arXiv subjects

Finn Buldt

Publications and source records attributed to Finn Buldt.

6 recordsLinked to original sources

arXiv2022

On the Generation of Topological Vector Solitons from Bessel-Like Beams

Coupled solitary waves in optics literature, are coined vector solitons to reflect their particle-like nature that remains intact even after mutual collisions. They are born from a nonlinear change in the refractive index of an optical material induced by the light intensity. We've discovered that the second harmonic intensity profile generated by Bessel-like beams, is composed of solitons of various geometries surrounded by concentric rings; one of which is two central solitons of similar radius knotted by ellipsoidal concentric rings. We observe that their geometry and intensity distribution is dependent on the topological charge of the fundamental Bessel beams incident on the nonlinear medium. We show that their spatial profile is invariant against propagation. We observe that their behavior is similar to that of screw dislocations in wave trains: they collide and rebound at a 90$^\circ$ angle from the beam propagation direction. In this way, we have generated linked frequency doubled Bessel-type vector solitons with different topologies, that are knotted as they oscillate along the optical axis, when propagating in the laboratory environment.

physics.optics↗

arXiv2022

Multiple feedback based wavefront shaping method to retrieve hidden signal

We present an optical wavefront shaping approach that allows tracking and localization of signal hidden inside or behind a scattering medium. The method combines traditional feedback based wavefront shaping together with a switch function, controlled by two different signals. A simple, in transmission imaging system is used with two detectors: one monitors the speckle signature and the other tracks the fully hidden signal (e.g., fluorescent beads). The algorithm initially finds the optimal incident wavefront to maximize light transmission to generate a focus in the scattering medium. This modulation process redirects the scattered input signal inducing instantaneous changes in both monitored signals, which in turn locates the hidden objects. Once the response from the hidden target becomes distinct, the algorithm switches to use this signal as the feedback. We provide experimental demonstrations as a proof of concept of our approach. Potential applications of our method include extracting information from biological samples and developing non-invasive diagnosis methods.

physics.optics↗

arXiv2022

Femtosecond Filament Coupled with Structured Light for Free Space Optical Communication

The generation of a laser filament through clouds produces a shockwave which displaces the small water droplets from the air to create a quasi-transparent channel through which, information can be transmitted. We present a robust method that utilizes the channel for free-space optical communication using structured light beams coupled with a femtosecond filament. Vortex beams based on their spatial profiles and non-diffractive characteristics are perfectly suited to propagate around the filament. We have also developed a 4-bit communication channel using these structured light beam. We introduce a method dubbed segmented space division multiplexing. Our system demonstrates resilience to noise and is unaffected by the filament. This method can improve the scalability, robustness, and capacity of the free optical channel.

physics.optics↗

arXiv2021

On the Generation of Topological Vector Solitons from Bessel Like Beams

Coupled solitary waves in optics literature, are coined vector solitons to reflect their particle--like nature that remains intact even after mutual collisions. They are born from a nonlinear change in the refractive index of an optical material induced by the light intensity. We've discovered that the second harmonic intensity profile generated by Bessel like beams, is composed of solitons of various geometries surrounded by concentric rings; one of which is two central solitons of similar radius knotted by ellipsoidal concentric rings. We observe that their geometry and intensity distribution is dependent on the topological charge of the fundamental Bessel beams incident on the nonlinear medium. We show that their spatial profile is invariant against propagation. We observe that their behavior is similar to that of screw dislocations in wave trains: they collide and rebound at a $90^\circ$ angle from the beam propagation direction. In this way, we have generated linked frequency doubled Bessel-type vector solitons with a with different topologies, that are knotted as they oscillate along the optical axis, when propagating in the laboratory environment.

physics.optics↗

arXiv2021

Nonlinear Conversion of Orbital Angular Momentum States of Light

We investigate the second harmonic generation of light field carrying orbital angular momentum in bulk $\chi^{(2)}$ material. We show that due to conservation of energy and momentum, the frequency doubled beam light has a modified spatial distribution and mode characteristics. Through rigorous phase matching conditions, we demonstrate efficient mode and frequency conversion based on three wave nonlinear optical mixing.

physics.optics↗

arXiv2021

Multi-qubit production in spontaneous parametric down conversion

We present a novel yet simple approach to produced multiple entangled photon pairs through spontaneous parametric downconversion. We have developed Gaussian masks to subdivide the pump beam before passing it through a nonlinear medium. In this way, we are able to observe simultaneous separate down-converted emission cones with spatial overlap. The technique we employ can be used to greatly increase the dimensionality of entangled photonic systems generated from spontaneous parametric down conversion, affording greater scalability to optical quantum computing than previously explored.

quant-ph↗