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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) - Birefringent Surface Gratings for Ultrafast Spin-VCSELs
摘要： The data rates required for optical interconnection in datacenters continue to increase. On the other hand, intensity-modulated vertical-cavity surface-emitting lasers (VCSELs), which are the preferred light source for this task, have a limited bandwidth of at present about 35 GHz [1]. This limit can be overcome with spin-VCSELs that show much faster polarisation and modulation dynamics [2]. In these devices, spin-polarised electrons are injected, by which the degree of circular polarisation of the emitted light can be changed and thus information be encoded. The characteristic eigenfrequency of the laser, corresponding to the resonance frequency in conventional laser diodes, is determined by the birefringence splitting B, namely the frequency difference between the two fundamental polarisation modes of a single-mode VCSEL. Recently a polarisation oscillation frequency of 212 GHz was demonstrated [2]. In that laser the birefringence was induced by bending the sample and employing the elasto-optic effect. Alternatively we have shown that the cavity birefringence can be tuned by mounting VCSELs on piezoelectric substrates or by asymmetric heating, which, however, leads to much lower B. Up to now no truly integrated B-inducing technique existed for a spin-VCSEL that would allow to maintain great similarity to the successful high-efficiency device platform of present oxide-confined VCSELs. In this work, for the first time, we present a VCSEL in which high B of almost 100 GHz stems from a tailored integrated surface grating.
关键词： ultrafast modulation,spin-VCSELs,optical interconnection,surface gratings,birefringence
更新于2025-09-12 10:27:22
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Zero-Birefringence Silicon Waveguides Based on Tilted Subwavelength Metamaterials
摘要： Polarization independent silicon-on-insulator nanowires are highly sought after, due the inherent high birefringence of this material platform. State-of-the-art designs of non-birefringent waveguides include ridge waveguides and square nanowires, which either imply large dimensions, multiple etching steps, low fabrication tolerances or high wavelength dependence. In this work, we overcome all the aforementioned limitations through tilted subwavelength structures which provide anisotropy control of the resulting metamaterial. With a waveguide cross section of only 300 nm x 550 nm (height x width), the zero-birefringence point is obtained for an approximately 48?-tilt of the subwavelength structure. Birefringence of the nominal design deteriorates by only 9.10?3 even in the presence of size deviations of ± 10 nm. Moreover, birefringence is maintained under 6.10?3 in a 100-nm bandwidth around the central wavelength of 1550 nm. This innovative approach is readly adaptable to a wide range of waveguide sizes, while maintaining single-etch-step fabrication.
关键词： polarization independence,silicon-on-insulator (SOI),sub-wavelength grating (SWG),Zero-birefringence waveguides,anisotropy engineering
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) - Complex-Birefringent and Chiral Waveplates with Metasurfaces
摘要： Metasurfaces composed of arrays of nano-resonators are a powerful tool for manipulation of polarization of light. All-dielectric metasurfaces do not suffer absorption losses and are highly transparent in contrast to metallic structures, and combined with recent advances in their design and fabrication, have enabled efficient polarization manipulation and arbitrary phase shaping. A new regime of complex-valued birefringence has been recently suggested, extending the notion of real-valued birefringence through the specially introduced polarization-sensitive loss or gain. This can enable fundamentally new possibilities for polarization control, such as amplifying the angle between polarization vectors to improve detection sensitivity. However, a practical realization of complex-valued birefringence concept was missing. In particular, the theoretical approach in Ref. [4] was based on a complicated metamaterial with loss and gain, which is challenging to fabricate and not suitable for quantum applications. Here, we report on a new conceptual approach for implementing arbitrary complex-valued birefringence with pairwise birefringent elements using high-index dielectric nanostructures. We formulate a practical design principle, which is optimal for achieving any desirable polarization transformation. While loss is inherently necessary for implementing complex birefringence, our all-dielectric metasurface design achieves the mathematically minimum required amount of loss through tailored diffraction without any material absorption.
关键词： metasurfaces,birefringence,polarization control,dielectric nanostructures
更新于2025-09-11 14:15:04
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Dispersive solitons in optical fibers and DWDM networks with Schr?dinger–Hirota equation
摘要： This paper secures dispersive solitons in polarization-preserving fibers, birefringent fibers and DWDM networks. The extended simplest equation approach analyzes the governing Schr?dinger–Hirota equation. A wide spectrum of soliton solutions is yielded.
关键词： Extended simplest equation,Dispersive solitons,Birefringence,DWDM
更新于2025-09-11 14:15:04
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[IEEE 2019 IEEE Avionics and Vehicle Fiber-Optics and Photonics Conference (AVFOP) - Arlington, VA, USA (2019.11.5-2019.11.6)] 2019 IEEE Avionics and Vehicle Fiber-Optics and Photonics Conference (AVFOP) - Barium Titanate Electro-Optic Modulators
摘要： Barium titanate is a highly desired material for the development of advanced linear phase modulators due to its exceptional electro-optic coefficient, r51, that is over 20 times larger than the largest used in lithium niobate, r33. While the large r51 value in barium titanate has been reported, its utilization in modulators has been limited due to the difficulty in aligning the optical polarization with the crystal axes to maximize the electro-optic effect. Here we discuss the use of off-diagonal electro-optic tensor elements in thin film barium titanate modulators, present recent results, and go into further detail about the challenges and opportunities of using r51 in modulators.
关键词： barium,optical polarization,birefringence,Electrooptic modulators,nonlinear optics,slot waveguide,titanate
更新于2025-09-11 14:15:04
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[IEEE 2019 IEEE Photonics Conference (IPC) - San Antonio, TX, USA (2019.9.29-2019.10.3)] 2019 IEEE Photonics Conference (IPC) - Polarization-Sensitive Optical Coherence Tomography with a Single Input Polarization State
摘要： Measuring depth-resolved birefringence traditionally requires at least two distinct input polarization states. We identified a constraint on the evolution of the polarization state as a function of the round-trip path-length into birefringent tissue that enables to recover comparable results using only a single input state.
关键词： polarization,Optical coherence tomography,birefringence
更新于2025-09-11 14:15:04
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Electro-optical, dielectric and optical properties of graphene oxide dispersed nematic liquid crystal composites
摘要： Graphene oxide (GO) in various concentrations (0.04 wt.%, 0.1 wt.% and 0.3 wt.%) was dispersed into nematic liquid crystal (LC) 5CB and studied for electro-optical, dielectric and optical responses. The textural and phase transition studies were investigated by optical polarising microscopy in the nematic phase. The effect of GO concentration on the micro-texture, phase transition temperatures, birefringence, threshold voltage, contrast ratio, dielectric permittivity, dielectric loss and conductivity was also investigated. The nematic–isotropic transition temperature slight increases (~3%) in the 0.04 wt.% and 0.1 wt.% GO dispersed 5CB composites as compared to 5CB. Threshold voltage decreases in the GO–5CB composites with the increase of GO concentration. Additionally, the effect of GO concentration on the optical absorbance of UV–visible light and energy bandgap is also considered.
关键词： graphene oxide,phase transitions,birefringence,threshold voltage,Nematic liquid crystals
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) - Zero-Birefringence Silicon Slot Waveguides with L-Rails
摘要： Silicon slot waveguides are widely used for photonic sensing [1] and optical signal procesing [2]. We propose a novel slot formed when a sub-micron rib waveguide is slit with vertical symmetry resulting in L shaped rails to have Zero Birefringence (ZB). This geometry gives the flexibility to choose the slab (strip-load) region for doping or modulation. Index modulation of the slab sidewall offers platform for Bragg gratings with sub-nanometer stop bands [3,4]. We show that slots with L-rails possess better confinement and higher tolerance to sidewall width variations compared to strip-rails [5] and ZB can be achieved by engineering the waveguide geometry. Optimal waveguide-dimensions at a wavelength λ = 1550 nm are designed from modal analysis through full-vectorial computations.
关键词： Zero Birefringence,optical signal processing,Silicon slot waveguides,photonic sensing,L-rails
更新于2025-09-11 14:15:04
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Influences of Asymmetrical Geometric Structures on the Birefringence of Index-Guiding Photonic Crystal Fiber
摘要： We have numerically investigated the influences of asymmetrical geometric structures on the birefringence of the index-guiding photonic crystal fiber (IG-PCF), by the finite element method. The structure of a reported highly birefringent (HB) PCF with artificial defect in the core is modified to destruct the symmetry. Our proposed structural modifications include elliptical air hole cladding, squeezing lattice of air holes, rotational elliptical air holes, and horizontally shifted air holes, in the cladding. It is found that the birefringence is sensitive to the modifications in different cases due to the different mechanisms. For 1550 nm wavelength, the optimized birefringence can be obtained to be 0.0328 by the elliptical air holes with the major semi-axis in the direction of the long side of the rectangular core region. Furthermore, for the HB-PCF by the asymmetric core shape, the structural factor restricting the further increase of birefringence is that continuous increase of asymmetry leading to the multi-core transmission. It seems to be that This work is not only a proposing of the optimal design of HB-PCF, but also a reference of founding the essence of geometric birefringence.
关键词： structural anisotropy,high birefringence,polarization-maintaining fiber,Photonic crystal fiber (PCF),geometric birefringence
更新于2025-09-10 09:29:36
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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