Double Waveguide Research Articles

Characteristic frequencies of transverse electric modes in a double negative slab waveguide with Kerr-type nonlinearity

The evolution equation for guided transverse electrical modes in a slab waveguide having a double negative core is derived for the electrical field. Special solutions of the dispersion equation for the case with double positive symmetric cladding are searched for. Relevant eigenmodes are formulated in terms of characteristic frequencies as a new method, and these frequencies corresponding to the oscillating guided modes are found for different wave numbers and core widths assuming the lossless Drude model can be used for the core medium with a Kerr-type nonlinearity. Results show that normalized characteristic frequencies increase with increasing wave numbers and mode numbers.

Investigation of GaAs-Based Laser Diode Adopting an Al Composition Gradient Double Waveguide Structure and its Photoelectric Properties

The double waveguide structure of a 1060 nm laser diode with different Al composition linear gradient was designed for achieving high output power. In contrast to the single waveguide layer with Al-free composition gradient structure, the double waveguide layer with a reverse Al composition gradient from n side to p side showed excellent optoelectronic properties. We found that the reverse Al composition gradient double waveguide layer could decrease injection potential barrier for electrons and holes, as well as has a high block leakage potential barrier, which can be help to increase carrier transport and optical confined factor. Meanwhile, it can improve sheet carrier concentration in order to decrease non-radiative recombination. When the injection current is 6 A, the maximal output power and peak wall-plug conversion efficiency are 6.12 W and 81.1%, respectively. The influencing mechanism of these photoelectric parameters on power and wall-plug conversion efficiency was discussed. The novel waveguide structure will be favorable for designing epitaxial structure and providing a theoretical basis for high-power laser diode.

Design and fabrication of polygonal grating waveguide display with full-color 2D eye-box expansion

Over the past few decades, the surface relief grating (SRG) based waveguide display technology has attracted significant interest in the augmented reality community due to its light weight, small form factor and ease of mass production. However, the intuition grating structure restricts the optimization freedom which limits the display quality of full-color SRG waveguide. To address this issue the 2D polygonal grating is presented since it has a higher freedom degree in optimizing color uniformity compared to intuition grating structure. By using the 2D polygonal grating we also proposed a design approach of full-color SRG waveguide with hierarchical optimization method. To validate this design, a 2D polygonal grating-based waveguide composed of double layers waveguide was fabricated by using EBL and nanoimprinting technology. The final experimental results show that the 2D eye-box expansion (EPE) waveguide has a field of view (FOV) of 40°, an eye-box of 15 mm × 12 mm, at an eye relief (ERF) of 25 mm, and the overall luminance uniformity is 60 %.

Improved relative gain in Nd3+doped GeO2-PbO glass with double waveguides irradiated by femtosecond laser micromachining and decorated with Au nanoparticles

The paper explores the effects of Au nanoparticle (NP) islands deposited by sputtering technique on the surface of Nd3+-doped GeO2-PbO glasses, with double-line waveguides, produced via femtosecond laser processing for photonics. A Ti:sapphire femtosecond laser operating at 800 nm was employed to inscribe the waveguides directly into the glass, 0.7 mm beneath the surface. These waveguides were structured as pairs of parallel lines separated 10 μm. Additional procedures were undertaken to position the waveguides on the glass surface where Au NPs were deposited. Refractive index change of 10−3 at 632 nm was observed in both horizontal and vertical directions. Similar results for the beam quality factors (Mx2 and My2) at 632 nm and 1064 nm indicated x, y-symmetrical guiding. Photoluminescence and relative gain growth were observed due to Au NP islands. The relative gain reached 3.0 dB/cm representing an increase of approximately 450 % when compared to samples without the Au NP islands, and was attributed to the local field growth in their vicinities. This study highlights the potential to change Nd3+-doped GeO2-PbO glasses optical properties with Au nanoparticle islands, opening up new and promising prospects for photonics and 1064 nm optical amplifiers.

Fano Resonance Thermo-Optic Modulator Based on Double T-Bus Waveguides-Coupled Micro-Ring Resonator

For the silicon optical computing chip, the optical convolution unit based on the micro-ring modulator has been demonstrated to have high integration and large computing density. To further reduce power consumption, a novel, simple Fano resonant thermo-optic modulator is presented with numerical simulation and experimental demonstration. This designed Fano resonator comprises double T-shaped waveguides and a micro-ring with a radius of 10 μm. Compared with the free use of bus waveguides, our double T-shaped waveguides generate a phase shift, along with a Fano-like line shape. The experimental results show that the resonant wavelength shift of the designed modulator is 2.4 nm with a driven power of 20 mW. In addition, the maximum spectral resolution and the extinction ratio are 70.30 dB/nm and 12.69 dB, respectively. For our thermo-optic modulator, the optical intensity power consumption sensitivity of 7.60 dB/mW is three times as large as that of the micro-ring modulator. This work has broad potential to provide a low-power-consumption essential component for large-scale on-chip modulation for optical computing with compatible metal oxygen semiconductor processes.

Waveguide‐based Raman enhancement strategies

AbstractWaveguide‐enhanced Raman scattering (WERS) is a powerful branch of enhanced Raman technologies that has gained significant progress in recent years because of its advantages, such as reproducibility and robustness. As a complementary tool to surface‐enhanced Raman spectroscopy (SERS), WERS provides a powerful solution for reproducible quantification of analytes. According to different Raman enhancement mechanisms, five major WERS implementation strategies, namely, (1) single‐mode dielectric waveguide, (2) liquid core waveguide, (3) metal cladding waveguide, (4) resonance mirror waveguide, and (5) double metal cladding waveguide, are classified and described in detail in this review. The flexibility of WERS structures makes them easy to be integrated with 2D devices to obtain a complete on‐chip detection scheme, allowing the WERS chip to combine excitation, detection, and data analysis in integrated chips, providing a powerful prospect for real‐time and on‐site analysis of target samples. This article highlights the principles, implementations, and application scenarios of WERS techniques and evaluates their advantages and limitations, respectively. Finally, the strengths and weaknesses of WERS techniques are summarized, and promising future applications are proposed. This review provides a panoramic view for researchers interested in waveguide‐enhanced Raman technology.

Exploiting Surface Plasmon with Dielectric Coating in Copper Wires Waveguide for the Propagation of Terahertz Waves

Recently, metallic wires have gained popularity for utilization as waveguides in propagating sub-THz and THz waves through surface plasmonic polaritons (SPPs). Single and double metallic wire waveguides have demonstrated the ability to propagate these high frequencies with minimal loss and nearly zero dispersion. However, wires typically installed commercially are often coated with dielectric material. Therefore, this paper investigated the effects of using two and four metallic copper wires, both with and without dielectric coating. The impact of various gap distances on different propagation characteristics was also analyzed. Computer Simulation Technology (CST) Microwave Studio was employed in this study for electromagnetic simulations of both uncoated and coated configurations of two and four wires. The introduction of a dielectric coating led to an enhancement in reducing conductor losses and improving energy confinement, with the goal of enhancing the overall efficiency of waveguide signal propagation.

Double slot micro ring resonators with inner wall angular gratings as ultra-sensitive biochemical sensors.

We simulate and demonstrate experimentally an inner-wall grating double slot micro ring resonator (IG-DSMRR) with a center slot ring radius of only 6.72 µm based on the silicon-on-insulator platform. This novel photonic-integrated sensor for optical label-free biochemical analysis boosts the measured refractive index (RI) sensitivity in glucose solutions to 563 nm/RIU with the limit of detection value being 3.7 × 10-6 RIU (refractive index units). The concentration sensitivity for sodium chloride solutions can reach 981 pm/%, with a minimum concentration detection limit of 0.02%. Using the combination of DSMRR and IG, the detection range is enlarged significantly to 72.62 nm, three times the free spectral range of conventional slot micro ring resonators. The measured Q-factor is 1.6 × 104, and the straight strip and double slot waveguide transmission losses are 0.9 dB/cm and 20.2 dB/cm, respectively. This IG-DSMRR combines the advantages of a micro ring resonator, slot waveguide, and angular grating and is highly desirable for biochemical sensing in liquids and gases offering an ultra-high sensitivity and ultra-large measurement range. This is the first report of a fabricated and measured double-slot micro ring resonator with an inner sidewall grating structure.

Demonstration of a Double Flat-Roofed Sine Waveguide Slow Wave Structure With Low Loss for 220-GHz Traveling-Wave Tube

A double flat-roofed sine waveguide (DFRSWG) slow wave structure (SWS) with low loss for 220-GHz traveling-wave tube (TWT) has been demonstrated in this letter. Through the simulation method, it is inferred that this structure has a large coupling impedance and excellent transmission properties. Besides, the experimental results demonstrate that the transmission loss of the circuit is only 0.62–0.75 dB/cm and the return loss is more than 19.3 dB in the frequency band of 210–250 GHz. Eventually, a two-section DFRSWG interaction circuit is designed to achieve stable device performance. Based on the particle-in-cell (PIC) simulation results, it can be predicted that the DFRSWG TWT can generate the maximum output power of 235 W at 220 GHz, which corresponds to a gain of 36.72 dB and an electronic efficiency of 6.06%.

Effect of Silver Nanoparticles on the Optical Properties of Double Line Waveguides Written by fs Laser in Nd3+-Doped GeO2-PbO Glasses

Nd3+-doped GeO2-PbO glass with silver (Ag) nanoparticles (NPs) are produced with double line waveguides through fs laser processing for photonic applications. A Ti:sapphire fs laser at 800 nm was used to write the waveguides directly into the glass 0.7 mm beneath the surface. This platform is based on pairs of parallel lines with spacing of 10 µm, each pair being formed by two identical written lines but in two different configurations of 4 or 8 separately processed lines, which are coincident. The results of optical microscopy, absorbance measurements, refractive index change, beam quality factor (at 632 and 1064 nm), photoluminescence, propagation losses, and relative gain at 1064 nm are presented. The structural changes in the glass due to the presence of Ag NPs were investigated by Raman spectroscopy. At 632 and 1064 nm, x,y-symmetrical guiding was observed, and for both kinds of overlapping pulses, a refractive index alteration of 10-3 was found in both directions. Photoluminescence growth of ~47% at 1064 nm was observed due to the plasmonic effect of Ag NPs. In dual waveguides containing Ag NPs, the relative gain obtained increased by 40% and 30% for four and eight overlapping lines, respectively, at 600 mW of 808 nm pump power, when compared to waveguides without those metallic NPs. We highlight the resultant positive internal gains of 5.11 and 7.12 dB/cm that showed a growth of ~40% and ~30%, respectively, with respect to the samples without Ag NPs. The increase in photoluminescence and relative gain were related to the local field growth produced by Ag NPs. The present results show that the addition of Ag NPs impacts positively on the optical performance at 1064 nm of double line waveguides processed by fs laser writing in Nd3+-doped GeO2-PbO glass, opening news perspectives for photonics.

Integrating Vernier spectrum with Fano resonance for high sensitivity of an all-optical sensor

Vernier and Fano resonances are promising approaches for enhancing the sensitivity of an all-optical sensor. A theoretical analysis was performed to integrate a Fano-like resonance shape with a Vernier resonance by considering the presence of partially reflective end facets at a double microring resonator waveguide. The system was developed based on scattering matrix and optical transfer function. The all-pass racetrack microring resonator (ARMRR) and the double racetrack microring resonator (DRMRR) were compared with and without the end facet at the waveguide to analyze the dynamic change of the output resonance spectrum. The spectrum was analyzed based on the free spectral range and resonance pattern. The resonator systems were applied to a refractive index-based sensing protocol, which was operated by a resonance wavelength shift with a refractive index change. The sensitivity was optimized by varying the configuration parameters such as the radius of the ring, the distance between the end facet, and the coupling coefficients. Integrating Vernier spectrum with Fano resonance improved the sensitivity for ARMRR configuration by 5.16% and the sensitivity for DRMRR configuration by 6.31%. The recorded limit of detection (LOD) of the DRMRR was 3.30 × 10-5.

Nonreciprocal and chiral single-photon scattering for giant atoms

Quantum optics with giant atoms has provided a new paradigm to study photon scatterings. In this work, we investigate the nontrivial single-photon scattering properties of giant atoms being an effective platform to realize nonreciprocal and chiral quantum optics. For two-level giant atoms, we identify the condition for nonreciprocal transmission: the external atomic dissipation is further required other than the breaking of time-reversal symmetry by local coupling phases. Especially, in the non-Markovian regime, unconventional revival peaks periodically appear in the reflection spectrum. To explore more interesting scattering behaviors, we extend the two-level giant-atom system to Δ-type and ∇ -type three-level giant atoms coupled to double waveguides with different physical mechanisms to realize nonreciprocal and chiral scatterings. Our proposed giant-atom structures have potential applications of high-efficiency targeted routers that can transport single photons to any desired port deterministically and circulators that can transport single photons between four ports in a cyclic way.

Fiber SPR two-dimensional micro displacement sensor based on the coaxial double waveguide with a conical structure.

Fiber SPR micro displacement sensor cannot be used for two-dimensional displacement sensing at present. In this paper, we proposed and demonstrated a fiber SPR two-dimensional micro displacement sensor based on the coaxial double waveguide with a conical structure. The coaxial double waveguide is fused into a cone as the light injection fiber, and two different forms of outgoing light fields can be obtained through two cores of the fiber. The horn shaped light field emitted by the ring core of the coaxial double waveguide can cooperate with the sensing fiber to realize the micro displacement sensing in the x-axis direction. And the straight beam emitted by the middle core of the coaxial double waveguide can cooperate with the sensing fiber to realize the micro displacement sensing in the y-axis direction. Through simulation analysis and experimental test, its average wavelength sensitivity and light intensity sensitivity of the x-axis displacement are 0.0537nm/µm and 0.000124a.u./µm, respectively. And that of the y-axis displacement are 0.315nm/µm and 0.00277a.u./µm, respectively. The proposed fiber sensor realizes the two-dimensional displacement sensing based on SPR, which can be widely used in the fields of two-dimensional micro displacement measurement and two-dimensional position precision positioning.

Integrated optical waveguide atomic force microscopy system with a differential splitter readout

There is an urgent need for high-speed atomic force microscopy (AFM) systems, and chip-AFM on an integrated optical waveguide provides a perfect solution. A differential splitter of double waveguides is introduced as a readout method of an integrated optical waveguide AFM to overcome the non-linear response of a conventional optical waveguide AFM. Results show that an optical waveguide AFM with a 190 nm width and 1 μm height nano-tip shows a good monotonic dependence on the cantilever deflection within a range of ± 0.4 μm using a differential splitter readout method.

Standard slot waveguide and double hybrid plasmonic waveguide configurations for enhanced evanescent field absorption methane gas sensing

Herein, a numerical study on standard slot waveguide and double hybrid plasmonic waveguide based on a silicon-on-insulator platform is presented. The geometric parameters of both the waveguides are optimized for the operational wavelength of 3.39 μm (absorption line of methane gas) to obtain the maximum evanescent field ratio (EFR). By utilizing Lambert-Beer’s law, the gas sensing capability of both the waveguides is determined. It is found out that both the waveguides of length 100 μm offer high EFR resulting in the 3dB decay of the propagating mode power for the methane gas concentration of 20-22 % in the chamber. The study provides the foundation for the practical realization of compact and highly sensitive gas sensors. Full Text: PDF ReferencesJ.Y. Yo, Y.S. Kwon, J.W. Lee, J.S. Park, B.H. Rho, W. II. Choi. "Acute Respiratory Distress Due to Methane Inhalation", Tuberculosis and Respiratory Diseases 74, 120-123 (2013). CrossRef M. A. Butt, S. A. Degtyarev, S. N. Khonina and N. L. Kazanskiy. "An evanescent field absorption gas sensor at mid-IR 3.39 μm wavelength", Journal of Modern Optics 64, 1892-1897 (2017). CrossRef M. A. Butt, S. N. Khonina and N. L. Kazanskiy. "Modelling of Rib channel waveguides based on silicon-on-sapphire at 4.67 μm wavelength for evanescent field gas absorption sensor", Optik 168, 692-697, (2018). CrossRef M. A. Butt, S. N. Khonina and S. N. Kazanskiy. "Silicon on silicon dioxide slot waveguide evanescent field gas absorption sensor", Journal of Modern Optics 65, 174-178, (2017). CrossRef S. N. Khonina, N. L. Kazanskiy and M. A. Butt. "Evanescent Field Ratio Enhancement of a Modified Ridge Waveguide Structure for Methane Gas Sensing Application", IEEE Sensors Journal 20, 8469-8476 (2020). CrossRef M.Vlk, A. Datta, S. Alberti, H.D. Yallew, V. Mittal, G. S. Murugan, J. Jagerska. "Extraordinary evanescent field confinement waveguide sensor for mid-infrared trace gas spectroscopy", Light: Science & Applications 10, 26 (2021). CrossRef M.A. Butt, S.N. Khonina, N.L. Kazankiy. "Enhancement of evanescent field ratio in a silicon strip waveguide by incorporating a thin metal film", Laser Physics 29, 076202 (2019). CrossRef M. A. Butt, N. L. Kazanskiy and S. N. Khonina, "Highly integrated plasmonic sensor design for the simultaneous detection of multiple analytes", Current Applied Physics 20, 1274-1280 (2020). CrossRef T. Milde, M. Hoppe, H. Tatenguem, C. Assmann, W. Schade, J. Sacher. "Comparison of the spectral excitation behavior of methane according to InP, GaSb, IC, and QC lasers as excitation source by sensor applications", Applied Optics 58, C84 (2019). CrossRef N. L. Kazanskiy, S.N. Khonina, M.A. Butt. "Polarization-Insensitive Hybrid Plasmonic Waveguide Design for Evanescent Field Absorption Gas Sensor", Photonic Sensors 11, 279-290 (2021). CrossRef D. Popa, F. Udrea. "Towards Integrated Mid-Infrared Gas Sensors", Sensors 19, 2076 (2019). CrossRef S-W. Kang, K. Sasaki, H. Minamitani. "Sensitivity analysis of a thin-film optical waveguide biochemical sensor using evanescent field absorption", Applied Optics 32, 3544-3549 (1993). CrossRef

Perovskite solar cell with light trappers fabricated by double metal cladding waveguide technology

Local surface plasmon resonance (LSPR) based on metal nanostructures was widely used in enhanced light capture and light absorption. In addition, LSPR can also facilitate processes such as exciton dissociation and charge transfer (CT) in solar cells. We developed perovskite solar cells (PSCs) by coating chips with hexagon-like nanostructures on the backside of Indium tin oxide (ITO) conductive glass using the double metal cladding waveguide (DMCW) technology. The optical absorption and photoelectric conversion efficiency (PCE) of the PSCs with different morphologies of chips were analyzed. The LSPR of the chips corresponded with the absorption capacity of perovskite. LSPR enhanced the scattering, gathering, and capture of light energy. Because the strong absorption rates at the long wavelengths after 600 nm in the ultraviolet visible (UV–Vis) spectrum, the properties of PSCs with the chips are improved. The PCE and short circuit current density (Jsc) increased by 27.21%, and 6.78%, respectively, attributed to the increase in the optical path of incident light and the light absorption capacity of the active layer.

Design of Large-Scale Microwave Cavity for Uniform and Efficient Plastic Heating.

To reduce carbon emissions during heating in the manufacturing processes, microwave technology has attracted significant attention. Microwaves have considerable advantages over traditional heating methods, including more rapid heating, lower thermal damage, and eco-friendly processes. To apply microwaves to the manufacturing process, uniform and efficient heating is required. We analyzed the effect of various design parameters for uniform and efficient heating by changing the cavity heights, application of the reflector, and number and positions of waveguides. We conducted a numerical simulation and verified the findings by experiments. The results showed that a slight change in the cavity height altered the electromagnetic field distribution and heating parameters, such as the coefficient of variance and power absorption efficiency. With reflectors installed, 66% of cases exhibited better comprehensive evaluation coefficient (CEC) with consideration of uniform heating and power absorption. The spherical reflector showed 81% of cases, better than those of the ordinary model without a reflector. Furthermore, when double waveguides were installed, the average coefficient of variance (COV) was improved by 22%, and power absorption efficiency was increased by 53% compared to the single waveguide case. When the power applied to the waveguides was doubled, the average COV values improved by 18%. This large-scale analysis will be helpful in applying microwaves to actual industrial sites.

Sensitive detection of orthogonal polarization intensity ratio via metal-cladding waveguide

A rapid and sensitive detection method of incident light with different orthogonal polarization intensity ratios based on the double metal-cladding waveguide has been demonstrated. The middle layer of the waveguide is a uniaxial negative crystal lithium niobate, resulting in distinct coupling angles for TE and TM polarization. The isolation of the device can reach 42 dB due to well separation of TE and TM polarization. The quantitative experiments to measure ratio of TE to TM incident light have been carried out. Meanwhile, this method can support polarization detection in ultraviolet, visible, and infrared region. This method will play a significant role in optical information processing system and the integrated system.

Graphene photodetector employing double slot structure with enhanced responsivity and large bandwidth

Silicon photonics integrated with graphene provides a promising solution to realize integrated photodetectors operating at the communication window thanks to graphene’s ultrafast response and compatibility with CMOS fabrication process. However, current hybrid graphene/silicon photodetectors suffer from low responsivity due to the weak light-graphene interaction. Plasmonic structures have been explored to enhance the responsivity, but the intrinsic metallic Ohmic absorption of the plasmonic mode limits its performance. In this work, by combining the silicon slot and the plasmonic slot waveguide, we demonstrate a novel double slot structure supporting high-performance photodetection, taking advantages of both silicon photonics and plasmonics. With the optimized structural parameters, the double slot structure significantly promotes graphene absorption while maintaining low metallic absorption within the double slot waveguide. Based on the double slot structure, the demonstrated photodetector holds a high responsivity of 603.92 mA/W and a large bandwidth of 78 GHz. The high-performance photodetector provides a competitive solution for the silicon photodetector. Moreover, the double slot structure could be beneficial to a broader range of hybrid two-dimensional material/silicon devices to achieve stronger light-matter interaction with lower metallic absorption.

All-photonic synapse based on iron-doped lithium niobate double metal-cladding waveguides

In an artificial neural network composed of neuromorphic computing units, the resistance of the memristor can be modulated dynamically and repeatedly under external stimuli, such as electric fields, magnetic fields, and light illumination, leading to variations in local conductivity and memory effects. Here we show, using an all-photonic memristor, that the memristance arises naturally in an optical system in which solid-state ionic transport is realized under low-power external incident light. These results show an extremely stable multilevel storage weight and a high signal-to-noise ratio. In all-photonic memristors, the light signal is employed as the extra stimuli of the memristor devices to ensure a large memory window and a variation margin of multiple storage levels.