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Schematic drawing of a grating and incident plane, including angles of incidence θ in and reflection θ out , diffraction order ( m = 0 , ± 1 , ± 2 … ) , pitch distance of grating Λ , and rotation angle between the incident light plane and the grating groove ϕ .
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We propose a method to directly visualize the photonic band-structure of micrometer-sized photonic crystals using wide-angle spectroscopy. By extending Fourier imaging spectroscopy sensitivity into the infrared range, we have obtained accurate measurements of the band structures along the high-symmetry directions (X-W-K-L-U) of polymeric three-dime...
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Citations
... However, various photonic structures, such as topological photonic crystals and metamaterials, are heavily applied in the near-infrared band (800-1700 nm) [21][22][23][24][25][26]; therefore, band information in this range is strongly desired. In this regard, in 2017, a research group at Bristol University successfully observed the wide-range band structure in three dimensions in the near-infrared band using Fourier image spectroscopy [27]. They achieved improved sensitivity by constructing an optical-fiber-based spectroscopic system on a variable stage for acquiring Fourier images from a device; however, this system has not shown sufficient performance for practical use from the viewpoint of resolution and measurement time. ...
In this study, we developed a photonic band microscope based on hyperspectral Fourier image spectroscopy. The developed device constructs an infrared photonic band structure from Fourier images for various wavelength obtained by hyperspectral imaging, which make it possible to speedily measure the dispersion characteristics of photonic nanostructures. By applying the developed device to typical photonic crystals and topological photonic crystals, we succeeded in obtaining band structures in good agreement with the theoretical prediction calculated by the finite element method. This device facilitates the evaluation of physical properties in various photonic nanostructures, and is expected to further promote related fields.
... Thus, infrared hyperspectral imaging can identify and distinguish the substance with high confidence. Existing hyperspectral imaging systems mostly use dispersive elements (e.g., prisms or diffraction gratings) [8], filters [9,10] or the Fourier transform infrared spectroscopy technique [11,12] to decompose lights into various wavelengths followed by an infrared focal plane array (IRFPA) to record them separately. Despite different principles and setups are used for the above mentioned hyperspectral imaging methods, one common idea is that photons are detected separately either in the spatial or spectral domain using a costly IRFPA. ...
... The compression ratio in our model can be represented by η = K MN for η ∈ [0, 1]. Following this, each spectral channel of the signal can be reconstructed based independently on Equation (8) or jointly on Equation (11). ...
Hyperspectral imaging (HSI) has been widely investigated within the context of computational imaging due to the high dimensional challenges for direct imaging. However, existing computational HSI approaches are mostly designed for the visible to near-infrared waveband, whereas less attention has been paid to the mid-infrared spectral range. In this paper, we report a novel mid-infrared compressive HSI system to extend the application domain of mid-infrared digital micromirror device (MIR-DMD). In our system, a modified MIR-DMD is combined with an off-the-shelf infrared spectroradiometer to capture the spatial modulated and compressed measurements at different spectral channels. Following this, a dual-stage image reconstruction method is developed to recover infrared hyperspectral images from these measurements. In addition, a measurement without any coding is used as the side information to aid the reconstruction to enhance the reconstruction quality of the infrared hyperspectral images. A proof-of-concept setup is built to capture the mid-infrared hyperspectral data of 64 pixels × 48 pixels × 100 spectral channels ranging from 3 to 5 m, with the acquisition time within one minute. To the best of our knowledge, this is the first mid-infrared compressive hyperspectral imaging approach that could offer a less expensive alternative to conventional mid-infrared hyperspectral imaging systems.
... A two-step process is used: 3D polymer woodpile templates are fabricated by a direct laser writing (DLW) method followed by chemical vapour deposition (CVD) of MoS2 [1]. The optical properties of the composite structures are examined by measuring reflection spectra changes after each 2 nm thin film coating via our angle-resolved Fourier imaging spectroscopy (FIS) system [2][3][4]. ...
... To visualize the modification of the photonic bandstructures, angle-resolved reflection spectra after each thin film deposition are measured via our angle-resolved Fourier imaging spectroscopy (FIS) system [2][3][4]. Figure 2 plots the measured angle-resolved reflection spectra for bcc woodpile structures with varying MoS2 thickness (0-15nm). The angles in Figure 2 correspond to the collection angle θ relative to the Z direction, in the YZ plane (See Figure 1(a)). ...
We study polymer photonic crystals coated with varying thickness of high refractive index material aiming to make functional photonic devices capable of controlling light through band structure and dispersion. We observed red shifts of partial bandgaps in the near infrared region when the thickness of deposited MoS<sub>2</sub> films increases. A ~150 nm red shift of the fundamental and high order bandgaps is measured after a ~15nm thick MoS<sub>2</sub> coating.
... It is monitored using a reflective Fourier optical microscope (RFOM) system as a function of temperature. 42 The experimental setup of the RFOM is illustrated in Fig. S4 (ESI †). As shown in Fig. S5 (ESI †), the reflectance band of the film can only red-shift with the increase in temperature higher than 90 1C, and its reflectance is maintained even when heated up to 120 1C. ...
Chameleons, which are among the poikilotherms, can rapidly change color for camouflage, communication and thermoregulation. These cold-blooded animals physiologically shift color through the active tuning of lattices of guanine nanocrystals within a superficial thick layer of dermal iridophores. This active tuning can be described as alternating different refractive indices of nano-reflectors, thereby generating interference of light waves. The self-regulation of the skin behind its dynamic color changing ability makes it the ultimate “biomimetic surface” and a continued source of inspiration. We presented a deformation-color multi-responsive actuator whose response is controlled by delicate light to mimic the adaptive functions. This soft smart material is developed by well-aligned cholesteric liquid crystal elastomers. It performs a 185 nm wavelength shift of selective reflection and is switched by reacting to exposure time. Effective optical management is critical for the operation of many modern technologies. These results demonstrate distinctive potential opportunities for LC elastomers to control light, thereby enabling new applications of modern technologies to textiles, optics, and architecture.
... The technique, which made use of pulsed lasers within the picosecond or femtosecond regime, was capable of defining any 3D geometry within a polymer, at a resolution of order 100 nm. From the 2000s onwards it has been used to great effect in order to realise photonic crystals [22][23][24][25][26], microfluidic channels [27] and cell scaffolds [28][29][30][31]. It would be another 15 years before the potential of two-photon lithography was exploited to realise 3D magnetic nanostructures. ...
Three-dimensional nanostructured magnetic materials have recently been the topic of intense interest since they provide access to a host of new physical phenomena. Examples include new spin textures that exhibit topological protection, magnetochiral effects and novel ultrafast magnetic phenomena such as the spin-Cherenkov effect. Two-photon lithography is a powerful methodology that is capable of realising 3D polymer nanostructures on the scale of 100 nm. Combining this with postprocessing and deposition methodologies allows 3D magnetic nanostructures of arbitrary geometry to be produced. In this article, the physics of two-photon lithography is first detailed, before reviewing the studies to date that have exploited this fabrication route. The article then moves on to consider how non-linear optical techniques and post-processing solutions can be used to realise structures with a feature size below 100 nm, before comparing two-photon lithography with other direct write methodologies and providing a discussion on future developments.
... The samples are characterized using Fourier image spectroscopy (FIS), as previously described in Ref. [26]. The image at the back focal plane of the objective lens contains the spatial Fourier transform of the sample's optical response, since every ray with the same spatial frequency is focused by the lens to the same position at this plane. ...
We experimentally demonstrate gold microdisc structures that produce confined Tamm plasmons (CTPs)— interface modes between a metal layer and a distributed Bragg reflector— resonant around 1.3 μm. Quantum dots grown within the structures show an order of magnitude increase in the photoluminescence emitted at room temperature. Varying the disc diameter, we show spectral tuning of the resonance and measure the dispersion relation as evidence of mode confinement. The simplicity of fabrication and tuneability of these structures make CTPs an ideal platform for making scalable telecom devices based on quantum dots.
... Two materials were chosen for this work: Sn-S and Ge-Sb-S, due to their high refractive index values and low absorption in the near-infrared region. Our approach results in chalcogenide inverse rod-connected diamond (RCD) structures and here we successfully demonstrate measurements (via home-built angular resolved spectroscopy [3]) showing a complete PBG at near infrared wavelength (0.9 -1.7 µm) with low refractive-index-contrast (RIC) (nhigh/nlow ~ 1.9:1 for Sn-S-O: air and 2:1 for Ge-Sb-S-O: air) materials. Fig. 1(d)], lattice constant a = 1 µm and elliptical rod height is 500 nm and width 400 nm; phase two [ Fig. 1(b)], high refractive index chalcogenide materials (Sn-S or Ge-Sb-S) are conformally deposited into the polymer templates, using an in-house built CVD system. ...
We present an inverse rod-connected diamond structure showing a complete bandgap with refractive index contrast down to nhigh/nlow ~ 1.9. The structures were fabricated using a low-temperature chemical vapor deposition process, via a single-inversion technique.
... The photonic band structures of the polymer templates are measured using wide-angle Fourier imaging spectroscopy and compared with the FDTD simulations. 30 The RCD tem-plate fabricated via the 2PP process is an air-polymer-based crystal, where the RIC is approximately 1:1.5. Figure 3 shows the angular reflection spectra comparison between measured polymer templates and simulations via FDTD. In the measurement result for the Sn-S-O structure (Figure 4a), a continuous reflec-tion peak (the fundamental PBG) across symmetry points X-W-K and L-U-X appears at around 1250 − 1500 nm with 15 − 35% reflectivity. ...
... We used an identical system to that described in our previous work. 30 This home-built Fourier imaging spectroscope uses a 4× objective lens to collimate a fiber (200 µm diameter) coupled white light source (Bentham Ltd. WLS100 300 − 2500 nm), focusing the light beam with an NA = 0.9, 60× objective lens on the sample. ...
Three-dimensional complete photonic bandgap materials or photonic crystals block light propagation in all directions. The rod-connected diamond structure exhibits the largest photonic bandgap known to date and supports a complete bandgap for the lowest refractive index contrast ratio down to nhigh/nlow ∼1.9. We confirm this threshold by measuring a complete photonic bandgap in the infrared region in Sn-S-O (n∽1.9) and Ge-Sb-S-O (n∽2) inverse rod-connected diamond structures. The structures were fabricated using a low-temperature chemical vapor deposition process, via a single-inversion technique. This provides a reliable fabrication technique of complete photonic bandgap materials and expands the library of backfilling materials, leading to a wide range of future photonic applications
... By a process called two-photon polymerization (2PP), in which only the liquid polymer exposed to a specific wavelength gets solidified, solid immersion lenses [16] and resonant disks [17] have been fabricated with quantum dots and nanodiamonds inside the structures, respectively. These polymer structures hold the potential for the realization of a fully integrated quantum optical chip incorporating single photon-emitters, SILs, resonant cavities, polymer waveguides [18] and polymer photonic crystals [19,20]. ...
... Afterwards we added a silver layer of 20 nm (thermal evaporative deposition) on top of our polymer to end up with a fully-developed hybrid Fabry-Pérot cavity with a ND inside [ Fig. 4]. White light reflectivity spectral measurements [ Fig. 5] for the hybrid planar cavity and substrate DBR was made with a home-built Fourier imaging spectroscopy system, which uses a high NA lens (0.75) to focus on samples and performs angular spectrum measurements as per angle [19]. Reflection at normal incidence was measured with a white light source and a spot size of 2. Fig. 4. A free spectral range (frequency separation between successive longitudinal modes) of 25 FSR THz = was measured from Fig. 5(a) and a total cavity length of 6 total L m μ = is calculated from / 2 total FSR c L = [26], where c is the lightspeed in vacuum. ...
For an efficient single-photon source a high-count rate into a well-defined spectral and spatial mode is desirable. Here we have developed a hybrid planar Fabry-Pérot microcavity by using a two-photon polymerization process (2PP) where coupling between single-photon sources (diamond colour centres) and resonance modes is observed. The first step consists of using the 2PP process to build a polymer table structure around previously characterized nitrogen-vacancy (NV) centres on top of a distributed Bragg reflector (DBR) with a high reflectivity at the NV zero-phonon line (ZPL). Afterwards, the polymer structure is covered with a silver layer to create a weak (low Q) cavity where resonance fluorescence measurements from the NVs are shown to be in good agreement with analytical and Finite Difference Time Domain (FDTD) results.
... [5][6] We choose here a metal-insulator-metal (MIM) device configuration due to its ability to support antisymmetric states, and thus magnetic plasmon resonances, using dielectric spacers much smaller than the wavelength. [24,29,[34][35] The latter point is especially important, as PCMs need to be melted and rapidly cooled down (>20°C/ns) for a successful amorphization process, and this is facilitated by restricting the volume of material that undergoes amorphization [14] . ...
The development of flat, compact beam-steering devices with no bulky moving parts is opening up a new route to a variety of exciting applications, such as LIDAR scanning systems for autonomous vehicles, robotics and sensing, free-space, and even surface wave optical signal coupling. In this paper, the design, fabrication and characterization of innovative, nonvolatile, and reconfigurable beam-steering metadevices enabled by a combination of optical metasurfaces and chalcogenide phase-change materials is reported. The metadevices reflect an incident optical beam in a mirror-like fashion when the phase-change layer is in the crystalline state, but reflect anomalously at predesigned angles when the phase-change layer is switched into its amorphous state. Experimental angle-resolved spectrometry measurements verify that fabricated devices perform as designed, with high efficiencies, up to 40%, when operating at 1550 nm. Laser-induced crystallization and reamorphization experiments confirm reversible switching of the device. It is believed that reconfigurable phase-change-based beam-steering and beam-shaping metadevices, such as those reported here, can offer real applications advantages, such as high efficiency, compactness, fast switching times and, due to the nonvolatile nature of chalcogenide phase-change materials, low power consumption.
