Photonic Crystals with a Defect Fabricated by Two-Photon Polymerization for the Infrared Spectral Range

One-dimensional photonic crystals composed of alternating layers with high- and low-density were fabricated using two-photon polymerization from a single photosensitive polymer for the infrared spectral range. By introducing single high-density layers to break the periodicity of the photonic crystals, a narrow-band defect mode is induced. The defect mode is located in the center of the photonic bandgap of the one-dimensional photonic crystal. The fabricated photonic crystals were investigated using infrared reflection measurements. Stratified-layer optical models were employed in the design and characterization of the spectral response of the photonic crystals. A very good agreement was found between the model-calculated and measured reflection spectra. The geometric parameters of the photonic crystals obtained as a result of the optical model analysis were found to be in good agreement with the nominal dimensions of the photonic crystal constituents. This is supported by complimentary scanning electron microscope imaging, which verified the model-calculated, nominal layer thicknesses. Conventionally, the accurate fabrication of such structures would require layer-independent print parameters, which are difficult to obtain with high precision. In this study an alternative approach is employed, using density-dependent scaling factors, introduced here for the first time. Using these scaling factors a fast and true-to-design method for the fabrication of layers with significantly different surface-to-volume ratios. The reported observations furthermore demonstrate that the location and amplitude of defect modes is extremely sensitive to any layer thickness non-uniformities in the photonic crystal structure. Considering these capabilities, one-dimensional photonic crystals engineered with defect modes can be employed as narrow band filters, for instance, while also providing a method to quantify important fabrication parameters.

Enhancement of second harmonic generation in a layered MoS2 nanoresonator

Molybdenum disulfide (MoS2) is a layered material with a high refractive index in the visible and infrared spectral range. In this work, we theoretically and experimentally demonstrate Mie-resonant MoS2 nanodisks. We show enhanced second harmonic generation from MoS2 nanodisk resonators due to the overlap of Mie-type resonances at the fundamental wavelength with the C-exciton resonance at the second-harmonic wavelength.

IEEE PROJECT 4001 – STANDARDS FOR CHARACTERIZATION AND CALIBRATION OF HYPERSPECTRAL IMAGING DEVICES

Hyperspectral imaging (HSI) systems have been invaluable tools for over two decades, but there are few authoritative standards that characterize these systems or define the data and metadata they produce. Manufacturers calibrate instruments and report specifications differently and, in some cases, the same term has different definitions among HSI programs.To address these inconsistencies, the Institute of Electrical and Electronics Engineers (IEEE) Geoscience and Remote Sensing Society (GRSS) sponsored Project 4001 (P4001), a Hyperspectral Working Group under the auspices of IEEE’s Standards Association. Since its inception in 2018, the IEEE P4001 Working Group has been working to specify testing and characterization methods for HSI device manufacturers, as well as recommend data structures and terminology for HSI products.P4001 focuses on the ultraviolet through the shortwave infrared spectral range (~250 to 2500 nm) and prioritizes camera technologies that are in widespread use. Many aspects of the standard will have wider applicability with respect to camera technology and wavelength range, and updates will expand the range of technologies and topics covered. Industrial, laboratory and geoscience use cases are informing the development of the standard. Utilization of the P4001 HSI standard will lead to HSI systems with consistent characterization and calibration criteria, as well as interoperable data products with a common lexicon for data and metadata.

Fluoroindate Glass Co-Doped with Yb3+/Ho3+ as a 2.85 μm Luminescent Source for MID-IR Sensing

This work reports on the fabrication and analysis of near-infrared and mid-infrared luminescence spectra and their decays in fluoroindate glasses co-doped with Yb3+/Ho3+. The attention has been paid to the analysis of the Yb3+→ Ho3+ energy transfer processed ions in fluoroindate glasses pumped by 976 nm laser diode. The most effective sensitization for 2 μm luminescence has been obtained in glass co-doped with 0.8YbF3/1.6HoF3. Further study in the mid-infrared spectral range (2.85 μm) showed that the maximum emission intensity has been obtained in fluoroindate glass co-doped with 0.1YbF3/1.4HoF3. The obtained efficiency of Yb3+→ Ho3+ energy transfer was calculated to be up to 61% (0.8YbF3/1.6HoF3), which confirms the possibility of obtaining an efficient glass or glass fiber infrared source for a MID-infrared (MID-IR) sensing application.