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Generating Radially and Azimuthally Polarized Beams by Using a Pair of Lateral Displacement Beamsplitters
摘要： This paper proposes a modified polarization converter for generating radially and azimuthally polarized beams. Based on a Mach–Zehnder-like interferometric structure, the device consists of a pair of lateral displacement beamsplitters (LDBs) and two half-wave plates that manipulate the states of polarization of incident linearly polarized light. Through the coherent superposition of two orthogonal Hermite–Gaussian modes in the far field, radially and azimuthally polarized beams can be obtained simultaneously. A prototype was assembled to demonstrate the feasibility of the design. The proposed design has the advantage of having a simple, symmetric, compact, and robust structure. In addition, the introduction of LDBs substantially reduces the cost of this device. Moreover, the design can be applied to a broadband pulsed laser with considerable potential in high-power applications.
关键词： coherence,interference,polarizations,waveplates,beam splitters
更新于2025-09-23 15:23:52
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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) - Single-Layered Metasurfaces as Spectrally Tunable Terahertz Half- and Quarter-Waveplates
摘要： A waveplate, well known as a phase retarder, manipulates the polarization state of incident light travelling through it and is a necessary component in many optical systems. Generally, waveplates are constructed out of birefringent materials which lead to the different phase retardation of incident light according to initial polarization state. For the terahertz (THz) spectral range, however, there are some limitations including thickness, transmission, and cost for the waveplate fabrication due to the lack of natural materials that possess strong birefringence in this region. Recently, THz waveplates based on metasurfaces have been proposed to overcome this limitation. Single-layered metasurfaces have been utilized as THz quarter-waveplates (QWPs), for which a retarded phase of 90 degrees is sufficient. [1]. To achieve phase retardation of 180 degrees and realize THz half-waveplates (HWP), stacked single-layered metasurfaces have been adopted [2], but this approach requires sophisticated fabrication processes and sacrifices structural simplicity. In this work, we propose a relatively simple single-layered metasurfaces that make possible to induce phase retardation of up to 90 and 180 degrees with a tunable operation frequency. The metasurfaces consist of rectangular ring resonators which are strongly coupled with each other and separated by a deep-wavelength gap, giving the metasurface an extraordinarily high anisotropic effective permittivity [3]. The x and y components of the effective permittivity of metasurface are closely associated with the gap widths of gx and gy along the x and y axes, respectively. The metasurface possesses strong birefringence when gx and gy are different and acts as the HWP and QWP at certain conditions depending on the operation frequency. To experimentally demonstrate the feasibility of the proposed metasurfaces, we optimized rectangular ring resonator size and gap width through Finite-Difference Time-Domain simulation and fabricated the metasurface on stretchable PDMS film for mechanical deformation. Subsequently, we confirmed the efficient performance of our single-layered metasurface as the THz HWP and QWP together with its spectral tunability through mechanical deformation of the metasurface by THz spectroscopy.
关键词： metasurfaces,waveplates,polarization,terahertz,birefringence
更新于2025-09-12 10:27:22
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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) - Compact Femtosecond Laser Direct Written Integrated Retarders Based on Embedded Nanogratings
摘要： Femtosecond Laser Direct Writing (FLDW) is a well-known rapid prototyping method to fabricate integrated optical circuits in glass chips. These circuits have been used to show various quantum information applications, using the states of photons as qubits. Generally, when transmitting information via single photons, it is desirable to make use of all possible degrees of freedom that this photon has to offer, in order to increase the amount of information transferred per photon. One of these degrees of freedom is the photon’s polarization. To make use of this degree of freedom, devices capable of manipulating the polarization are required. Various approaches for manipulating the polarization of photons in a FLDW circuit have been demonstrated before, of which some were used for quantum information applications. In our work, we present a novel method of polarization control using embedded nanogratings as waveplates. These nanogratings are highly birefringent self-assembled structures. Due to their relatively high form birefringence on the order of Δn = 10^-3, they can be used as a compact waveplate enabling further miniaturization of integrated optical circuits. The properties of these gratings can be altered by using different laser parameters during the inscription process. We have added various waveplates made of nanogratings into FLDW waveguides. We demonstrate their functionality as waveplates of different retardation and optical axis orientations using crossed polarizer birefringence measurements. Due to the chosen writing geometry, a full control over the direction of the optical axis can be achieved. The thickness of these structures is on the order of a few hundred micrometers. Former approaches for polarization control in FLDW circuits required structures in the range of millimetres to centimeters. Some of these approaches were limited in the achievable optical axis orientations. Our waveplates can be both used for classical applications and as single qubit quantum gates, which will be demonstrated. Waveplate structures usable as Hadamard, Pauli-x, Pauli-z and Pi/8th gates have been fabricated. The transferability to fibers will be discussed.
关键词： integrated optical circuits,polarization control,quantum information applications,waveplates,nanogratings,Femtosecond Laser Direct Writing
更新于2025-09-11 14:15:04
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Multipolar-interference-assisted terahertz waveplates via all-dielectric metamaterials
摘要： Polarization control via metamaterials boosts the design of polarimetric devices in the realm of terahertz technology for sensitive detection, bio-imaging, and wireless communication. Here, we propose all-dielectric metamaterials composed of silicon brick arrays that operate as terahertz quarter- and half-waveplates with close to unity transmission. Spherical multipole decomposition calculation indicates that the silicon brick can support multiple Mie-type resonances, such as electric dipole, electric quadrupole, magnetic dipole, and magnetic quadrupole modes. By tailoring the multipolar interference among these resonances, near unity transmission can be obtained with over p phase delay. We experimentally realize dielectric terahertz metamaterials that function as a quarter-wave plate at 0.79 THz and a half-wave plate at 0.91 THz with insertion losses of 0.54 and 1.25 dB, respectively. Such anisotropic dielectric metamaterials promise an exotic approach to engineer the interference among multipolar resonances and reveal the feasibility to realize functional, ef?cient, and compact terahertz meta-devices.
关键词： terahertz,waveplates,silicon brick arrays,all-dielectric metamaterials,multipolar interference
更新于2025-09-10 09:29:36
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[IEEE 2018 International Conference Laser Optics (ICLO) - Saint Petersburg, Russia (2018.6.4-2018.6.8)] 2018 International Conference Laser Optics (ICLO) - Anisotropic optical interference coatings for polarization control in high-power lasers
摘要： Optical anisotropy played a crucial role in development of advanced optical systems. In this study, a novel multi-layer approach of high band-gap birefringent coatings was proposed and investigated. Zero-order thin film retarders and normal incidence polarizers based on all-silica nanostructures are fabricated by oblique angle deposition process. Low optical losses and the potential to withstand high laser fluence in nanosecond regime at 355 nm wavelength for both elements were demonstrated.
关键词： waveplates,polarizers,nanostructured coatings,high-power lasers
更新于2025-09-09 09:28:46