Search

Ultrafast nonlinear dynamics driven by high-peak-power ultrashort mid-infrared (mid-IR) pulses gives rise to ultrabroadband radiation whose spectrum spans over multiple decades, stretching from the terahertz (THz) to the microwave range. We show that, despite its enormous, multidecade bandwidth, an accurate spectral and spatial-mode characterization of this radiation is possible via a suitable combination of mutually complementary signal-analysis methods borrowed from ultrafast optics, radio electronics, THz photonics, and microwave engineering. This analysis reveals intense subgigahertz radiation emitted as a part of mid-IR-driven supercontinuum generation and shows that microwave-to-THz field waveforms can almost reach the diffraction limit in their beam focusability, yielding field strengths above 3 MV/cm.

We demonstrate how the Hong-Ou-Mandel (HOM) interference with polarization-entangled photons can be used to probe ultrafast dephasing. We can infer the optical properties like the real and imaginary parts of the complex susceptibility of the medium from changes in the position and the shape of the HOM dip. From the shift of the HOM dip, we are able to measure 22 fs dephasing time using a continuous-wave (CW) laser even with optical loss > 97%, while the HOM dip visibility is maintained at 92.3~\% (which can be as high as 96.7%). The experimental observations, which are explained in terms of a rigorous theoretical model, demonstrate the utility of HOM interference in probing ultrafast dephasing., 12 pages, 7 figures

We demonstrate an adaptive wave-front shaping of optical beams transmitted through fiber bundles as a powerful resource for multisite, high-resolution bioimaging. With the phases of all the beamlets delivered through up to 6000 different fibers within the fiber bundle controlled individually, by means of a high-definition spatial light modulator, the overall beam transmitted through the fiber bundle can be focused into a beam waist with a diameter less than 1 μm within a targeted area in a biotissue, providing a diffraction-limited spatial resolution adequate for single-cell or even subcellular bioimaging. The field intensity in the adaptively-focused continuous-wave laser beam in our fiber-bundle-imaging setting is more than two orders of magnitude higher than the intensity of the speckle background. Once robust beam focusing was achieved with a suitable phase profile across the input face of the fiber bundle, the beam focus can be scanned over a targeted area with no need for a further adaptive search, by applying a physically intuitive, wave-front-tilting phase mask on the field of input beamlets. This method of beam-focus scanning promises imaging speeds compatible with the requirements of in vivo calcium imaging.

Modern optical physics provides means to detect and resolve ultrafast processes on a time scale of tens of attoseconds. The physical interpretation of such measurements, however, remains the focus of heated debate. In its conceptual dimension, this debate reflects fundamental difficulties in defining time in quantum mechanics. En route toward resolving this difficulty, we are led to extend universal uncertainty relations to ultrafast light–matter interactions. Such a generalized uncertainty sets a lower bound on the response time inherent in attosecond electronic dynamics driven by ultrashort laser pulses, dictating a speed limit for next-generation photonic information systems — systems of petahertz optoelectronics.

The smallness of the velocity $$v$$ of laser-field-induced motion of electrons compared to the speed of light c is one of the fundamental physical factors limiting the efficiency of nonlinear optical processes in plasma media. It has been shown in this work that the use of intense ultrashort mid-infrared pulses makes it possible to significantly enhance a wide class of $$v{\text{/}}c$$ -weak plasma nonlinearities primarily related to plasma currents induced by the laser field. This allows implementing laser plasma schemes of the efficient generation of coherent broadband terahertz and microwave radiation, i.e., terahertz–microwave supercontinuum.

The effect of laser radiation with a wavelength near 1.55 µm on the photoluminescence properties of “nitrogen-vacancy” (NV) color centers in diamond has been studied experimentally. The effect of radiation of an infrared laser on the charge state of color centers redistributes the spectral intensity of photoluminescence in the ensemble of NV centers. In the case of neutral NV centers, the quenching of photoluminescence reaching about 60% has been observed. A feature of the laser excitation of NV centers by this method is the absence of competition with stimulated emission and two-photon excitation, which is observed with an increase in the power of infrared radiation at other wavelengths.

We demonstrate a versatile framework for cellular brain imaging in awake mice based on suitably tailored segments of graded-index (GRIN) fiber. Closed-form solutions to ray-path equations for graded-index waveguides are shown to offer important insights into image-transmission properties of GRIN fibers, suggesting useful recipes for optimized GRIN-fiber-based deep-brain imaging. We show that the lengths of GRIN imaging components intended for deep-brain studies in freely moving rodents need to be chosen as a tradeoff among the spatial resolution, the targeted imaging depth and the degree of fiber-probe invasiveness. In the experimental setting that we present in this paper, the head of an awake mouse with a GRIN-fiber implant is fixed under a microscope objective, but the mouse is free to move around an in-house-built flat-floored air-lifted platform, exploring a predesigned environment, configured as an arena for one of standard cognitive tests. We show that cellular-resolution deep-brain imaging can be integrated in this setting with robust cell-specific optical neural recording to enable in vivo studies with minimal physical restraints on animal models. The enhancement of the information capacity of the fluorescence signal, achieved via a suitable filtering of the GRIN-fiber readout, is shown to open routes toward practical imaging modalities whereby the deep-brain neuronal dynamics and axonal connections underpinning the integrative functions of essential brain structures can be studied in awake rodent models.

We present an experimental framework and methodology for in vivo studies on rat stroke models that enable a real-time fiber-optic recording of stroke-induced hydrogen peroxide and pH transients in ischemia-affected brain areas. Arrays of reconnectable implantable fiber probes combined with advanced optogenetic fluorescent protein sensors are shown to enable a quantitative multisite time-resolved study of oxidative-stress and acidosis buildup dynamics as the key markers, correlates and possible drivers of ischemic stroke. The fiber probes designed for this work provide a wavelength-multiplex forward-propagation channel for a spatially localized, dual-pathway excitation of genetically encoded fluorescence-protein sensors along with a back-propagation channel for the fluorescence return from optically driven fluorescence sensors. We show that the spectral analysis of the fiber-probe-collected fluorescence return provides means for a high-fidelity autofluorescence background subtraction, thus enhancing the sensitivity of real-time detection of stroke-induced transients and significantly reducing measurement uncertainties in in vivo acute-stroke studies as inherently statistical experiments operating with outcomes of multiply repeated measurements on large populations of individually variable animal stroke models.

We present all-optical high-resolution temperature measurements in the brain of freely behaving mice using an implantable thermometer that integrates a reconnectable two-section fiber-optic probe a...

Thermogenetics appeared recently as an evolutionary advance in methods of optical stimulation of nerve cells and uses focused light to activate light-sensitive cation channels in the neuron membrane. Light activation and opening of light-sensitive channels, which can be expressed genetically in any type of neuron, induces neuron membrane depolarization and a resultant action potential. In contrast to classical methods of optogenetics, which use the visible spectrum, thermogenetics uses channels sensitive to warming. This provides the opportunity for additional activation of these channels not only using IR light, but also other methods of warming nervous tissue, such as ultrasound or microwave radiation. The penetrability of living tissue to stimulation with IR radiation is an order of magnitude greater than that for visible spectrum radiation, which allows thermogenetics methods to be used in vivo without invasive surgical methods to “clear the way” for optogenetic stimulation. On the other hand, the thermal nature of the stimulation imposes additional limits on use of the method, as heating must be sufficiently gentle so as not to induce heat shock at the cellular level, and the threshold of activation must be sufficiently high for channel opening not to occur spontaneously at normal physiological temperatures.

Dr Deborah Birx, the White House Coronavirus Task Force coordinator, told NBC News on "Meet the Press"that "[T]he U S needs a 'breakthrough' in coronavirus testing to help screen Americans and get a more accurate picture of the virus' spread "We have been involved with biopathogen detection since the 2001 anthrax attacks and were the first to detect anthrax in real-time A variation on the laser spectroscopic techniques we developed for the rapid detection of anthrax can be applied to detect the Severe Acute Respiratory Syndrome-Corona Virus-2 (SARS-CoV-2 virus) In addition to detecting a single virus, this technique allows us to read its surface protein structure In particular, we have been conducting research based on a variety of quantum optical approaches aimed at improving our ability to detect Corona Virus Disease-2019 (COVID-19) viral infection Indeed, the detection of a small concentration of antibodies, after an infection has passed, is a challenging problem Likewise, the early detection of disease, even before a detectible antibody population has been established, is very important Our team is researching both aspects of this problem The paper is written to stimulate the interest of both physical and biological scientists in this important problem It is thus written as a combination of tutorial (review) and future work (preview) We join Prof Federico Capasso and Editor Dennis Couwenberg in expressing our appreciation to all those working so heroically on all aspects of the COVID-19 problem And we thank Drs Capasso and Couwenberg for their invitation to write this paper © 2020 Navid Rajil et al , published by De Gruyter, Berlin/Boston 2020

Quantum entanglement is a powerful resource that revolutionizes information science, opens new horizons in communication technologies, and pushes the frontiers of sensing and imaging. Whether or not the methods of quantum entanglement can be extended to life-science imaging is far from clear. Live biological systems are eluding quantum-optical probes, proving, time and time again, too lossy, too noisy, too warm, and too wet to be meaningfully studied by quantum states of light. The central difficulty that puts the main roadblock on the path toward entanglement-enhanced nonlinear bioimaging is that the two-photon absorption (TPA) of entangled photons can exceed the TPA of uncorrelated photons only at the level of incident photon flux densities as low as one photon per entanglement area per entanglement time. This fundamental limitation has long been believed to rule out even a thinnest chance for a success of bioimaging with entangled photons. Here, we show that new approaches in nonlinear and quantum optics, combined with the latest achievements in biotechnologies, open the routes toward efficient photon-entanglement-based strategies in TPA microscopy that can help confront long-standing challenges in life-science imaging. Unleashing the full potential of this approach will require, however, high throughputs of virus-construct delivery, high expression efficiencies of genetically encodable fluorescent markers, high-brightness sources of entangled photons, as well as a thoughtful entanglement engineering in time, space, pulse, and polarization modes. We demonstrate that suitably tailored nonlinear optical fibers can deliver entangled photon pairs confined to entanglement volumes many orders of magnitude smaller than the entanglement volumes attainable through spontaneous parametric down-conversion. These ultracompact modes of entangled photons are shown to enable a radical enhancement of the TPA of entangled photons, opening new avenues for quantum entanglement in life-science imaging.

Integrated photonics will play a key role in quantum systems as they grow from few-qubit prototypes to tens of thousands of qubits. The underlying optical quantum technologies can only be realized through the integration of these components onto quantum photonic integrated circuits (QPICs) with accompanying electronics. In the last decade, remarkable advances in quantum photonic integration have enabled table-top experiments to be scaled down to prototype chips with improvements in efficiency, robustness, and key performance metrics. These advances have enabled integrated quantum photonic technologies combining up to 650 optical and electrical components onto a single chip that are capable of programmable quantum information processing, chip-to-chip networking, hybrid quantum system integration, and high-speed communications. In this roadmap article, we highlight the status, current and future challenges, and emerging technologies in several key research areas in integrated quantum photonics, including photonic platforms, quantum and classical light sources, quantum frequency conversion, integrated detectors, and applications in computing, communications, and sensing. With advances in materials, photonic design architectures, fabrication and integration processes, packaging, and testing and benchmarking, in the next decade we can expect a transition from single- and few-function prototypes to large-scale integration of multi-functional and reconfigurable devices that will have a transformative impact on quantum information science and engineering., JPhys Photonics, 4 (1), ISSN:2515-7647

We identify the physical factors that limit the terahertz (THz) yield of an optical rectification (OR) of ultrashort multiterawatt laser pulses in large-area quadratically nonlinear crystals. We show that the THz yield tends to slow its growth as a function of the laser driver energy, saturate, and eventually decrease as the laser beam picks up a spatiotemporal phase due to the intensity-dependent refraction of the OR crystal. We demonstrate that, with a careful management of the driver intensity aimed at keeping the nonlinear length larger than the coherence length, OR-based broadband THz generation in large-area lithium niobate (LN) crystals is energy-scalable, enabling an OR of multiterawatt laser pulses, yielding ∼ 10 µ J / c m 2 of THz output energy per unit crystal area. With a 27-fs, 10-TW, 800-nm Ti:sapphire laser output used as a driver for OR in large-area LN crystals, this approach is shown to provide a THz output with a pulse energy above 10 µJ and a bandwidth extending well beyond 6 THz, supporting single-cycle THz waveforms.

Enhanced-resolution imaging in complex scattering media is revisited from a parameter estimation perspective. A suitably defined Fisher information is shown to offer useful insights into the limiting precision of parameter estimation in a scattering environment and, hence, into the limiting spatial resolution that can be achieved in imaging-through-scattering settings. The Fisher information that defines this resolution limit via the Cramér–Rao lower bound is shown to scale with the number of adaptively controlled space–time modes of the probe field, suggesting a physically intuitive generalization of the Abbe limit to the spatial resolution attainable for complex scattering systems. In a conventional, direct-imaging microscopy setting, this bound is shown to converge to the canonical Abbe limit.

We present a closed-form analytical description for the metrological performance of a generic superposition of spin coherent states (SSCS) used as probes for quantum phase estimation. Working in this framework, we derive transparent analytical expressions for the pertinent quantum Fisher information and identify a general class of spin coherent states enabling quantum metrology with Heisenberg-limit precision. Bloch-sphere analysis of antipodal SSCS shows that the phase-estimation precision attainable with such states increases with the distance from the equator of the Bloch sphere, growing from the shot-noise limit level for the equatorial states all the way up to the Heisenberg limit for SSCS that can be represented as superpositions of the poles of the Bloch sphere.

Ultrafast laser-plasma interactions driven by ultrashort terawatt laser pulses are shown to give rise to a bright multioctave microwave radiation, whose polarization and spatial mode structure provides a sensitive probe for laser-driven plasma electrodynamics, helping detect the symmetries of plasma currents and signatures of multiple ionization. Polarization mode structure of this radiation is dominated, as polarization-resolved measurements show, by a radially polarized mode, indicating the significance of ponderomotively driven plasma currents as sources of microwave emission. Angle-resolved analysis of microwave supercontinua reveals regimes in which the microwave emission is drastically enhanced, via coherence buildup, manifested in a well-resolved Cherenkov-emission cone.

Cherenkov radiation is one of the central effects in relativistic electrodynamics, which lends its name to a vast class of optical phenomena in which a moving source emits off-axis radiation, giving rise to a signature Cherenkov emission cone. When a radiation source is confined to a finite path, however, translational symmetry of its motion is removed, giving rise to edge effects that modify the canonical picture of conical emission. Here, we focus on one class of such edge effects as the key to understanding the properties of secondary radiation by laser-induced filaments. Charge-current transients near the edges of laser filaments are shown to couple Cherenkov emission to bremsstrahlung and transition radiation, giving rise to filament-length-sensitive features in the radiation field structure. We present a unified description of this class of radiation phenomena with a continuous analytical crossover from the subluminal to the superluminal setting of radiating currents and with the low-frequency cutoff in the radiation spectrum defined by the filament length.

We find that stimulated Raman excitation of an atom by a two-photon pulse can be enhanced by orders of magnitude if the photons are simultaneously frequency correlated and spatially anticorrelated. That is, a correlated photon pair must have an inherent time delay between its constituent photons. This counterintuitive feature is a manifestation of the uncertainty principle, which yields that frequency-correlated photons cannot be time (spatially) correlated. This is opposite to two-photon absorption by a three-level atom, for which the enhancement occurs if photons in the pulse are frequency anticorrelated and spatially correlated, that is, photons in the pair simultaneously interact with the atom. Our findings can be useful for imaging and spectroscopy of biological samples which demand low illumination intensity.

Vectorial four-wave mixing of low-power ultrashort laser pulses in a highly nonlinear fiber with a properly optimized dispersion profile is shown to enable an efficient generation of high-quality photon pairs with photon-pair count rates above 10 6 pairs/(s mW). A superbunching regime of photon-pair generation with the correlation coefficients g ( 2 ) ( 0 ) exceeding 1200 is demonstrated with pump powers p as low as 0.1 mW. Very low values of heralded-photon correlation coefficients, g c 2 0 3 ⋅ 1 0 − 3 , achieved in the low-p regime reveal a strong antibunching in the signal-photon channel, indicating that more than 99.7% of the signal counts correspond to truly single-photon states.

A harmonically driven cavity QED system consisting of two cavities and a two-level qubit is shown to enable the generation of a vast class of maximally entangled states suitable for measurements with a Heisenberg-limit precision. As one of its modalities, this system can serve as a quantum beam splitter, converting an |N〉 ⊗ |0〉 input into a maximally entangled N00N state (|N〉 ⊗ |0〉 + |0〉 ⊗ |N〉)/$$\sqrt{{\bf{2}}}$$2 at its output. A network of such quantum beam splitters is shown to provide a source of multimode N00N-type entanglement.

Accurate, high spatial resolution thermal measurements have provided fundamental insights into many fields of study; however, existing thermometer technology often suffers from one or more limitati...

We report an observation of the linear Stark effect in a ${\mathrm{Tm}}^{3+}:{\mathrm{Y}}_{3}{\mathrm{Al}}_{5}{\mathrm{O}}_{12}$ crystal with the distribution of the Stark coefficient over the ion ensemble. We associate this effect with local lattice distortions near the positions of ${\mathrm{Tm}}^{3+}$ ions. Using this effect, the addressable storage of a series of weak light pulses in a cavity-assisted scheme of the revival of silenced echo quantum memory protocol is implemented. In this memory scheme, we also demonstrate storage of a light pulse on the few photon level. The application of an optical resonator makes it possible to increase the memory efficiency in this crystal and to reduce the minimal number of photons in the input signal pulse to 5.6 for the signal-to-noise ratio of 1 in the retrieved echo pulse. The results are in good agreement with the theoretical analysis. The possible ways of the further improvement of the implemented memory scheme are also discussed.

We propose to enhance the performance of localized plasmon structured illumination microscopy (LP-SIM) via intensity correlations. LP-SIM uses sub-wavelength illumination patterns to encode high spatial frequency information. It can enhance the resolution up to three-fold before gaps in the optical transfer function (OTF) support arise. For blinking fluorophores or for quantum antibunching, an intensity correlation analysis induces higher harmonics of the illumination pattern and enlarges the effective OTF. This enables ultrahigh resolutions without gaps in the OTF support, and thus a fully deterministic imaging scheme. We present simulations that include shot and external noise and demonstrate the resolution power under realistic photon budgets. The technique has potential in light microscopy where low-intensity illumination is paramount while aiming for high spatial but moderate temporal resolutions.

Ischemic cerebral stroke is one of the leading causes of death and disability in humans. However, molecular processes underlying the development of this pathology remain poorly understood. There are major gaps in our understanding of metabolic changes that occur in the brain tissue during the early stages of ischemia and reperfusion. In particular, it is generally accepted that both ischemia (I) and reperfusion (R) generate reactive oxygen species (ROS) that cause oxidative stress which is one of the main drivers of the pathology, although ROS generation during I/R was never demonstrated in vivo due to the lack of suitable methods. In the present study, we record for the first time the dynamics of intracellular pH and H2O2 during I/R in cultured neurons and during experimental stroke in rats using the latest generation of genetically encoded biosensors SypHer3s and HyPer7. We detect a buildup of powerful acidosis in the brain tissue that overlaps with the ischemic core from the first seconds of pathogenesis. At the same time, no significant H2O2 generation was found in the acute phase of ischemia/reperfusion. HyPer7 oxidation in the brain was detected only 24 h later. Comparison of in vivo experiments with studies on cultured neurons under I/R demonstrates that the dynamics of metabolic processes in these models significantly differ, suggesting that a cell culture is a poor predictor of metabolic events in vivo., Highlights • The dynamics of stroke-induced changes in intracellular pH and H2O2 was recorded. • Ischemia leads to immediate acidification of the affected part of the brain. • Only slight increase in H2O2 in the brain tissue occurs during ischemia/reperfusion. • The pronounced increase in H2O2 in the brain occurs next day after I/R. • Neurons show different I/R-induced pH and H2O2 dynamics in vitro and in vivo.

High-resolution thermal and magnetic vector gradient imaging is demonstrated using diamond quantum sensors in a microstructured fiber probe platform. These sensors are capable of in situ magnetic field and temperature measurements with 160 pT / Hz and 25 mK / Hz sensitivities.

The spectrum of atomic hydrogen has long been viewed as a Rosetta stone that bears the key to decode the writings of quantum mechanics in a vast variety of physical, chemical, and biological systems. Here, we show that, in addition to its role as a basic model of quantum mechanics, the hydrogen atom provides a fundamental building block of quantum information. Through its electron and nuclear spin degrees of freedom, the hydrogen atom is shown to lend a physically meaningful frame and a suitable Hilbert space for bipartite entanglement, whose two-qubit concurrence and quantum coherence can be expressed in terms of the fundamental physical constants -- the Planck and Boltzmann constants, electron and proton masses, the fine-structure constant, as well as the Bohr radius and the Bohr magneton. The intrinsic, natural entanglement that the hyperfine-structure (HFS) states of the H atom store at low temperatures rapidly decreases with a growth in temperature, vanishing above a $\tau_c$ $\approx$ 5.35 $\mu$eV threshold. An external magnetic field, however, can overcome this thermal loss of HFS entanglement. As one of the central findings of this work, we show that an external magnetic field can induce and sustain an HFS entanglement, against all the odds of thermal effects, at temperatures well above the $\tau_c$ threshold, thus enabling magnetic-field-assisted entanglement engineering in low-temperature gases and solids., Comment: 6 pages, 4 figures

We present experiments on cell cultures and brain slices that demonstrate two-photon optogenetic pH sensing and pH-resolved brain imaging using a laser driver whose spectrum is carefully tailored to provide the maximum contrast of a ratiometric two-photon fluorescence readout from a high-brightness genetically encoded yellow-fluorescent-protein-based sensor, SypHer3s. Two spectrally isolated components of this laser field are set to induce two-photon-excited fluorescence (2PEF) by driving SypHer3s through one of two excitation pathways - via either the protonated or deprotonated states of its chromophore. With the spectrum of the laser field accurately adjusted for a maximum contrast of these two 2PEF signals, the ratio of their intensities is shown to provide a remarkably broad dynamic range for pH measurements, enabling high-contrast optogenetic deep-brain pH sensing and pH-resolved 2PEF imaging within a vast class of biological systems, ranging from cell cultures to the living brain. This article is protected by copyright. All rights reserved.

Lateral flow assay (LFA) has long been used as a biomarker detection technique. It has advantages such as low cost, rapid readout, portability, and ease of use. However, its qualitative readout process and lack of sensitivity are limiting factors. We report a photon-counting approach to accurately quantify LFAs while enhancing sensitivity. In particular, we demonstrate that the density of SARS-CoV-2 antibodies can be quantified and measured with an enhanced sensitivity using this simple laser optical analysis.

We demonstrate a reconnectable implantable ultraslim fiber-optic microendoscope that integrates a branching fiber bundle (BFB) with gradient-index fiber lenses, enabling a simultaneous fluorescence imaging of individual cells in distinctly separate brain regions, including brain structures as distant as the neocortex and hippocampus. We show that fluorescence images of individual calcium-indicator-expressing neurons in the brain of freely moving transgenic mice can be recorded, via the implanted BFB probe, in parallel with time- and cell-resolved traces of calcium signaling, thus enabling correlated circuit-dynamics studies at -multiple sites within the brain of freely moving animals.

Ultrashort high-energy pulses at wavelengths longer than 1 µm are now desirable for a vast variety of applications in ultrafast and strong-field physics. To date, the main answer to the wavelength tunability for energetic, broadband pulses still relies on optical parametric amplification (OPA), which often requires multiple and complex stages, may feature imperfect beam quality, and has limited conversion efficiency into one of the amplified waves. In this work, we present a completely different strategy to realize an energy-efficient and scalable laser frequency shifter. This relies on the continuous red shift provided by stimulated Raman scattering (SRS) over a long propagation distance in nitrogen-filled hollow-core fibers (HCF). We show a continuous tunability of the laser wavelength from 1030 nm up to 1730 nm with a conversion efficiency higher than 70% and high beam quality. The highly asymmetric spectral broadening, arising from the spatiotemporal nonlinear interplay between higher-order modes of the HCF, can be readily employed to generate pulses ( ∼ 20 f s ) significantly shorter than the pump ones ( ∼ 200 f s ) with high beam quality, and the pulse energy can further be scaled up to tens of millijoules. We envision that this technique, coupled with the emerging high-power Yb laser technology, has the potential to answer the increasing demand for energetic multi-TW few-cycle sources tunable in the near-IR.

We present an optical scientist vision for a photonic platform for real-time polymerase chain reaction (qPCR) and reverse-transcription qPCR (qRT-PCR) that integrates a rapid-cycle fiber-optic PCR chamber with feedback-controlled laser heating, online fluorometric detection of PCR products, and all-optical thermometry using an optical readout from color centers of diamond nanoparticles. We show that, with a careful optimization of laser-induced heating and heat-removal geometry, this approach can radically shorten the qPCR thermal cycle relative to standard PCR systems, paving the way toward credit-card-size testing kits for fast point-of-care infection diagnosis. Faster photonic qPCR/qRT-PCR will enable a rapid and highly specific early detection of infections, including new viruses, such as SARS-CoV-2 at very early stages-in most cases, even before the onset of disease, providing much-needed lead time for early treatment and disease spread prevention.

Remarkable advancements in the ability to create, manipulate, and measure quantum systems are paving the way to build next generations of devices based on quantum physics. Quantum technologies in Russia are on the list of strategically important cross-cutting directions in the framework of the National Technology Initiative programs and the Digital Economy National Program. The broad focus includes quantum computing and simulation, quantum communications, quantum metrology and sensing. This paper reviews existing research on quantum science and technologies in Russia and summarizes the main goals for the next few years that form the basis of an upcoming major national initiative.

Electron tunneling induced by a strong-field laser driver can lead to an ultrafast stepwise buildup of the photoelectron density \ensuremath{\rho}. When the laser field is strong enough, each such step in the temporal profile of \ensuremath{\rho} is confined well within the field cycle, providing an ultrabroadband, multidecade force that drives the photoelectron current $j$. However, whether or not the photocurrent can emit electromagnetic radiation with such an extraordinarily broad spectrum depends on the damping, which defines the low-frequency cutoff in the spectrum of this radiation. We show that, with a suitable choice of the gas pressure and parameters of the laser driver, the laser-induced tunneling photocurrent can serve as a source of a remarkably broadband electromagnetic radiation with a multidecade spectrum stretching from the vacuum ultraviolet all the way down to the microwave range. We demonstrate that the supercontinuum fields emitted by individual photocurrent steps, induced by different field half cycles, can coherently combine, giving rise to well-resolved high-order harmonics on the high-frequency end of the spectrum yoked to a bright midinfrared to microwave supercontinuum, dominating the long-wavelength part of the multidecade radiation output.

At the level of peak powers needed for a Kerr-lens mode-locked operation of solid-state soliton short-pulse lasers, a periodic perturbation induced by spatially localized pulse amplification in a laser cavity can induce soliton instability with respect to resonant dispersive-wave radiation, eventually leading to soliton blowup and pulse splitting of the laser output. Here, we present an experimental study of a high-peak-power self-mode-locking Cr:forsterite laser, showing that, despite its complex, explosion-like buildup dynamics, this soliton blowup can be captured and quantitatively characterized via an accurate cavity-dispersion- and gain-resolved analysis of the laser output. We demonstrate that, with a suitable cavity design and finely tailored balance of gain, dispersion, and nonlinearity, such a laser can be operated in a subcritical mode, right beneath the soliton blowup threshold, providing an efficient source of sub-100-fs 15–20 MHz repetition-rate pulses with energies as high as 33 nJ.

All-optical thermometry presents a promising avenue of investigation for sensitive biological and electronic systems, with methods free of radio-frequency interference of particular importance. In this work, an all-optical scanning fiber thermometer is tested and shown to possess $5\phantom{\rule{0.2em}{0ex}}\ensuremath{\mu}\mathrm{m}$ spatial and $20\phantom{\rule{0.2em}{0ex}}\mathrm{mK}/\sqrt{\mathrm{Hz}}$ temperature resolution. This probe is then used to generate noncontact scanning thermal images of active circuit elements with microscale thermal features.

We present brain imaging experiments on rat cortical areas, demonstrating that, when combined with a suitable high-brightness, cell-specific genetically encoded fluorescent marker, three-photon-excited fluorescence (3PEF), enables subcellular-resolution, cell-specific 3D brain imaging that is fully compatible and readily integrable with other nonlinear-optical imaging modalities, including two-photon-fluorescence and harmonic-generation microscopy. With laser excitation provided by sub-100-fs, 1.25-µm laser pulses, cell-specific 3PEF from astrocytes and their processes detected in parallel with a three-photon-resonance-enhanced third harmonic from blood vessels is shown to enable a high-contrast 3D imaging of gliovascular interfaces.