- 标题
- 摘要
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Steering Second Harmonic Beam in Nanophotonic Waveguides by Gratings
摘要： Efficient manipulation of the wavefront at the nanoscale is important for optical beaming, signal encoding, and nonlinear phase matching, etc. Diffraction gratings are widely adapted for the control of the wavefront of lightwaves, but predominantly in linear optics. Here, we demonstrated the flexible steering of the second harmonic (SH) beams in nanophotonic waveguides using gratings. The emission angle of the SH signals can be shifted by an amount of 60° from the waveguide axis into the collection cone, allowing the detection of the otherwise undetectable SH from co-propagating waveguide modes in the high-loss waveguides. The SH conversion efficiency (3 × 10?5 W?1) from co-propagating modes contributes up to 26.7% of the total SH signal. As the pump wavelength varies from 770 to 840 nm, the SH beam is swept by up to 22°. This design functions as a nonlinear grating coupler for nanophotonic systems and could be used for efficient nonlinear coherent light generation and integrated nonlinear nanophotonics.
关键词： Fourier imaging,nanophotonics,second harmonic generation,nonlinear grating coupler,beam steering
更新于2025-09-11 14:15:04
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Intra-Cavity Mode-Selective Coupler Assisted Ultrafast Cylindrical Vector Fiber Laser
摘要： Cylindrical vector beam (CVB) fiber lasers have attracted great attentions due to their promising applications in optical communications, super-resolution imaging and optical trapping. Recently, it has been proved that mode-selective coupler (MSC) is an efficient method for generating CVBs in all-fiber lasers [1-3]. However, to date, the reported MSC-assisted CVB lasers have a common feature that the fundamental transverse mode (LP01) oscillates in the laser cavity whereas the high-order modes are outside the laser cavity. To some extent, such cylindrical vector lasers belong to the external mode conversion, rather than the direct generation of high-order modes inside the laser cavity. In this contribution, we present an intra-cavity MSC assisted CVB fiber laser in a compact linear-cavity mode-locked by using a semiconductor saturable absorber mirror (SESAM). The laser architecture is shown in Fig. 1(a), which consists of a 5 m Er-doped fiber, a 980/1550 wavelength-division multiplexer (WDM) pumped by a 980 nm laser, a polarization controller (PC), a 90% high coupling ratio MSC with an insertion loss of 0.3 dB. A fiber end-facet mirror is sandwiched between the two fiber ferrules and a SESAM mode locker has a modulation depth of 18%. The rest of cavity consists of ~14.3 m standard single-mode fiber (SMF) and ~0.6 m few mode fiber (FMF). Self-started mode-locking occurs when the pump power reaches ~35 mW. Thanks to the high coupling efficiency of intra-cavity mode converter, LP01 mode in the SMF is sufficiently coupled to LP11 mode in the FMF when it passes through the MSC. The reflected LP11 mode from the mirror can be partially coupled back to the SMF with a low loss, resulting in the laser oscillation. In this case, the laser operates between MSC and the mirror in the LP11 mode, which outputs from the FMF, meanwhile the LP01 mode oscillates in the remaining section of the linear-cavity. Eventually, the laser can allow the direct generation of LP11 mode from the laser cavity. Typical laser output characteristics such as broadband spectra, pulse train and output power are shown in Fig. 1(b)-(e). The laser operates at the wavelength of 1562 nm with a 3-dB bandwidth of ~4.4 nm and a repetition rate of 5.2 MHz. Radially polarized and azimuthally polarized ultrafast CVBs are obtained by adjusting the PC, and corresponding donut beam profiles are demonstrated by checking the rotating intensity distribution through the linear polarizer, as presented in Fig. 1(f).
关键词： Cylindrical vector beam,mode-selective coupler,ultrafast,fiber laser
更新于2025-09-11 14:15:04
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A high efficiency silicon nitride waveguide grating coupler with a multilayer bottom reflector
摘要： We propose a high efficiency apodized grating coupler with a bottom reflector for silicon nitride photonic integrated circuits. The reflector consists of a stack of alternate silicon nitride and silicon dioxide quarter-wave films. The design, fabrication and optical characterization of the couplers has been presented. The measured fiber to detector insertion loss was ?3.5 dB which corresponds to a peak coupling efficiency of ?1.75 dB. A 3 dB wavelength bandwidth of 76.34 nm was demonstrated for the grating coupler with a 20-layer reflector. The fabrication process is CMOS-compatible and requires only a single etching step.
关键词： apodization,grating coupler,photonic integrated circuits,silicon nitride,multilayer reflector
更新于2025-09-11 14:15:04
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[IEEE 2019 International Workshop on Electromagnetics: Applications and Student Innovation Competition (iWEM) - Qingdao, China (2019.9.18-2019.9.20)] 2019 International Workshop on Electromagnetics: Applications and Student Innovation Competition (iWEM) - Ka-band Six-Port Network Using Double Ridge Gap Waveguide Technology
摘要： For microwave and millimeter-wave measurement, a six-port network based on double ridge gap waveguide (DRGW) is proposed, and it is the first attempt to design the six-port network by using gap waveguide technology. In this work, DRGW power divider and DRGW 90 degrees - 3dB coupler are regarded as the basic elements, and they are designed by DRGW according to the schematic diagram. By simulation, the six-port network is designed to operate at 40 GHz with the fractional bandwidth of 8.5%, and performance indicators of phase and amplitude between different ports are satisfied with design requirements.
关键词： coupler,double ridge gap waveguide (DRGW),six-port network,power divider
更新于2025-09-11 14:15:04
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One-Body 2-D Beam-Switching Butler Matrix with Waveguide Short-Slot 2-Plane Couplers
摘要： A 42 × 42-way one-body 2-D beam-switching Butler matrix with waveguide short-slot 2-plane couplers is designed and fabricated in the 22 GHz band. The one-body con?guration using the commutativity and the overlapping of units allows reducing the size and loss in comparison with a cascade of matrices beam-switching for the horizontal and the vertical planes. It is achieved by replacing 2×2-way 1-plane couplers in the conventional block con?guration for a Butler matrix with 22 × 22-way 2-plane couplers. The measured bandwidth is approximately 2% restricted by the frequency characteristics of the 2-plane couplers. In the radiation from the aperture array antenna of the 42 output ports, the 3.9 dB-down coverage of 3-D solid angle by the sixteen beams is around 1.72 steradian which is same as 27.4% of hemisphere at the design frequency for the aperture spacing of 0.73 × 0.73 wavelength.
关键词： waveguide short-slot coupler,beam-switching,Butler matrix
更新于2025-09-11 14:15:04
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Applications of Silicon Photonics in Sensors and Waveguides || New Approach to Mach-Zehnder Interferometer (MZI) Cell Based on Silicon Waveguides for Nanophotonic Circuits
摘要： In this chapter, we present a new scheme for Mach-Zehnder Interferometer (MZI) structure based on only one 4×4 multimode interference (MMI) coupler. We design the new MZI cell on the silicon on insulator (SOI) platform. The MZI based on directional coupler and 2×2 MMI coupler is also investigated in detail. The new MZI cell is a basic building block for photonic applications such as optical quantum gate, optical computing and reconfigurable processors. The numerical simulations show that our approach has advantages of compact size, ease of fabrication with the current complementary metal oxide semiconductor (CMOS) circuitry.
关键词： multimode interference,finite difference time difference,directional coupler,modified effective index method,multimode waveguide,finite difference method,silicon on insulator
更新于2025-09-11 14:15:04
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[IEEE 2019 16th International Symposium on Wireless Communication Systems (ISWCS) - Oulu, Finland (2019.8.27-2019.8.30)] 2019 16th International Symposium on Wireless Communication Systems (ISWCS) - A Differential Reflection-Type Phase Shifter Based on CPW Coupled-Line Coupler in 45nm CMOS SOI
摘要： This paper presents a mm-wave fully differential coplanar waveguide (CPW) vertically-coupled lines coupler and a reflection type phase shifter (RTPS) based on the proposed coupler. The use of grounded strip line structure for vertical coupling in CPW based coupler provides not only the improved coupling properties than the edge coupling but also provides the opportunity of using surrounding area efficiently to reduce area. The proposed coupler and phase shifter are designed and fabricated in 45nm CMOS SOI technology. Measured insertion loss of the coupler is ~ 6 dB from 18 to 43 GHz. A digitally controlled parallel LC load is used for controlling the phase of the phase shifter. Measured phase tuning range is 115 degrees, with insertion loss variation of 4.5 to 9 dB, for a frequency range of 39 GHz to 45 GHz. Total drawn area of the phase shifter is 0.214 mm2. The area of the proposed RTPS is smaller than the recently published state-of-the-art structures.
关键词： 5G,mmWave,Phased Array,Hybrid Coupler,Phase shifter,CMOS SOI
更新于2025-09-11 14:15:04
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[IEEE 2019 49th European Microwave Conference (EuMC) - Paris, France (2019.10.1-2019.10.3)] 2019 49th European Microwave Conference (EuMC) - Waveguide Coupler Design Method for Permittivity Measurement at millimeter-wave applications
摘要： In this paper, novel waveguide coupler technique for relative permittivity measurement of dielectric materials is proposed. Unlike two conventional port methods measurements, this technique provides extra information to precisely measure tangent loss and permittivity. This type of coupler is composed of a waveguide section of four arms connected by a central junction. Quasi-optical coupler technique is realized on standard waveguide by simply inserting circular holes with different values of permittivity in the central section to act as a mirror. Characteristics of the proposed coupler are introduced and studied with regard to different parameters. This design provides an precise technique for measuring permittivity and tangent loss throughout two extra ports. A prototype at mm-wave is designed, fabricated and measured. Experimental results show that the proposed waveguide coupler has accurate measured results of permittivity for milk 2 % and creamer 10 %.
关键词： Permittivity measurements,Waveguide coupler,millimetres wave applications,Four ports devices
更新于2025-09-11 14:15:04
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Generation of entangled states by a linear coupling coupler pumped in two modes induced by broadband laser
摘要： We research on a Kerr nonlinear coupler comprising two nonlinear oscillations linearly couple with each other. This coupler is pumped by external classical fields, which are supposed to be decomposed into two parts: a coherent part and a randomly fluctuating chaotic component (white noise). We can see that the quantum evolution of the pumped couplers is closed in a Hilbert space of two-qubit spanned by single-photon and vacuum states only. Hence, the pumped couplers can treat as a system of two-qubit. Analysis of time evolution of the quantum entanglement shows that maximally entangled states can be generated in the system and compare these results with that obtained previously by other authors.
关键词： quantum entanglement,Generation of entangled states,Bell-like states,white noise,Kerr nonlinear coupler
更新于2025-09-11 14:15:04
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Small coupling length with a low confinement loss dual-core liquid infiltrated photonic crystal fiber coupler
摘要： In this paper, a dual-core liquid ?lled photonic crystal ?ber coupler (PCFC) with rectangular (RPCFC) and hexagonal (HPCFC) geometry is presented from the 1200 to 1800 nm wavelength range. In the proposed design, super ?int (SF10) glass is used as the background material and water, chloroform, and benzene are in?ltrated in the dual-core, independently. The properties of the guided modes are studied by the ?nite di?erence time domain (FDTD) method with a perfectly matched layer (PML) boundary condition. Results reveal very small con?nement loss with a low coupling length and birefringence for the wide wavelength range. At the 1.55 μm wavelength, RPCFC shows 0.000318, 0.000358, and 0.000379 m coupling lengths for the water, chloroform, and benzene ?lled dual-core, respectively. Additionally, the con?nement loss of 1.57×10?7, 1.22×10?7, and 1.05×10?7 db/km is achieved through RPCFC. Moreover, both the PCFCs present a small polarization variation. Therefore, the proposed PCFC models can be used in optical communication systems, and polarization-independent and high temperature-sensitive applications areas.
关键词： coupling length,liquid filled,birefringence,dual-core,photonic crystal fiber coupler,confinement loss
更新于2025-09-10 09:29:36