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Considering the spatial distribution of laser beams and phonon waves, the SRS coupling wave equations in the transient regime are derived and normalized for the first time. The synchronously pumped solid-state Raman laser is simulated numerically to investigate the influences of the cavity length detuning, output coupling rate, dispersion, Raman gain and dephasing time of Raman mode on laser performances. It is found that the intensive pulse compression of first Stokes laser in synchronously pumped solid-state Raman laser stems from pulse width gain narrowing and intensity oscillation effects. The cavity length detuning, dispersion, Raman gain and dephasing time considerably affect the pulse width gain narrowing and intensity oscillation processes. The theoretical results can help the design and optimization of synchronously pumped solid-state Raman laser to generate ultrafast Raman laser output efficiently.This work contributes experimental demonstrations and comprehensive comparisons of various modulation and coding techniques for 200 Gb/s intensity modulation and direct detection links including four-level pulse amplitude modulation (PAM-4), PAM-6, trellis-coded modulation (TCM) over PAM and discrete multi-tone (DMT) transmission. Both C-band Mach-Zehnder modulator and O-band electro-absorption modulated laser transmitters were examined for intra-data center applications based on state-of-the-art commercial components.The concept of perfect invisibility in free space implies an object neither reflects nor refracts optical waves coming from arbitrary directions, regardless of its shape and size. MGH-CP1 An optimal solution to realize such a peculiar phenomenon is to tune the constitutive parameters of the object to be identical to air. In particular, to render zero extinction from an existing object by covering some additional structures, is of importance for practical implementations, which is challenging. Here, we demonstrate and propose that a thin metallic wire can be tuned to be air-like under TE polarization, with the aid of an external enclosure. This is achieved through a precise dispersion engineering with independently controllable electric and magnetic responses. Consequently, an electrically large cluster composed of multiple thin wires can be safely hidden in free space, without any macroscopic cloaking structure, which is verified by full-wave simulations and experiments. The measured results on an electrically large airplane-like sample show the excellent performance of 2D omnidirectional invisibility at the designed frequency. This proposed metamaterial would be helpful in enhancing the mechanical stability, electrical conduction, and heat dissipation of a device (or system) by extra wires (or pipes), without disturbing its electromagnetic characteristics.Multi-view architectures using lens arrays can bring interesting features like 3D or multispectral imagery over single aperture cameras. Combined with super-resolution algorithms, multi-view designs are a way to miniaturize cameras while maintaining their resolution. These optical designs can be adapted for thermal infrared imagery and can thus answer the size, weight and power (SWAP) challenge with advanced imagery functions. However, in this spectral range, the choice of an uncooled microbolometer detector imposes a high numerical aperture for the system which increases the size of the optics and makes difficult a multi-channel arrangement combined with a single focal plane array (FPA). In this paper, we theoretically investigate several asymmetric or decentered multi-view designs that allow both a high aperture for the optical channels and the use of a single FPA for the sub-images. Ray-traced designs will illustrate this study and their image quality will be checked with modulation transfer functions (MTF) for different field points.The stacked array piezoelectric deformable mirror (DM) used in adaptive optics (AO) systems usually has actuator-corresponding high-frequency temperature-induced distortion (TID) on its mirror surface when the working temperature is different from the design temperature, which is harmful to beam quality. To effectively eliminate the actuator-corresponding high-frequency TID, we introduce a hybrid connection structure deformable mirror (H-DM), which adopts a magnetic connection structure besides the conventional adhesive connection structure. The TID characteristics of the H-DM are analyzed using the finite element method, and the wavefront compensation capability of the novel H-DM is also investigated in simulation. In the experiment, the initial surface shape and the TID characteristics of a lab-manufactured H-DM are measured. The experimental results show that the H-DM has a good initial surface shape, and no actuator-corresponding high-frequency distortion exists in the surface shape of the H-DM when the environment temperature changes. Thus it can be seen the TID could be well corrected by the H-DM itself, and thereby the environmental adaptability of the DM could be improved substantially.Passive silicon photonic waveguides are exposed to gamma radiation to understand how the performance of silicon photonic integrated circuits is affected in harsh environments such as space or high energy physics experiments. The propagation loss and group index of the mode guided by these waveguides is characterized by implementing a phase sensitive swept-wavelength interferometric method. We find that the propagation loss associated with each waveguide geometry explored in this study slightly increases at absorbed doses of up to 100 krad (Si). The measured change in group index associated with the same waveguide geometries is negligibly changed after exposure. Additionally, we show that the post-exposure degradation of these waveguides can be improved through heat treatment.Graphene-based terahertz (THz) metasurfaces have the advantages of ultra-small thickness, electrical tunability, and fast tuning speed. However, many such structures suffer low efficiency, especially for transmissive devices. Here we propose a hybrid structure for focusing THz waves with tunability and enhanced focusing efficiency, which is composed of a graphene-loaded metallic metasurface sandwiched by two mutually orthogonal gratings. Experimental results show that due to the multi-reflection between the metasurface layer and the grating layer, the focusing efficiency is enhanced by 1.8 times, and the focal length of the metalens is increased by 0.61 mm when the applied gate voltage on the graphene is increased from 0 V to 1.4 V. We hope the proposed structure may open a new avenue for reconfigurable THz metasurfaces with high efficiencies.
Homepage: https://www.selleckchem.com/products/mgh-cp1.html
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