Slot radiators or slot antennas are antennas that are used in the frequency range from about 300 MHz to 25 GHz. They are often used in navigation radar usually as an array fed by a waveguide. But also older large phased array antennas used the principle because the slot radiators are a very inexpensive way for frequency scanning arrays. Slot antennas are an about λ/2 elongated. When these slot waveguides are part of a more complex device, a ring resonator 7. SLOT-WAVEGUIDE SIMULATION For a real study and design of this slot structures, a 3D analysis must be done. With the aid of COMSOL multiphysics, finite difference time domain method (FDTD) uses a brute force discretization of Maxwell's equations.
- Slot Waveguide Comsol
- Slot Waveguide Modes
- Slot Waveguide Modulator
- Slot Waveguide Modulator
- Slot Waveguide Antenna
Omnidirectional Sector Waveguide SLOT Antenna L and C Band (1296 & 2320 MHz) The slotted waveguide has achieved most of its success when used in an omnidirectional role. It is the simplest way to get a real 10dB gain over 360 degrees of beamwidth.
A slot-waveguide is an optical waveguide that guides strongly confined light in a subwavelength-scale low refractive index region by total internal reflection.
A slot-waveguide consists of two strips or slabs of high-refractive-index (nH) materials separated by a subwavelength-scale low-refractive-index (nS) slot region and surrounded by low-refractive-index (nC) cladding materials. Best free blackjack trainer app.
Principle of operation[edit]
The principle of operation of a slot-waveguide is based on the discontinuity of the electric field (E-field) at high-refractive-index-contrast interfaces. Maxwell's equations state that, to satisfy the continuity of the normal component of the electric displacement fieldD at an interface, the corresponding E-field must undergo a discontinuity with higher amplitude in the low-refractive-index side. That is, at an interface between two regions of dielectric constants εS and εH, respectively:
- DSN=DHN
- εSESN=εHEHN
- nS2ESN=nH2EHN
where the superscript N indicates the normal components of D and E vector fields. Thus, if nS<H, then ESN>>EHN.
![Waveguide Waveguide](https://www.sciencenewsforstudents.org/wp-content/uploads/2019/11/860-header-Rotating_marine_radar_-_rotating_waveguide_antenna.gif)
Given that the slot critical dimension (distance between the high-index slabs or strips) is comparable to the exponential decay length of the fundamental eigenmode of the guided-wave structure, the resulting E-field normal to the high-index-contrast interfaces is enhanced in the slot and remains high across it. The power density in the slot is much higher than that in the high-index regions. Since wave propagation is due to total internal reflection, there is no interference effect involved and the slot-structure exhibits very low wavelength sensitivity.[1]
Invention[edit]
The slot-waveguide was born in 2003 as an unexpected outcome of theoretical studies on metal-oxide-semiconductor (MOS) electro-opticmodulation in high-confinement silicon photonic waveguides by Vilson Rosa de Almeida and Carlos Angulo Barrios, then a Ph.D. student and a Postdoctoral Associate, respectively, at Cornell University. Theoretical analysis [1] and experimental demonstration [2] of the first slot-waveguide implemented in the Si/SiO2 material system at 1.55 μm operation wavelength were reported by Cornell researchers in 2004.
Slot Waveguide Comsol
Since these pioneering works, several guided-wave configurations based on the slot-waveguide concept have been proposed and demonstrated. Relevant examples are the following:
In 2005, researchers at the Massachusetts Institute of Technology proposed to use multiple slot regions in the same guided-wave structure (multi-slot waveguide) in order to increase the optical field in the low-refractive-index regions.[3] The experimental demonstration of such multiple slot waveguide in a horizontal configuration was first published in 2007.[4]
In 2006, the slot-waveguide approach was extended to the terahertz frequency band by researchers at RWTH Aachen University.[5] Researchers at the California Institute of Technology also demonstrated that a slot waveguide, in combination with nonlinear electrooptic polymers, could be used to build ring modulators with exceptionally high tunability.[6] Later this same principle enabled Baehr-Jones et al. to demonstrate a mach-zehnder modulator with an exceptionally low drive voltage of 0.25 V[7][8]
In 2007, a non-planar implementation of the slot-waveguide principle of operation was demonstrated by researchers at the University of Bath. They showed concentration of optical energy within a subwavelength-scale air hole running down the length of a photonic-crystal fiber.[9]
Recently, in 2016, it is shown [10] that slots in a pair of waveguides if off-shifted away from each other can enhance the coupling coefficient even more than 100% if optimized properly, and thus the effective power coupling length between the waveguides can significantly be reduced. Hybrid slot (having vertical slot in one waveguide and horizontal slot in the other) assisted polarization beam splitter is also numerically demonstrated. Though, the losses are high for such slot structures, this scheme exploiting the asymmetric slots may have potential to design very compact optical directional couplers and polarization beam splitters for on-chip integrated optical devices.
The slot waveguide bend is another structure essential to the waveguide design of several Integrated micro- and nano-optics devices. One of the benefits of waveguide bends is the reduction of the footprint size of the device. There are two approaches based on the similarity of Si rails width to form the sharp bend in slot waveguide, which are the symmetric and asymmetric slot waveguides [11].
Fabrication[edit]
Planar slot-waveguides have been fabricated in different material systems such as Si/SiO2[2][12][13] and Si3N4/SiO2.[14] Both vertical (slot plane is normal to the substrate plane) and horizontal (slot plane is parallel to the substrate plane) configurations have been implemented by using conventional micro- and nano-fabrication techniques. These processing tools include electron beam lithography, photolithography, chemical vapour deposition [usually low-pressure chemical vapour deposition (LPCVD) or plasma enhanced chemical vapour deposition (PECVD)], thermal oxidation, reactive-ion etching and focused ion beam.
Poker hand rankings wikipedia nfl. In vertical slot-waveguides, the slot and strips widths are defined by electron- or photo-lithography and dry etching techniques whereas in horizontal slot-waveguides the slot and strips thicknesses are defined by a thin-film deposition technique or thermal oxidation. Thin film deposition or oxidation provides better control of the layers dimensions and smoother interfaces between the high-index-contrast materials than lithography and dry etching techniques. This makes horizontal slot-waveguides less sensitive to scattering optical losses due to interface roughness than vertical configurations.
Fabrication of a non-planar (fiber-based) slot-waveguide configuration has also been demonstrated by means of conventional microstructured optical fiber technology.[9]
Applications[edit]
A slot-waveguide produces high E-field amplitude, optical power, and optical intensity in low-index materials at levels that cannot be achieved with conventional waveguides. This property allows highly efficient interaction between fields and active materials, which may lead to all-optical switching,[15]optical amplification[16][17] and optical detection [6] on integrated photonics. Strong E-field confinement can be localized in a nanometer-scale low-index region. As firstly pointed out in,[1] the slot waveguide can be used to greatly increase the sensitivity of compact optical sensing devices [18][19][20][21][22][23][24] or to enhance the efficiency of near-field optics probes.At Terahertz frequencies, slot waveguide based splitter has been designed which allows for low loss propagation of Terahertz waves. The device acts as a splitter through which maximum throughput can be achieved by adjusting the arm length ratio of the input to the output side.[25]
References[edit]
- ^ abcAlmeida, Vilson R.; Xu, Qianfan; Barrios, Carlos A.; Lipson, Michal (2004-06-01). 'Guiding and confining light in void nanostructure'. Optics Letters. The Optical Society. 29 (11): 1209–11. doi:10.1364/ol.29.001209. ISSN0146-9592. PMID15209249.
- ^ abXu, Qianfan; Almeida, Vilson R.; Panepucci, Roberto R.; Lipson, Michal (2004-07-15). 'Experimental demonstration of guiding and confining light in nanometer-size low-refractive-index material'. Optics Letters. The Optical Society. 29 (14): 1626–8. doi:10.1364/ol.29.001626. ISSN0146-9592. PMID15309840.
- ^Feng, N.-N.; Michel, J.; Kimerling, L.C. (2006). 'Optical Field Concentration in Low-Index Waveguides'. IEEE Journal of Quantum Electronics. Institute of Electrical and Electronics Engineers (IEEE). 42 (9): 883–888. doi:10.1109/jqe.2006.880061. ISSN0018-9197. S2CID46700811.
- ^Sun, Rong; Dong, Po; Feng, Ning-ning; Hong, Ching-yin; Michel, Jurgen; Lipson, Michal; Kimerling, Lionel (2007). 'Horizontal single and multiple slot waveguides: optical transmission at λ = 1550 nm'. Optics Express. The Optical Society. 15 (26): 17967–72. doi:10.1364/oe.15.017967. ISSN1094-4087. PMID19551093.
- ^Nagel, Michael; Marchewka, Astrid; Kurz, Heinrich (2006). 'Low-index discontinuity terahertz waveguides'. Optics Express. The Optical Society. 14 (21): 9944–54. doi:10.1364/oe.14.009944. ISSN1094-4087. PMID19529388.
- ^ abBaehr-Jones, T.; Hochberg, M.; Wang, Guangxi; Lawson, R.; Liao, Y.; Sullivan, P. A.; Dalton, L.; Jen, A. K.-Y.; Scherer, A. (2005). 'Optical modulation and detection in slotted Silicon waveguides'. Optics Express. The Optical Society. 13 (14): 5216–26. doi:10.1364/opex.13.005216. ISSN1094-4087. PMID19498512.
- ^Baehr-Jones, Tom; Penkov, Boyan; Huang, Jingqing; Sullivan, Phil; Davies, Joshua; et al. (2008-04-21). 'Nonlinear polymer-clad silicon slot waveguide modulator with a half wave voltage of 0.25V'. Applied Physics Letters. AIP Publishing. 92 (16): 163303. doi:10.1063/1.2909656. ISSN0003-6951.
- ^Witzens, Jeremy; Baehr-Jones, Thomas; Hochberg, Michael (2010-07-26). 'Design of transmission line driven slot waveguideMach-Zehnder interferometers and application to analog optical links'. Optics Express. The Optical Society. 18 (16): 16902–28. doi:10.1364/oe.18.016902. ISSN1094-4087. PMID20721082.
- ^ abWiederhecker, G. S.; Cordeiro, C. M. B.; Couny, F.; Benabid, F.; Maier, S. A.; et al. (2007). 'Field enhancement within an optical fibre with a subwavelength air core'. Nature Photonics. Springer Science and Business Media LLC. 1 (2): 115–118. doi:10.1038/nphoton.2006.81. ISSN1749-4885.
- ^Haldar, Raktim; Mishra, V; Dutt, Avik; Varshney, Shailendra K (2016-09-09). 'On-chip broadband ultra-compact optical couplers and polarization splitters based on off-centered and non-symmetric slotted Si-wire waveguides'. Journal of Optics. IOP Publishing. 18 (10): 105801. doi:10.1088/2040-8978/18/10/105801. ISSN2040-8978.
- ^Al-Tarawni, Musab A. M.; Bakar, A. Ashrif A.; Zain, Ahmad Rifqi Md.; Tarawneh, Mou'ad A.; Ahmad, Sahrim Hj. (2019-02-08). 'Enhancing the performance of strip and 180-deg slot waveguide bends for integrated optical waveguide modulator'. Optical Engineering. SPIE-Intl Soc Optical Eng. 58 (2): 027104. doi:10.1117/1.oe.58.2.027104. ISSN0091-3286. S2CID126965871.
- ^Baehr-Jones, Tom; Hochberg, Michael; Walker, Chris; Scherer, Axel (2005-02-21). 'High-Q optical resonators in silicon-on-insulator-based slot waveguides'. Applied Physics Letters. AIP Publishing. 86 (8): 081101. doi:10.1063/1.1871360. ISSN0003-6951.
- ^Schrauwen J., Van Lysebettens J., Vanhoutte M., Van Thourhout D. et al., 'Iodine enhanced focused ion beam etching of silicon for photonic device modification and prototyping (2008)', International Workshop on FIB for Photonics, 1st, Proceedings (2008)
- ^Barrios, C. A.; Sánchez, B.; Gylfason, K. B.; Griol, A.; Sohlström, H.; Holgado, M.; Casquel, R. (2007). 'Demonstration of slot-waveguide structures on silicon nitride / silicon oxide platform'. Optics Express. The Optical Society. 15 (11): 6846–56. doi:10.1364/oe.15.006846. ISSN1094-4087. PMID19546997.
- ^Barrios, C.A. (2004). 'High-performance all-optical silicon microswitch'. Electronics Letters. Institution of Engineering and Technology (IET). 40 (14): 862-863. doi:10.1049/el:20045179. ISSN0013-5194.
- ^Barrios, Carlos Angulo; Lipson, Michal (2005). 'Electrically driven silicon resonant light emitting device based on slot-waveguide'. Optics Express. The Optical Society. 13 (25): 10092–101. doi:10.1364/opex.13.010092. ISSN1094-4087. PMID19503222.
- ^A. Armaroli, A. Morand, P. Benech, G. Bellanca, S. Trillo, 'Comparative Analysis of a Planar Slotted Microdisk Resonator,' Lightwave Technology, Journal of , vol.27, no.18, pp.4009,4016, Sept.15, 2009
- ^Barrios, Carlos Angulo (2006). 'Ultrasensitive Nanomechanical Photonic Sensor Based on Horizontal Slot-Waveguide Resonator'. IEEE Photonics Technology Letters. Institute of Electrical and Electronics Engineers (IEEE). 18 (22): 2419–2421. doi:10.1109/lpt.2006.886824. ISSN1041-1135. S2CID32069322.
- ^Barrios, Carlos A.; Gylfason, Kristinn B.; Sánchez, Benito; Griol, Amadeu; Sohlström, H.; Holgado, M.; Casquel, R. (2007-10-17). 'Slot-waveguide biochemical sensor'. Optics Letters. The Optical Society. 32 (21): 3080–2. doi:10.1364/ol.32.003080. ISSN0146-9592. PMID17975603.
- ^Dell'Olio, Francesco; Passaro, Vittorio M. (2007). 'Optical sensing by optimized silicon slot waveguides'. Optics Express. The Optical Society. 15 (8): 4977–93. doi:10.1364/oe.15.004977. ISSN1094-4087. PMID19532747.
- ^Barrios, Carlos A.; Bañuls, María José; González-Pedro, Victoria; Gylfason, Kristinn B.; Sánchez, Benito; et al. (2008-03-28). 'Label-free optical biosensing with slot-waveguides'. Optics Letters. The Optical Society. 33 (7): 708–10. doi:10.1364/ol.33.000708. ISSN0146-9592. PMID18382525.
- ^Robinson, Jacob T.; Chen, Long; Lipson, Michal (2008-03-13). 'On-chip gas detection in silicon optical microcavities'. Optics Express. The Optical Society. 16 (6): 4296–301. doi:10.1364/oe.16.004296. ISSN1094-4087. PMID18542525.
- ^Witzens, Jeremy; Hochberg, Michael (2011-03-29). 'Optical detection of target molecule induced aggregation of nanoparticles by means of high-Q resonators'. Optics Express. The Optical Society. 19 (8): 7034–61. doi:10.1364/oe.19.007034. ISSN1094-4087. PMID21503017.
- ^Ghosh, Souvik; Rahman, B. M. A. (2017). 'An Innovative Straight Resonator Incorporating a Vertical Slot as an Efficient Bio-Chemical Sensor'(PDF). IEEE Journal of Selected Topics in Quantum Electronics. Institute of Electrical and Electronics Engineers (IEEE). 23 (2): 132–139. doi:10.1109/jstqe.2016.2630299. ISSN1077-260X. S2CID10903140.
- ^Pandey, Shashank; Kumar, Gagan; Nahata, Ajay (2010-10-22). 'Slot waveguide-based splitters for broadband terahertz radiation'. Optics Express. The Optical Society. 18 (22): 23466–71. doi:10.1364/oe.18.023466. ISSN1094-4087. PMID21164689.
Slot Waveguide Modes
Slot Waveguide Modulator
A slot antenna consists of a metal surface, usually a flat plate, with one or more holes or slots cut out. When the plate is driven as an antenna by an applied radio frequency current, the slot radiates electromagnetic waves in a way similar to a dipole antenna. The shape and size of the slot, as well as the driving frequency, determine the radiation pattern. Slot antennas are usually used at UHF and microwave frequencies at which wavelengths are small enough that the plate and slot are conveniently small. At these frequencies, the radio waves are often conducted by a waveguide, and the antenna consists of slots in the waveguide; this is called a slotted waveguide antenna. Multiple slots act as a directivearray antenna and can emit a narrow fan-shaped beam of microwaves. They are used in standard laboratory microwave sources used for research, UHF television transmitting antennas, antennas on missiles and aircraft, sector antennas for cellular base stations, and particularly marine radar antennas. A slot antenna's main advantages are its size, design simplicity, and convenient adaptation to mass production using either waveguide or PC board technology.
Structure[edit]
As shown by H. G. Booker in 1946, from Babinet's principle in optics a slot in a metal plate or waveguide has the same radiation pattern as a driven rod antenna whose rod is the same shape as the slot, with the exception that the electric field and magnetic field directions are interchanged; the antenna is a magnetic dipole instead of an electric dipole; the magnetic field is parallel to the long axis of the slot and the electric field is perpendicular. Thus the radiation pattern of a slot can be calculated by the same well-known equations used for rod element antennas like the dipole. The waves are linearly polarized perpendicular to the slot axis. Slots up to a wavelength long have a single main lobe with maximum radiation perpendicular to the surface.
Antennas consisting of multiple parallel slots in a waveguide are widely used array antennas. They have a radiation pattern similar to a corresponding linear array of dipole antennas, with the exception that the slot can only radiate into the space on one side of the waveguide surface, 180° of the surrounding space. There are two widely used types:
- Longitudinal slotted waveguide antenna - The slots' axis is parallel to the axis of the waveguide. This has a radiation pattern similar to a collinear dipole antenna, and is usually mounted vertically. The radiation pattern is almost omnidirectional in the horizontal plane perpendicular to the antenna over the 180° azimuth in front of the slot, but narrow in the vertical plane, with the vertical gain increasing approximately 3 dB with each doubling of the number of slots. The radiation is horizontally polarized. It is used for vertical omnidirectional transmitting antennas for UHF television stations. For broadcasting, a cylindrical or semicircular waveguide is sometimes used with several columns of slots cut in different sides to give an omnidirectional 360° radiation pattern.
- Transverse slotted waveguide antenna - The slots are almost perpendicular to the axis of the waveguide but skewed at a small angle, with alternate slots skewed at opposite angles. This radiates a dipole pattern in the plane perpendicular to the antenna, and a very sharp beam in the plane of the antenna. Its largest use is for microwave marine radar antennas. The antenna is mounted horizontally on a mechanical drive that rotates the antenna about a vertical axis, scanning the antenna's vertical fan-shaped beam 360° around the water surface surrounding the ship out to the horizon with each revolution. The wide vertical spread of the beam ensures that even in bad weather when the ship and the antenna axis is being rocked over a wide angle by waves the radar beam will not miss the surface.
History[edit]
The slot antenna was invented in 1938 by Alan Blumlein, while working for EMI. He invented it in order to produce a practical type of antenna for VHF television broadcasting that would have horizontal polarization, an omnidirectional horizontal radiation pattern and a narrow vertical radiation pattern.[1][2]
Prior to its use in surface search radar, such systems used a parabolic segment reflector, or 'cheese antenna'. The slotted waveguide antenna was the result of collaborative radar research carried on by McGill University and the National Research Council of Canada during World War II.[3] The co-inventors, W.H. Watson and E.W. Guptill of McGill, were granted a United States patent for the device, described as a 'directive antenna for microwaves', in 1951.[4]
Other uses[edit]
In a related application, so-called leaky waveguides are also used in the determination of railcar positions in certain rapid transit applications. They are used primarily to determine the precise position of the train when it is being brought to a halt at a station, so that the doorway positions will align correctly with queuing points on the platform or with a second set of safety doors should such be provided.
Slot Waveguide Modulator
See also[edit]
- Microwave Radiometer (Juno) (has a slot array antenna)
- RIMFAX (radar for Mars rover has slot antenna design)
References[edit]
- ^Blumlein, Alan (1938-03-07), 'Improvements in or relating to high frequency electrical conductors or radiators', British patent no. 515684
- ^Burns, Russell (2000). The life and times of A.D. Blumlein. Institution of Engineering and Technology. ISBN0-85296-773-X.
- ^Covington, Arthur E. (1991). 'Some recollections of the radio and electrical engineering division of the National Research Council of Canada, 1946-1977'. Scientia Canadensis: Canadian Journal of the HIstory of Science, Technology and Medicine. 15 (2): 155–175. doi:10.7202/800334ar.
- ^Watson, William Heriot; Guptill, Ernest Wilmot (6 November 1951), Directive Antenna for Microwaves, retrieved 20 December 2016
External links[edit]
Slot Waveguide Antenna
- 'Slot Antennas'. Antenna Theory.
- Slotted Waveguide Antennas Antenna-Theory.com