Tailored Multi‐Color Dispersive Wave Formation in Quasi‐Phase‐Matched Exposed Core Fibers

Abstract

Widely wavelength‐tunable femtosecond light sources in a compact, robust footprint play a central role in many prolific research fields and technologies, including medical diagnostics, biophotonics, and metrology. Fiber lasers are on the verge in the development of such sources, yet widespan spectral tunability of femtosecond pulses remains a pivotal challenge. Dispersive wave generation, also known as Cherenkov radiation, offers untapped potentials to serve these demands. In this work, the concept of quasi‐phase matching for multi‐order dispersive wave formation with record‐high spectral fidelity and femtosecond durations is exploited in selected, partially conventionally unreachable spectral regions. Versatile patterned sputtering is utilized to realize height‐modulated high‐index nano‐films on exposed fiber cores to alter fiber dispersion to an unprecedented degree through spatially localized, induced resonances. Nonlinear optical experiments and simulations, as well as phase‐mismatching considerations based on an effective dispersion, confirm the conversion process and reveal unique emission features, such as almost power‐independent wavelength stability and femtosecond duration. This resonance‐empowered approach is applicable to both fiber and on‐chip photonic systems and paves the way to instrumentalize dispersive wave generation as a unique tool for efficient, coherent femtosecond multi‐frequency conversion for applications in areas such as bioanalytics, life science, quantum technology, or metrology.

Neuromorphic Computing via Fission‐based Broadband Frequency Generation

“…Our accessible implementation uses exclusively off‐the‐shelf telecom fiber components and is, in principle, transferable to on‐chip nanophotonic devices [ 45 , 46 ] and novel material fiber systems. [ 33 , 47 ] In particular, photonic chip technologies offer full system integration, higher energy efficiency, and potentially picosecond inference latencies for cm‐scale waveguides. Also, on‐chip solutions offer highly reproducible waveguide properties and might allow for the direct transfer of trained weights from one chip to another.…”

“…In practice, the training of the waveguide parameters is very challenging as it requires precise control over local waveguide properties, such as dispersion and nonlinearity, which are typically static after fabrication. While some solutions to this challenge exist (e.g., dispersion‐varying fibers [ 31 , 32 , 33 ] ), a posteriori training at system input or output is more straightforward toward tailoring the nonlinear wave dynamics. This approach exploits the system's sensitivity to phase and amplitude variations at the input.…”

Tailored dispersive wave generation in quasi-phase-matched liquid core fibers

“…16 The usually employed PM-condition then is amended by the additional term qλ/Λ (ref. 15 and corrected version of ref. 16 ), leading to:…”

“…14 In the realm of fiber optics, our recent research delved into the subject of QPM in the context of dispersive wave (DW) generation. 15 By arranging nanofilms periodically on the core of microstructured optical fibers, we introduced spatially controlled resonances into the system. This resulted in the creation of narrowband sidebands induced by DWs, which fell outside the spectral range of the SCG that would be generated without this modulation.…”

Temperature‐Sensitive Dual Dispersive Wave Generation of Higher‐Order Modes in Liquid‐Core Fibers

“…[8] Hybrid-material fibers have been proven to yield unprecedented features in this context, for instance through inducing nano-film mediated resonances. [20,21] A successful scheme for reconfigurable tuning of SCG relies on modifying pressure in gas-filled hollow core fibers, [6,7] allowing to change bandwidths [22] or to shift spectral features far into the visible or ultraviolet. [5] Despite their great re-configurability, such platforms are relatively power-hungry and grant only limited dispersion control through constant pressure or linear pressure gradients, necessitating complex differential pumping schemes.…”