All-optical reconfigurable photonic crystal-microring hybrid cavities with high-efficiency tuning via the mechanical Kerr effect

All-optical control of silicon photonic integrated devices is crucial for on-chip applications such as signal processing, computing, and switching. A key limitation of current integrated devices is high power consumption, stemming from the weak nonlinear effects of silicon. An alternative nonlinear effect in deformable platforms is the mechanical Kerr effect (MKE), which arises from the optical gradient force (OGF) generated by highly localized optical fields that can deflect freestanding waveguides near a dielectric substrate. In this work, we present a hybrid optomechanical cavity design, driven by OGF, which integrates a compact microring resonator (MRR) with a radius of 10.08 µm and a quadratically tapered photonic crystal nanobeam cavity (PCNC). This design results in two distinct types of resonant modes, enabling mode-dependent wavelength routing. Due to strong localization and intensity enhancement, the tuning range and efficiency are significantly improved compared to conventional MRRs. An experimental 1.98 nm redshift is achieved in the probe PCNC mode, corresponding to a tuning efficiency of 142 GHz/mW. Additionally, substantial mode splitting is observed due to the mode-dependent tuning capability of the device. This design holds great potential for wavelength routing applications, particularly in advanced all-optical tunable optical filtering systems

Dual-wavelength distributed feedback laser array based on four-phase-shifted sampled Bragg grating for terahertz generation

We propose and experimentally demonstrate a dual-wavelength distributed feedback (DFB) laser array utilizing a four-phase-shifted sampled Bragg grating. By using this grating, the coupling coefficient is enhanced by approximately 2.83 times compared to conventional sampled Bragg gratings. The devices exhibit a stable dual-mode lasing achieved by introducing further π-phase shifts at 1/3 and 2/3 positions along the cavity. These devices require only one stage of lithography to define both the ridge waveguide and the gratings, mitigating issues related to misalignment between them. A dual-wavelength laser array has been fabricated with frequency spacings of 320 GHz, 500 GHz, 640 GHz, 800 GHz, and 1 THz. When integrated with semiconductor optical amplifiers, the output power of the device can reach 23.6 mW. Furthermore, the dual-wavelength lasing is maintained across a wide range of injection currents, with a power difference of <3 dB between the two primary modes. A terahertz (THz) signal has been generated through photomixing in a photoconductive antenna, with the measured power reaching 12.8 µW

Simultaneous multi-wavelength mode-locked DFB laser based on waveguide Bragg grating microcavities

We demonstrate, for the first time to the best of our knowledge, a monolithic multi-wavelength mode-locked distributed feedback (DFB) laser based on waveguide Bragg grating microcavities, achieving simultaneous three-wavelength lasing near 1.55 μm within a single cavity. The device exhibits a uniform free spectral range of 0.46 nm (57.4 GHz), a side mode suppression ratio exceeding 30 dB, and near-transform-limited pulses (6.25 ps, time-bandwidth product = 0.359). The structure requires only one metalorganic vapor phase epitaxy growth and a single III-V material dry etching step, significantly simplifying fabrication and enhancing reproducibility. By halving and doubling the central cavity length, we also demonstrate dual- and six-wavelength operation with free spectral ranges of 0.75 nm and 0.27 nm, respectively highlighting the design versatility in tailoring the channel count and repetition frequency. This compact platform enables seamless photonic integration with semiconductor optical amplifiers, electroabsorption modulators, and other on-chip components, making it suitable for dense wavelength division multiplexing, coherent optical communications, and photonic sensing

A reconfigurable multi-channel on-chip photonic filter for programmable optical frequency division

Recent advancements have broadened the application of photon filters based on Bragg gratings within optical communication networks and optical input/output interfaces. Traditional gratings, however, suffer from a fixed refractive index modulation distribution once manufactured, constraining their adaptability and flexibility. This study introduces a reconfigurable multi-channel photon filter on a silicon nitride on insulator platform. The filter incorporates an equivalent linearly chirped four-phase-shifted sampled Bragg grating with micro-heaters to enable thermo-optic tuning, facilitating programmable control over transmission spectral features. Experimental outcomes indicate the filter’s capability to seamlessly transition among single, dual, and quad-band configurations, as well as a band-stop mode, with independent tuning of each band. Moreover, optical frequency division multiplexing experiments using a 50 GHz semiconductor mode-locked laser have affirmed the filter’s tunability. In quad-band mode, band separations of 50, 100, and 150 GHz are achievable; in dual and single-band modes, band intervals extend from 150 to 250 GHz, allowing for precise single-wavelength selection. Featuring high tunability, minimal insertion losses, and superior signal side-mode suppression ratio, this filter structure supports the integration of programmable photonic devices into space optical communications, photonic integrated networks, and elastic optical networks

Optimizing the Radius of Curvature of Black Silicon Peaks for Solar Cell Using Matlab Simulations

    As part of our research on efficiency improvement of PERC (Passivated Emitter Rear Solar Cell), achieving very low reflectivity values of solar cell surface is a must. One of the most advance technologies to do so is the use of advanced texturing for the front surface of the cells. This texture, also known as Black Silicon, consists of peaks and valleys of nano metric dimensions and capable of dramatically reducing the reflectance of the front surface. A reflectance around 5%  was reached ,using simulation, when using a Black-Silicon texturing with height of 50nm with peak rounding of 5nm. Even though this texturing may affect other parameters such as series resistance or surface recombination, as a starting point,  simulation was used to find the optimum peak rounding, where the radius of curvature of the peak is maximum, while keeping reflectance as low as possible.</jats:p

Assessment of Heavy Metal Contamination in Urban Soils of selected areas in Hilla City, Babylon, Iraq

       Modern cities suffer from heavy metal pollution due to urban expansion and population increase. Heavy metals have a great impact on human health. The objective is to determine the contamination level of heavy metals Cr, Mn, Ni, Cu, Zn, As, Zr and Pb at industrial and residential in Hilla city. The mean concentration of Cr, Mn, Ni, Cu, Zn, As, Zr and Pb enrichment factors of the investigated industrial soils are 3.43, 0.74, 6.45, 3.95, 5.60, 3.44, 1.17 and 11.44, respectively. The means of Cr, Mn, Ni, Cu, Zn, As, Zr and Pb in residential soils are 3.30, 1.09, 11.40, 0.94, 2.08, 5.39, 0.9 and 3.6, respectively. The I-geo mean values of heavy elements in the industrial area may be ordered in the following: Mn&gt; Pb&gt; Ni&gt; Zn&gt; Cu&gt; As&gt; Cr&gt; Zr. While in the residential area ordered Mn&gt; Ni&gt; As&gt;Cr&gt; Pb&gt; Zn&gt; Cu &gt; Zr. Integrated Pollution Load Index categories results showed high contamination in industrial and residential areas. The main sources of heavy elements pollution in the study area  has been regarded as anthropogenic sources.</jats:p