman band and varying the excitation ratio of the pump modes. This study introduces a scheme for a fiber-based source of photon pairs with spatial-polarization-frequency entanglement.

physics.optics↗

arXiv2023

Quantum dots as optimized chiral emitters for photonic integrated circuits

Chiral coupling, which allows directional interactions between quantum dots (QDs) and photonic crystal waveguide modes, holds promise for enhancing the functionality of quantum photonic integrated circuits. Elliptical polarizations of QD transitions offer a considerable enhancement in directionality. However, in epitaxial QD fabrication, the lack of precise control over lateral QD positions still poses a challenge in achieving efficient chiral interfaces. Here, we present a theoretical analysis in which we propose to optimize the polarization of a QD emitter against the spatially averaged directionality and demonstrate that the resulting emitter offers a considerable technological advantage in terms of the size and location of high-directionality areas of the waveguide as well as their overlap with the regions of large Purcell enhancement, thereby improving the scalability of the device. Moreover, using $\mathbf{\mathit{k}}\cdot\mathbf{\mathit{p}}$ modeling, we demonstrate that the optimal elliptical polarization can be achieved for neutral exciton transitions in a realistic QD structure. Our results present a viable path for efficient chiral coupling in QD-based photonic integrated circuits, to a large extent overcoming the challenges and limitations of the present manufacturing technology.

quant-ph↗

arXiv2022

Experimental observation of spontaneous emission of space-time wavepacket in a multimode optical fiber

We provide a complete analysis, from theory to experiment, of the spontaneous emergence of a discretized conical wave of X-type (i.e., a localized 2D+1 space-time wavepacket) when an intense ultrashort pulse nonlinearly propagates in a multimode fiber. In particular, we reveal that this spatiotemporal phenomenon corresponds to broadband intermodal dispersive wave emission from an unsteady localized wave structure formed during nonlinear propagation. Theoretical phase-matching predictions are experimentally and numerically confirmed in a commercially-available step-index multimode fiber. Our results provide a general understanding of phase-matched radiations emitted by nonlinear waves in multidimensional dispersive optical system.

physics.optics↗

arXiv2022

Soliton trapping and orthogonal Raman scattering in a birefringent microstructured fiber

We report on trapped pulse generation in birefringent microstructured optical fiber. Linearly polarized fs pulses are injected into the microstructured fiber in anomalous dispersion regime. We observed experimentally that soliton pulse polarized along the fast fiber axis partially transfers its energy to the orthogonal polarization. The generated pulse is amplified through the orthogonal Raman gain. The two polarization components are located at group-velocity matched wavelengths. The experimental works are supported with numerical simulations. The obtained results are important for the light sources using self-frequency shifted solitons in applications demanding high polarization purity.

physics.optics↗

arXiv2022

Multiple intermodal-vectorial four-wave-mixing bands generated by selective excitation of orthogonally polarized LP01 and LP11 modes in a birefringent fiber

This study investigated the nonlinear frequency conversions between the six polarization modes of a two-mode birefringent fiber. The aim was to demonstrate that the selective excitation of different combinations of linearly polarized spatial modes at the pump wavelength initiates distinct intermodal vector four-wave mixing processes. In particular, this study shows that exciting two orthogonally polarized LP01 and LP11 modes can result in simultaneous generation of up to three pairs of different spatial modes of orthogonal polarizations at different wavelengths. The role of the phase birefringence of the spatial modes in the phase-matching of such a four-wave mixing process was explained. Moreover, the theoretical predictions were verified through numerical simulations based on coupled nonlinear Schrodinger equations and also confirmed experimentally in a commercially available birefringent fiber.

physics.optics↗

arXiv2021

gnlse-python: Open Source Software to Simulate Nonlinear Light Propagation In Optical Fibers

The propagation of pulses in optical fibers is described by the generalized nonlinear Schrodinger equation (GNLSE), which takes into account the fiber losses, nonlinear effects, and higher-order chromatic dispersion. The GNLSE is a partial differential equation, whose order depends on the accounted nonlinear and dispersion effects. We present gnlse-python, a nonlinear optics modeling toolbox that contains a rich set of components and modules to solve the GNLSE using the split-step Fourier transform method (SSFM). The numerical solver is freely available, implemented in Python language, and includes a number of optical fiber analysis tools. Code and data are available at https://github.com/WUST-FOG/gnlse-python.

physics.optics↗

arXiv2021

Dual-wavelength pumped highly birefringent microstructured silica fiber for widely tunable soliton self-frequency shift

We report the design of a microstructured silica-based fiber for widely tunable soliton self-frequency shift, suitable for pumping with two most common fiber laser wavelengths: 1.04 μm and 1.55 μm. Depending on the pump source, the output spectrum can be continuously tuned up to 1.67 μm (pump at 1.04 μm) or 1.95 μm (pump at 1.55 μm) in the same 1.5 m-long fiber sample, with pump-to-soliton conversion efficiency higher than 20%. The fiber is highly birefringent, which results in an excellent polarization extinction ratio of the soliton, reaching 26 dB. The shifted solitons have a high degree of coherence confirmed by pulse-to-pulse interference measurement. The available soliton tuning range covers the wavelengths inaccessible for fiber lasers, e.g., 1.3 μm and 1.7 μm, highly important for multi-photon microscopy and imaging. Our work shows that it is possible to design and fabricate one universal optical fiber that supports soliton shift when pumped at two different wavelengths separated by over 500 nm.

physics.optics↗