Periodic structures with dimensions on the order of the wavelength of light can tailor and improve the performance of optical components, and they can enable the creation of devices with new functionalities. For examp...
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Periodic structures with dimensions on the order of the wavelength of light can tailor and improve the performance of optical components, and they can enable the creation of devices with new functionalities. For example, distributed Bragg reflectors (DBRs), which are created by periodic modulations in a structure's dielectric medium, are essential in dielectric mirrors, vertical cavity surface emitting lasers, fiber Bragg gratings, and single-frequency laser diodes. This work introduces nanoscale DBRs integrated directly into gallium nitride (GaN) nanowire waveguides. Photonic band gaps that are tunable across the visible spectrum are demonstrated by precisely controlling the grating's parameters. Numerical simulations indicate that in-wire DBRs have significantly larger reflection coefficients in comparison with the nanowire's end facet. By comparing the measured spectra with the simulated spectra, the index of refraction of the GaN nanowire waveguides was extracted to facilitate the design of photonic coupling structures that are sensitive to phase-matching conditions. This work indicates the potential to design nanowire-based devices with improved performance for optical resonators and optical routing.
In this work, we analysed the polarization of guided light in femtosecond laser written waveguides. The studied waveguides were performed with different laser pulse energies in an x-cut lithium niobate crystal. The gu...
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In this work, we analysed the polarization of guided light in femtosecond laser written waveguides. The studied waveguides were performed with different laser pulse energies in an x-cut lithium niobate crystal. The guided intensities were experimentally measured and compared with numerical simulations reaching a qualitatively good accordance. This comparison allowed a verification of the "mechanical expansion theory" which is useful to compute the refractive index field. Also, information related to the modelling of waveguides generated with different laser pulse energies was obtained. Both of these facts are keys to design and manufacture optical circuits by using thiS technological approach. (C) 2015 Elsevier B.V. All rights reserved.
Integrated power dividers (PDs) are essential in terahertz (THz) communication and radar systems, but miniaturization often leads to performance degradation due to fabrication inaccuracies and sharp bends. Topological...
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Integrated power dividers (PDs) are essential in terahertz (THz) communication and radar systems, but miniaturization often leads to performance degradation due to fabrication inaccuracies and sharp bends. Topological photonics offers a solution to these issues, yet creating THz power dividers with arbitrary splitting ratios remains challenging. We present a design methodology for on-chip topological THz power dividers with customizable splitting ratios using valley-locked photonic crystals. These crystals feature a tri-layered structure with two distinct valley Chern number layers and an intermediate semimetal layer. Utilizing the Jackiw-Rebbi model, we show that the characteristic impedance of the valley-locked photonic crystals, and thus the power division ratio, can be tuned by adjusting the semimetal layer width. Our approach is validated through simulations and experiments for both equal (1:1) and unequal (4:9) power ratios. This method enables efficient navigation around sharp bends and robust THz on-chip connectivity. (c) 2024 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.
Radiation-free photonic bound states in the continuum (BIC) in metasurfaces allow ultrahigh quality (Q) factor and strongly confined mode volume, which are extremely advantageous in the development of ultrasensitive m...
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Radiation-free photonic bound states in the continuum (BIC) in metasurfaces allow ultrahigh quality (Q) factor and strongly confined mode volume, which are extremely advantageous in the development of ultrasensitive micro- cavity sensors. However, the conventional isolated BICs are susceptible to failure due to symmetry breaking caused by fabrication imperfection and nonzero incident angle. Here, we propose a silicon nitride-based metasurface with multiple BIC merging. The merging of accidental BIC and symmetry-protected BIC can increase the Q- factor near the Brillouin zone Gamma point and thus robustly induces a figure of merit (FOM) of refractive index sensing at small incident angles two orders of magnitude higher than that in isolated BIC configuration. Specifically, the FOM in merging BIC reaches 108 at a 2 degrees incident angle. The BIC merging can be universally achieved in square lattices with C 4 symmetry, and slower decay of Q-factor and higher FOM can further occur in hexagonal lattices benefiting from higher- order topological charges. The advantage of merging BIC is also maintained when considering in-plane and out-of-plane symmetry breaking. These results offer a unique design path for high-performance metasurface sensors and can be extended to other high-Q applications such as low-threshold lasers, nonlinear frequency conversion, and low-loss waveguides. (c) 2024 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.
Topological edge states (TESs) and topological corner states (TCSs) in photonic crystals (PCs) provide an effective way to control the propagation and localization of light. The topological performance of integrated p...
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Topological edge states (TESs) and topological corner states (TCSs) in photonic crystals (PCs) provide an effective way to control the propagation and localization of light. The topological performance of integrated photonic devices can be improved by introducing the basic structural unit of photonic quasicrystals (PQCs) into PCs. However, the previous works arranged the basic structural unit of Stampfli-type and 12-fold Penrose-type photonic quasicrystals into triangular lattices, which have a complex structure and allow light to only propagate around 60 degrees or 120 degrees corners, limiting their applications. In this paper, a Penrose-square PC is proposed, which realizes both TESs and TCSs, and light successfully propagates around 90 degrees corners. This work may reduce the difficulties encountered in the preparation of topological photonic crystals (TPCs) structured by arranging the basic structural units of PQCs periodically. It also provides a new, to the best of our knowledge, platform for studying TPCs and new ideas for improving the performance of integrated photonic devices. (c) 2024 Optica Publishing Group
Abstract: The process of formation and propagation of pulse pairs in a quadratically nonlinear crystal with two waveguides was investigated with varying parameters related to the position of the waveguides relative to...
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Germanium-on-silicon is a highly promising platform for planar photonics for the midinfrared, due to germanium's wide transparency range. In this letter, we report Ge-on-Si waveguides with record low losses of onl...
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Germanium-on-silicon is a highly promising platform for planar photonics for the midinfrared, due to germanium's wide transparency range. In this letter, we report Ge-on-Si waveguides with record low losses of only 0.6 dB/cm, which is achieved using a 2.9-mu m thick germanium layer, thus minimizing mode interaction with dislocations at the germanium/silicon interface. Using these waveguides, multimode interferometers with insertion losses of only 0.21 +/- 0.02 dB are also demonstrated.
Precise on-chip phase control of microwave transmission is critical to today's signal processing and wireless communication electronics. Thus far, achieving even modest phase-shifting resolution has involved a com...
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Precise on-chip phase control of microwave transmission is critical to today's signal processing and wireless communication electronics. Thus far, achieving even modest phase-shifting resolution has involved a complex mix of semiconductor switches and passive electromagnetic structures. These delay circuits operate near resonances that heavily attenuate and distort signals, limiting modulation bandwidth. In this article, we introduce a mechanism whereby miniature waveguide reflectors based on coupled resonances can be reprogrammed to evade loss. Central to their operation is that loss from these resonances is confined to low frequencies, while at high frequencies, the waveguides' reflectivity is maximized and broadband phase variations, induced by those resonances, still persist. Since performance in the low-loss post-resonance spectrum is largely agnostic to the number of switches, ultra-fine digital tuning is possible. This breaks the historical tradeoff between loss and precision. When inserted in a reflective-type structure, a phase resolution of under 0.3 (degrees) is achieved, surpassing state-of-the-art CMOS circuits by over three orders (bits) of magnitude while incurring only 5 +/- 2.5 dB of loss over the 20-30 GHz 5G MIMO band. The phase-shifter is highly linear, with an input third-order intercept point (IIP3) of over 25 dBm. Moreover, it consumes no DC power and occupies a sub-wavelength footprint of 0.064 mm(2) in a 28 nm Fully Depleted Silicon-on-Insulator (FDSOI) CMOS platform. This makes it an optimal candidate for seamless integration in on-chip multi-gigabit data links, radio astronomy transceivers and control hardware for millimeter-wave qubits.
We have proposed and investigated two kinds of waveguide systems (i.e., dielectric-dielectric-metal and dielectric-metal-dielectric waveguides) which are able to support low-loss slow-light guided mode at telecommunic...
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We have proposed and investigated two kinds of waveguide systems (i.e., dielectric-dielectric-metal and dielectric-metal-dielectric waveguides) which are able to support low-loss slow-light guided mode at telecommunication regime of 1.55 mu m. Simulation results demonstrate that the propagation length of the proposed waveguides is as long as tens or even hundreds of micrometers, which is more than ten times higher than that of the traditional metal-dielectric-metal waveguides. Moreover, the proposed waveguides have better slow light performance and a figure of merit that can reach a value as high as 18 000. In addition, the slow-down factor can be flexibly tuned by adjusting the geometrical parameters. The proposed waveguide have advantages of low loss and compact configuration, which can find potential applications, such as optical buffers, in highly integrated optical communication systems.
作者：
Xu, QingxiPeng, YuchenShi, AoqianPeng, PengLiu, JianjunHunan Univ
Key Lab Micro Nano Optoelect Devices Minist Educ Sch Phys & Elect Changsha 410082 Peoples R China Hunan Univ
Sch Phys & Elect Hunan Prov Key Lab Low Dimens Struct Phys & Devic Changsha 410082 Peoples R China Hunan Univ
Greater Bay Area Inst Innovat Guangzhou 511300 Peoples R China
Topological rainbows (TRs) possess the potential to separate and localize topological photonic states across different frequencies. However, previous works on TRs have been confined to a single -frequency band. Furthe...
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Topological rainbows (TRs) possess the potential to separate and localize topological photonic states across different frequencies. However, previous works on TRs have been confined to a single -frequency band. Furthermore, the achievement of multiband TRs within a single structure is still a significant challenge. In this paper, a composed structure waveguide is designed based on Penrose -triangle photonic crystals. By adjusting the size of scatterers and introducing non -Hermitian terms, we successfully realize dual -band TRs. This achievement will not only enhance the uniformity of the electric field intensity distribution but also provide the potential to introduce a new avenue for the development of robust photonic devices dedicated to processing vast amounts of data information. (c) 2024 Optica Publishing Group
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