Self-powered electrochromic devices with tunable infrared intensity

Triboelectric nanogenerator （TENG） is an efficient way to convert ambient mechanical energy into electricity to power up portable electronics. In this work, a flexible inflared electrochromical device （IR-ECD） with stable performances was assembled with a TENG for building self-powered infrared detector with tunable intensity. As driven by TENG, the electrochromic device could be operated in the mid-lR region due to the reversible electrochromic reactions. An average infrared reflectance contrast of 46% was achieved in 8-14 μm regions and as well a clear thermal image change can be observed. This work indicates that the TENG-driven infrared electrochromical device has potential for use in self-powered camouflage and tbermal control.

Er^(3+)-doped fluorogallate glass for mid-infrared applications

We report an Er3＋-doped fluorogallate glass with good thermal and chemical stability. The low maximum phonon energy and high mid-infrared （IR） transmittance of the glass are confirmed by Raman and IR spectra, respectively. Based on Judd-Ofelt theory, intensity parameters and radiative properties are determined from the absorption and emission spectra. The proposed glass possesses a large fluorescence branching ratio β （21.71%） and a maximum stimulated emission cross-section σem of Er3＋：4 I11/2 → 4 I13/2 transition at 2.71 μm （1.04 × 10^-20 cm2）. The results indicate that it can be potentially applied in high-power 2.7 μm fiber lasers.

Efficiency-enhanced picosecond mid-infrared optical parametric downconversion based on a cascaded optical superlattice

We demonstrate an efficiency-enhanced picosecond （ps） mid-infrared radiation via optical parametric downconversion. Based on a cascaded periodically poled MgO-doped stoiehiometric lithium tantalate crystal （MgO：sPPLT）, a tandem optical parametric oscillation-optical parametric amplification （OPO-OPA） process is achieved. Compared with a single OPO process, the conversion efficiency obtains an enhancement of 71%.

Modeling visible and near-infrared snow surface reflectance-simulation and validation

Retrieving snow surface reflectance is difficult in optical remote sensing. Hence, this letter evaluates five surface reflectance models, including the Ross-Li, Roujean, Walthall, modified Rahman and Staylor models, in terms of their capacities to capture snow reflectance signatures using ground measurements in Antarctica. The biases of all the models are less than 0.0003 in both visible and near-infrared regions. Moreover, with the exception of the Staylor model, all models have root-mean-square errors of around 0.02, indicating that they can simulate the reflectance magnitude well. The R2 performances of the Ross-Li and Roujean models are higher than those of the others, indicating that these two models can capture the angle distribution of snow surface reflectance better.

Tunable and coherent nanosecond 7.2-12.2 μm mid-infrared generation based on difference frequency mixing in ZnGeP_2 crystal

A coherent mid-infrared laser source,which can be tuned from 7.2 μm to 12.2 μm based on the type-Ⅰ phase-matched difference frequency generation(DFG) in an uncoated ZnGeP2(ZGP) crystal,is reported.The two pump waves are from a type-Ⅱ phase-matched dual-wavelength KTP optical parametric oscillator(OPO) of which the signal and idler waves are tuned during 1.85-1.96 μm(extraordinary wave) and 2.5-2.33 μm(ordinary wave),respectively.The maximum energy of the generated mid-infrared laser is 10 μJ at 9.22 μm,corresponding to the peak power of 2.2 kW.

Static light scattering properties of a ZnO nanosphere aqueous suspension at visible and near-infrared wavelengths

The scattering properties of ZnO nanospheres with four different particle diameters of 10, 50, 100, and 200 nm suspended in water are investigated theoretical and experimentally in the spectral range of the entire visible range and part of the near-infrared region. The scattering properties of ZnO nanospheres suspended in water are described by employing three main parameters： the angular distribution of the scattering intensity I, the scattering extinction coefficient ascat, and the scattering cross section ascat. The results indicate that （i） at a certain wavelength, the angular distribution of the scattering intensity appears as an obviously forward- propagating feature, and the forward-scattering intensity is dominant gradually when the particle diameter in- creases from 10 to 200 nm, and （ii） the scattering extinction coefficient and cross section can be determined by using the measured transmittance changes of a pure water sample and a given ZnO sample; they all are shown to be dependent on the particle size and incident wavelength. The experimental results of four different scattering samples agree well with the theoretical predictions within the given wavelength range.

Steady-state Raman gain in visible and near-infrared waveband of Sr WO_4 and Ba WO_4 crystals

The steady-state stimulated Raman scattering （SRS） gain with different excitation wavelengths ranging from 400 to 1100 nm of tungstate crystals, SrWO4 and BaWO4, is systematically researched. As excitation frequency is close to electronic transition frequency, molecular polarizability is not a constant, which has to be taken into account in our work. The experiment and theory agree well with each other and show that SRS gain is not only proportional to Stokes light frequency, but is also inversely proportional to biquadratic excitation frequency.

Highly efficient mid-infrared metasurface based on metallic rods and plate

Metasurface is a new kind of 2D metamaterial that is able to manage a variety of light beam modulations through steering the phase of the scattering waves. In this work, we utilize the metasurface to manipulate the light beam in the mid-infrared regime. By using the metallic rod and the plate structure, the metasurface presents a high polarization conversion efficiency and a wide working bandwidth. With specially rotated metallic rods, the meta- surface can realize various light beam manipulations, such as negative reflection, beam collimation, and focusing. All of these results show that such a metasurface will have potential applications in future mid-infrared optics.

Enhanced cooperative near-infrared quantum cutting in Pr～(3+)-Yb～(3+)co-doped phosphate glass

Pr3+and Yb3+co-doped phosphate glasses are prepared to study their optical properties.Excitation and emission spectra and decay curves are used to characterize their luminescence.We demonstrate that upon excitation of Pr3+ion with one high energy photon at 470 nm,two near-infrared(NIR)photons are emitted at 950-1100 nm(Yb3+:2F 5/2 →2F 7/2)through an efficient cooperative energy transfer(CET)from Pr3+to Yb3+.The maximum energy transfer efficiency(ETE)and the corresponding quantum efficiency approach up to 90.17%and 190.17%,respectively.The glass materials might find potential application for improving the efficiency of silicon-based solar cells.

Pattern design and realization for calibrating near infrared camera in surgical navigation

A calibration board composed of 8×8 near-infrared surface-mounted diodes(NIR-SMDs)(940 nm)is designed.Meanwhile,a common binocular measurement system with the average error less than 0.1320 mm is used to obtain the geometric information of this board.A calibration method with the designed pattern is performed to obtain the parameters of the near-infrared camera(NIRC).In the experiment,the average relative errors of focal length and principal point are 0.244%and 0.735%,respectively.The mean of image residuals is less than 0.01 pixel.The error of three-dimensional(3D)measurement is less than 0.3 mm.All those results indicate that the designed calibration board is suitable and accurate for calibrating NIRC.

Ultra-broad near-infrared emission of Bi-doped SiO_2 Al_2O_3 GeO_2 optical fibers

Bi-doped SiO2-Al2O3-GeO2 fiber preforms are prepared by modified chemical vapor deposition （MCVD） and solution doping process. The characteristic spectra of the preforms and fibers are experimentally investigated, and a distinct difference in emission between the two is observed. Under 808-nm excitation, an ultra-broad near-infrared （NIR） emission with full-width at half-maximum （FWHM） of 495 nm is observed in the Bi-doped fiber. This observation, to our knowledge, is the first in this field. The NIR emission consists of two bands, which may be ascribed to the Bi0 and Bi＋ species, respectively. This Bi-doDed fiber is promising for broadband or）tical amolification and widely tunable laser.

Near-infrared electroluminescent diodes based on copper hexadecafluorophthalocyanine CuPcF_(16)

We demonstrate the near-infrared （NIR） organic light-emitting devices （OLEDs） based on copper hexade-cafluorophthalocyanine （CuPcF16） doped into 2,2,2”-（1,3,5-benzenetriyl）tris-[1-phenyl-1H-benzimidazole] （TPBI）. The device structure is ITO/ NPB/ TPBI：CuPcF16/BCP/Alq3/Al. Room-temperature electro- luminescence is observed at about 1106 nm due to transitions from the first excited triplet state to the ground state （T1-S0） of CuPcF16. The result indicates that FSrster and Dexter energy transfers play a minor role in these devices, while the direct charge trapping is the dominant mechanism. The absorption spectra of CuPeF16 solution in pyridine and vacuum sublimed films on quartz have also been investigated.

Highly enhanced broadband infrared absorption of germanium by multi-layer plasmonic nano-antenna

High-sensitivity and broad bandwidth photo-detector devices are important for both fundamental studies and high-technology applications. Here, by using three-dimensional （3D） finite-difference time-domain simulation, we design an optimized 3D multi-layer gold nano-antenna to enhance the near-infrared （NIR） absorption of germanium nanoparticles. The key ingredient is the simultaneous presence of multiple plasmonic resonance modes with strong light-harvesting effect that encompass a broad bandwidth of germanium absorption band. The simulation results show more than two orders of magnitude enhanced absorption efficiency of gernanium around 1550 nm. The design opens up a promising way to build high-sensitivity and broad bandwidth NIR photo-detectors.

Polarization sensitivity contributes to multiple band spectra of one mid-infrared absorber

The emerging perfect-absorber metamaterials （PAMs） provide an alternative material approach for the next generation of electromagnetic detection at any frequency band of interest. One type of dual cross-shaped PAMs is developed to obtain multiplex-band spectrum absorption at mid-infrared region. Three distinct absorption peaks are attributed to the polarization sensitivity excitation of the plasmonic resonance. The charge density distributions, which are excited by resonant electromagnetic waves passing through the PAMs medium, provide insights into the observed absorption behavior. We find that the retrieved optical properties of the PAMs including permittivity and permeability are still consistent with the sum of the Drude and Lorentz type models at wavelengths ranging from 2.0 to 10.0μm. Such multiplex-band absorption properties enable the proposed PAMs a powerful tool for the direct detection of multiple molecular vibrational structures, and for multiple spectra infrared detection.

Fenestration operation in middle ear bone with pulsed infrared lasers: an in-vivo study

The feasibility of fenestration operation in middle ear bone with pulsed infrared laser is evaluated. Healthy male New Zealand rabbits in vivo are used in the experiment. Middle ear mastoid bone of animal model is completely exposed with conventional methods, and then a pulsed CO2 laser （10.6 μm） and an Er：YAG laser （2.94 μm） are used to perform the fenestration operation. Diamond drill is also used as a control group. The total operation time and light irradiation time are recorded and the opening efficiency is assessed. The morphological changes and thermal damage around the opening window on the middle ear bone are examined. It is shown that both laser systems are suitable for the fenestration operation in middle ear bone, and this no-touch technique has a lot of benefits compared with traditional methods. The bleeding during operation has an important effect on operation time and thermal injury and needs to be controlled efficiently in further study.

Fabrication of air-bridged Kerr nonlinear polymer photonic crystal slab structures in near-infrared region

Fabrication details of air-bridged Kerr nonlinear polymer photonic crystal slab structures are presented. Both the two-dimensional photonic crystal slab and the one-dimensional nanobeam structures are fabricated using direct focused ion beam etching and subsequent wet chemical etching. The scanning electron microscopy images show the uniformity and homogeneity of the cylindrical air holes. The optical measurement in the near-infrared region is implemented using the tapered fiber coupling method, and the results agree with the numerical calculations by using the three-dimensional finite-difference time-domain method.

Contribution of multiple electron rescatterings on high-order harmonic generation in the mid-infrared wavelength regime

We theoretically investigate multiple electron rescatterings in high-order harmonic generation with a wide range of driving laser wavelengths. In order to obtain a clear and intuitive insight, the time-frequency analysis of the dipole acceleration calculated by the numerical solution of the time-dependent SchrSdinger equation is per- formed and compared with the classical electron trajectory calculation. The result shows that in the mid-infrared regime, the high-order electron trajectory associated with multiple rescatterings plays a more important role than the usually referred-to ＂long and ＂short＂ electron trajectories. To provide quantitative evidence, the strong-field approximation is used to calculate the yield ratio of the high-order harmonic generation from the first rescattering and the multiple rescatterings.

Compact static infrared broadband snapshot imaging spectrometer

A compact static infrared broadband snapshot imaging spectrometer （IBSIS） is presented. It consists of a telescope, three prisms, a focusing lens, and a detector. The first prism disperses sharply in the near-infrared （NIR） range along the vertical direction, and it is relatively non-dispersive in the mid-wave infrared （MWIR） range. The second prism is substantially more dispersive in the MWIR range than in the NIR range along the horizontal direction. The beam deviation caused by the first and second prisms can be controlled by the third prism. The IBSIS yields a two-dimensional dispersion pattern （TDP）. The formulas and numerical simulation of the TDP are presented. The methods of target location calculation and spectral signature extraction are described. The IBSIS can locate multiple targets using only one frame of data, which allows for real-time detection and measurement of the energetic targets.

Temperature characteristics of near infrared SPR sen sors with Kretschmann configuration

The temperature characteristics of near infrared surface plasmon resonance （SPR） sensors with Kretschmann configuration are studied theoretically and experimentally. The experimental results match with the numerical simulations in the temperature range from 10 ℃ to 40.℃. With the increase of temperature, the resonance angle for gas increases slightly, but that for aqueous solution decreases obviously. No matter the dielectric layer is gas or aqueous solution, the resonance peaks are both broadened.

Broadband near-infrared luminescence and energy trans-fer in Bi singly-doped and Bi/Yb co-doped titanate glasses

Super-broadband near-infrared(NIR)emission from 1100 nm to 1600 nm is observed in Bi-doped titanate glasses at the excitation of 808 nm laser diode(LD).The effects of Bi content on the optical spectra are investigated.It is also found that the Bi-related emission intensity can be enhanced by Yb3+co-doping at the excitation of 980 nm LD.It should be ascribed to the energy transfer from Yb3+to active Bi ions.The energy transfer processes are studied based on the Inokuti-Hirayama(I-H)model,and the energy transfer of electric dipole-dipole interaction is confirmed to be dominant in Bi/Yb co-doped glasses.