A versatile moment method solution of the conventional and modifiedcoplanar waveguide T-junctions

The conventional and modified coplanar waveguide (CPW) T-junctions, both symmetric and nonsymmetric, are investigated using the full wave moment method with duality for the electric and magnetic currents. The method is shown to be accurate and computationally more efficient than the finite-difference-time-domain (FDTD) method previously used to solve these T-junctions. The results show that the dispersion in the S-parameters of the different types of CPW T-junctions investigated can be minimized by a proper choice of the dimensions and locations of the air bridges. The versatility of the method is demonstrated by its ability to solve complicated CPW structures with different types of air bridges, such as the modified CPW T-junction     

Wide-band guided-wave acoustooptic Bragg cells in GaAs-GaAlAs waveguide

One of the key components in future GaAs-based monolithic integrated acoustooptic modules or circuits is an efficient and wide-band acoustooptic Bragg cell. In this paper, design, fabrication, and performance characteristics of compact miniaturized GaAs-GaAlAs waveguide acoustooptic Bragg cells that operate at the acoustic frequency from 190 to 625 MHz are reported. A 201 MHz bandwidth has been obtained with the Bragg cell that employs a single tilted-finger chirp transducer centering at 360 MHz. The acoustic propagation losses in the GaAs-GaAlAs waveguides that were measured using acoustooptic Bragg diffraction as a probe are also presented.     

High-efficiency native-oxide-passivated high-index-contrast ridge waveguide lasers

A GaAs-based high-index-contrast ridge waveguide laser is fabricated using a self-aligned process of deep dry etching plus oxygen-enhanced wet thermal oxidation of low Al-content AlGaAs. Lasers operating at /spl lambda/=813 nm (CW, 300 K) with external differential quantum efficiencies as high as 78% are demonstrated, indicating effective passivation of the directly-oxidised etched active region sidewall surface.     

Airbridged high-speed AlGaAs-GaAs ridge waveguide lasers

The design of a high modulation response multiple-quantum-well ridge waveguide laser in AlGaAs-GaAs, with low parasitics is discussed. The device was fabricated on a semi-insulating substrate with a wide top contact, and airbridges have been used to connect the ridge top contact to the bonding pads on the semi-insulating substrate. The 3-dB frequency response of the laser has been measured to be 21 GHz, which is a record for unstrained quantum-well AlGaAs-GaAs lasers.     

一种新颖的脊波导功分器

针对通常波导传输的功率分配器中T形接头体积大的不足,基于脊波导和阶梯阻抗变换对导波系统中电磁波传播性能的影响,提出了一种新颖的脊波导H面T形分支结构,利用高频仿真软件HFSS进行仿真优化,结果显示该结构在全X波段内匹配。以此结构为基础,设计加工一个一分六的脊波导功分器,得到较好的实测结果。实际内部尺寸比普通波导功分器减小46%,回波损耗小于20 dB,单路信号波动在±0.35 dB内。这种脊波导H面T形分支结构简单,适合于实际的工程应用。     

Low-divergence single-mode ridge waveguide diode lasers

Ridge waveguide laser diodes of a GaAs-AlGaAs separate-confinement graded-index monolithically stacked triple-quantum-well structure have been fabricated. Chemically assisted ion beam etching (CAIBE) was used to etch a 4- mu m-wide mesa which serves as the waveguide for the device. Results for 4- mu m-wide by 600- mu m-long optically coated devices are presented. Single-longitudinal mode, CW output power in excess of 90 mW and a far-field divergence of 21 degrees *3.5 degrees are demonstrated.<>     

Asymmetric ridge waveguide radiating element for a scanned planararray

A novel linear array radiating element for use in a large low-sidelobe, planar slot array electronically scanned in azimuth is described. The planar array consists of many vertical resonant linear array elements; i.e. single ridge waveguides with broadwall shunt slots, closely spaced to avoid array grating lobes when the array is scanned in azimuth. Traditional linear broadwall slot arrays require alternating slot displacement from the waveguide centerline, which generates undesirable secondary beams in skewed directions during electronic scan. To eliminate the secondary beams, a design has been devised in which all slots are exactly collinear and lie on the waveguide centerline. The methods considered to achieve the required waveguide asymmetry, the design procedure used in the successful approach, and the experimental results obtained with a demonstration model are presented     

脊的变化对双脊波导场图的影响分析

对称双脊波导脊的大小变化改变其传输特性参数,采用亥姆霍兹方程有限元方法计算出双脊波导主模截止波长数值,结果与文献结果对比说明计算方法精确有效,求对应的特征向量,就可得到脊波导横截面上的电场分布,从而分析脊大小变化对场结构图的影响。     

Compact ridge waveguide slot antenna array fed by convex waveguide divider

A ridge waveguide longitudinal-slot antenna array with a compact transverse dimension is introduced. To broaden the bandwidth of the array, it is divided into two sub-arrays fed by a novel compact convex waveguide divider. A 16-element uniform linear array at X-band was fabricated and measured to verify the validity of the design. The measured bandwidth of S/sub 11//spl les/-15 dB reaches 14.9% while the measured cross-polarisation level is less than -36 dB over the entire bandwidth.     

基片集成脊波导传输特性的研究

将构成基片集成脊波导脊的一排金属针等效成实金属脊。基于基片集成波导等效宽度计算公式推导了基片集成脊波导等效脊宽的计算公式。运用横向谐振法推导了TE_m0模基片集成脊波导截止频率的计算公式,同时运用这些公式分别计算了TE₁₀模、TE₂₀模和TE₃₀模基片集成脊波导的截止频率,并与仿真软件计算的结果和参考文献所给结果进行了比较。结果显示:利用所给公式计算的结果具有较高的精度,且使用方便。此外,还研究了截止频率与脊宽和脊隙之间的关系,对一种适合宽带应用的宽脊结构进行了讨论。     

Design and fabrication of ridge waveguide folded-cavity in-planesurface-emitting lasers

A 45° angled reactive ion etching combined with an in situ monitoring technique was used to fabricate ridge waveguide folded-cavity in-plane surface-emitting lasers. This laser structure, with two 45°C angle-etched internal total-reflection mirrors and an epitaxially grown distributed Bragg reflector, is very promising for OEIC applications. Laser-structure design and laser fabrication are addressed. A continuous-wave threshold current of 8 mA, the lowest reported in the literature, was achieved on 3-μm-wide, 350-μm long devices     

Design of layered ridge dielectric waveguide for millimeter and sub-millimeter wave circuits

Design rules for Layered Ridge Dielectric Waveguide (LRDW) are presented for the first time through simple figures and closed form equations. The Effective Dielectric Constant (EDC) method is used to develop the design rules that account for typical circuit specifications such as higher order mode suppression, dispersion, attenuation, and coupling between adjacent transmission lines. Comparisons between the design of LRDW, image guide, and millimeter-wave dielectric ridge guide are made.     

Analysis of a ridge waveguide using overlapping T-blocks

A T-block (TB) approach is proposed to analyze the dispersion relation of a ridge waveguide. The field representations of a TB are obtained with the Green's function and mode-matching technique. Rigorous, yet simple dispersion equations for symmetric and asymmetric ridge waveguides are presented using a superposition of overlapping TBs. The rapid convergence characteristics of the dispersion equation are illustrated in terms of the cutoff wavenumbers. A closed-form dispersion relation, based on a dominant-mode approximation, is shown to be accurate for most practical applications such as couplers, filters, and polarizer designs.     

A distributed feedback ridge waveguide quantum well heterostructurelaser

A method for incorporating distributed feedback in a ridge waveguide laser by means of lateral gratings and a single growth step is discussed. The necessary Bragg condition for distributed feedback is satisfied by etching gratings along the ridge in the top confining layer of the laser on either side of the contact stripe. Both Fabry-Periot modes and a single emission peak away from the peak of the gain profile are observed in lasers with cleaved facets. The Bragg reflection emission peak does not shift with increasing drive current, which is characteristic of a distributed-feedback (DFB) laser     

Multi-λ ridge waveguide gain-coupled DFB laser array

Multi-wavelength gain-coupled quantum well DFB laser array has been fabricated on an InP substrate by simply varying the ridge waveguide width of the element lasers. Owing to the gain-coupling effect, seven singlemode lasing wavelengths around 1.55 μm with ~2 nm spacing were obtained simultaneously. The lasers had low threshold currents and small beam divergence     

One dimensional scaling of 100 ridge waveguide amplifiers

We have demonstrated the concept of scaling large numbers of laser diodes to achieve high power with good beam quality. We have achieved a system based on scaling 100 ridge waveguide amplifiers with a coherent optical signal distribution network and phase modulators on a 12.2 mm×4.4 mm chip called a unit cell. The unit cell delivers 1.63 W of CW power in the central lobe with diffraction-limited performance. A high performance cooler allows high power CW performance. A custom lens array and computer-controlled phase modulators allow the beam to be collimated with flat phase front     

低阈值电流、高量子效率脊形波导激光器

研制了低阈值电流、高量子效率670nm压缩应变单量子阱GaInP/AIGalnP脊形波导激光器。测量解理成的激光器条,腔长为300μm时,阈值电流为12．8mA,双面外部量子效率之和达到94．6％。     

脊双模波导滤波器的分析及设计

介绍了一种能实现脊双模波导滤波器的新型结构,分析了其腔内模式的耦合极性,利用不同的耦合极性对频率响应的影响可实现具有一对传输零点的双模滤波器,也可实现无传输零点的双模滤波器.以相同脊谐振单元不同的放置方向组成的两种带通滤波器为例,利用AnsoftHFSS仿真得到了两种不同的频率响应,结果与理论分析一致.最后设计出了一个六阶三传输零点的双通带滤波器,带内插损均小于0.6 dB,回波损耗小于-15 dB.     

High-efficiency GaInP-AlGaInP ridge waveguide single-mode lasersoperating at 650 nm

In this letter, the authors report a very high quantum efficiency of 91% for antireflection/high-reflection-coated GaInP-AlGaInP ridge waveguide laser diodes operating at 650 nm range. The laser structure was grown by solid-source molecular beam epitaxy. The laser diodes performed stable single-mode operation up to 60 mW. Threshold current as low as 50 mA was measured for 5.5×600 μm² laser diodes. To the authors' best knowledge, this is among the best ever reported efficiency for visible lasers     

Gain saturation in traveling-wave ridge waveguide semiconductor laser amplifiers

The saturation behavior of traveling-wave ridge waveguide diode amplifiers is studied both numerically and analytically. It is shown that an 'effective saturation power' can be used to characterize the saturation of these devices by up to 4 dB. The effective saturation power, which is sensitive to device geometry, carrier density, and operating wavelength, is useful in the design of the ridge waveguide optical amplifiers.<>