Aleksandr Lanin - Academia.edu (original) (raw)

Papers by Aleksandr Lanin

Photonics, 2021

We demonstrate an adaptive wave-front shaping of optical beams transmitted through fiber bundles ... more 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 fu...

Nonlinear microscopy techniques are widely used in the field of biophotonics thanks to their abil... more Nonlinear microscopy techniques are widely used in the field of biophotonics thanks to their ability to image in highly scattering tissues such as brain [1]. Techniques that use intrinsic sources of contrast rather than exogenous labels are of great interest, because they are suitable not only for fundamental biological research but also for clinical applications [2]. Neurons are the most studied cells in the central nervous system of mammals. However, in certain parts of brain glial cells called astrocytes outnumber neurons. Historically, astrocytes considered to be simple support cells that structure the brain and control blood brain barrier, but recently were discovered to have great functional diversity and play many roles in healthy tissues as well as in CNS disorders [3].

Optics Letters, 2019

Polarization maps of high-order harmonics are shown to enable a full vectorial characterization o... more Polarization maps of high-order harmonics are shown to enable a full vectorial characterization of petahertz electron currents generated in a crystalline solid by an ultrashort laser driver. As a powerful resource of this methodology, analysis of energy-momentum dispersion landscapes, defined by the electron band structure, can help identify, as our analysis shows, special directions within the Brillouin zone that can provide a preferable basis for polarization-sensitive high-harmonic mapping of anisotropic petahertz photocurrents in solids.

Journal of Raman Spectroscopy, 2020

Journal of Biophotonics, 2019

We demonstrate an accurate quantitative characterization of absolute two- and three-photon absorp... more We demonstrate an accurate quantitative characterization of absolute two- and three-photon absorption (2PA and 3PA) action cross sections of a genetically encodable fluorescent marker Sypher3s. Both 2PA and 3PA action cross sections of this marker are found to be remarkably high, enabling high-brightness, cell-specific two- and three-photon fluorescence brain imaging. Brain imaging experiments on sliced samples of rat's cortical areas are presented to demonstrate these imaging modalities. The 2PA action cross section of Sypher3s is shown to be highly sensitive to the level of pH, enabling pH measurements via a ratiometric readout of the two-photon fluorescence with two laser excitation wavelengths, thus paving the way toward fast optical pH sensing in deep-tissue experiments. This article is protected by copyright. All rights reserved.

Journal of Biophotonics, 2019

Methods of nonlinear optics provide a vast arsenal of tools for label-free brain imaging, offerin... more Methods of nonlinear optics provide a vast arsenal of tools for label-free brain imaging, offering a unique combination of chemical specificity, the ability to detect fine morphological features, and an unprecedentedly high, subdiffraction spatial resolution. While these techniques provide a rapidly growing platform for the microscopy of neurons and fine intraneural structures, optical imaging of astroglia still largely relies on filament-protein-antibody staining, subject to limitations and difficulties especially severe in live-brain studies. Once viewed as an ancillary, inert brain scaffold, astroglia are being promoted, as a part of an ongoing paradigm shift in neurosciences, into the role of a key active agent of intercellular communication and information processing, playing a significant role in brain functioning under normal and pathological conditions. Here, we show that methods of nonlinear optics provide a unique resource to address long-standing challenges in label-free astroglia imaging. We demonstrate that, with a suitable beam-focusing geometry and careful driver-pulse compression, microscopy of second-harmonic generation (SHG) can enable a high-resolution label-free imaging of fibrillar structures of astrocytes, most notably astrocyte processes and their endfeet. SHG microscopy of astrocytes is integrated in our approach with nonlinear-optical imaging of red blood cells based on third-harmonic generation (THG) enhanced by a three-photon resonance with the Soret band of hemoglobin. With astroglia and red blood cells providing two physically distinct imaging contrasts in SHG and THG channels, a parallel detection of the second and third harmonics enables a high-contrast, high-resolution, stain-free stereoimaging of gliovascular interfaces in the central nervous system. Transverse scans of the second and third harmonics are shown to resolve an ultrafine texture of blood-vessel walls and astrocyte-process endfeet on gliovascular interfaces with a spatial resolution within 1 μm at focusing depths up to 20 μm inside a brain. This article is protected by copyright. All rights reserved.

Journal of Raman Spectroscopy, 2019

Therapeutic Delivery, 2017

Most diseases and disorders of the brain require long-term therapy and a constant supply of drugs... more Most diseases and disorders of the brain require long-term therapy and a constant supply of drugs. Implantable drug-delivery systems provide long-term, sustained drug delivery in the brain. The present review discusses different type of implantable systems such as solid implants, in situ forming implants, in situ forming microparticles, depot formulations, polymeric-lipid implants, sucrose acetate isobutyrate and N-stearoyl L-alanine methyl ester systems for continuous drug delivery into brain for various brain diseases including glioblastomas, medulloblastoma, epilepsy, stroke, schizophrenia and Alzheimer's diseases. Implantable neural probes and microelectrode array systems for brain are also discussed in brief.

Neuroscience Letters, 2018

Thermogenetics is a promising innovative neurostimulation technique, which enables robust activat... more Thermogenetics is a promising innovative neurostimulation technique, which enables robust activation of single neurons using thermosensitive cation channels and IR stimulation. The main advantage of IR stimulation compared to conventional visible light optogenetics is the depth of penetration (up to millimeters). Due to physiological limitations, thermogenetic molecular tools for mammalian brain stimulation remain poorly developed. Here, we tested the possibility of employment of this new technique for stimulation of neocortical neurons. The method is based on activation gating of TRPV1-L channels selectively expressed in specific cells. Pyramidal neurons of layer 2/3 of neocortex were transfected at an embryonic stage using a pCAG expression vector and electroporation in utero. Depolarization and spiking responses of TRPV1L+ pyramidal neurons to IR radiation were recorded electrophysiologically in acute brain slices of adult animals with help of confocal visualization. As TRPV1L-expressing neurons are not sensitive to visible light, there were no limitations of the use of this technique with conventional fluorescence imaging. Our experiments demonstrated that the TRPV1-L + pyramidal neurons preserve their electrical excitability in acute brain slices, while IR radiation can be successfully used to induce single neuronal depolarization and spiking at near physiological temperatures. Obtained results provide important information for adaptation of thermogenetic technology to mammalian brain studies in vivo.

Chemistry of Materials, 2017

Stimuli-responsive materials, such as thermochromics, have found mass usage and profitability in ... more Stimuli-responsive materials, such as thermochromics, have found mass usage and profitability in manufacturing and process control. Imparting charge-transfer-based functional supramolecular materials with tunable thermochromism emerges as an ideal strategy to construct optically responsive multifunctional assemblies. Herein, the authors report a new series of thermochromic charge-transfer-based supramolecular materials assembled in water. These assemblies are composed of a bis-bipyridiniumderived acceptor and a series of commercially available donorsnamely, the neurotransmitter melatonin and its analogue bioisosteres. When the chemical structure of the donors are tailored, the strength of the chargetransfer interactions can be tuned. Thermochromic aerogels and inks of these materials are prepared, with a large selection of colors, in environment-friendly solvents and demonstrate tunable thermochromic transition temperatures ranging from 45 to 105°C. Favorable compatibility of these materials with commercial inks and inkjet printers afford excellent pattern quality with extended color options. Mechanistic studies reveal that the two types of water molecules were bound to the supramolecular complexes with differing strengths, and that the more weakly bound water is responsible for the thermochromic transitions.

Journal of Raman Spectroscopy, 2016

We demonstrate a compact laser platform that integrates stimulated and coherent Raman microscopy ... more We demonstrate a compact laser platform that integrates stimulated and coherent Raman microscopy with high-resolution nonlinear Raman spectroscopy. Ultrashort laser pulses with a carefully managed, broadly tunable chirp are shown to enable a comfortable switching between the high-contrast microscopy and high-resolution spectroscopy modalities in both stimulated and coherent versions of nonlinear Raman scattering. Sub-10-cm À1 spectral resolution in stimulated Raman spectroscopy is demonstrated through a careful compensation of nonlinear phase distortions of ultrashort laser pulses. This offers a powerful tool for a reliable identification of molecular vibrations with close frequencies, enhancing the chemical selectivity of spectroscopic analysis of complex multicomponent systems.

Nature communications, Jan 22, 2017

Thermogenetics is a promising innovative neurostimulation technique, which enables robust activat... more Thermogenetics is a promising innovative neurostimulation technique, which enables robust activation of neurons using thermosensitive transient receptor potential (TRP) cation channels. Broader application of this approach in neuroscience is, however, hindered by a limited variety of suitable ion channels, and by low spatial and temporal resolution of neuronal activation when TRP channels are activated by ambient temperature variations or chemical agonists. Here, we demonstrate rapid, robust and reproducible repeated activation of snake TRPA1 channels heterologously expressed in non-neuronal cells, mouse neurons and zebrafish neurons in vivo by infrared (IR) laser radiation. A fibre-optic probe that integrates a nitrogen-vacancy (NV) diamond quantum sensor with optical and microwave waveguide delivery enables thermometry with single-cell resolution, allowing neurons to be activated by exceptionally mild heating, thus preventing the damaging effects of excessive heat. The neuronal re...

Laser Physics Letters, 2015

We propose simple, yet efficient strategies of pulse-width optimization applicable for nonlinear ... more We propose simple, yet efficient strategies of pulse-width optimization applicable for nonlinear Raman brain imaging. With the spectral bandwidth of laser pulses accurately matched against the bandwidth of molecular vibrations, the coherent Raman signal is shown to be radically enhanced, enabling higher sensitivities and higher frame rates in nonlinear Raman brain imaging. As a specific example, we show that subpicosecond pulses offer a powerful tool for the detection of brain tumors using stimulated Raman microscopy, as they provide a strong signal without compromising the molecular specificity.

Optics and Spectroscopy, 2015

Optical physics and laser technologies are rapidly moving in the direction of exploring the midin... more Optical physics and laser technologies are rapidly moving in the direction of exploring the midinfrared spectral range. New methods of mid-IR ultrashort pulse generation allow forming very short flashes of electromagnetic radiation with record high peak power for this range. The first experiments conducted with such systems make possible implementing new regimes of laser–matter interaction and shed light on unusual properties of the nonlinear-optical response of materials in the mid-IR spectral range.

Optics letters, Jan 15, 2015

Strongly coupled nonlinear spatiotemporal dynamics of ultrashort mid-infrared pulses undergoing s... more Strongly coupled nonlinear spatiotemporal dynamics of ultrashort mid-infrared pulses undergoing self-focusing simultaneously with soliton self-compression in an anomalously dispersive, highly nonlinear solid semiconductor is shown to enable the generation of multioctave supercontinua with spectra spanning the entire mid-infrared range and compressible to subcycle pulse widths. With 7.9 μm, 150 fs, 2 μJ, 1 kHz pulses used as a driver, 1.2 cycle pulses of mid-infrared supercontinuum radiation with a spectrum spanning the range of wavelengths from 3 to 18 μm were generated in a 5 mm GaAs plate. Further compression of these pulses to subcycle pulse widths is possible through compensation of the residual phase shift.

AIP Conference Proceedings, 2010

In the early days of CARS, stimulated Raman scattering (SRS) has been successfully used to genera... more In the early days of CARS, stimulated Raman scattering (SRS) has been successfully used to generate the Stokes field for time-resolved measurements [1] of vibrational lifetimes of molecules in liquids and phonons in solids. Dye lasers and optical parametric sources ...

Optics Letters, 2010

We measured the MCAP (middle cerebral artery pressure)/MSBP (mean systemic blood pressure) ratio ... more We measured the MCAP (middle cerebral artery pressure)/MSBP (mean systemic blood pressure) ratio in 76 patients who underwent an EIAB (extracranial-intracranial arterial bypass). Patients were divided into groups on the basis of angiographic findings. We found a definite correlation between increasing angiographic cerebral vascular occlusive disease and lower MCAP/MSBP ratios. Six of 32 patients with a preoperative neurologic deficit demonstrated mild but definite postoperative neurologic improvement. The mean MCAP/MSBP ratio in these six patients was significantly lower than that for the remainder of this group (p < .05). Finally, postoperative filling of the middle cerebral artery territory through the graft was found to correlate in an inverse linear relationship with MCAP/MSBP. Evidence is presented that hypoperfusion produced by occlusion of major cranial vessels plays an important role in temporary and permanent neurological deficits seen in patients with cerebrovascular disease.

Journal of Modern Optics, 2010

ABSTRACT

Conference on Lasers and Electro-Optics, 2016

We demonstrate a robust, all-solid-state approach for the generation of microjoule subcycle pulse... more We demonstrate a robust, all-solid-state approach for the generation of microjoule subcycle pulses in the mid-infrared through a cascade of carefully optimized parametric-amplification, difference-frequency-generation, spectral-broadening, and chirp-compensation stages. This method of subcycle waveform generation becomes possible due to an unusual, ionizationassisted solid-state pulse self-compression dynamics, where highly efficient spectral broadening is enabled by ultrabroadband four-wave parametric amplification phase-matched near the zero-group-velocity wavelength of the material. Rapidly progressing photonic technologies offer an unprecedented control over optical field waveforms, enabling the generation of extremely brief flashes of electromagnetic radiation with accurately controlled shape, spectrum, and phase [1, 2]. At the forefront of the ongoing quest for ultrashort optical probes that would be capable of resolving extremely fast processes in gas-phase [3] and solid-state [4, 5] systems, technologies allowing the generation of electromagnetic lightwaves with temporal envelopes shorter than the field cycle have been developed [6-10], paving the ways toward an ultimate time resolution in electron-dynamic studies and subcycle precision in lightwave sculpting. Subcycle field waveform generation has been demonstrated for the visible, nearinfrared, terahertz, and x-ray ranges [7, 9]. In the mid-infrared region, on the other hand, subcycle field waveform generation has been only possible through a two-color filamentation

Photonics, 2021

We demonstrate an adaptive wave-front shaping of optical beams transmitted through fiber bundles ... more 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 fu...

Nonlinear microscopy techniques are widely used in the field of biophotonics thanks to their abil... more Nonlinear microscopy techniques are widely used in the field of biophotonics thanks to their ability to image in highly scattering tissues such as brain [1]. Techniques that use intrinsic sources of contrast rather than exogenous labels are of great interest, because they are suitable not only for fundamental biological research but also for clinical applications [2]. Neurons are the most studied cells in the central nervous system of mammals. However, in certain parts of brain glial cells called astrocytes outnumber neurons. Historically, astrocytes considered to be simple support cells that structure the brain and control blood brain barrier, but recently were discovered to have great functional diversity and play many roles in healthy tissues as well as in CNS disorders [3].

Optics Letters, 2019

Polarization maps of high-order harmonics are shown to enable a full vectorial characterization o... more Polarization maps of high-order harmonics are shown to enable a full vectorial characterization of petahertz electron currents generated in a crystalline solid by an ultrashort laser driver. As a powerful resource of this methodology, analysis of energy-momentum dispersion landscapes, defined by the electron band structure, can help identify, as our analysis shows, special directions within the Brillouin zone that can provide a preferable basis for polarization-sensitive high-harmonic mapping of anisotropic petahertz photocurrents in solids.

Journal of Raman Spectroscopy, 2020

Journal of Biophotonics, 2019

We demonstrate an accurate quantitative characterization of absolute two- and three-photon absorp... more We demonstrate an accurate quantitative characterization of absolute two- and three-photon absorption (2PA and 3PA) action cross sections of a genetically encodable fluorescent marker Sypher3s. Both 2PA and 3PA action cross sections of this marker are found to be remarkably high, enabling high-brightness, cell-specific two- and three-photon fluorescence brain imaging. Brain imaging experiments on sliced samples of rat's cortical areas are presented to demonstrate these imaging modalities. The 2PA action cross section of Sypher3s is shown to be highly sensitive to the level of pH, enabling pH measurements via a ratiometric readout of the two-photon fluorescence with two laser excitation wavelengths, thus paving the way toward fast optical pH sensing in deep-tissue experiments. This article is protected by copyright. All rights reserved.

Journal of Biophotonics, 2019

Methods of nonlinear optics provide a vast arsenal of tools for label-free brain imaging, offerin... more Methods of nonlinear optics provide a vast arsenal of tools for label-free brain imaging, offering a unique combination of chemical specificity, the ability to detect fine morphological features, and an unprecedentedly high, subdiffraction spatial resolution. While these techniques provide a rapidly growing platform for the microscopy of neurons and fine intraneural structures, optical imaging of astroglia still largely relies on filament-protein-antibody staining, subject to limitations and difficulties especially severe in live-brain studies. Once viewed as an ancillary, inert brain scaffold, astroglia are being promoted, as a part of an ongoing paradigm shift in neurosciences, into the role of a key active agent of intercellular communication and information processing, playing a significant role in brain functioning under normal and pathological conditions. Here, we show that methods of nonlinear optics provide a unique resource to address long-standing challenges in label-free astroglia imaging. We demonstrate that, with a suitable beam-focusing geometry and careful driver-pulse compression, microscopy of second-harmonic generation (SHG) can enable a high-resolution label-free imaging of fibrillar structures of astrocytes, most notably astrocyte processes and their endfeet. SHG microscopy of astrocytes is integrated in our approach with nonlinear-optical imaging of red blood cells based on third-harmonic generation (THG) enhanced by a three-photon resonance with the Soret band of hemoglobin. With astroglia and red blood cells providing two physically distinct imaging contrasts in SHG and THG channels, a parallel detection of the second and third harmonics enables a high-contrast, high-resolution, stain-free stereoimaging of gliovascular interfaces in the central nervous system. Transverse scans of the second and third harmonics are shown to resolve an ultrafine texture of blood-vessel walls and astrocyte-process endfeet on gliovascular interfaces with a spatial resolution within 1 μm at focusing depths up to 20 μm inside a brain. This article is protected by copyright. All rights reserved.

Journal of Raman Spectroscopy, 2019

Therapeutic Delivery, 2017

Most diseases and disorders of the brain require long-term therapy and a constant supply of drugs... more Most diseases and disorders of the brain require long-term therapy and a constant supply of drugs. Implantable drug-delivery systems provide long-term, sustained drug delivery in the brain. The present review discusses different type of implantable systems such as solid implants, in situ forming implants, in situ forming microparticles, depot formulations, polymeric-lipid implants, sucrose acetate isobutyrate and N-stearoyl L-alanine methyl ester systems for continuous drug delivery into brain for various brain diseases including glioblastomas, medulloblastoma, epilepsy, stroke, schizophrenia and Alzheimer's diseases. Implantable neural probes and microelectrode array systems for brain are also discussed in brief.

Neuroscience Letters, 2018

Thermogenetics is a promising innovative neurostimulation technique, which enables robust activat... more Thermogenetics is a promising innovative neurostimulation technique, which enables robust activation of single neurons using thermosensitive cation channels and IR stimulation. The main advantage of IR stimulation compared to conventional visible light optogenetics is the depth of penetration (up to millimeters). Due to physiological limitations, thermogenetic molecular tools for mammalian brain stimulation remain poorly developed. Here, we tested the possibility of employment of this new technique for stimulation of neocortical neurons. The method is based on activation gating of TRPV1-L channels selectively expressed in specific cells. Pyramidal neurons of layer 2/3 of neocortex were transfected at an embryonic stage using a pCAG expression vector and electroporation in utero. Depolarization and spiking responses of TRPV1L+ pyramidal neurons to IR radiation were recorded electrophysiologically in acute brain slices of adult animals with help of confocal visualization. As TRPV1L-expressing neurons are not sensitive to visible light, there were no limitations of the use of this technique with conventional fluorescence imaging. Our experiments demonstrated that the TRPV1-L + pyramidal neurons preserve their electrical excitability in acute brain slices, while IR radiation can be successfully used to induce single neuronal depolarization and spiking at near physiological temperatures. Obtained results provide important information for adaptation of thermogenetic technology to mammalian brain studies in vivo.

Chemistry of Materials, 2017

Stimuli-responsive materials, such as thermochromics, have found mass usage and profitability in ... more Stimuli-responsive materials, such as thermochromics, have found mass usage and profitability in manufacturing and process control. Imparting charge-transfer-based functional supramolecular materials with tunable thermochromism emerges as an ideal strategy to construct optically responsive multifunctional assemblies. Herein, the authors report a new series of thermochromic charge-transfer-based supramolecular materials assembled in water. These assemblies are composed of a bis-bipyridiniumderived acceptor and a series of commercially available donorsnamely, the neurotransmitter melatonin and its analogue bioisosteres. When the chemical structure of the donors are tailored, the strength of the chargetransfer interactions can be tuned. Thermochromic aerogels and inks of these materials are prepared, with a large selection of colors, in environment-friendly solvents and demonstrate tunable thermochromic transition temperatures ranging from 45 to 105°C. Favorable compatibility of these materials with commercial inks and inkjet printers afford excellent pattern quality with extended color options. Mechanistic studies reveal that the two types of water molecules were bound to the supramolecular complexes with differing strengths, and that the more weakly bound water is responsible for the thermochromic transitions.

Journal of Raman Spectroscopy, 2016

We demonstrate a compact laser platform that integrates stimulated and coherent Raman microscopy ... more We demonstrate a compact laser platform that integrates stimulated and coherent Raman microscopy with high-resolution nonlinear Raman spectroscopy. Ultrashort laser pulses with a carefully managed, broadly tunable chirp are shown to enable a comfortable switching between the high-contrast microscopy and high-resolution spectroscopy modalities in both stimulated and coherent versions of nonlinear Raman scattering. Sub-10-cm À1 spectral resolution in stimulated Raman spectroscopy is demonstrated through a careful compensation of nonlinear phase distortions of ultrashort laser pulses. This offers a powerful tool for a reliable identification of molecular vibrations with close frequencies, enhancing the chemical selectivity of spectroscopic analysis of complex multicomponent systems.

Nature communications, Jan 22, 2017

Thermogenetics is a promising innovative neurostimulation technique, which enables robust activat... more Thermogenetics is a promising innovative neurostimulation technique, which enables robust activation of neurons using thermosensitive transient receptor potential (TRP) cation channels. Broader application of this approach in neuroscience is, however, hindered by a limited variety of suitable ion channels, and by low spatial and temporal resolution of neuronal activation when TRP channels are activated by ambient temperature variations or chemical agonists. Here, we demonstrate rapid, robust and reproducible repeated activation of snake TRPA1 channels heterologously expressed in non-neuronal cells, mouse neurons and zebrafish neurons in vivo by infrared (IR) laser radiation. A fibre-optic probe that integrates a nitrogen-vacancy (NV) diamond quantum sensor with optical and microwave waveguide delivery enables thermometry with single-cell resolution, allowing neurons to be activated by exceptionally mild heating, thus preventing the damaging effects of excessive heat. The neuronal re...

Laser Physics Letters, 2015

We propose simple, yet efficient strategies of pulse-width optimization applicable for nonlinear ... more We propose simple, yet efficient strategies of pulse-width optimization applicable for nonlinear Raman brain imaging. With the spectral bandwidth of laser pulses accurately matched against the bandwidth of molecular vibrations, the coherent Raman signal is shown to be radically enhanced, enabling higher sensitivities and higher frame rates in nonlinear Raman brain imaging. As a specific example, we show that subpicosecond pulses offer a powerful tool for the detection of brain tumors using stimulated Raman microscopy, as they provide a strong signal without compromising the molecular specificity.

Optics and Spectroscopy, 2015

Optical physics and laser technologies are rapidly moving in the direction of exploring the midin... more Optical physics and laser technologies are rapidly moving in the direction of exploring the midinfrared spectral range. New methods of mid-IR ultrashort pulse generation allow forming very short flashes of electromagnetic radiation with record high peak power for this range. The first experiments conducted with such systems make possible implementing new regimes of laser–matter interaction and shed light on unusual properties of the nonlinear-optical response of materials in the mid-IR spectral range.

Optics letters, Jan 15, 2015

Strongly coupled nonlinear spatiotemporal dynamics of ultrashort mid-infrared pulses undergoing s... more Strongly coupled nonlinear spatiotemporal dynamics of ultrashort mid-infrared pulses undergoing self-focusing simultaneously with soliton self-compression in an anomalously dispersive, highly nonlinear solid semiconductor is shown to enable the generation of multioctave supercontinua with spectra spanning the entire mid-infrared range and compressible to subcycle pulse widths. With 7.9 μm, 150 fs, 2 μJ, 1 kHz pulses used as a driver, 1.2 cycle pulses of mid-infrared supercontinuum radiation with a spectrum spanning the range of wavelengths from 3 to 18 μm were generated in a 5 mm GaAs plate. Further compression of these pulses to subcycle pulse widths is possible through compensation of the residual phase shift.

AIP Conference Proceedings, 2010

In the early days of CARS, stimulated Raman scattering (SRS) has been successfully used to genera... more In the early days of CARS, stimulated Raman scattering (SRS) has been successfully used to generate the Stokes field for time-resolved measurements [1] of vibrational lifetimes of molecules in liquids and phonons in solids. Dye lasers and optical parametric sources ...

Optics Letters, 2010

We measured the MCAP (middle cerebral artery pressure)/MSBP (mean systemic blood pressure) ratio ... more We measured the MCAP (middle cerebral artery pressure)/MSBP (mean systemic blood pressure) ratio in 76 patients who underwent an EIAB (extracranial-intracranial arterial bypass). Patients were divided into groups on the basis of angiographic findings. We found a definite correlation between increasing angiographic cerebral vascular occlusive disease and lower MCAP/MSBP ratios. Six of 32 patients with a preoperative neurologic deficit demonstrated mild but definite postoperative neurologic improvement. The mean MCAP/MSBP ratio in these six patients was significantly lower than that for the remainder of this group (p < .05). Finally, postoperative filling of the middle cerebral artery territory through the graft was found to correlate in an inverse linear relationship with MCAP/MSBP. Evidence is presented that hypoperfusion produced by occlusion of major cranial vessels plays an important role in temporary and permanent neurological deficits seen in patients with cerebrovascular disease.

Journal of Modern Optics, 2010

ABSTRACT

Conference on Lasers and Electro-Optics, 2016

We demonstrate a robust, all-solid-state approach for the generation of microjoule subcycle pulse... more We demonstrate a robust, all-solid-state approach for the generation of microjoule subcycle pulses in the mid-infrared through a cascade of carefully optimized parametric-amplification, difference-frequency-generation, spectral-broadening, and chirp-compensation stages. This method of subcycle waveform generation becomes possible due to an unusual, ionizationassisted solid-state pulse self-compression dynamics, where highly efficient spectral broadening is enabled by ultrabroadband four-wave parametric amplification phase-matched near the zero-group-velocity wavelength of the material. Rapidly progressing photonic technologies offer an unprecedented control over optical field waveforms, enabling the generation of extremely brief flashes of electromagnetic radiation with accurately controlled shape, spectrum, and phase [1, 2]. At the forefront of the ongoing quest for ultrashort optical probes that would be capable of resolving extremely fast processes in gas-phase [3] and solid-state [4, 5] systems, technologies allowing the generation of electromagnetic lightwaves with temporal envelopes shorter than the field cycle have been developed [6-10], paving the ways toward an ultimate time resolution in electron-dynamic studies and subcycle precision in lightwave sculpting. Subcycle field waveform generation has been demonstrated for the visible, nearinfrared, terahertz, and x-ray ranges [7, 9]. In the mid-infrared region, on the other hand, subcycle field waveform generation has been only possible through a two-color filamentation