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1.
Far-field patterns and Gaussian-beam coupling efficiencies are investigated for a double-slot antenna placed on hemispherical lenses with varying extension lengths. The radiation patterns of a double-slot antenna on a silicon dielectric lens are computed using ray-tracing inside the dielectric lens and electric and magnetic field integration on the spherical dielectric surface. The measured radiation patterns at 246 GHz and Gaussian-beam coupling efficiencies show good agreement with theory. The theoretical results are presented in terms of extension-length/radius and radius/λ, and therefore result in universal design curves for silicon lenses of different diameters and at different frequencies. The theoretical and experimental results indicate that for single units, there exists a wide range of extension lengths which result in high Gaussian-coupling efficiencies (50-60%) to moderately high f 's. These Gaussian-coupling efficiencies can be increased to 80-90°% with the use of a λm/4 matching-cap layer. For imaging array applications with high packing densities, an extension-length/radius of 0.38 to 0.39 (depending on frequency) will result in peak directivity and a corresponding Gaussian-coupling efficiency 15-20% lower than for single units 相似文献
2.
《Microwave Theory and Techniques》1978,26(9):665-666
A new type of compact Iight-weight Gaussian-beam launcher for producing a focused-microwave exposure field in biological experiments is described. This launcher is identical to the structure described by the authors elsewhere, except that a simple circular waveguide aperture, instead of a corrugated pipe is used to illuminate a dielectric sphere lens with the result that a considerable weight and size reduction of the launcher is achieved. The proposed structure consists of a simple cylindrical waveguide excited with a balanced mixture of complementary modes and the diffracted field due to this waveguide aperture is made to illuminate a dielectric sphere (lens). It is shown that a near-circular Gaussian beam is then pruduced in the image space of the sphere with a high focusing factor. Design details, theoretical calculation, and experimental results concerning a practical launcher are presented. Suitability of this compact structure for diathermy applications at a frequency of 2450 MHz is mentioned. 相似文献
3.
Filipovic D.F. Gauthier G.P. Raman S. Rebeiz G.M. 《Antennas and Propagation, IEEE Transactions on》1997,45(5):760-766
The theoretical far-field patterns and Gaussian-beam coupling efficiencies are investigated for a double-slot antenna placed off aids on extended hemispherical silicon and quartz lenses. Measured off-axis radiation patterns at 250 GHz agree well with the theory. Results are presented that show important parameters versus off-axis displacement: scan angle, directivity, Gaussicity, and reflection loss. Directivity contour plots are also presented and show that near-diffraction limited performance can be achieved at off-axis positions at nonelliptical extension lengths. Some design rules are discussed for imaging arrays on dielectric lens antennas 相似文献
4.
《Microwave Theory and Techniques》1979,27(9):797-799
A new type of Gaussian-beam luncher for producing a focused-microwave exposure field in biological experiments for selective partial-body irradiation is studied. The proposed launcher consists of a scalar horn (corrugated cylindrical open-ended waveguide) excited with a balanced hybrid (HE/sub 11/) mode and the aperture of the horn is loaded with a dielectric hemisphere. This Iauncher is similar to the structure described by one of the authors elsewhere, except that a dielectric hemisphere instead of a full sphere is used, with the result that the spherical aberration is considerably reduced, as well as that the weight and the size are, to a certain extent, reduced. It is shown that the present structure also produces in the image space of hemispherical lens, a near-circular Gaussian beam with a high-focusing factor. Design details, theoretical calculations, and experimental results conceming a practical X-band launcher are presented. 相似文献
5.
A technique for computing the total aperture-blockage effect of a loaded wire antenna feeding a paraboloidal reflector is described. First an analytical formulation for determining the fields scattered by a field incident upon a loaded wire antenna is described, and then an iterative procedure utilizing this result to obtain the aperture blockage effect is given. Typical results are presented for both simple and complex feed structures. 相似文献
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提供了一种简便易行的靶面激光光斑尺寸原位测量的方法。从高斯光束的横向光强分布特性出发,建立了激光烧蚀斑半径与辐照激光能量、光斑尺寸、烧蚀阈值间的关系式,模拟分析发现辐照激光光斑尺寸对烧蚀斑半径随辐照能量变化曲线有较大影响。对于脉宽为2 ms,波长为1064 nm的激光,实验测量了不同能量激光辐照下相纸烧蚀斑半径,并用推导出的关系式拟合测量数据,获得了靶面处光斑尺寸和样品烧蚀阈值。同时,也测量了不同位置处的光斑尺寸和样品烧蚀阈值,对高斯光束束腰位置和样品烧蚀阈值的光斑尺寸效应进行了验证。研究结果表明该技术结果可靠,简单高效。该技术可以为高能激光与固体物质相互作用的基础研究和激光加工等应用领域中实现简单方便地测量靶面光斑尺寸提供帮助。 相似文献
8.
Simple formulas are given for trapped-mode power excited by a spot of light illuminating an optical fibre. The results are used to discuss features of Gaussian-beam excitation. 相似文献
9.
Mitomi O. Yoshimoto N. Magari K. Ito T. Kawaguchi Y. Suzuki Y. Tohmori Y. Kasaya K. 《Lightwave Technology, Journal of》1999,17(7):1255-1262
This paper describes a semivectorial wide-angle finite-element beam propagation method (FE-BPM) that uses the Pade approximation and that can allow efficient and accurate analyzes of the polarization dependence in arbitrary step-index optical waveguide devices. It also reports the use of this method to analyze the polarization dependence of coupling loss between a semiconductor tapered-waveguide spot-size converter and a single-mode optical fiber. It is shown that semiconductor spot-size converters having cores with a small cross-section provide low-loss and polarization-insensitive coupling to flat-end fibers. A low-loss (far less than 1 dB) and completely polarization-insensitive spot-size converter can be made using a lightly n-doped InP substrate for the tapered waveguide. These spot-size converters are consequently potentially useful for making polarization-insensitive semiconductor optical devices such as optical amplifier gate switches 相似文献
10.
Itoh M. Saida T. Hida Y. Ishii M. Inoue Y. Hibino Y. Sugita A. 《Electronics letters》2002,38(2):72-74
Reduction of singlemode fibre coupling loss in 1.5% Δ planar lightwave circuits from 1.8 to 0.2 dB/point is achieved using simple vertically and laterally tapered spot-size converters. These spot-size converters were used to realise an arrayed-waveguide grating with a very low insertion loss of 0.7 dB 相似文献
11.
In this communication a note on the coupling efficiency between an antenna and a Gaussian beam is presented. The calculations of the coupling efficiency from both methods, a nomorlized inner product between the antenna radiation pattern and the Gaussian-beam pattern or alternatively, between the electric field at the antenna aperture and a two-dimensional field representation of a Gaussian beam, are compared for different aperture size in wavelength. How a correct solution can be gotten is stated. 相似文献
12.
Mitomi O. Kasaya K. Tohmori Y. Suzaki Y. Fukano H. Sakai Y. Okamoto M. Matsumoto S. 《Lightwave Technology, Journal of》1996,14(7):1714-1720
Structures of spot size converters that allow low loss and easy coupling between an optical semiconductor device and a fiber are proposed and designed theoretically. These spot-size converters have a tapered small core for expanding the mode field. They also have a double cladding region which consists of an n+-doped InP substrate as the outer cladding and a p-doped or nondoped InP layer as the inner cladding with a ridge structure. This double cladding utilizes the plasma effect of a carrier which makes the refractive index of highly doped n-InP lower than that of p-doped or nondoped InP. The double-cladding structure can tightly confine an expanded mode field in the inner cladding, and results in low radiation loss at the tapered waveguide, in addition, this structure reforms the mode field shape into a Gaussian-like shape and achieves a low loss coupling of less than 1 dB with a large misalignment tolerance for fiber coupling. These spot-size converters are easily fabricated and applicable to all types of optical semiconductor devices 相似文献
13.
Suzaki Y. Iga R. Kishi K. Kawaguchi Y. Matsumoto S. Okamoto M. Yamamoto M. 《Quantum Electronics, IEEE Journal of》1998,34(4):686-690
We have demonstrated an optical transceiver diode integrated with a spot-size converter. We clarify that the design of a detection layer is essential for the temperature- and polarization-insensitive characteristics of the responsivity. Because the detection layer was introduced, 0.65 dB of responsivity deviation was obtained in the wide temperature range of -10°C-85°C with a high laser performance. A spot-size converter enables the coupling loss to be 1.8 dB for a flat-end optical fiber. The frequency response was also obtained up to 1 GHz in both laser and detector modes 相似文献
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Sang-Wan Ryu Sung-Bock Kim Jae-Sik Sim Jeha Kim 《Photonics Technology Letters, IEEE》2003,15(1):12-14
A 1.55-/spl mu/m spot-size converter integrated laser diode is demonstrated with conventional buried-heterostructure laser process. For the spot-size converter, we employed a double-waveguide structure in which a ridge-based passive waveguide was incorporated. The passive waveguide was optically combined with a laterally tapered active waveguide to control mode size. The threshold current was measured to be 5 mA together with high slope efficiency of 0.45 W/A. The beam divergence angles in the horizontal and vertical directions were as small as 9.0/spl deg/ and 7.8/spl deg/, respectively. 相似文献
16.
A passive InP/InGaAsP spot-size transformer for low-loss coupling of semiconductor optoelectronic devices to single-mode fibres has been fabricated entirely on InP. Using a buried two-layer laterally tapered section, spot-size transformation is demonstrated from below 2 mu m up to 8 mu m, the spot size of a dispersion-shifted fibre at 1550 nm. For a chip without antireflection coating a total insertion loss of 2.7 dB was achieved at a taper length of approximately 600 mu m.<> 相似文献
17.
利用数值模拟方法研究了高斯光束在弱湍流大气中闪烁的空间分布问题.详细给出了计算闪烁指数的方法,分析得出了闪烁指数空间分布的一般特征:闪烁指数在光轴上最小,随着离开光轴距离的增大而增大.模拟结果与Rytov理论预期的结果基本吻合,从而验证了两种方法的可靠性. 相似文献
18.
Suzaki Y. Magari K. Kondo Y. Kawaguchi Y. Kadota Y. Yoshino K. 《Lightwave Technology, Journal of》2001,19(11):1745-1750
We propose a high-gain semiconductor optical amplifier with an integrated bent spot-size converter (BEND SS-SOA). A straight active waveguide enables us to use a pn-buried heterostructure (pn-BH) with a high current-blocking effect and uniform characteristics. We can optimize a bent spot-size converter waveguide to provide low optical feedback from the facets and high-coupling efficiency to a flat-end optical fiber with low radiation loss due to the bend. The devices we fabricated achieve a high fiber-to-fiber gain of 18 dB with a coupling efficiency of -3.5 dB, and we have demonstrated a four-channel array with uniform characteristics 相似文献
19.
Sakai Y. Kurosaki T. Sato R. Tohmori Y. Suzuki S. Mitomi O. Sugie T. 《Electronics letters》1995,31(21):1858-1860
Dynamic characteristics are clarified for a laser diode integrated with a spot-size converter coupled to a silica planar lightwave circuit. The laser was developed with a butt-jointed selectively grown spot-size converter. A maximum coupling efficiency of -0.74 dB was achieved. Bit error rate performances are estimated to clarify the allowable reflection when optical feedback from the fibre output end occurs 相似文献
20.
Bissessur H. Graver C. Le Gouezigou O. Michaud G. Gaborit F. 《Photonics Technology Letters, IEEE》1998,10(9):1235-1237
We report on a 1.55-μm InGaAsP MQW laser diode with an integrated spot-size converter fabricated in a single epitaxial step using conventional photolithography. The laser structure uses a conventional ridge guide for the active layers and a second larger ridge for the passive waveguide. Low-beam divergence of typically 9°×9° results in about 3-dB coupling losses, with a cleaved optical fiber 相似文献