Compact W-band E-plane Waveguide Filter with High Selectivity

Journal of Infrared, Millimeter, and Terahertz Waves - In this letter, an E-plane substrate is inserted into the W-band standard waveguide to construct a bandpass filter (BPF) with high...     

Tapered Corrugated Waveguide Low-pass Filters

Several new synthesis techniques are described for the design of tapered corrugated waveguide low-pass filters. Previous techniques are based on image-parameter methods which are both nonoptimum and difficult to apply to new specifications. The new synthesis methods give filters which can be constructed to work directly from dimensions generated by a computer. The impedance tapering implies that the terminating impedance transformers used in the image-parameter designs may be either eliminated or reduced in length.     

Tapered waveguide InGaAs/InGaAsP multiple-quantum-well lasers

The use of ultrathin etch-stop techniques to expand the vertical optical mode size adiabatically in 1.5-μm InGaAs/InGaAsP MQW lasers using a tapered-core passive intracavity waveguide structure is discussed. 30% differential quantum efficiency out the tapered facet, far-field FWHM of ~12° and a butt-coupling efficiency into a cleaved fiber of -4.2 dB, with -1-dB alignment tolerances of ~±3 μm, were achieved     

Realization of Tapered Waveguide by Stretching the Rod Waveguide

By stretching the rod waveguide with different velocities in opposite directions, the tapered waveguide can be fabricated. In condition of taking no account of volume expansion caused by heating and under the assumptions of volume conservation,the rod waveguide can be stretched freely in the heated region without being stretched outside of the heated region. A model,which shows the relation of the transition shape and the two factors, that is the ratio of two velocity and the heated region length, is presented for the shape of the taper transition through mathematic deduction. Based on this model, a desired tapered waveguide can be fabricated. The tapered waveguide are widely used for fabricating tapered fiber couplers and sensors. In addition, the conclusion can be used for fabricating fused fiber coupler.     

High Aspect-Ratio Coplanar Waveguide Wideband Bandpass Filter With Compact Unit Cells

This paper introduces a micromachined thick single-metal-layer high aspect-ratio coplanar waveguide (CPW) wideband bandpass filter with compact unit cells based on the electromagnetic bandgap (EBG) concept. The filter is miniaturized as a result of using the EBG concept in design, and also by realizing high aspect-ratio structures with polymer-based deep X-ray lithography fabrication. Cascaded unit cells in the EBG model consist of capacitive and inductive parallel periodically loaded transmission lines, which determine the filter bandwidth. Compact unit cells are realized by using high aspect-ratio CPW stepped-impedance resonators. The main advantage of this approach is that the high aspect-ratio CPW structures make short unit cells practically realizable, resulting in a compact filter structure. A bandpass filter with 47% bandwidth is designed and fabricated using deep X-ray lithography, and the performance and physical size is compared to a conventional quarter-wavelength-based admittance inverter filter.      

A Novel Intracavity Lens Design for Compact and High Efficiency Tapered Laser Diode

An integrated parabolic lens capable of introducing a diverging effect to the optical mode propagating within the cavity of a tapered laser is proposed and demonstrated. This idea allows broader high-power beams to be generated by shorter cavities. Diverging lenses with etch depths of 0.13 and 0.27 mum are implemented, with 12 (9.5%) and 16.8 mum (13.3%) overall broadening of the near-fields widths measured at 1/e² intensity. The peak output power as well as the threshold current is found to increase following the lens etching process, confirming the beneficial broadening effect introduced by the diverging lens     

Reflection of a Pyramidally Tapered Rectangular Waveguide

The reflection coefficient Gamma of a pyramidally tapered rectangular waveguide is derived by assuming that the taper impedance is proportional to the height and guide wavelength and inversely proportional to the width of the taper cross section. It is a shown that the loci of Gamma, plotted in the K plane as a function of taper length for some conventional tapers, do not pass through the center of the chart at multiples of a half-guide wavelength as for an exponential line, but instead they converge almost concentrically. The frequency characteristic of the pyramidally tapered waveguide is compared with other types of tapers. Typical 7-kmc experimental results for several tapers differing in length are presented.     

硅基波导共振增强型光电探测器的设计与模拟

SiGe是间接带隙材料,吸收系数非常小,因而SiGe探测器在红外波段的量子效率很低.本文提出一种新型的探测器结构,即波导共振增强型光电探测器,该器件主要由两个介质布拉格反射镜和波导吸收区构成,器件尺寸较传统波导型探测器大为减小,吸收区的长度不受SiGe临界厚度的限制,实现了量子效率和响应速度的优化.本文在数值模拟的基础上,对器件结构进行了优化设计,结果表明7.6μm长的波导探测器可以得到20%以上的量子效率.     

硅基波导共振增强型光电探测器的设计与模拟

SiGe是间接带隙材料,吸收系数非常小,因而SiGe探测器在红外波段的量子效率很低.本文提出一种新型的探测器结构,即波导共振增强型光电探测器,该器件主要由两个介质布拉格反射镜和波导吸收区构成,器件尺寸较传统波导型探测器大为减小,吸收区的长度不受SiGe临界厚度的限制,实现了量子效率和响应速度的优化.本文在数值模拟的基础上,对器件结构进行了优化设计,结果表明7.6μm长的波导探测器可以得到20%以上的量子效率.     

Output Saturation and Linearity of Waveguide Unitraveling-Carrier Photodiodes

Waveguide unitraveling-carrier photodiodes (UTC-PDs) with different absorber and collector layer doping levels have been fabricated and characterized. These photodiode (PD) structures are fabricated on a platform that allows for the monolithic integration of multiquantum-well optical phase modulators and couplers for realizing novel coherent receivers. Compared to PD A, PD B has a lower and more graded p-doping profile in the absorber layer and also a higher n-doping level in the collector layer. For PD B a larger field is induced in the absorber layer at high photocurrent levels. Also the higher n-doping in the collector layer is adequate for providing charge compensation. For PD B, there is an enhancement in the RF response as the photocurrent level is increased. At a frequency of 1 GHz, the saturation current for PD A is around 65 mA and that for PD B is around 63 mA. For PD B, the third-order output intercept point at photocurrent levels of 30 and 40 mA is 37.2 and 34.9 dBm, respectively. That for PD A is 35.8 and 30.4 dBm. PD B is, therefore, favorable for linear operation at high current levels.     

Fabrication of Butt‐Coupled SGDBR Laser Integrated with Semiconductor Optical Amplifier Having a Lateral Tapered Waveguide

We have demonstrated a high‐power widely tunable sampled grating distributed Bragg reflector (SGDBR) laser integrated monolithically with a semiconductor optical amplifier (SOA) having a lateral tapered waveguide, which is the first to emit a fiber‐coupled output power of more than 10 dBm using a planar buried heterostructure (PBH). The output facet reflectivity of the integrated SOA using a lateral tapered waveguide and two‐layer AR coating of TiO₂ and SiO₂ was lower than 3 × 10^?4 over a wide bandwidth of 85 nm. The spectra of 40 channels spaced by 50 GHz within the tuning range of 33 nm were obtained by a precise control of SG and phase control currents. A side‐mode suppression ratio of more than 35 dB was obtained in the whole tuning range. Fiber‐coupled output power of more than 11 dBm and an output power variation of less than 1 dB were obtained for the whole tuning range.     

锥形光波导耦合特性研究

基于耦合模理论,数值仿真了两种耦合结构(FW和WF)下的耦合损耗随锥形光波导芯层尺寸的变换规律;进一步分析了两种耦合结构下锥形光波导端面粗糙度对其模式耦合损耗特性的影响,表明不同模式其端面散射损耗不同;实验结果表明,锥形光波导的输入端芯层尺寸、输出端芯层尺寸及光波导长度,对FW结构下的耦合损耗影响较小,对WF结构下的耦合损耗影响较大。     

On the Optimum Design of Tapered Waveguide Transitions

It has been found experimentally that the conventional optimization of waveguide tapers for the interconnection of circular waveguides with different diameters fails if the ratio in the diameters becomes too large. With the aid of an accurate numerical analysis program, the reason for the failure was found to be the reconversion from the unwanted mode to the main mode, which is neglected in all known synthesis procedures. The performance of tapers can be considerably improved by the implementation of other design equations and establishing new design criteria. This results in somewhat longer tapers. Various tapers were designed according to these procedures for a maximum of -40-dB H/sub 02/-mode level between 40 and 110 GHz, and preliminary measurements on fabricated units substantiate the improvement. It is further shown that the mode conversion at cutoff does not exhibit any singularity.     

Characteristics of Semi-conductor Laser Diode with Nonlinearly Tapered Waveguide

A novel semiconductor laser diode with nonlinearly tapered waveguide is proposed, and analyzed by a finite element beam propagation method (FM-BPM). The results show that the coupling efficiency is increased, and the laser's far field divergence is decreased effectively.     

一种共面波导馈电的双陷波渐变槽天线

为了滤除WIMAX(3.3～3.8 GHz)和WLAN(5.125～5.825 GHz)窄带信号对超宽带系统的干扰,该文提出一款共面波导馈电的小型化双陷波渐变槽天线。共面波导结构可以有效地扩展天线的带宽,实现对整个UWB(3.1～10.6 GHz)频段的全覆盖。通过在天线的馈线上开L型缝隙和在辐射贴片上开一对E字型缝隙的方法,有效实现了在3.15～3.97 GHz和4.94～6.05 GHz频段的双陷波特性,能够抑制WIMAX和WLAN对超宽带系统的干扰。该天线结构简单紧凑,尺寸非常小,仅为40 mm×18 mm×0.813 mm。仿真和实测结果表明该天线在超宽带波段内具有良好的陷波特性、增益特性,可以应用于小型化超宽带系统中。文中方法对于陷波渐变槽天线的研究具有一定的借鉴意义。     

一种带有锥形多模过渡区的Y分支光波导

为减小Y分支波导的分支损耗,提出在输入波导和两输出波导间引入锥形多模过渡波导.与已被用于减小Y分支波导分支损耗的矩形多模过渡波导相比,所引入的锥形多模过渡波导,不仅可以减小过渡波导的长度,还可进一步减小分支损耗.利用三维有限差分光束传播法,对具有锥形过渡波导的退火质子交换铌酸锂Y分支光波导进行了数值模拟.数值结果为该类Y分支光波导的设计和制备提供参考.     

基片集成波导正弦渐变槽单脉冲天线

为拓展工作带宽,以传统正反渐变槽天线为基础,利用基片集成波导馈电,该文提出了两种高增益、宽频带的正弦渐变槽天线。利用矩形波导3 dB定向耦合器和90移相器工作原理设计了半模基片集成波导单脉冲馈电网络,进而得到了对称型和非对称型正弦渐变槽单脉冲天线,带宽均超过了3.0 GHz,带内和波束最大增益在9.0 dBi左右,差波束零深在10.0 GHz处均低于-20 dB。其中,非对称型正弦渐变槽单脉冲天线具有更宽的工作频带和更平稳的天线增益,可以广泛应用于微波定向探测系统中。     

一种结构紧凑的毫米波波导滤波器的设计

提出了一种新颖的毫米波波导滤波器的设计方法,以常用的H面膜片波导滤波器为基础,配合并不常用的基于磁耦合原理的波导同轴转换,从波导短路端面引入E面耦合环,使输入输出方向在一条直线上,并将两者做一体化设计,在保证良好性能指标的情况下,结构设计更为紧凑,体积更小。该设计保证了在星载或机载设备上空间结构受限的情况下,器件安装与电缆连接的便利。借助HFSS全波电磁场仿真,成功地运用在中心频率30GHz毫米波波导带通滤波器的设计上,使设计方法更为简便实用。     

电极分离的980nm锥形激光器的研制

对脊形波导区和锥形区电极分离的980nm锥形激光器(简称电极分离的980nm锥形激光器)改变脊形波导区所加电流,测试激光器的P-I特性和光束质量因子,与脊形波导区和锥形区共用电极的980nm锥形激光器(简称电极共用的980nm锥形激光器)的测量参数进行对比.发现电极分离的980nm锥形激光器的P-I特性曲线比较光滑,没有明显的扭折.随着脊形波导区的电流逐渐超过150mA以后,器件的最大输出功率逐渐达到4.28W,与电极共用的980nm锥形激光器相同并趋于饱和,光束质量因子从3.79降到2.45(输出功率为1W).     

Design of High Dynamic Range Fully Integratable Translinear Filters

This paper addresses the non-linear noise and dynamic-range properties of bipolar and MOS (both in weak and in strong inversion) translinear integrators, following a systematic top-down approach. Several design principles to achieve an optimal dynamic range are derived. A qualitative comparison of a bipolar or weak-inversion class-AB translinear integrator and the well-known linear g _m – C integrator reveals that the former is an interesting candidate, especially for low-voltage and/or low-power operation. As an example, a ±1.65-V bipolar translinear integrator is presented that makes dynamic-range optimization possible by adjusting just one bias current. Its application in an audio filter yields a 63-dB dynamic range and a virtual dynamic range of 76 dB, while the current consumption can be as low as 310 nA.