Silicon Cladding Research Articles

All-Optical XOR, AND, OR, NOT, NOR, NAND, and XNOR Logic Operations Based on M-Shaped Silicon Waveguides at 1.55 μm.

Silicon waveguides are essential to integrated photonics, which is where optical and electronic components are coupled together on a single silicon chip. These waveguides allow for the integration of signal processing and optical transmission, which advances data centers, telecommunications, and other optical applications. Thus, our study involves the simulation of essential all-optical logic operations, namely XOR, AND, OR, NOT, NOR, NAND, and XNOR, and utilizes M-shaped silicon optical waveguides at a wavelength of 1.55 μm. This simulation is conducted through Lumerical FDTD solutions. The suggested waveguide comprises four identical slots, configured in the shape of the letter 'M', and all of which are formed of core silicon and silica cladding. These logic operations work based on constructive and destructive interferences that are caused by phase changes in the input optical beams. The contrast ratio (CR) is employed to quantitatively and comparatively assess the degree to which the target logic operations are efficiently executed. The simulation results indicate that, compared to other reported designs, the considered logic functions constructed using the proposed waveguide can be implemented with higher CRs. The outcomes of this paper can be utilized regarding the implementation of optoelectronic combinational logic circuits of enhanced functionality.

Selective distributed optical fiber sensing system based on silicone cladding optical fiber and Rayleigh backscattering reflectometry for the detection of hydrocarbon leakages

A new system that exploits optical fiber distributed sensing for the detection of hydrocarbons is presented. The system relies on a custom-designed silica core/thin silicone cladding optical fiber to provide a quick and selective absorption of oil products through the cladding; moreover, it exhibits insensitivity to water. Optical fiber sensor interrogation is performed by detecting Rayleigh backscattering using an optical time domain reflectometer or, in a high-resolution version, an optical frequency domain reflectometer. The Rayleigh backscattering signal is influenced by a change in the refractive index of the cladding, which locally modifies the guiding properties of the fiber; and by the swelling of the cladding, resulting from hydrocarbon diffusion, that produces local stress and results in an associated increased reflection. The system has been tested with different solvents and has exhibited selectivity and a rapid response to exposure to high refractive index hydrocarbons, with the sensing fiber yielding a response time of the order of 1 s. The system, in its high-resolution version, is able to accurately locate leakages with an accuracy of 14 cm.

Ultrahigh-Q on-chip silicon–germanium microresonators

To date, integrated waveguides with the lowest losses have all relied at least in part on amorphous materials. In this work, we demonstrate fully crystalline, single-mode integrated microresonators comprising epitaxially grown S i 0.86 G e 0.14 waveguide cores with silicon claddings. This platform supports ultrahigh-quality-factor resonances, with Q reaching 1.71 ± 0.06 × 10 8 , corresponding to a loss rate of 0.39 ± 0.02 d B / m . This Q is nearly an order-of-magnitude improvement over that seen in prior integrated Si waveguides. Together with silicon’s strong Kerr nonlinearity, our results could unlock important new avenues for microwave photonics, optomechanics, and quantum transduction.

Selective Distributed Optical Fiber Sensing System Based on Silicone Cladding Optical Fiber and Rayleigh Backscattering Reflectometry for the Detection of Hydrocarbon Leakages

Selective Distributed Optical Fiber Sensing System Based on Silicone Cladding Optical Fiber and Rayleigh Backscattering Reflectometry for the Detection of Hydrocarbon Leakages

Effect of thermal conductivity of substrate board for temperature control of electronic components: A numerical study

The current study deals with the numerical investigation of the substrate board characteristics using different materials (FR4, silicon cladding and copper cladding) on which nine nonidentical electronic components (ECs) are mounted, which are supplied with nonuniform heat flux. The study is conducted for natural and forced convection (3[Formula: see text]m/s and 5[Formula: see text]m/s) modes of heat transfer. It is observed that for 5[Formula: see text]m/s the temperature of the ECs is dropped by 30–47∘C using copper cladding board in comparison to FR4 and silicon cladding board. It is also noted that with the use of copper cladding board the velocity of air required for cooling the ECs is substantially reduced by 2[Formula: see text]m/s and the temperature of the IC chip is reduced by 1.50–11.12∘C.

All-optical fiber filter based on an FBG inscribed in a silica/silicone composite fiber.

An all-optical tunable filter based on a fiber Bragg grating (FBG) inscribed in a self-heated silica/silicone composite fiber is demonstrated. A thin silicone film is coated inside the suspended core fiber), which acts as the silicone cladding. A periodic refractive index modulation is inscribed in the silicone cladding by UV irradiation. Silicone is an organic material whose optical properties are different than silica, which leads to interesting applications. The high thermo-optic properties are studied and applied here. A 1550 nm pump laser is utilized to heat the silicone grating where a wavelength shift is observed for the gratings when subjected to different pump powers. Experimental results indicate a wavelength tuning coefficient of -0.128nm/mW with a response time of 0.5 s to obtain a wavelength shift of 1 nm under periodic pump light. The new design of this miniature all-optical filter is cost-effective and can potentially be adhered in optical fiber sensing and communication systems.

LSPR Excitation on Au Nanorings From Integrated Hybrid Plasmonic Aperture Waveguide and Its Application in Methanol Detection in the IR-Band

The presented work deals with an infra-red (IR)-band methanol sensor, which has been realized in an integrated device having hybrid plasmonic aperture waveguide and Au-nanoring array over broad wall of it covered by porous silicon clad. Through modeling and numerical simulations, we have shown that suitable synthesized aperture in the waveguide can excite localized surface plasmon resonance (LSPR) on the nanorings of suitable diameter via radiative field coupling, whereas LSPR can be tuned with the received methanol by the porous silicon clad. Thus, by contrasting the power available at the sense port of the waveguide with null and finite methanol doses, we have determined sensitivity (STM) and figure of merit (FOM) of the sensor, and our further analyses suggest that the sensor response can be tailored by diameter of aperture and ring, and by the porosity of the silicon cladding medium. In this respect, we have found that, for 20%-45% clad porosity, S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">TM</sub> = 77.95-66.66 nm/RIU and FOM = 17.51-7.66/RIU can be achieved during methanol detection.

Coupler for butt-coupling between edge-emitting lasers and inverted Si taper waveguide

A novel design and analysis of a butt-coupler are presented to be coupled with an edge-emitting laser and a silicon waveguide. The coupler is fairly effective when used with an edge-emitting laser of a certain integrated size and a high refractive index core material. Butt-coupling is not sensitive to polarization as both TE and TM modes achieve similar efficiency. The laser alignment tolerance and silicon waveguide gap in both lateral and vertical positions were studied. Although the air gap between the laser and the silicon cladding reduces coupling efficiency greatly, gap filling can help solve this problem. This design is proved to be quite effective in dealing with high index contrast and huge size mismatch between the laser and semiconductor waveguide.

Highly Sensitive Small Pressure Monitoring Using Hyperelastic Silicone-Cladding/Silica-Core Composite Optical Fiber

We have fabricated a composite optical fiber with hyperelastic silicone cladding and silica core, and demonstrated a simple and highly sensitive pressure sensor based on the light coupling between two such composite fibers twisted together. The hyperelastic silicone has very low Young's modulus which makes the fiber deformation easier even under small pressure and hence improves the light coupling and pressure sensitivity. Both simulation and experiment show that the light coupling based pressure sensor using the composite fibers is very sensitive to small pressure (e.g., several newtons) compared with those using conventional silica fibers and polymethyl methacrylate resin polymer fibers, which almost have no response to small pressure. With excellent sensitivity and fast response time ( $\ll 1\;{\rm{s}}$ ), both static and dynamic side pressure have been successfully detected. The sensing configuration is simple without any complicated structures and would be a cost-effective candidate for highly sensitive small pressure monitoring.

Stretchable Optical Fibers: Threads for Strain‐Sensitive Textiles

Soft, stretchable, sewable, and strain‐sensitive optical fibers are reported. Intrinsically stretchable optical waveguides capable of &gt;100% strain are formed by coating a commercially available elastic urethane fiber (“Stretch Magic”) with a silicone cladding having a lower refractive index. These 1–2 mm diameter fibers can be attached to textiles using a sewing machine. Because the attaching threads create microbends in the fiber, the sewn fibers are prestrained for monotonic intensity‐versus‐strain behavior. Installed in a stretchable piece of athletic tape, they detect strains originating from changing muscle shapes during weight‐bearing activity.

Highly Directive Hybrid Yagi-Uda Nanoantenna for Radition Emission Enhancement

In this paper, a novel design of Yagi–Uda nanoantenna is introduced and numerically analyzed using finite integration technique via computer simulation technology software. The proposed nanoantenna consists of five core-shell nanowires with silicon cladding and silver core to achieve high directivity for wireless point to point applications. The proposed design shows a high directivity of 17.21 at a wavelength of 500 nm, which exceeds the spherical dielectric counterparts with directivity of 12. Therefore, an enhancement of 43.41% is achieved, which is mainly useful for spontaneous emission manipulation and photon detection. This enhancement is attributed to the silicon dielectric shell that exhibits magnetic mode with high refractive index, as well as the surface plasmon mode supported by the silver core. Additionally, the proposed cylindrical design has advantages in terms of high homogeneity of the field distribution, which overcomes the inhomogeneity field distribution of the nanosphere-based design.

Effect of dielectric cladding on active plasmonic device based on InGaAsP multiple quantum wells.

The Surface Plasmon Polariton (SPP) planar waveguide with amorphous silicon (α-Si) cladding is studied, for empowering the device modulation response. The device is fabricated with multiple quantum wells (MQWs) as the gain media electrically pumped for compensating SPP propagation loss on Au film waveguide. The SPP propagation greatly benefits from the modal gain for the long-range hybrid mode, which is optimized by adopting an α-Si cladding layer accompanied with minimal degradation of mode confinement. The proposed structure presented more sensitive response to electrical manipulation than the one without cladding in experiment.

An Optomechanical Transducer Platform for Evanescent Field Displacement Sensing

We demonstrate an integrated waveguide platform and optomechanical transduction circuit for chip-scale displacement sensing. The waveguide consists of a thin silicon nitride core layer, a thick silicon oxide bottom cladding, and a top air cladding with a large evanescent field at the waveguide surface. Although the structures feature subwavelength (<;λ/4n <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">core</sub> ) vertical confinement, they are fabrication tolerant with micrometer-scale lateral features. We demonstrate via simulations and measurements that the waveguides exhibit a low confinement with a maximized evanescent field as well as an effective index only slightly larger than the SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> bottom cladding index. Despite the low confinement, the waveguide platform enables complex photonic circuits. As a demonstration of this technology, we fabricate and characterize an unbalanced Mach-Zehnder interferometer for chip-scale displacement sensing. A micrometer-scale fiber taper interacts with the waveguide's evanescent field and induces a phase shift proportional to displacement, thereby acting as an optomechanical transducer. We analyze the responsivity, displacement limit of detection, and strength of optomechanical coupling for high-resolution sensing. An outlook toward other applications is also given.

Long-period waveguide gratings with amorphous silicon cladding layer on silicon-on-insulator substrates realized by anisotropic wet etching

Long-period waveguide gratings (LPWGs) are designed and fabricated on silicon-on-insulator (SOI) substrates with an amorphous silicon (a-Si) layer incorporated as the cladding layer. Specifically, ridge waveguides are etched and patterned on SOI wafers via anisotropic wet etching and a-Si is deposited using a plasma-enhanced chemical vapor deposition (PECVD) system. The experimental results confirm that the resonant wavelengths of LPWG devices are within the range of 1563–1580 nm and that an LPWG ridge waveguide of 8 µm wide yields a dip contrast as high as 29.5 dB and an FWHM as narrow as 1.76 nm when the input light is transverse-electric (TE)-polarized. As for the transverse-magnetic (TM)-polarized input light, an LPWG waveguide of 10 µm width yields a dip contrast as high as 14.5 dB and a measured FWHM as narrow as 1.32 nm.

Photocatalytic Degradation of Methylene Blue with Side-glowing Optical Fiber Deliverying Visible Light

The side-glowing optical fibers (SOFs) were chosen as the conducting medium of endogenous light; and 20 mg·L−1 methylene blue was chosen as the target to be degraded. The SOF is made up of quartz core with a silicon cladding, which can emit light through side surface more uniformly and transmit light for longer distance to avoid attenuation of light by liquid medium. The filament lamp was chosen as visible light source. Different reaction conditions, such as the presence of optical fiber or not, the quantity of SOF, light irradiation intensity were tested by measuring the methylene blue degradation of methylene blue. The results show that suitable reaction conditions were 1.167 gL−1 Ag+/TiO2 with 7% (by mass) of Ag+ doped in TiO2, and 500 roots of SOF (30 cm length in solution). The photocatalytic degradation efficiency under 300W lamp irradiation for 8h was about 97%. And the photocatalytic degradation efficiency of methylene blue degradation was proportional to SOF quantity, light irradiation intensity and catalytic dosage within a certain range. Compared with general UV and visible light SOFs could save a huge amount of energy and cost, in the potential applications in dealing with organic pollutants on a large scale.

Three dimensional integration of waveguides in bulk silicon

Abstract We demonstrated the ability to achieve three-dimensional (3D) vertical stacking of waveguides in bulk silicon using proton beam irradiation with electrochemical etching in hydrofluoric acid. With low fluence irradiation, the ion beam acts to selectively stop etching only at the end-of-range, resulting in a silicon core that is embedded in porous silicon cladding. By using the well-defined ion path, we are able to build a 2 and 3 level waveguide systems with single and double energy irradiation through a patterned mask respectively. This means more devices can be packed densely on a single chip for greater functionality and economic returns.

The radiation hardness of silica optical fiber used in the LED-fiber monitor of BLM and BESIII EMC

LED-fiber system has been used to monitor BLM and BESIII EMC. A radiation hard silica optical fiber is essential for its stability and reliability. Three types of silica optical fibers, silicone-clad silica optical fiber with high OH − content (SeCS), silica-clad silica optical fiber with low OH − content (SCSL) and silica-clad silica opical fiber with high OH − content (SCSH) were studied. In the experiment, 12 groups of fiber samples were irradiated by 60Co and 3 groups of fiber samples were irradiated by BEPCII background radiation. Radiation hardness: the radiation hardness of SCSH is best and meets the radiation hardness requirement for LED-fiber monitor of BLM and BESIII EMC. The transmission of SeCS and SCSH decreased to around 80% under the 60Co-irradiation of 5 Gy and 10 Gy, respectively. The radiation hardness of SeCS is worst because of its silicone cladding. Recovery characteristics: 60Co-irradiated by the same doses, there were both more annealable and more permanent color centers formed in SeCS than SCSL, and for the same kind of fibers, as long as the irradiated doses are under a certain amount (for example, less than 5 Gy for SeCS), the higher the doses, both the more annealable and the more permanent color centers are formed.

Embedded air core optical nano-waveguides

We propose a nanometer-scale hollow core waveguide that can be fabricated with standard methods on a silicon-on-insulator substrate. High optical confinement in the core is possible, making such a waveguide structure suitable for sensing applications, applications making use of strong optical nonlinearities, and optofluidics applications. We extend a historical method (Marcatili’s method) to provide analytical solutions for field distributions in the device and simulate power confinement, intensity, and parametric dependencies with beam propagation and finite-difference time-domain methods for two polarizations. In an example worked out, the optical confinement in the air core is ~40% of the total waveguide power, which is favorable to that of a standard slot waveguide. The intensity per μm2 in the hollow core is 95% higher than in the silicon cladding region, indicating that avoiding optical nonlinearities is also possible.

Reduction of AlGaAs Heterostructure High-Index-Contrast Ridge Waveguide Scattering Loss by Sidewall Smoothing Through Oxygen-Enhanced Wet Thermal Oxidation

We demonstrate the efficacy of oxidation smoothing of sidewall roughness in high-index-contrast AlGaAs heterostructure ridge waveguides via oxygen-enhanced nonselective wet thermal oxidation for reducing scattering loss. Single-mode waveguides of core widths between 1.5 and 2.2 ?m are fabricated using both the inward growth of a ~ 600-nm sidewall-smoothing native oxide outer cladding and, for comparison, encapsulation of an unoxidized etched ridge with a ~ 600-nm deposited silicon oxide cladding layer. On average, measured loss coefficients are reduced by a factor of 2 with the oxidation smoothing process.

Study on mode-filtered light sensor for methane detection

A novel mode-filtered light gas sensor has been reported. It was constructed by inserting an optical fiber deposited by a thin silicone cladding of cryptophane A into a fused-silica capillary. When different concentration of methane gas was introduced to the sensor, the phenomenon that mode-filtered light intensity decreased with the increasing concentration of methane was observed. And a linear relationship was obtained within the methane concentration range of 0.0–16.0% (v/v). The detection limit was 0.06% (v/v). The mode-filtered light sensor has been exploited to respond to various concentrations of methane gas at room temperature.