Ultrashort pulsed Bessel beams with intrinsic nondiffractive character and potential strong excitation confinement down to 100nm can show a series of advantages over Gaussian beams in fabricating efficient Bragg grati...
详细信息
Ultrashort pulsed Bessel beams with intrinsic nondiffractive character and potential strong excitation confinement down to 100nm can show a series of advantages over Gaussian beams in fabricating efficient Bragg grating waveguides(BGWs).In this work, we focus on parameter management for the inscription of efficient BGWs using the point-by-point method employing Bessel *** to their high aspect ratio, the resulting one-dimensional void-like structures can section the waveguides and interact efficiently with the optical modes. Effective first-order BGWs with low birefringence can then be fabricated in bulk fused silica. By controlling the size and the relative location of grating voids via the Bessel pulse energy and scan velocities, the resonant behaviors of BGWs can be well regulated.A high value of 34 dB for 8 mm length is achieved.A simple predictive model for BGWs is proposed for analyzing the influences of processing parameters on the performance of BGWs. The technique permits multiplexing several gratings in the same *** to eight grating traces were straightforwarcliy inscribed into the waveguide in a parallel-serial combined mode, forming the multiplex *** an application, the multiplex BGW sensor with two resonant peaks is proposed and fabricated for improving the reliability of temperature detection.
An all-optically reconfigurable generation of optical vortices would be highly beneficial to the implementation of next-generation optical communication and advanced information processing. The previously demonstrated...
详细信息
An all-optically reconfigurable generation of optical vortices would be highly beneficial to the implementation of next-generation optical communication and advanced information processing. The previously demonstrated approaches based on the parametric nonlinear optical processes, however, have exhibited limited conversion efficiency due to the group velocity mismatch and nonlinear phase shifts, and require the cumbersome preparation of either the optical element or initial seed beam having a non-zero topological charge. Here, we propose and analyze a novel scheme for highly efficient all-optical generation and control of optical vortices based on the dynamic acoustic vortex grating created by forward stimulated intermodal Brillouin scattering in a subwavelength-hole photonic waveguide. The dual-frequency pump beams in two different hybrid optical modes drive an acoustic vortex mode, which transforms a signal in the fundamental optical mode into an optical vortex mode. This scheme not only eliminates the need for the initial preparation of an angular-momentum-carrying medium or an optical vortex seed but also guarantees high modal purity and nearly 100% conversion efficiency assisted by the energymomentum conservation. We also investigate the feasibility and practicability of the subwavelength-hole waveguides by examining the intermodal conversion efficiency and robustness of guidance of the optical vortices,taking into account the impact of the Kerr-type nonlinear effects on the intermodal Brillouin interactions based on our rigorous full-vectorial analytical theory.
Efficient light coupling between two dissimilar optical modes, such as that between optical fiber modes and deeply sub-wavelength nanophotonic or nanoplasmonic waveguides, is a classic challenge for interfacing integr...
详细信息
Efficient light coupling between two dissimilar optical modes, such as that between optical fiber modes and deeply sub-wavelength nanophotonic or nanoplasmonic waveguides, is a classic challenge for interfacing integrated optical devices with the outside world. Solutions to this problem generally require a mode-converter to address the mismatch in both size and wave-vector between the input/output modes. Recently, we have developed a novel nanophotonic silicon v-groove waveguide geometry which achieves ultra-low mode areas, on par with plasmonic nano-wires but in an all-dielectric platform. However, accessing such an ultra-low mode area waveguide, with a modal area >10-100x smaller than a conventional silicon strip waveguide, requires overcoming a significant mode mismatch. We theoretically investigate a means for achieving efficient optical coupling between conventional silicon strip waveguides and our ultra-low mode area silicon waveguides in a directional coupler configuration. We find high peak coupling efficiencies and examine fabrication tolerances and operating bandwidth. By employing numerical mode solver and coupled mode theory while considering silicon height, critical dimensions, waveguide widths and gaps, our designs achieve over 99% peak coupling efficiency and 0.5 dB bandwidth of ~100 nm. Our device addresses the mode mismatch between diffraction limited strip and deeply sub-wavelength dielectric waveguides and is compatible with standard CMOS processing.
Surface plasmon polaritons（SPPs） are evanescent waves propagating along metal-dielectric interfaces, which provide an effective way to realize optical wave guiding with subwavelength confinement. Metallic nanostruct...
详细信息
Surface plasmon polaritons（SPPs） are evanescent waves propagating along metal-dielectric interfaces, which provide an effective way to realize optical wave guiding with subwavelength confinement. Metallic nanostructures supporting SPPs,that is, plasmonic waveguides, are considered as required components to construct nanophotonic devices and circuits with a high degree of miniaturization and integration. In this paper, various types of plasmonic waveguides operating in the visible, infrared, and terahertz regions are reviewed, and the status of the research on their fundamentals, fabrications,and applications is provided as well. First, we discuss the mechanisms of SPPs beyond the diffraction limit, and their launching methods. Then, the characteristics of SPPs on various plasmonic waveguides are reviewed, including top-down and bottom-up fabricated types. Considering applications, certain prototypes of plasmonic devices and circuits constructed by plasmonic waveguides for bio/chemo sensing, router, and light modulation are demonstrated. Finally, a summary and future outlook of plasmonic waveguides are given.
Spiral waveguides on a new germanium-on-silicon nitride (GON) platform with a wide transparency and a large core-clad index contrast for mid-infrared (mid-IR) sensing applications are demonstrated. Spiral waveguide se...
详细信息
Spiral waveguides on a new germanium-on-silicon nitride (GON) platform with a wide transparency and a large core-clad index contrast for mid-infrared (mid-IR) sensing applications are demonstrated. Spiral waveguide sensors with a low bending loss on this platform enable compact sensors for mid-IR absorption spectroscopy. A minimum volumetric concentration of 5% isopropanol (IPA) in an IPA-acetone mixture is measured. This detection limit is three times lower than the counterpart waveguide, fabricated on the regular germanium-on-silicon platform with similar propagation loss at 3.73 mu m wavelength. This silicon-compatible GON sensor is promising for applications such as environmental studies, industrial leak detection, process control, medical breath analysis, and many more.
Non-contact printing methods such as inkjet, electro hydrodynamic, and aerosol printing have attracted attention for their precise deposition of functional materials that are needed in printed electronics, optoelectro...
详细信息
Non-contact printing methods such as inkjet, electro hydrodynamic, and aerosol printing have attracted attention for their precise deposition of functional materials that are needed in printed electronics, optoelectronics, photonics, biotechnology, and microfluidics. In this article, we demonstrate printing of tapered optical waveguides with losses of 0.61 +/- 0.26 dB/cm, with the best performing structure achieving 0.19 dB/cm. Such continuous features are indispensable for successfully printing functional patterns, but they are often corrupted by capillary forces. The proposed inkjet printing method uses these forces to align liquid bridges into continuous features, enabling the printing of smooth lines on substrates with arbitrary contact angles. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
We consider the propagation of waves in a waveguide with Neumann boundary conditions. We work at low wavenumber with only one propagating mode in the leads, all the other modes being evanescent. We assume that the wav...
详细信息
We consider the propagation of waves in a waveguide with Neumann boundary conditions. We work at low wavenumber with only one propagating mode in the leads, all the other modes being evanescent. We assume that the waveguide is symmetric with respect to an axis orthogonal to the longitudinal direction and is endowed with a branch of height L whose width coincides with the wavelength of the propagating modes. In this setting, tuning the parameter L, we prove the existence of simple geometries where the transmission coefficient is equal to one (perfect invisibility). We also show that these geometries, for possibly different values of L, support so-called trapped modes (non-zero solutions of finite energy of the homogeneous problem) associated with eigenvalues embedded in the continuous spectrum.
Lithium niobate-on-insulator (LNOI) waveguides fabricated on a silicon wafer using a room-temperature bonding method have potential application as Si-based high-density photonic integrated circuits. A surface-activate...
详细信息
Lithium niobate-on-insulator (LNOI) waveguides fabricated on a silicon wafer using a room-temperature bonding method have potential application as Si-based high-density photonic integrated circuits. A surface-activated bonding method using a Si nanoadhesive layer was found to produce a strong bond between LN and SiO2/Si at room temperature, which is sufficient to withstand both the wafer-thinning (LN thickness <5 mu m) and surface micromachining processes used to form the strongly confined waveguides. In addition, the bond quality and optical propagation characteristics of the resulting LNOI waveguides were investigated, and the applicability of this bonding method to low-loss LNOI waveguide fabrication is discussed. The propagation loss for the ridged waveguide was approximately 2 dB/cm at a wavelength of 1550 nm, which was sufficiently low for the device application. The results of the present study will be of significant use in the development of fabrication techniques for waveguides with any bonded materials using this mom-temperature bonding method, and not only LN core/SiO2 cladding waveguides. (C) 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
We demonstrate maskless lithography fabrication of nanolayered heterostructured hybrid plasmonic waveguides. This includes the measured optical properties of pulsed magnetron sputtered 15 nm films of aluminum oxide an...
详细信息
We demonstrate maskless lithography fabrication of nanolayered heterostructured hybrid plasmonic waveguides. This includes the measured optical properties of pulsed magnetron sputtered 15 nm films of aluminum oxide and aluminum nitride. Hybrid plasmonic waveguides, where the modes highest intensity is largely confined to the thin aluminum oxide layer, were constructed by maskless lithography using an aperture-type near-field scanning optical microscope. (C) 2018 Society of Photo-Optical Instrumentation Engineers (SPIE)
A dielectric-based multilayer structure composed of U-shaped rings (ML-UR) is used to develop a class of novel electromagnetic band gap (EBG) slab waveguide. The structure has two band gaps that narrow down as dielect...
详细信息
A dielectric-based multilayer structure composed of U-shaped rings (ML-UR) is used to develop a class of novel electromagnetic band gap (EBG) slab waveguide. The structure has two band gaps that narrow down as dielectric constant is increased. The EBG slab waveguide is created by embedding a single-layer line defect inside the 3D crystal of the EBG slab guide. Unlike our previously published foam-based EBG structure, the use of dielectric spacer in the EBG waveguides offers significant advantages in terms of overall size, structure reliability, and design flexibility. The waveguide structures reported in this paper are designed to operate at X-band (8-12 GHz) while being fed by coplanar-slotline transitions. Prototypes were fabricated and characterized experimentally. The insertion loss decreases by decreasing the number of full lattices of ML-UR surrounding the channels. The proposed waveguide has potential in microwave components such as directional couplers, phase shifters, and antenna array feeding networks.
暂无评论