Results in Optics最新文献

A compact high-power 2.8-µm laser with a 2 at.%-doped Er³⁺:CaF₂ crystal was demonstrated, which delivered a maximum output power of 2.848 W with a slope efficiency of 26.3 %. To the best of our knowledge, this is the highest output power among all the reported LD end-pumped Er³⁺-doped fluoride crystal lasers. Experimentally, the negative thermal lens effect was characterized and the thermal lens optical diopters for two axes were obtained as M_x = -0.21 m⁻¹/W and M_y = -0.33 m⁻¹/W. In addition, the visible fluorescence spectra of Er³⁺:CaF₂ crystal with and without laser operation were measured and analyzed. With Fe²⁺:ZnSe as saturable absorber, a passively Q-switched 2.759-µm Er³⁺:CaF₂ laser with an average output power of 75 mW, a peak power of 2.39 W, a single pulse energy of 1.81 µJ, and a pulse width of 755.3 ns was obtained at a repetition rate of 41.55 kHz.

Relief patterns were photoinduced on the surface of a thin film floating on water. The structures have a length of several millimeters with a width of 33 μm. Both the intensity and the polarization of the irradiated light change the characteristics of the generated patterns. The light induced structuration is the result of simultaneously a reversible material transport originated by photoisomerization of azobenzene units and a process of self-organization of the molecules. The structures were used as waveguide or grating to couple light at the air/liquid interface on a short or long distance. The fabrication of waveguides can be extended to any liquid substrates.

Recently, a lot of focus has been placed on cesium lead iodide (CsPbI₃) since it is considered a potentially useful inorganic halide perovskite with improved stability. Moreover, another potential absorber material is the mixed chalcogenide CZTSSe, which is abundant on Earth, cheap, environmentally acceptable, and has excellent photovoltaic performance. This research numerically simulated a novel double absorber solar cell structure employing CsPbI₃ and CZTSSe absorbers in the active layer in SCAPS-1D. The current study analyses the effects of various electron and hole transport materials, back contact material's work functions, working temperatures, variations in defect concentration, and absorber thickness on the performance of photovoltaic devices. After researching a variety of distinct arrangements of double absorber solar cells, it was realized that the FTO/STO/CsPbI₃/CZTSSe/NiO/W cell configuration exhibited the best overall performance with an open circuit voltage (V_oc) at 1.0207 V, a short circuit current density (J_sc) at 41.815426 mA/cm², Fill Factor (FF) at 87.50 %, and a Power Conversion Efficiency (PCE) at 37.35 %. The modeling of the device showed that a thickness of around 1.4 µm for the CZTSSe absorber is optimal. This simulation shows that when the working temperature in the cell and the defect concentration in the absorber increase, the efficiency of the device reduces uniformly, and the device is stable at 300 K temperature. In conclusion, if the material's work function is greater than 5.20 eV, then it is suitable for use as an anode.

Dye-sensitized solar cells (DSSC) are considered as one of the most promising photovoltaic technologies, while exploring alternatives to traditional silicon-based solar cells. Dye sensitizer is a very important component of DSSC and the use of natural dyes in these cells is a promising development for this technology, as it has non-hazardous impact on the environment. This work reports the new natural dye extracted from Brassica Napus flower petals and used as sensitizer in TiO₂ based DSSC. UV–Vis spectra showed the presence of carotenoid and flavonoid pigments along with broad absorption in dye loaded TiO₂. FITR revealed functional groups in the Brassica Napus dye extract. Mass spectroscopy was used to find major constituents present in extract. With the natural Brassica Napus sensitizer and TiO₂, photovoltaic performance results viz. conversion efficiency (ɳ%) 0.062, short circuit current density (J_sc) 0.45 mA/cm², open circuit voltage (V_oc) 0.260 V and fill factor (FF) 0.52 were observed. Further, HOMO-LUMO levels of constituents present in Brassica Napus have been measured via CV measurements and compared with relative energetic obtained by computational studies. The transport characteristics revealed from EIS studies were used to rationalize the observed photo-voltaic performance of the DSSC.

This work proposes a design of a porous-core photonic crystal fiber (PC-PCF) made of a cyclic olefin copolymer, Zeonex, with a hybrid cladding for low-loss terahertz (THz) wave transmission. A combination of circular and elliptical air holes is employed, resulting in a very low material absorption loss of 0.045 ${\mathrm{cm}}^{-1}$ at $D_{\mathrm{core}}$ = 450 µm and f = 1 THz. A flat dispersion of 0.73 ± 0.13 ps/THz/cm is obtained for a broad frequency range of 0.5–1.4 THz. Core diameter and frequency response of other key features such as normalized frequency (V-parameter), confinement loss, effective area, nonlinearity and the percentage of the power flow through different sections of the proposed PC-PCF are also analyzed. Comparing to state-of-the-art, our design is superior in terms of loss, dispersion and power fraction. Our proposed design can be manufactured using the established extrusion process and be used for long distance low-loss Terahertz (THz) communication.

HiLo microscopy is a powerful, low-cost, and easily configurable technique for acquiring high-contrast optically-sectioned images. However, traditional HiLo microscopes are based on coherent light sources with diffusive glass plates or incoherent light sources with digital mirror devices (DMD) and spatial light modulators (SLM), which are more expensive. Here, we propose a new low-cost HiLo microscopy technique using MLAs and incoherent LED light sources. We simulated structured illumination (SI) patterns and HiLo image generation. To observe how MLAs affect HiLo images, we used three common MLAs with specific microlens pitch and numerical aperture (NA) to generate periodic illumination patterns. Our simulations concluded that the MLA's NA does not significantly affect HiLo images, and a larger lens pitch can bring a higher image contrast. However, there is an optimized lens pitch. If the lens pitch is equal to or higher than 140 μm, artifacts are observed in HiLo images. Based on our simulations, employing the cross-type MLA with a 0.01NA and a period of 120 μm yields the optimal HiLo image (94.6 % contrast). In our quantitative analysis with the traditional HiLo, where SI patterns were set with the same period, we calculated the SSIM index between each HiLo-Ground Truth image pair. The cross-type MLA HiLo performed slightly better (SSIM = 0.9554) than the traditional HiLo (SSIM = 0.9396). However, when using the hexagon-type MLA, artifacts were evident in the final HiLo image (SSIM = 0.9054). The cylinder-type MLA HiLo result (SSIM = 0.9366) is similar to the traditional HiLo. To our knowledge, this is the first numerical study about MLA-based HiLo microscopy. This study can benefit researchers using MLAs and incoherent light sources to configure their low-cost HiLo microscopes.

I propose combining of all-optical devices to produce an all-optical device that exhibits a desired input–output (I/O) characteristic (i.e., a desired functionality). There could be infinite distinct combinations of same/different all-optical devices of same/different parameters resulting in possibility of infinite number of all-optical devices with distinct I/O characteristics, and hence, the proposal presented here opens-up a gateway to synthesis of all-optical devices of desired functionalities. To give a few of examples in support of the proposal, I show certain series and parallel combinations of nonlinear Mach-Zehnder interferometers (NMZIs) to synthesize an (i) ideal optical switch (with step like I/O characteristic), (ii) optical isolator/optical stabilizer (iii) optical pulse generator (iv) optical power filter and (v) optical limiter. The analytical findings are verified using BPM simulations in presence of losses also.

Spectroscopic ellipsometry is a reproducible and non-invasive characterization technique that allows the evaluation of multilayered structures. However, it is an indirect technique and requires the use of well-calibrated models to correctly analyze the materials. In this work, we report a multilayer modeling approach to investigate the optical properties of the three layers of interest typically employed on an inverted perovskite solar cells structure, namely, indium-tin-oxide (ITO) as a transparent anode, poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) as a hole transport layer, and methylammonium lead iodide (MAPbI₃) as the perovskite layer. The parameterized optical constants based on oscillator models were simultaneously fitted to ellipsometry and intensity-transmission data and validated with ultraviolet–visible (UV–Vis) spectroscopy and profilometry. We propose this multilayer modeling approach as a method to be employed throughout the different stages of the fabrication process to study the distinct mechanisms that impact the final performance of a photovoltaic device.

We construct proper microscopic propositions to consistently capture and explain the interference patterns obtained for electrons and photons, detected individually or otherwise, in one- and two-slit experiments. We propose that for single-photon detections (after time integration), no interference pattern is obtained if one uses non-transparent slit material with slit holes (not diffraction slits). The non-transparent slit material does not permit photons to transmit, reflect internally nor refract. However, the same slit holes can produce the usual interference pattern with electromagnetic waves due to interfering in-phase and out-of-phase light waves. As for the electrons, detected individually or not, partial interference patterns can always be obtained from the two-slit experiment when one of the slits is closed (one at a time), which then can be manually overlapped to produce the complete interference pattern of a double-slit experiment. These new theoretically constructed experimental results for photons and electrons can be readily verified with our current technology using suitable optically non-transparent (for photons) and highly insulating (for electrons) slit materials.

Oxy Fluoro Borate (OFB) Glasses mixed with Sesquioxide ions (Al³⁺/Y³⁺/Sb³⁺) were synthesized using the traditional melt quenching technique. The properties of the structure of the glasses prepared are investigated by SEM, EDS and XRD methods. Variations in properties like density in glasses allow Nickel/Aluminium/Antimony/Yttrium ions to go through the borate glass matrix with an increase in respective dopant mole fraction. The decrease in the values of different elastic constants with B-O-Ni/Al/Sb/Y bonds and alsoby the function of NiO/Al₂O₃/Sb₂O₃/Y₂O₃ as a modifier and converting a portion of BO₃ tetrahedral units into BO₄octahedral units indicates the depolymerization in the glass matrix. The I.R. spectra and FTIR spectra show an increment in the occupation of cations Ni²⁺, Y³⁺, Sb³⁺ and Al³⁺ ions in the octahedral positions of the glass matrix with an enhancement in their molefraction. Creation of NBOs owing to the transformation of BO₃ to BO₄ units is greater in Al³⁺ and the smallest in Y³⁺ with an increment in the sesquioxide concentration at a 1.00 mol% NiO concentration. The dominance of the nickel ions octahedral occupancy in the glasses prepared is revealed by the optical absorption spectra, which may be because of the ligand fields produced by various ions of sesquioxides present within the glass matrix creating NBO and many trapped electrons at the donor centers. Photoluminescence spectra of the prepared glasses show the octahedral occupation of the Ni²⁺ ions that is indicated by the transitions ³A_2g(F) ↔ ³T_1g(P) and ³T_1g(P) → ³T_2g(F). The synthesized glasses exhibit effective luminescence by Nickel ions, and the AlNi and NiAl glass series exhibit superior luminescence properties owing to their highest emission cross-sections compared with the other series of prepared glasses.