Mid-infrared Radiation Research Articles

Parametrically Tunable Mid-Infrared Resonant Radiation by Four-Wave Mixing in Silicon Nitride Nanophotonic Waveguides

The direct generation of mid-infrared light is of significant interest for various applications including spectroscopy, detection system, optical sensing and biophotonics. Ultrashort-pulse nonlinear interaction can be viewed as four-wave mixing process, which can generate new spectral components under appropriate conditions. Here, we numerically demonstrate a fully, yet effective, spectral conversion scheme where the effective portion and components of femtosecond pulses can access the mid-infrared region directly by four-wave mixing process in silicon nitride integrated photonics waveguide. Wideband conversions occur mainly towards the mid-infrared region around the traditional red-shift phase-matching point without the adjustment of waveguide geometry. The corresponding conversion mechanisms can be attributed to nonlinear interaction of optical waves, resulting in the dispersive wave generation, the soliton-probe collision and the phase-sensitive scattering process. Our results provide an alternative route to realize wideband tunable mid-infrared frequency conversion in silicon nitride system on a chip.

Doping effect on the light absorption and photoluminescence of Ge/Si quantum dots in the infrared spectral range

The results of comprehensive studies of near-infrared photoluminescence and mid-infrared equilibrium and photoinduced absorption spectra in structures with Ge/Si quantum dots with different doping levels at different optical pumping intensities and different temperatures are presented. Obtained dependences of interband photoluminescence spectra on temperature and optical pumping intensity are explained by the change in the intensities of direct and indirect in real space electron-hole recombination in Ge/Si quantum dots. The spectra of equilibrium and photoinduced absorption of polarized mid-infrared radiation demonstrate peaks associated with transitions of holes from the ground and excited states to continuum states above quantum dots and with optical transitions from the ground states to excited ones.

Transition from Phononic to Geometrical Mie Modes Measured in Single Subwavelength Polar Dielectric Spheres

Spherical dielectric resonators are highly attractive for light manipulation, thanks to their intrinsic electric and magnetic resonances. Here, we present measurements of the mid-infrared far-field thermal radiation of single subwavelength dielectric spheres deposited on a gold substrate, of radii ranging from 1 to 2.5 μm, which agree quantitatively with simulated absorption cross sections. For SiO2 microspheres, we evidence the excitation of both surface phonon-polariton (SPhP) modes and geometrical electric and magnetic Mie modes. The transition from a phonon-mode-dominated to a Mie-mode-dominated emission spectrum is observed, with a threshold radius of ∼1.5 μm. We also show that the presence of the metallic substrate augments the computed spheres absorption cross-section due to increased local field enhancement, arising from the near-field interaction of the spheres oscillating charges with their image in the metallic mirror. In contrast, measurements of single subwavelength SPhP-inactive PTFE spheres reveal that the mid-infrared response of such lossy spheres is dominated by their bulk absorption. Our results demonstrate how engineering the geometrical and dielectric properties of subwavelength scatterers can enable the control of thermal emission near room temperature, with exciting perspectives for applications such as radiative cooling.

Результаты воздействия лазерного излучения среднего инфракрасного диапазона на оболочки глаза

Purpose. Evaluate the impact of mid-infrared laser radiation on the eye. Material and methods. An experimental laser device “Laser scalpel in the mid-IR range 2–8µm for precision surgery” was used, developed at the Vavilov State Optical Institute. The retina, choroid, and sclera of pig eyes were used as biological tissue. The experiment was carried out in air. The impact of laser radiation on eye tissues was assessed using an EVO LS10 scanning electron microscope from Zeiss (Germany). The depth and diameter of the crater at the site of laser exposure and the width of the collateral injury were assessed. Results and discussion. When exposed to a single laser pulse with an energy of 1 mJ, a through defect of the retina was observed. Under continuous exposure of the choroid to laser radiation with an energy of 1 to 3 mJ, the average depth of the crater was 135 µm, the width of the crater was 97 µm, and the zone of collateral damage was 59 µm. With continuous exposure to laser radiation with similar parameters on the sclera, the depth of the crater, the width of the crater, and the zone of collateral damage were greater. Conclusion. The depth, width of the crater, the zone of collateral damage when exposed to laser radiation depend on the time, frequency and energy of the radiation. This laser can be useful in ophthalmic surgery. However, further studies are needed to optimize the parameters of laser radiation. Keywords: vitrectomy; laser vitrectomy; photovitrectomy; Er:YAG laser; mid-infrared spectrum; laser ablation; precision surgery.

Radiative Cooling Nanofabric for Personal Thermal Management.

A wearable textile that is engineered to reflect incoming sunlight and allow the transmission of mid-infrared radiation simultaneously would have a great impact on the human body's thermal regulation in an outdoor environment. However, developing such a textile is a tough challenge. Using nanoparticle-doped polymer (zinc oxide and polyethylene) materials and electrospinning technology, we have developed a nanofabric with the desired optical properties and good applicability. The nanofabric offers a cool fibrous structure with outstanding solar reflectivity (91%) and mid-infrared transmissivity (81%). In an outdoor field test under exposure of direct sunlight, the nanofabric was demonstrated to reduce the simulated skin temperature by 9 °C when compared to skin covered by a cotton textile. A heat-transfer model is also established to numerically assess the cooling performance of the nanofabric as a function of various climate factors, including solar intensity, ambient air temperature, atmospheric emission, wind speed, and parasitic heat loss rate. The results indicate that the nanofabric can completely release the human body from unwanted heat stress in most conditions, providing an additional cooling effect as well as demonstrating worldwide feasibility. Even in some extreme conditions, the nanofabric can also reduce the human body's cooling demand compared with traditional cotton textile, proving this material as a feasible solution for better thermoregulation of the human body. The facile fabrication of such textiles paves the way for the mass adoption of energy-free personal cooling technology in daily life, which meets the growing demand for healthcare, climate change, and sustainability.

Multidimensional wearable self-powered personal thermal management with scalable solar heating and a triboelectric nanogenerator

Global climate change is increasing the frequency of cold events, which can threaten health and enhance the demand for energy, inhibiting the society to prosper in a sustainable way. Having sun as the heat and body radiation as warmth preservation source, the need to save energy is mitigated through personal thermal management (PTM). Herein, we report a self-powered woven Kevlar fiber (WKF)-based flexible PTM device with a porous Ag@MoxFe1−xSe nanostructure (NS) between a substrate of WKF and Ti3C2 MXene film dispersed in polydimethylsiloxane (PDMS). Effective thermotherapeutic ability is demonstrated by the composite (80 °C at 3 V through Joule heating). The porous NS between the WKF and MXene/PDMS layers selectively reflected mid-infrared radiation (97.4%) and absorbed UV–vis–NIR (87.1%). The PTM increased the silicone heater temperature by 10 °C in an indoor setting; in direct sunlight, it raised the heater temperature by 20 °C demonstrating its passive and solar heating-mode. The fabricated device harvests energy from human body movements and simulated raindrops, exhibiting high self-powered heating efficiency and has a maximum power density of 1.5 mW cm−2 at low frequency (5 Hz). The WKF/Ag@MoxFe1−xSe/MXene/PDMS displayed high tensile strength, excellent breathability and durability. This work demonstrates the advantages of this multifunctional energy-reducing device addressing the world energy crisis, which is effective both indoors and outdoors in cold climates, and in sunny and rainy weather.

A large-region fog detection algorithm at dawn and dusk for high-frequency Himawari-8 satellite data

ABSTRACT Satellite remote sensing provides effective methods for fog detection at large scales. At dawn or dusk, however, the separation of fog from the surface remains a great challenge because of the minor radiation difference between fog and the surface. This study develops a novel algorithm for fog detection suitable for dawn and dusk from high-frequency data of the Himawari-8 satellite. Methodologically, the area was divided into three subregions according to the distance of the terminator line. In regions at daytime that are far from the terminator line, a fog detection index of the low solar altitude angle (FDI LSAA) was built to isolate the fog through the relationship between the mid-infrared (MIR) brightness temperature (I MIR ) and its difference with the thermal infrared (TIR) brightness temperature (BTD = I MIR – I TIR , where I MIR and I TIR are the brightness temperatures at the MIR and TIR bands). In regions near the terminator line, the fog was extracted from the surface by a Gaussian mixture model (FD-GMM NTL) by the differences in MIR and TIR radiation changes. After that, the fog was further extracted from the low and mid-high clouds by the enhanced low cloud detection index (ELCDI) and by the difference in BTD and TIR characteristics. In regions at night, a BTD threshold value was adopted to detect fog. Validation results demonstrated that the algorithm in this study could precisely detect large-region radiation fog including dawn and dusk, with the overall probability of detection (POD) accuracies range from 76.3% to 89.2% at dawn and 67.3% to 77.0% at dusk. The relatively low accuracy at dusk was mainly attributed to desert in the study area, which has a similar BTD with fog after a day of solar radiation. Results of this study provide new insight for fog detection at dawn and dusk, which enhances the application of remote sensing in meteorology forecasting.

High Harmonic Generation from Oriented Asymmetric Molecules in the Presence of Static Electric Field

Abstract We investigate the high harmonic generation during the interaction of the femtosecond laser field with oriented asymmetric diatomic molecules in the presence of an external static electric field. Based on the numerical solution of the time-dependent Schrödinger equation for the model one-electron system, we calculate the high harmonic generation spectrum for a wide range of static-field strengths. The possibilities for visualizing low-frequency (terahertz and mid-infrared) radiation using time-delay measurements of even high harmonics intensities are discussed.

IRFEL Selective Irradiation of Amorphous Solid Water: from Dangling to Bulk Modes

Amorphous solid water (ASW) is one of the most widely studied solid phase systems. A better understanding of the nature of inter- and intramolecular forces in ASW is, however, still required to correctly interpret the catalytic role of ASW in the formation and preservation of molecular species in environments such as the icy surfaces of Solar System objects, on interstellar icy dust grains, and potentially even in the upper layers of the Earth's atmosphere. In this work, we have systematically exposed porous ASW (pASW) to mid-infrared radiation generated by a free-electron laser at the HFML-FELIX facility in The Netherlands to study the effect of vibrational energy injection into the surface and bulk modes of pASW. During multiple sequential irradiations on the same ice spot, we observed selective effects both at the surface and in the bulk of the ice. Although the density of states in pASW should allow for a fast vibrational relaxation through the H-bonded network, part of the injected energy is converted into structural ice changes as illustrated by the observation of spectral modifications when performing Fourier transform infrared spectroscopy in reflection-absorption mode. Future studies will include the quantification of such effects by systematically investigating ice thickness, ice morphology, and ice composition.

Anisotropic absorber and tunable source of MIR radiation based on a black phosphorus-SiC metasurface

We propose a black phosphorus-silicon carbide (BP-SiC) metasurface with in-plane structural symmetry that can act as both a nearly perfect anisotropic absorber and tunable polarized source of mid-infrared (MIR) radiation. The metasurface is a periodic array of square SiC patches integrated with a BP flake at the top and separated from a bottom reflector by a BaF2 spacer. We first use analytical calculations and numerical simulations to study the hybridization of the anisotropic plasmons of BP with isotropic phonons of SiC. We also analyze the in-plane characteristics of the resulting hybrid modes of the BP/SiC heterostructure and the BP-SiC metasurface. It is then demonstrated that the proposed metasurface can serve as a nearly perfect anisotropic absorber of MIR radiation with highly selective and omnidirectional features. It is also shown that the metasurface can be used as a polarized MIR source with tunable temperature, which is determined by the thermal equilibrium between the matter and radiation. The suggested design holds promise for artificial coatings that can tune the blackbody thermal signatures, MIR sensing, and highly directional in-plane transportation of the MIR energy.

Воздействие лазера среднего инфракрасного диапазона на ткани глаза

Purpose. To study the effect of mid-infrared laser radiation on eye tissues. Material and methods. As a laser, an experimental laser device “Laser scalpel in the middle infrared range 2-8µm for precision surgery” developed at the Vavilov State Optical Institute. The experiment was carried out at a laser radiation wavelength of 3µm, which coincides with the peak of the spectral absorption of water. The retina, choroid, and sclera of pig eyes were used as biological tissue. The effect of laser radiation on tissue was carried out in air. The impact of laser radiation on eye tissues was assessed using an EVO LS10 scanning electron microscope from Zeiss (Germany). After obtaining an image on an electron microscope using the GNU Image Manipulation Program, the depth and diameter of the crater and the width of the collateral damage were calculated. Results and discussion. When exposed to a single laser pulse with an energy of 1 MJ, a through retinal defect was observed. With continuous exposure to laser radiation on the choroid with an energy from 1 to 3 MJ, the crater depth was 128–150 microns, the crater width was 87–110 microns, the collateral damage zone was 50–71 microns. With continuous exposure to laser radiation with similar parameters on the sclera, the depth of the crater, the width of the crater and the area of collateral damage were larger. Conclusions. The depth, width of the crater, the zone of collateral damage when exposed to laser radiation are directly proportional to the time, frequency and energy of the radiation. This laser can be useful in ophthalmic surgery, in particular in vitreoretinal surgery. However, further studies are needed to optimize the parameters of laser radiation. Keywords: vitrectomy, laser vitrectomy, photovitrectomy, Er:YAG laser, mid-infrared spectrum, laser ablation, precision surgery.

Project Hephaistos – I. Upper limits on partial Dyson spheres in the Milky Way

ABSTRACT Dyson spheres are hypothetical megastructures built by advanced extraterrestrial civilizations to harvest radiation energy from stars. Here, we combine optical data from Gaia DR2 with mid-infrared data from AllWISE to set the strongest upper limits to date on the prevalence of partial Dyson spheres within the Milky Way, based on their expected waste-heat signatures. Conservative upper limits are presented on the fraction of stars at G ≤ 21 that may potentially host non-reflective Dyson spheres that absorb 1–90 per cent of the bolometric luminosity of their host stars and emit thermal waste-heat in the 100–1000 K range. Based on a sample of ≈2.7 × 105 stars within 100 pc, we find that a fraction less than ≈2 × 10−5 could potentially host ∼300 K Dyson spheres at 90 per cent completion. These limits become progressively weaker for less complete Dyson spheres due to increased confusion with naturally occurring sources of strong mid-infrared radiation, and also at larger distances, due to the detection limits of WISE. For the ∼2.9 × 108 stars within 5 kpc in our Milky Way sample, the corresponding upper limit on the fraction of stars that could potentially be ∼300 K Dyson spheres at 90 per cent completion is ≲8 × 10−4.

Strong Nonreciprocal Mid-infrared Radiation at Small Angles Based on the Excitation of Guided Modes

Strong Nonreciprocal Mid-infrared Radiation at Small Angles Based on the Excitation of Guided Modes

Coupling of molecular vibration and metasurface modes for efficient mid-infrared emission

We demonstrate extraordinarily spectrally selective narrowband mid-infrared radiationviacoupling of plasmon resonance and molecular vibration. Absorbance and thermal emittance with resonant peak FWHM ≤ 124 nm atλ= 5.73 μm, corresponding to aQ-factor of ∼92.3 were obtained.

Enhanced Near- and Mid-Infrared Radiation Property of Mgcr2o4 by Doping with Cu Ions

Enhanced Near- and Mid-Infrared Radiation Property of Mgcr2o4 by Doping with Cu Ions

Efficient Electroabsorption Modulation of Mid- and Far-Infrared Radiation by Driving the Band-Inversion Transition of InAs / GaSb Type-II Quantum Wells

Based on the self-consistent calculations of the eight-band $\mathbf{k}\ensuremath{\cdot}\mathbf{p}$ model and Poisson equation, we theoretically demonstrate that the intersubband optical absorption of $\mathrm{In}\mathrm{As}$/$\mathrm{Ga}\mathrm{Sb}$ type-II quantum wells (QWs) is effectively tuned by the electric-field-driven band-inversion transition. By utilizing this property, $\mathrm{In}\mathrm{As}$/$\mathrm{Ga}\mathrm{Sb}$ QWs can be made into highly efficient electroabsorption modulators (EAMs) for TM-polarized mid-infrared radiation (MIR) (approximately $4.2$--$12\phantom{\rule{0.2em}{0ex}}\ensuremath{\mu}\mathrm{m}$) and TE-polarized far-infrared radiation (FIR) (approximately $12$--$100\phantom{\rule{0.2em}{0ex}}\ensuremath{\mu}\mathrm{m}$). At low temperature, an example $p$-$i$-$n$ waveguide EAM composed of six-period $\mathrm{In}\mathrm{As}$/$\mathrm{Ga}\mathrm{Sb}$ QWs achieves a drive voltage of $<0.5$ V, a 3-dB cutoff bandwidth of approximately $24.6$ GHz, and a dynamic power consumption of $\ensuremath{\le}\phantom{\rule{0.2em}{0ex}}0.06$ mW/GHz for a 20-dB on:off ratio modulation of $4.46$-$\ensuremath{\mu}\mathrm{m}$ TM-polarized radiation. Although the modulation efficiencies drop by 70%--80% when the temperature increases, the performance of $\mathrm{In}\mathrm{As}$/$\mathrm{Ga}\mathrm{Sb}$ EAMs is (at least) comparable with conventional $1.55$-$\ensuremath{\mu}\mathrm{m}$ EAMs at 300 K. These results suggest that $\mathrm{In}\mathrm{As}$/$\mathrm{Ga}\mathrm{Sb}$ EAMs are promising devices for high-speed and low-power-consumption MIR (or FIR) free-space optical communications.

Synergistic modulation of solar and thermal radiation in dynamic energy-efficient windows

Current technologies about the dynamic window in buildings, vehicles, and greenhouses primarily focus on solar radiation modulation for interior lighting, heating and cooling regulation. Mid-infrared thermal radiation of windows, as another important factor for interior thermal load, can be dynamically optimized to further improve energy efficiency. However, it is challenging to achieve synergistic solar and thermal radiation modulation of a window for optimal energy efficiency management. Herein, based on the estimation of the energy-saving potential of a midrise building by controlling the window emissivity, we propose an energy-efficient dynamic window that can synergistically modulate solar and thermal radiation. The prototype of such windows with sequence photonic structures could perform the function of synergistic multiband modulation by loading mechanical strain, and achieve a broad modulation ranges up to 55% in solar transmittance and 25% in mid-infrared thermal emittance. The dynamic window can regulate the steady-state interior temperature of a chamber up to ~4 °C in real-time testing, which could potentially provide annual energy-saving from ~45.5 to ~166.5 MJ m−2 for a typical midrise building located in 11 cities around the world. The intelligent dynamic window system with fast response to the changing weather can further improve home convenience, comfort and artistry and realize an energy-saving residential setting.

Infrared nanoscopy and tomography of intracellular structures

Although techniques such as fluorescence-based super-resolution imaging or confocal microscopy simultaneously gather both morphological and chemical data, these techniques often rely on the use of localized and chemically specific markers. To eliminate this flaw, we have developed a method of examining cellular cross sections using the imaging power of scattering-type scanning near-field optical microscopy and Fourier-transform infrared spectroscopy at a spatial resolution far beyond the diffraction limit. Herewith, nanoscale surface and volumetric chemical imaging is performed using the intrinsic contrast generated by the characteristic absorption of mid-infrared radiation by the covalent bonds. We employ infrared nanoscopy to study the subcellular structures of eukaryotic (Chlamydomonas reinhardtii) and prokaryotic (Escherichia coli) species, revealing chemically distinct regions within each cell such as the microtubular structure of the flagellum. Serial 100 nm-thick cellular cross-sections were compiled into a tomogram yielding a three-dimensional infrared image of subcellular structure distribution at 20 nm resolution. The presented methodology is able to image biological samples complementing current fluorescence nanoscopy but at less interference due to the low energy of infrared radiation and the absence of labeling.

Theoretical Investigation of Mid Infrared Temperature Sensor Based on Sagnac Interferometer Using Chloroform Filled Photonic Crystal Fiber

In this paper, a novel Sagnac Interferometer (SI) based chalcogenide Photonic Crystal Fiber (PCF) temperature sensor is theoretically and numerically analyzed operating in the mid infrared (MIR) region. The PCF cladding air holes are proposed to be filled with a highly temperature sensitive liquid chloroform to enhance the temperature sensitivity. The temperature sensing characteristics of three different infiltration technique is investigated theoretically and compared by Finite Element Method (FEM). Simulation results show that full infiltration performs better than partial infiltration. In the numerical analysis two sensing dips with high linearity is achieved for full infiltration which shows sensitivity of −5.77 nm/°C and 8.49 nm/°C when the temperature increases from 25 to 85 °C for the specific fiber length of 1.532 mm. The R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> values are 0.957446809 and 0.97680771 for the respective two sensing dips. The proposed highly sensitive sensor has broad detection window which can be applied in fingerprint unlocking, MIR radiation detection in human body, biomedicine applications, and environmental temperature monitoring.

(Invited) Multi-Modal Nanowire Sensors Using Electrical Resonance Approach

There is an ever increasing demand for nanosensors with enhanced characteristics such as miniature size, low power consumption, higher sensitivity and selectivity, ease of manufacturing, decreased cost, simultaneous detection of multi-analytes, etc. As a result, the area of nanoscale sensing remains an area of rich opportunity to develop new ideas for immediate applications ranging from health and environmental monitoring to military and homeland defense. Therefore, these sensor technologies have great potential to revolutionize science and to influence major economic, agricultural, environmental, social, and health issues. Recent advances in our understanding of 1-D nanomaterials are paving the way for developing novel platforms for sensors and devices based on multi-physics, multi-modal approaches. Optically induced surface state (or defect states) population-depopulation in nanomaterials with extremely small thermal mass changes its electrical resonance and serves as a bridge to nano-world for developing next-generation, miniature spectrometers and molecular sensors with unprecedented selectivity and sensitivity. Modulating the defect state population in wide bandgap materials using optically-induced thermal pathways offers a new approach for designing advanced sensors and devices based on nanowire resonators with extremely low thermal mass. Resonant excitation of molecules adsorbed on these nanowires using tunable mid-infrared radiation heats the nanowires during the de-excitation process affecting the surface state population which can be sensitively monitored as changes in the dissipation at its electrical resonance frequency as a function of illumination wavelength and mimics the infrared absorption spectra of the physisorbed molecules offering excellent molecular selectivity. Since the mid-IR spectra are free of overtones (molecular fingerprint regime) and the spectrum of individual molecular species are linearly independent, this approach offers a new paradigm for chemical vapor sensing with high sensitivity and selectivity. Further, monitoring the dissipation variations at resonance as a function of temperature can provide information on thermally induced desorption and polarization or depolarization of adsorbed chemical species. The temperature response of the nanowire at resonance can be used to discriminate different vapors based on differential calorimetry due to a difference in the dipole moments.