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A ridge-type semiconductor laser with partially formed anti-guiding cladding layers is proposed, and lasing characteristics are simulated. With increases in the height and the width of the partially formed anti-guiding cladding layers, both kink-level and threshold current increase. When the height is 100 nm and the width is greater than or equal to 15  $$\upmu \hbox {m}$$ for the partially formed anti-guiding cladding layers, kink-free operation is obtained up to the injected current of 2 A. The lowest threshold current for the kink-free operation is 57.0 mA when the height is 100 nm and the width is 15  $$\upmu \hbox {m}$$ for the partially formed anti-guiding cladding layers.

In this paper, a surface illuminated InAsSbP/InAs photodetector has been analyzed for operation in 2.0–3.5 μm wavelength region. The influence of different dark current components on the resistance-area product (RA) of the photodetector has been estimated theoretically. The results obtained on the basis of the model are found to be in good agreement with the experimental data reported by others. The high value of detectivity of the device at room temperature will make it attractive for use in optical gas sensor.

The possibilities of high-current laser operation in Ne-TlCl and He-Kr discharges are studied using a multiple-anode helical hollow cathode design of the laser tube. Lasing on two thallium and two krypton-ion lines is obtained. The processes limiting the c.w. mode of operation are discussed.

This study proposes a simple design of a wideband metamaterial absorber (MMA) that functions in the visible and near-infrared range. The proposed absorber is composed of a multilayer structure with two-dimensional (2D) Ti3C2Tx (MXene) layer and top mounted structure of titanium nitride (TiN). It is observed that the proposed absorber absorbs above 85% of incident light in the visible and near-infrared regime, ranging from 400 to 1600 nm for the normal incidence of light. The results show that this significant absorption was produced by 2D nanostructure MXene and top-mounted TiN disk structure due to a wide range of localized surface plasmonic resonance (LSPR). It is noticed that the proposed absorber exhibits polarization-insensitivity and shows a similar absorption for transverse electric (TE) mode and transverse magnetic (TM) mode. Further, the LSPR is less sensitive to the obliquity incidence of the light, and demonstrates wide-range angular stability. High tunability and effective heat-light energy conversion are two benefits of employing MXene and high-performance plasmonic properties of TiN in creating the proposed wideband absorber; these characteristics make them ideal for various applications, including solar energy systems and filters.

This paper uses analytical expressions for the nonlinear optical absorption of superlattices by treating them as anisotropic media. The controllable system shows that the nonlinearities increase with anisotropy suggesting that strongly anisotropic materials such as those used for solar cells may also be useful for nonlinear optical applications.