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It is widely discussed in the literature that a problem of reduction of thermal noise of mid-wave and long-wave infrared (MWIR and LWIR) cameras and focal plane arrays (FPAs) can be solved by using light-concentrating structures. The idea is to reduce the area and, consequently, the thermal noise of photodetectors, while still providing a good collection of photons on photodetector mesas that can help to increase the operating temperature of FPAs. It is shown that this approach can be realized using microconical Si light concentrators with (111) oriented sidewalls, which can be mass-produced by anisotropic wet etching of Si (100) wafers. The design is performed by numerical modeling in a mesoscale regime when the microcones are sufficiently large (several MWIR wavelengths) to resonantly trap photons, but still too small to apply geometrical optics or other simplified approaches. Three methods of integration Si microcone arrays with the focal plane arrays are proposed and studied: (i) inverted microcones fabricated in a Si slab, which can be heterogeneously integrated with the front illuminated FPA photodetectors made from high quantum efficiency materials to provide resonant power enhancement factors (PEF) up to 10 with angle-of-view (AOV) up to 10°; (ii) inverted microcones, which can bemore »monolithically integrated with metal-Si Schottky barrier photodetectors to provide resonant PEFs up to 25 and AOVs up to 30° for both polarizations of incident plane waves; and iii) regular microcones, which can be monolithically integrated with near-surface photodetectors to provide a non-resonant power concentration on compact photodetectors with large AOVs. It is demonstrated that inverted microcones allow the realization of multispectral imaging with ∼100 nm bands and large AOVs for both polarizations. In contrast, the regular microcones operate similar to single-pass optical components (such as dielectric microspheres), producing sharply focused photonic nanojets.

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In terahertz (THz) photonics, there is an ongoing effort to develop thin, compact devices such as dielectric photonic crystal (PhC) slabs with desirable light–matter interactions. However, previous works in THz PhC slabs have been limited to rigid substrates with thicknesses$\sim <\#comment/>100\mathrm{s}$of micrometers. Dielectric PhC slabs have been shown to possess in-plane modes that are excited by external radiation to produce sharp guided-mode resonances with minimal absorption for applications in sensors, optics, and lasers. Here we confirm the existence of guided resonances in a membrane-type THz PhC slab with subwavelength (${\mathrm{\lambda <\#comment/>}}_0/6-<\#comment/>{\mathrm{\lambda <\#comment/>}}_0/12$) thicknesses of flexible dielectric polyimide films. The transmittance of the guided resonances was measured for different structural parameters of the unit cell. Furthermore, we exploited the flexibility of the samples to modulate the guided modes for a bend angle of$\mathrm{\theta <\#comment/>}\ge <\#comment/>5^{\circ <\#comment/>}$, confirmed experimentally by the suppression of these modes. The mechanical flexibility of the device allows for an additional degree of freedom in system design for high-speed communications, soft wearable photonics, and implantable medical devices.

The development of active metadevices continues to present keystone challenges in fields of plasmonics and photonics. Here, we demonstrate an analogue of electromagnetically induced transparency (EIT) effect in a far-infrared metasurface device via near-field coupling of bright and quasi-dark resonances resonating at nearly the same frequency with contrasting line widths. The proposed metasurface was further optimized numerically in order to demonstrate a reconfiguration effect (frequency-shift of the spectral response). The tunability property of the device is achieved by incorporating a thin layer of Ge 2 Sb 2 Te 5 (GST), a temperature-driven phase change material (PCM). Theoretical analysis based on a coupled Lorentz oscillator model explains the physical mechanism in the proposed design and shows a good agreement with the observed results. Such active hybrid EIT metadevices could have applications in tunable slow-light effects, delay bandwidth management and ultrafast laser induced switching.