Light: Science & Applications

Journal: Light: Science & Applications

Abbreviation

Light Sci Appl

Publisher

Nature

ISSN

2047-7538

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Publications1 - 10 of 34

Non-invasive large-scale imaging of concurrent neuronal, astrocytic, and hemodynamic activity with hybrid multiplexed fluorescence and magnetic resonance imaging (HyFMRI)
Chen , Zhenyue; Chen , Yi; Gezginer , Irmak; et al. (2025)
Light: Science & Applications
A critical gap currently exists in systematic understanding and experimental validation of the role of astrocytes in neurovascular coupling and their functional links with other brain cells. Despite a broad selection of functional neuroimaging tools for multi-scale brain interrogations, no methodology currently exists that can discern responses from neural and glial cells while simultaneously mapping the associated hemodynamic activity on a large scale. We present a hybrid multiplexed fluorescence and magnetic resonance imaging (HyFMRI) platform for measuring neuronal and astrocytic activity registered to concurrently recorded brain-wide hemodynamic responses. It features a fiberscope-based imaging system for multichannel fluorescence and optical intrinsic signal recordings and a custom surface radiofrequency coil, which are incorporated into the bore of a preclinical magnetic resonance imaging (MRI) scanner. We used HyFMRI to study peripheral-stimulus-evoked brain responses in mice differentially labeled with RCaMP and GCaMP genetically-encoded calcium indicators. Stimulation-evoked neuronal responses displayed the fastest kinetics and highest activation amplitude followed by astrocytic signals and the hemodynamic responses simultaneously recorded with functional MRI. In addition, the activation traces from neurons and astrocytes exhibited high linear correlation, thus providing direct evidence of astrocytic mediation in neurovascular coupling. This newly developed capacity to capture cell-type-specific calcium signaling alongside whole-brain hemodynamics enables the simultaneous investigation of neuro-glial-vascular interactions in health and disease. HyFMRI thus expands the current neuroimaging toolbox for a wide range of studies into synaptic plasticity, neural circuitry, brain function and disorders.
Toward noninvasive optoacoustic imaging of whole-heart dynamics in mice
Kalva , Sandeep Kumar; Özsoy, Cagla; Nozdriukhin, Daniil; et al. (2025)
Light: Science & Applications
High-speed volumetric optoacoustic tomography (VOT) offers powerful means for noninvasive, detailed visualization of rapid cardiac dynamics in mice. However, current implementations suffer from non-uniform light delivery into the thoracic area, which results in diminished penetration depth, limited field-of-view, and compromised quantification abilities. In this work, we devised a new VOT approach featuring hexagonally-shaped light delivery optimized for whole-heart imaging and an expedited imaging speed of 200 volumes per second using a custom-made spherical array transducer. The enhanced imaging performance was confirmed with calibration phantoms and noninvasive imaging of the murine heart. We capitalized on the reduced hemoglobin absorption in the second near-infrared (NIR-II) spectral window to mitigate the strong light attenuation by whole blood within the cardiac chambers while further employing copper sulfide nanoparticles featuring a strong NIR-II absorption to quantify cardiac functional parameters across the entire heart in vivo. The new approach can thus facilitate the monitoring of cardiac abnormalities and assessment of therapeutic interventions.
100 GHz silicon–organic hybrid modulator
Alloatti, Luca; Palmer, Robert; Diebold, Sebastian; et al. (2014)
Light: Science & Applications
Electro-optic modulation at frequencies of 100 GHz and beyond is important for photonic-electronic signal processing at the highest speeds. To date, however, only a small number of devices exist that can operate up to this frequency. In this study, we demonstrate that this frequency range can be addressed by nanophotonic, silicon-based modulators. We exploit the ultrafast Pockels effect by using the silicon–organic hybrid (SOH) platform, which combines highly nonlinear organic molecules with silicon waveguides. Until now, the bandwidth of these devices was limited by the losses of the radiofrequency (RF) signal and the RC (resistor-capacitor) time constant of the silicon structure. The RF losses are overcome by using a device as short as 500 µm, and the RC time constant is decreased by using a highly conductive electron accumulation layer and an improved gate insulator. Using this method, we demonstrate for the first time an integrated silicon modulator with a 3dB bandwidth at an operating frequency beyond 100 GHz. Our results clearly indicate that the RC time constant is not a fundamental speed limitation of SOH devices at these frequencies. Our device has a voltage–length product of only VπL=11 V mm, which compares favorably with the best silicon-photonic modulators available today. Using cladding materials with stronger nonlinearities, the voltage–length product is expected to improve by more than an order of magnitude.
Programmable Bell state generation in an integrated thin film lithium niobate circuit
Maeder, Andreas; Chapman, Robert; Sabatti, Alessandra; et al. (2026)
Light: Science & Applications
Entanglement is central to quantum technologies such as cryptography, sensing, and computing. Photon pairs generated via nonlinear optical processes are excellent for preparing entangled states due to their long coherence times and compatibility with fiber optic networks. Steady progress in nanofabrication has positioned lithium niobate-on-insulator (LNOI) as a leading platform for monolithic integration of photon pair sources into optical circuits, leveraging its strong second-order nonlinearity. Here, we present a reconfigurable photonic integrated circuit on LNOI, which combines two on-chip photon pair sources with programmable interferometers, enabling the generation of entangled states. The photon pair sources achieve a source brightness of 26 MHz nm⁻¹ mW⁻¹ while maintaining a coincidence-to-accidental ratio above 100. We successfully interfere the two sources with 99.0 ± 0.7% visibility, demonstrating the indistinguishability required for producing entanglement on-chip. We show the preparation of any of the maximally entangled Bell states with fidelity above 90% verified by quantum state tomography. These results establish LNOI as a compelling, scalable platform to explore integrated quantum photonic technologies enabled by high-brightness sources of entangled quantum states.
Photo-induced macro/mesoscopic scale ion displacement in mixed-halide perovskites: ring structures and ionic plasma oscillations
Sun, Xiaoxiao; Zhang, Yong; Ge, Weikun (2022)
Light: Science & Applications
Contrary to the common belief that the light-induced halide ion segregation in a mixed halide alloy occurs within the illuminated area, we find that the Br ions released by light are expelled from the illuminated area, which generates a macro/mesoscopic size anion ring surrounding the illuminated area, exhibiting a photoluminescence ring. This intriguing phenomenon can be explained as resulting from two counter-balancing effects: the outward diffusion of the light-induced free Br ions and the Coulombic force between the anion deficit and surplus region. Right after removing the illumination, the macro/mesoscopic scale ion displacement results in a built-in voltage of about 0.4V between the ring and the center. Then, the displaced anions return to the illuminated area, and the restoring force leads to a damped ultra-low-frequency oscillatory ion motion, with a period of about 20-30 h and lasting over 100 h. This finding may be the first observation of an ionic plasma oscillation in solids. Our understanding and controlling the "ion segregation" demonstrate that it is possible to turn this commonly viewed "adverse phenomenon" into novel electronic applications, such as ionic patterning, self-destructive memory, and energy storage.
Ultrawideband high density polymer-based spherical array for real-time functional optoacoustic micro-angiography
Subochev, Pavel V.; Deán-Ben, Xosé Luís; Chen, Zhenyue; et al. (2025)
Light: Science & Applications
Owing to its unique ability to capture volumetric tomographic information with a single light flash, optoacoustic (OA) tomography has recently demonstrated ultrafast imaging speeds ultimately limited by the ultrasound time-of-flight. The method's scalability and the achievable spatial resolution are yet limited by the narrow bandwidth of piezo-composite arrays currently employed for OA signal detection. Here we report on the first implementation of high-density spherical array technology based on flexible polyvinylidene difluoride films featuring ultrawideband (0.3-40 MHz) sub mm2 area elements, thus enabling real-time multi-scale volumetric imaging with 22-35 mu m spatial resolution, superior image fidelity and over an order of magnitude signal-to-noise enhancement compared to piezo-composite equivalents. We further demonstrate five-dimensional (spectroscopic, time-resolved, volumetric) imaging capabilities by visualizing fast stimulus-evoked cerebral oxygenation changes in mice and performing real-time functional angiography of deep human micro-vasculature. The new technology thus leverages the true potential of OA for quantitative high-resolution visualization of rapid bio-dynamics across scales.
Giant non-linear susceptibility of hydrogenic donors in silicon and germanium
Le, Nguyen H.; Lanskii, Grigory V.; Aeppli, Gabriel; et al. (2019)
Light: Science & Applications
Implicit summation is a technique for the conversion of sums over intermediate states in multiphoton absorption and the high-order susceptibility in hydrogen into simple integrals. Here, we derive the equivalent technique for hydrogenic impurities in multi-valley semiconductors. While the absorption has useful applications, it is primarily a loss process; conversely, the non-linear susceptibility is a crucial parameter for active photonic devices. For Si:P, we predict the hyperpolarizability ranges from χ(3)/n3D = 2.9 to 580 × 10−38 m5/V2 depending on the frequency, even while avoiding resonance. Using samples of a reasonable density, n3D, and thickness, L, to produce third-harmonic generation at 9 THz, a frequency that is difficult to produce with existing solid-state sources, we predict that χ(3) should exceed that of bulk InSb and χ(3)L should exceed that of graphene and resonantly enhanced quantum wells.
Fieldoscopy at the quantum limit
Zimin, Dmitry A.; Ashoka, Arjun; Reiter, Florentin; et al. (2026)
Light: Science & Applications
We demonstrate a novel concept for measuring time-varying electric field transients of petahertz-scale photons down to a single-photon regime. We observe a clear breakdown of the classical regime consistent with our Monte Carlo model. We reach unprecedented yoctojoule-level (10⁻²⁴ J) sensitivity and a dynamic range exceeding 90 decibels. We utilize this capability to measure intrapulse light coherence - a regime inaccessible to conventional, time-averaged spectroscopy. This opens new avenues for quantum information, cryptography, and quantum light-matter interactions on sub-cycle time scales with attosecond precision.
In situ frequency gating and beam splitting of vacuum- and extreme-ultraviolet pulses
Rajeev, Rajendran; Hellwagner, Johannes; Schumacher, Anne; et al. (2016)
Light: Science & Applications
Recent advances in ultrafast semiconductor disk lasers
Tilma, Bauke W.; Mangold, Mario; Zaugg, Christian A.; et al. (2015)
Light: Science & Applications
The performance of ultrafast semiconductor disk lasers has rapidly advanced in recent decades. The strong interest from industry for inexpensive, compact, and reliable ultrafast laser sources in the picosecond and femtosecond domains has driven this technology toward commercial products. Frequency metrology and biomedical applications would benefit from sub-200-femtosecond pulse durations with peak powers in the kilowatt range. The aim of this review is to briefly describe the market potential and give an overview of the current status of mode-locked semiconductor disk lasers. Particular focus is placed on the ongoing efforts to achieve shorter pulses with higher peak powers.

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