We verified the DSS method using a 152 mm diameter optical flat mirror and determined the root-mean-square (rms) measurement error to be only 0.2 nm, which was comparable to the error of the full-aperture interferometric measurement. In addition, we tested a 1.2 m diameter flat mirror with a reference sphere with an aperture of 0.8 m and measured its SFE to be 11.9±0.5nm rms.In this paper, by considering wave phase analysis, the density of modes, group velocity, and lateral shift in one-dimensional multilayer are theoretically computed by using the transfer matrix method in the terahertz domain. The proposed structure is based on the Fibonacci sequence constituted of uniaxial indefinite medium and SiO2 layers. It is found that for both TE and TM beams, around an angle of 90º, the lateral shift is highly negative, while it is positive at the rest of the angles. Also, for non-vertical angles, a positive peak is observed about an angle of 60º (near the Brewster angle). Our numerical analysis shows that at angles less than about 10º, the lateral shift is negative for the TM mode. It is shown that for both polarizations the density of states (the group velocity) has maximum (minimum) value near the band gap edges, while inside the band gap it becomes minimum (maximum). Superluminal and subluminal cases can be defined here.We have proposed a polarization-independent directional coupler (DC) by using sections with optimal coupling strength designs on the lithium-niobate-on-insulator platform. With this design, arbitrary polarization-independent coupling ratio ranging from 0% to 100% can be achieved by tuning the length of the identical coupling region. The DC exhibits ultralow excess losses ( less then 0.1dB) and polarization-dependent losses ( less then 0.05dB for the complete coupling) over a bandwidth of 100 nm. GDC-0068 mw Moreover, the proposed DC is compact in size, simple in structure, and easy to fabricate.In this work, the influence of strong optical feedback on the emission behavior of distributed Bragg-reflector ridge waveguide diode lasers emitting at 1120 nm with different cavity lengths and facet reflectivities is investigated. Based on measurements of the optical output power, central emission wavelength, and spectral emission width, the different diode laser types are compared while optical feedback up to -8dB is applied. The observed changes of the optical output power and emission wavelength as well as the occurrence of coherence collapse states give insight into the resistance against feedback of the different diode laser types.Organic solar cells are attractive for various applications with their flexibility and low-cost manufacturability. In order to increase their attractiveness in practice, it is essential to improve their energy conversion efficiency. In this work, semi-cylindrical-shell-shaped structures are proposed as one of the approaches, aiming at absorption enhancement in an organic solar cell. Poly(3-hexylthiophene-2,5-diyl) blended with indene-C60 bisadduct (P3HTICBA) is considered as the active layer. Light coupling to the guided modes and a geometrical advantage are attributed to this absorption enhancement. Finite-difference time-domain methods and finite element analysis are used to examine the absorption spectra for two types of devices, i.e., a debossed type and an embossed type. It is shown that absorption enhancement increases as the radius of the cylinder increases, but reaches a saturation at about 4-µm radius. The average absorption enhancement with an active layer thickness of 200 nm and radius of 4 µm, and for incidence angles between 0° and 70°, is found as 51%-52% for TE-polarized input and as 30%-33% for TM-polarized input when compared to a flat structure. Another merit of the proposed structures is that the range of incidence angles where the integrated absorption is at the level of the normal incidence is significantly broadened, reaching 70°-80°. This feature can be highly useful especially when organic solar cells are to be placed around a round object. The study results also exhibit that the proposed devices bear broadband absorption characteristics.As forest terrain is complex, containing leaves and other obstacles, it is difficult to distinguish the signal of forest-fire smoke when using single-channel lidar. To address this difficulty, a scanning micropulse polarization lidar system is developed, and a new method to detect forest fires is proposed in this study. Based on the characteristics of the depolarization ratio of in-scene obstacles, a matrix is constructed to remove obstacle signals, which in turn reduces the misidentification rate. Artificial forest-fire tests are carried out to verify the correctness of the proposed method and the feasibility of early forest-fire detection using the scanning polarization lidar system. In the working mode, the developed polarizing lidar system can locate a forest fire within three minutes with the proposed method. The experimental results show that forest fires can be accurately detected in real time when using scanning polarization lidar.Poor visual quality of color retinal images greatly interferes with the analysis and diagnosis of the ophthalmologist. In this paper, we propose an enhancement method for low-quality color retinal images based on the combination of the Retinex-based enhancement method and the contrast limited adaptive histogram equalization (CLAHE) algorithm. More specifically, we first estimate the illumination map of the entire image by constructing a Retinex-based variational model. Then, we restore the reflectance map by removing the illumination modified by Gamma correction and directly enable the reflectance as the initial enhancement. To further enhance the clarity and contrast of blood vessels while avoiding color distortion, we apply CLAHE on the luminance channel in CIELUV color space. We collect 60 low-quality color retinal images as our test dataset to verify the reliability of our proposed method. Experimental results show that the proposed method is superior to the other three related methods, both in terms of visual analysis and quantitative evaluation while testing on our dataset.