Energy consumption is on track to become a serious bottleneck in integrating quantum technologies with existing information and communication infrastructure. In photonic quantum technologies, a considerable portion of the energy overhead stems from the use of lasers, whose high coherence has long been considered indispensable for preparing quantum states of light. Here, we demonstrate that despite their low optical coherence, natural sources of light, such as sunlight, can produce quantum-entangled photon states by means of nonlinear optical effects. From spontaneous parametric down-conversion pumped by sunlight, we detect polarization-entangled photon pairs with a concurrence of C = 0.905 ± 0.053, a purity of P = 0.919 ± 0.045, and a fidelity to a Bell state of F = 0.939 ± 0.027. The resulting two-photon state violates Bell's inequality with S = 2.5408 ± 0.2171, which exceeds the threshold value of 2 to confirm quantum behavior. More importantly, we observe a photon pair generation rate of ~1600 s⁻¹ (mW of pump power)⁻¹, which is comparable to that of laser-pumped SPDC when normalized for the spectral bandwidth of the pump. Our work paves the way for developing sustainable and accessible photonic quantum technologies, especially for implementation in resource-constrained areas such as the Arctic region and satellites in space for interplanetary missions.
The oscillating electric field emitted by excitons in layered antiferromagnets reveals how quasiparticles synchronize into collective coherence and shows that a complex multi-peak spectrum can arise from a single excitonic resonance dynamically modulated by spin and lattice excitations.
Ultrafast nonlinear dynamics of indium tin oxide nanocrystals probed via fieldoscopy
Andreas Herbst,
Anchit Srivastava,
Kilian Scheffter,
Soyeon Jun,
Steffen Gommel,
Luca Rebecchi,
Sidharth Kuriyil,
Andrea Rubino,
Nicolo Petrini, et al.
Scalable, high-speed, small-footprint photonic switching platforms are essential for advancing optical communication. An effective optical switch must operate at high duty cycles with fast recovery times, while maintaining substantial modulation depth and full reversibility. Colloidal nanocrystals, such as indium tin oxide (ITO), offer a scalable platform to meet these requirements. In this work, the transmission of ITO nanocrystals near their epsilon-near-zero wavelength is modulated by two-cycle optical pulses at a repetition rate of one megahertz. The modulator exhibits a broad bandwidth spanning from 2 to 2.5 µm. Sensitive fieldoscopy measurements resolve the transient electric-field response of the ITO for the first time, showing that the modulation remains reversible for excitation fluences up to 1.2 mJ cm−2 with a modulation depth of 10%, and becomes fully irreversible beyond 3.3 mJ cm−2, while reaching modulation depth of up to 20%. Field sampling further indicates that at higher excitation fluences, the relative contribution from the first cycle of the optical pulses is reduced. These findings are crucial for the development of all-optical switching, telecommunications, and sensing technologies capable of operating at terahertz switching frequencies.
Solar-pumped lasers, predominantly based on neodymium gain media, offer a promising route to renewable laser-energy conversion and space-based photonics; however, their performance has been constrained by thermal loading and limited power scalability. Here, we propose and numerically investigate a solar-pumped ytterbium thin-disk gain medium in combination with a dome concentrator that enables multipass solar pumping and enhanced absorption. The design yields comparably low lasing thresholds for neodymium- and ytterbium-doped media, while ytterbium provides superior power scalability, enabling up to threefold higher output power. We further identify ytterbium-doped medium combined with a spherical concentrator as a viable solar-pumped, radiation-balanced configuration, achieving self-cooled lasing at solar pump intensities of 28.5 kW cm-2 within the 1020-1033 nm window of the solar spectrum. The spherical concentrator increases the averaged fluence of the solar pump while permitting anti-Stokes fluorescence to escape efficiently. These results establish multi-pass, solar-pumped thin-disk ytterbium lasers as a compact, scalable, and sustainable platform for high-performance solar-pumped lasers
Kontakt
Forschungsgruppe Hanieh Fattahi
Max-Planck-Institut für die Physik des Lichts Staudtstr. 2 91058 Erlangen
