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Fruhling, Colton

Publications and source records attributed to Fruhling, Colton.

8 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Photophysics and Carrier Dynamics of Lasing in Quasi-2D Lead Halide Perovskites

Quasi-2D perovskites have recently been extensively studied due to their narrow-bandwidth-tunable emission, solution processability, and applicability as optical gain media. Quasi-2D perovskites are composed of inorganic perovskite crystal layers encapsulated with a bulky organic ligand such as phenylethylammonium, endowing the perovskite with a quantum-well structure and improved stability. In this article, we explore the photophysics of a quasi-2D metal halide perovskite as a promising light-harvesting and emitting medium. We find it exhibits high optical absorption (~10 5 cm -1 ) and an optically pumped amplified spontaneous emission threshold at 623 μJ/cm 2 . We study charge transfer processes in the complex mixed quantum wells of these perovskites through transient absorption and time-resolved photoluminescence measurements and develop a phenomenological model that incorporates optical gain for lasing. Further, while both free carriers and excitons are observed, we show surprisingly that photoluminescence is dominated by excitons despite the relatively small binding energy (~16 meV) of the low-energy band edge. Additionally, we extract the rates of exciton relaxation pathways, revealing a relatively large radiative term of 4.6 x 10 8 s -1 as well as an exciton-exciton annihilation term of 3.6 x 10 -13 cm 3 s -1 that is 3 orders of magnitude smaller than in similar quasi-2D perovskites.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Photonic time-crystals - fundamental concepts [Invited]

Photonic Time-Crystals (PTCs) are materials in which the refractive index varies periodically and abruptly in time. This medium exhibits unusual properties such as momentum bands separated by gaps within which waves can be amplified exponentially, extracting energy from the modulation. This article provides a brief review on the concepts underlying PTCs, formulates the vision and discusses the challenges.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Photonic time crystals: a materials perspective [Invited]

Recent advances in ultrafast, large-modulation photonic materials have opened the door to many new areas of research. One specific example is the exciting prospect of photonic time crystals. In this perspective, we outline the most recent material advances that are promising candidates for photonic time crystals. We discuss their merit in terms of modulation speed and depth. We also investigate the challenges yet to be faced and provide our estimation on possible roads to success.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Coherent Random Lasing in Subwavelength Quasi‐2D Perovskites

Abstract Quasi‐2D lead halide perovskites have garnered increasing interest as lasing gain media. Relatively simple fabrication, high refractive index, and unique quantum well structure encourage their use in traditional cavity lasers and cavity‐free systems called random lasers (RLs). Despite tremendous advances reported thus far, coherent random lasing in quasi‐2D perovskite subwavelength films has not been reported. Consequently, coherent optical feedback mechanisms in quasi‐2D perovskite systems are still unexplored. Here, this work reports the observation of coherent random lasing in subwavelength quasi‐2D perovskite films. Statistical analysis of spectral measurements reveals Lévy‐like intensity fluctuations, replica symmetry breaking confirms random lasing, and the coherent modes are studied with spectral and spatial correlation techniques. The observed coherent lasing modes are found to be extended states that arise from the random crystal grain structure during fabrication and span the entire pump volume. These modes out‐compete diffusive lasing due to their coherence.

47 OTHER INSTRUMENTATION↗
DOE OSTI2022

Transverse oscillating bubble enhanced laser-driven betatron X-ray radiation generation

Abstract Ultrafast high-brightness X-ray pulses have proven invaluable for a broad range of research. Such pulses are typically generated via synchrotron emission from relativistic electron bunches using large-scale facilities. Recently, significantly more compact X-ray sources based on laser-wakefield accelerated (LWFA) electron beams have been demonstrated. In particular, laser-driven sources, where the radiation is generated by transverse oscillations of electrons within the plasma accelerator structure (so-called betatron oscillations) can generate highly-brilliant ultrashort X-ray pulses using a comparably simple setup. Here, we experimentally demonstrate a method to markedly enhance the parameters of LWFA-driven betatron X-ray emission in a proof-of-principle experiment. We show a significant increase in the number of generated photons by specifically manipulating the amplitude of the betatron oscillations by using our novel Transverse Oscillating Bubble Enhanced Betatron Radiation scheme. We realize this through an orchestrated evolution of the temporal laser pulse shape and the accelerating plasma structure. This leads to controlled off-axis injection of electrons that perform large-amplitude collective transverse betatron oscillations, resulting in increased radiation emission. Our concept holds the promise for a method to optimize the X-ray parameters for specific applications, such as time-resolved investigations with spatial and temporal atomic resolution or advanced high-resolution imaging modalities, and the generation of X-ray beams with even higher peak and average brightness.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Experimental observation of polarization-resolved nonlinear Thomson scattering of elliptically polarized light

We report experimental results from a study of nonlinear Thomson scattering of elliptically polarized light. Polarization-resolved radiation patterns of the scattered light are measured as a function of the elliptical polarization state of the incident laser light. The relativistic electron trajectory in intense elliptically polarized fields leads to the formation of unique radiated polarization states, which are observed by our measurements and predicted by a theoretical model. The polarization of Thomson scattered light depends strongly on the intensity of the incident light due to nonlinearity. The results are relevant to high-field electrodynamics and to research and development of light sources with novel capabilities.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Generation of ultrafast electron bunch trains via trapping into multiple periods of plasma wakefields

We demonstrate a novel approach to the generation of femtosecond electron bunch trains via laser-driven wakefield acceleration. We use two independent high-intensity laser pulses, a drive, and an injector, each creating their own plasma wakes. The interaction of the laser pulses and their wakes results in a periodic injection of free electrons in the drive plasma wake via several mechanisms, including ponderomotive drift, wake-wake interference, and pre-acceleration of electrons directly by strong laser fields. Electron trains were generated with up to four quasi-monoenergetic bunches, each separated in time by a plasma period. In conclusion, the time profile of the generated trains is deduced from an analysis of beam loading and confirmed using 2D particle-in-cell simulations

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗