相对论绕射辐射振荡器的三维粒子模拟

开展了具有同轴波纹渐变式反射器与光滑漂移段结构的相对论绕射辐射振荡器的研究,并运用全三维粒子模拟软件CHIPIC对其进行数值模拟仿真,分析了漂移段、反射器等结构对输出功率的影响,探讨了反射器位置和输出功率的关系。仿真结果表明:合适的漂移段与反射器的引入,能大大提高输出功率。优化结构参数,在输入电压480kV下,平均输出功率达到774.5MW,平均功率效率为32.3%。     

矩形槽同轴布拉格结构的模式匹配分析方法及实验验证

基于模式匹配法建立了矩形槽同轴布拉格结构的全波耦合分析模型, 推导出了不同模式反射率和传输率的计算式, 并采用公开报道的实验数据验证了该理论模型. 在此基础上就本文理论与其他相关的理论方法进行了比较, 发现以前的理论近似模型由于忽略了矩形槽中的消失模而使传输率的频率响应曲线发生偏差. 本文建立的理论方法有望为矩形槽同轴布拉格结构的特性研究和工程实践提供一种理论分析手段. 关键词： 同轴布拉格结构 矩形波纹 模式匹配法 模式耦合     

波纹误差对同轴布拉格结构反射特性的影响

利用模式匹配法建立了分析波纹参数具有随机误差的矩形槽同轴布拉格结构反射特性的理论模型,并以一个以基模(TEM)工作于220GHz附近的矩形槽同轴布拉格结构为例,研究了矩形凹槽的深度、宽度、周期长度以及位置的随机误差对其反射率频率响应的影响。数值模拟结果表明:在给定的误差范围条件下,凹槽宽度与位置的随机误差对该结构的反射性能影响较小,而凹槽深度与周期长度的随机误差是影响结构反射特性的主要因素,因此在结构的加工制备过程中应视器件性能要求严格控制两者的制造公差。     

双光栅绕射辐射器件谐振系统Q值分析与结构优化

对双光栅绕射辐射器件谐振系统的Q值特性进行了分析,研究了谐振系统结构参数对Q值的影响及其优化措施。结果表明,双光栅绕射辐射器件谐振结构的Q值受矩形槽宽度和球面开放腔长度的影响最为明显。与奥罗管相比,双光栅绕射辐射器件中光栅的引入对Q值的影响要小得多,且光栅齿宽和齿深的增加都会导致谐振系统Q值降低。     

具有坡度的同轴布喇格结构的频率响应特性

 在CST软件平台上,对具有坡度的同轴布喇格结构的频率响应特性进行了数值模拟。结果表明：具有正圆锥形坡度的同轴布喇格结构,其带宽随着所加坡度角的增大而变窄;而具有倒圆锥形坡度的同轴布喇格结构,其带宽随着所加坡度角的增大而变宽。采用窗函数技术可以有效地抑制具有坡度的同轴布喇格结构的频率响应曲线的残余旁瓣。汉明窗函数、汉宁窗函数及布拉克曼窗函数均有利于改善同轴布喇格结构作为反射器或者滤波器的性能。     

同轴波纹返波管色散特性研究及粒子模拟

 计算了同轴波纹慢波结构的色散特性，分析了波纹周期长度、波纹幅值大小以及同轴内导体半径对慢波结构色散特性的影响。研究表明内导体的存在使系统截止频率升高,系统尺寸可比普通波纹波导慢波系统更大, 并且可以采用大半径电子注并工作在低磁场状态。运用Magic软件对同轴波纹返波管进行了数值模拟, 发现同轴波导内场分布有利于注波互作用,在数值模拟基础上设计出高效率、低磁场的非均匀同轴波纹返波管,互作用效率达60%,聚束磁场小于1 T。     

高功率毫米波绕射辐射振荡器高频特性研究

 讨论了高功率毫米波绕射辐射振荡器的高频特性。利用线性理论和PIC模拟相结合的方法对器件的高频特性进行了比较仔细的分析。分析结果表明，合理地选择电子注的参量（电流、电压）及高频结构的尺寸（波纹深度、半径、周期等）可以获得较高的输出功率并且具有较好的频谱纯度。     

中等能量P波段相对论返波振荡器的理论设计与粒子模拟

提出了一种新型的中等能量P波段相对论返波振荡器,该器件将慢波结构由低波段普遍采用的同轴外波纹结构变为同轴双波纹结构,使得径向束-波作用空间扩大了2倍,一定程度上增加了器件的功率容量;另外同轴双波纹结构还较大提高了器件的时间增长率,从而有效地减小了微波输出饱和时间.经优化设计,该结构在二极管电压300 kV、电流3 kA...     

高效率超辐射相对论返波管

对新型同轴单程超辐射相对论返波管振荡器进行了进一步的研究。该振荡器的互作用区为同轴结构,外导体为一波纹波导,内导体为一光滑圆波导;辐射场从左端耦合到圆波导后输出,不需要截止颈。通过增加波纹周期数并调整互作用区末端波纹深度,器件的功率转换效率得到进一步的提高。当电子束电压为360 kV,电流为9.15 kA,外加磁场强度为2.7 T时,通过参数优化,模拟获得了瞬时峰值功率超过18 GW、脉冲宽度约400 ps,中心频率为8.1 GHz的微波输出,平均功率转换效率达到了275%。     

菲涅尔区修正圆柱面天线的辐射特性

在圆柱面上进行一维菲涅尔区相位修正结构设计，可以构成一类新型的点源馈电透镜天线。本文利用矢量场绕射理论研究菲涅尔区修正圆柱面天线的辐射特性，并进一步分析馈源阵列作用下的辐射性能。文中天线远场方向图的计算结果与有关文献中的结果吻合。     

缺陷态同轴布拉格波导传输特性

采用基于Ansoft HFSS的电磁仿真平台,研究了一个工作于Ka波段（37.5 GHz附近）的缺陷态同轴布拉格波导在不同的开槽方式及缺陷位置条件下的传输特性。结果表明:该波导只有在内外导体壁单面开槽并引入缺陷,或者双面开槽且两个开槽面同时引入缺陷的条件下才能够有效地产生出传输通带;对于后者而言,将内外导体壁的波纹初始相位差设置为且让缺陷位于波导中间时,可以获得带宽极窄、阻带抑制范围较宽的传输通带,此时,给内外导体壁的缺陷引入适度的错位能够对通带的中心频率、带宽等性能指标起到微调作用,而引入大间距的错位则能够在禁带中产生出多个通带,从而起到多通道滤波的作用。     

Analysis of the relative intensity noise behaviour in tunable two- and three-section distributed Bragg reflector lasers

A theoretical analysis is made of the relative intensity noise (RIN) in tunable two- and three-section distributed Bragg reflector (DBR) lasers by taking into account the actual frequency dependence of the Bragg reflector. The RIN is shown to depend significantly on the tuning current, especially at low frequencies and for low and moderate values of the grating coupling coefficient. For high values of this coefficient the dependence is insignificant when the tuning is performed through the DBR section, in accordance with the experimental results recently reported. The RIN spectrum is more significantly affected, however, when the phase control current in the three-section device is used for tuning.     

Mode selective properties of coaxial gyrotron resonators

In this paper, the mode-selective properties of coaxial gyrotron resonators are discussed for different cavity configurations. Expressions are derived for the ohmic loading of a coaxial conductor with longitudinal corrugations where the RF field inside the corrugations is fully taken into account, and for the diffractive quality factor in coaxial cavities with tapered inner conductor relative to that of an empty cylindrical cavity. The competing action of a kind of “surface mode” that appears in corrugated structures is investigated by considering its diffractive and ohmic quality factors. Additional mode competition problems that can arise in coaxial cavities with corrugated inner conductor due to second cyclotron harmonic interaction are investigated and solutions to the problem are proposed     

锥形半导体激光器研究进展

锥形半导体激光器具有高功率、高光束质量等特点,因此受到广泛关注并成为研究热点。从3种结构(传统结构、分布式布拉格反射(DBR)结构、侧向光栅条纹结构)的锥形半导体激光器出发,对国内外近十年具有代表性研究成果进行综述,介绍其理论研究和实验进展,并对锥形半导体激光器的未来发展进行展望。     

Spatial and spectral filtering of tapered lasers by using tapered distributed Bragg reflector grating

A 1040 nm tapered laser with tapered distributed Bragg reflector (DBR) grating is designed and fabricated. By designing the grating with tapered layout, the tapered DBR grating exhibits the scattering effect on side backward-traveling waves, thus achieving additional suppression of parasitic oscillation. Under the suppression of parasitic oscillation, the spatial and spectral characteristics of the tapered laser are improved. The experimental results show that a near-Gaussian far-field distribution and a kink-free P-I characteristics are achieved, and a single peak emission with a wavelength of 1046.84 nm and a linewidth of 56 pm is obtained.     

Lateral characteristics improvements of DBR laser diode with tapered Bragg grating

Broad area semiconductor laser (BAL) has poor lateral beam quality due to lateral mode competition, which limits its application as a high-power optical source. In this work, the distributed Bragg reflector laser diode with tapered grating (TDBR-LD) is studied. By changing the lateral width, the tapered grating increases the loss of high-order lateral modes, thus improving the lateral characteristics of the laser diode. The measuring results show that the TDBR-LD can achieve a single-lobe output under 0.9 A. In contrast to the straight distributed Bragg reflector laser diode (SDBR-LD), the lateral far field divergence of TDBR-LD is measured to be 5.23° at 1 A, representing a 17% decline. The linewidth of TDBR-LD is 0.4 nm at 0.2 A, which is reduced by nearly 43% in comparison with that of SDBR-LD. Meanwhile, both of the devices have a maximum output power value of approximate 470 mW.