We demonstrate direct bandwidth measurement of 11-cm-long multimode polymer waveguides based on an optical sampling technique for the first time, to our knowledge. The pulse shape can be recovered after transmission d...
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We demonstrate direct bandwidth measurement of 11-cm-long multimode polymer waveguides based on an optical sampling technique for the first time, to our knowledge. The pulse shape can be recovered after transmission due to the advantages such as high bandwidth and high refresh rate of optical sampling technology. A reduction in averaged bandwidth (bandwidth-length product) from 241 GHz (27 GHz.m) to 180 GHz(20 GHz.m) of straight waveguides is observed when using mode scramblers to fully stimulate the higher-order modes. The effects such as bending and crossing structure of the waveguides on the bandwidth are also investigated. The proposed method is effective for measuring the bandwidth and dispersion of meter- and centimeter-long waveguides, fibers, and optical devices. (C) 2021 Optical Society of America
There are two kinds of exceptional points of degeneracy (EPD) in waveguides: those in the absence of loss and gain, related to slow light, and those where the waveguide has distributed gain and/or loss. Here, we discu...
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A waveguide based upon the Pancharatnam-Berry phase (PBP) confines light even in the absence of a refractive index gradient. Here, we investigate theoretically the properties and the robustness of the PBP waveguide. &...
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Many optoelectronic devices embedded in a sil icon photonic chip, like photodetectors, modulators, and attenuators, rely on waveguide doping for their operation. However, the doping level of a waveguide is not always ...
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Many optoelectronic devices embedded in a sil icon photonic chip, like photodetectors, modulators, and attenuators, rely on waveguide doping for their operation. However, the doping level of a waveguide is not always reflecting in an equal amount of free carriers available for conduction because of the charges and trap energy states inevitably present at the Si/SiO2 interface. In a silicon-on-insulator technology with 10(15) cm(-3) p-doped native waveguides, this can lead to a complete depletion of the core from free carriers and to a consequently very high electrical resistance. This Letter experimentally quantifies this effect and shows how the amount of free carriers in a waveguide can be modified and restored to the original doping value with a proper control of the chip substrate potential. A similar capability is also demonstrated by means of a specific metal gate integrated above the waveguide that allows fine control of the conductance with high locality level. This paper highlights the linearity achievable in the conductance modulation that can be exploited in a number of possible applications. (C) 2020 Optical Society of America
This paper investigates and develops an automated design procedure for acoustic waveguides, to modify them to be better at supporting single parameter (1P) wave propagation. The design process is driven by two new per...
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We demonstrate a new variety of spoof surface plasmon polariton (SSPP) waveguides and notch filters with periodic arrays of ultra-thin metallic meander-strip units for high-efficiency and strong confinement microwave ...
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We demonstrate a new variety of spoof surface plasmon polariton (SSPP) waveguides and notch filters with periodic arrays of ultra-thin metallic meander-strip units for high-efficiency and strong confinement microwave SSPPs transmission and notch rejection. Firstly, the dispersion characteristics of the proposed SSPPs waveguide based on meander-strip units are investigated. The dispersion curve of the proposed waveguide presents a unique negative group velocity characteristic, and the asymptotic frequency greatly reduces to near half as that of SSPP waveguide based on traditional rectangular-grooved units with the same transverse size. To validate the proposed design, an SSPP waveguide prototype is fabricated and tested, showing good lowpass filtering performances with a high transmission coefficient (S21 > -1 dB) and a low reflection coefficient (S11 < -15 dB) below the asymptotic frequency of 5.2 GHz. Based on this waveguide structure, a notch filter is designed by loading a split ring resonator (SRR). The transmission coefficient (S21) of this filter is -18 dB at the notch frequency of 2.52 GHz. Furthermore, a PIN diode is integrated into the SRR of the notch filter to make the notch frequency switchable. As the PIN diode turns from the ON state to the OFF state, the notch frequency switches from 2.5 GHz to 3.5 GHz. The proposed waveguides and notch filters with electronically adjustable functionalities may have great potential applications in microwave integrated plasmon circuits and programmable systems.
Symmetry is one of the cornerstones of modern physics and has profound implications in different areas. In symmetry-protected topological systems, symmetries are responsible for protecting surface states, which are at...
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Symmetry is one of the cornerstones of modern physics and has profound implications in different areas. In symmetry-protected topological systems, symmetries are responsible for protecting surface states, which are at the heart of the fascinating properties exhibited by these materials. When the symmetry protecting the edge mode is broken, the topological phase becomes trivial. By engineering losses that break the symmetry protecting a topological Hermitian phase, we show that a new genuinely non-Hermitian symmetry emerges, which protects and selects one of the boundary modes: the topological monomode. Moreover, the topology of the non-Hermitian system can be characterized by an effective Hermitian Hamiltonian in a higher dimension. To corroborate the theory, we experimentally investigated the non-Hermitian one- and two-dimensional SSH models using photonic lattices and observed dynamically generated monomodes in both cases. We classify the systems in terms of the (non-Hermitian) symmetries that are present and calculate the corresponding topological invariants.
We investigate a T-shaped single-photon router constructed by two waveguides connected via a giant Lambda-type three-level atom. Under a real-space approach, the analytical expressions of the single-photon transmissio...
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We investigate a T-shaped single-photon router constructed by two waveguides connected via a giant Lambda-type three-level atom. Under a real-space approach, the analytical expressions of the single-photon transmission and reflection amplitudes are obtained. It is shown that a high transfer-rate routing between two waveguides can be effectively achieved by modulating the phase difference, the accumulated phase and the atom-waveguide coupling strengths, and its frequencies can be tuned with a classical driving field. Interestingly, chiral scattering and a single-photon targeted router with direction selectivity have been realized by the ideally equivalent atom-waveguide interaction. We believe that our results have potential applications in constructing optical quantum devices and designing the single-photon quantum routing using the giant-atom setup.
We developed a simple multi-foci-shaped femtosecond pulsed (MFSFP) method for processing circular cross section waveguides in transparent materials. With this flexible processing method, the focus energy distribution ...
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We developed a simple multi-foci-shaped femtosecond pulsed (MFSFP) method for processing circular cross section waveguides in transparent materials. With this flexible processing method, the focus energy distribution can be designed freely and arbitrarily, and single-mode waveguides with cross section circularity better than 96.0% were achieved. The mode shape difference (1.93%) of circular waveguides is smaller than the difference (7.01%) of normal elliptical waveguides. The coupling abilities of the two kinds of waveguides were investigated with three-dimensional (3D) directional couplers in both experiments and theoretical simulations. The coupling coefficient difference of circular waveguides in vertical and horizontal coupling directions was similar to 0.01 mm(-1), which was smaller than 0.33 mm(-1) of normal waveguides. The circular symmetric wavegu ides will play an important role in large-scale high-intensity 3D photonic integrated circuits. (C) 2021 Optical Society of America
The polarization beam splitter is a key component for polarization manipulation in photonic integrated circuits,but it is challenging to design for low-refractive-index optical materials,due to the low birefringence o...
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The polarization beam splitter is a key component for polarization manipulation in photonic integrated circuits,but it is challenging to design for low-refractive-index optical materials,due to the low birefringence of the *** propose what we believe is a novel compact vertical-dual-slot waveguide-based coupling scheme for silicon carbide,enabling efficient low-birefringence polarization splitting by extensively modulating the transverse-magnetic mode *** numerically and experimentally demonstrate the device in the 4H-siliconcarbide-on-insulator integrated platform,with a small footprint of 2.2 μm × 15 μ*** device,easy to fabricate via a single lithography process as other components on the chip,exhibits low insertion loss of <0.71 dB and <0.51 dB for the transverse-electric and transverse-magnetic polarized light,respectively,and polarization extinction ratio of >13 dB,over 80 nm wavelength range.
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