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Direct laser writing of birefringent photonic crystals for the infrared spectral range
摘要： Infrared optical photonic crystals fabricated using direct laser writing, which is based on the two-photon polymerization of suitable monomers, have received substantial interest since the emergence of this process. Two-photon polymerization could be a disruptive technology for the fabrication of all-dielectric photonic crystals in the infrared spectral range, as it allows the synthesis of large scale arrays of uniform structures with arbitrary geometries and arrangements. However, all-dielectric photonic crystals that provide birefringent optical responses in the infrared spectral range have not yet been demonstrated using direct laser writing techniques. Here, the authors explore the form birefringence observed in photonic crystals composed of arrays of subwavelength-sized slanted polymer microwires. The photonic crystals investigated here were fabricated in a single fabrication step using direct laser writing of an infrared transparent photoresist (IP-Dip). A strong contrast of the cross-polarized re?ectance of photonic crystals as a function of the in-plane orientation is observed in the mid-infrared spectral range at λ ≈ 6:5 μm. This observation is indicative of an anisotropic optical behavior. Finite element based techniques corroborate the experimentally observed responses qualitatively.
关键词： two-photon polymerization,direct laser writing,infrared spectral range,birefringent photonic crystals,all-dielectric photonic crystals
更新于2025-11-14 15:18:02
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Surface Polariton‐Like s‐Polarized Waveguide Modes in Switchable Dielectric Thin Films on Polar Crystals
摘要： Surface phonon polaritons (SPhPs) and surface plasmon polaritons (SPPs), evanescent modes supported by media with negative permittivity, are a fundamental building block of nanophotonics. These modes are unmatched in terms of field enhancement and spatial confinement, and dynamical all-optical control can be achieved, e.g., by employing phase-change materials. However, the excitation of surface polaritons in planar structures is intrinsically limited to p-polarization. On the contrary, waveguide modes in high-permittivity films can couple to both p- and s-polarized light, and in thin films, their confinement can become comparable to surface polaritons. Here, it is demonstrated that the s-polarized waveguide mode in a thin Ge3Sb2Te6 (GST) film features a similar dispersion, confinement, and electric field enhancement as the SPhP mode of the silicon carbide (SiC) substrate, while even expanding the allowed frequency range. Moreover, it is experimentally shown that switching the GST film grants nonvolatile control over the SPhP and the waveguide mode dispersions. An analytical model is provided for the description of the GST/SiC waveguide mode and it is shown that the concept is applicable to the broad variety of polar crystals throughout the infrared spectral range. As such, complementarily to the polarization-limited surface polaritons, the s-polarized waveguide mode constitutes a promising additional building block for nanophotonic applications.
关键词： waveguide modes,infrared spectral range,phase-change materials,surface plasmon polaritons,silicon carbide,nanophotonics,Ge3Sb2Te6,surface phonon polaritons,s-polarized light
更新于2025-09-19 17:13:59
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Chalcogenide || Lead salt photodetectors and their optoelectronic characterization
摘要： Lead salt photoconductors produced by chemical bath deposition are popular IR photodetectors due to their outstanding performance-to-cost ratio, high room temperature performance (D(cid:3) . 1E10) and availability of large area detectors. History of lead salt detectors has been reviewed recognizing some more recent research developments. The chemical bath deposition technique for production of the lead salt detectors has been outlined, followed by a review of the basics for their characterization. Spectral responses of both PbS and PbSe detectors collected in a wide temperature range and properly corrected have been presented.
关键词： PbSe,chemical bath deposition,photoconductors,Lead salt photodetectors,PbS,infrared spectral range
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Rare-Earth Doped Oxide Glasses and Fibers for Lasers Emitting in the 2÷3 μm Spectral Range
摘要： The aim of this investigation is the search of novel promising materials for solid-state and fiber lasers emitting in the spectral range 2÷3 microns, i.e. out of the range where the well-developed rare-earth doped silica fibers can successfully operate. We have stopped our choice on tellurite and calcium aluminate glasses. In contrast to silica glasses, both these glass types can contain high (>1021 cm-3) amounts of rare earth dopants. In contrast to ZBLAN glass that is widely used for mid-infrared fiber lasers, both tellurite and aluminate glasses can be quite stable to air moisture. Furthermore, calcium aluminate glasses are prominent for their extraordinary mechanical properties (better than those of fused silica). Our spectral investigations have shown that deeply dehydrated tellurite glasses (TG) are very suitable hosts for 2.3 μm Tm3+ lasers and can be also used as a host for 2.7 μm Er3+ lasers. As for calcium aluminate glasses (CAG), their phonon spectrum is not suitable for 2.7 for μm lasers. But the emission properties of Tm3+ ions in this host show some unusual feature. Two-micron Tm3+ emission band in CAG is anomalously widened and red shifted so that it overlaps well with the 2.3μm emission band. Thus continuous tuning of Tm doped CAG fiber laser from ~2μm up to ~2.4μm is conceivable. Figures 1 and 2 give some examples of bulk Tm-doped TG and CAG lasing properties. Fig. 1 shows the 2.3μm lasing parameters of 30 mm long TG sample when pumped by a pulsed ruby laser. CAG in similar conditions showed cascade lasing at 2.3μm and 2.1μm. Fig. 2 shows the lasing parameters of a quasi CW diode-pumped CAG chip laser, operating at the wavelength of 2.1 μm. Surely most practical applications of such laser glasses require fiber configuration. We have developed the laboratory technology of TG multimode and single-mode double-cladding fibers fabrication. In Tm doped TG fibers laser action at 1.9 μm and 2.3 μm was successfully demonstrated. Er doped fibers were also manufactured but 2.7 μm laser action in them requires highly reflective fiber Bragg gratings to be made in them. Fabrication of CAG fibers is a very complicated technological task due to high tendency of CAG to devitrification. Nevertheless, using “rod-in-tube” method we have prepared an optical fiber starting from Tm-doped CAG rod in a silica tube. Unfortunately, the core of this fiber contained too much SiO2 diffused from the cladding. The choice of a suitable lower-melting cladding glass should solve the problem. Thus, the properties of deeply dehydrated rare-earth doped tellurite and calcium-aluminate glasses are shown to be quite pertinent for lasers emitting in the 2÷3 μm spectral range.
关键词： rare-earth doped oxide glasses,mid-infrared spectral range,fiber lasers,tellurite glasses,calcium aluminate glasses
更新于2025-09-11 14:15:04