矩(方)形激光波导共振腔的耦合损耗

本文利用数值法计算了矩(方)形激光波导共振腔反射镜对最低阶波导模(EH11模)的耦合损耗。文中给出了在不同矩(方)、形波导截面尺寸下,耦合损耗与反射镜位置、曲率半径、波导截面尺寸间的依赖关系。     

矩形波导CO_2激光器谐振腔耦合效率研究

为了实现波导CO_2激光调Q脉冲输出,需要搭建半外腔激光器以在谐振腔内插入Q开关。实验研究了波导纵横比m=2的半外腔矩形波导CO_2激光器的输出功率与谐振腔光学结构参数之间的关系,对比了平面反射镜紧贴波导口激光器的输出功率,得到谐振腔模式耦合进入波导口的损耗与谐振腔全反镜曲率半径R以及全反射镜至波导口的距离d的关系。基于菲涅耳衍射积分理论,采用变步长辛普森算法理论计算了m=2的矩形波导谐振腔耦合效率与R、d之间的关系。基于实验及理论结果,得到了适合高纵横比矩形波导CO_2激光器半外腔搭建的两个耦合效率较高的谐振腔光学及结构参数:d=10mm、d=R的位置,并且R越大这两个位置对应的耦合效率越高。     

GaAs激光器激发带球面透镜圆柱套层光波导纤维的理论分析与计算

本文分析和计算了GaAs激光器对带球面透镜圆柱套层光波导纤维的模式激发效率,给出了获取最佳耦合的参数,得到基模的激发效率可高达90％以上。     

二维光子晶体对耦合波导激光器侧模的调制研究

利用光子晶体的自准直效应来调制耦合波导激光器的侧模,并用时域有限差分（FDTD）方法对五通道和九通道耦合波导激光器进行仿真,成功改变了模式的传播方向,使得相邻光场之间的相位差从兀变为零。在两种耦合波导结构中分别获得了远场发散角为12°和7°的单峰,既兼顾了激光器的稳定性,又得到了高质量的光束。     

EAST 装置电子回旋共振加热系统波纹圆波导研究*

在EAST装置上正在建设140GHz/4MW/1000s电子回旋共振加热(ECRH)系统,单个回旋管输出的1MW功率通过波纹圆波导传输到天线聚焦镜上,然后经天线反射镜进入等离子体。运用表面阻抗法对波纹圆波导进行了理论分析,针对EAST装置ECRH系统需求的140GHz波纹圆波导进行了设计研究,所设计的波导传输模式为HE11模,具备1MW连续波运行能力且欧姆损耗低于0.02d B/100m,同时分析了HE11模在波导口外辐射模式及其与TEM00模耦合特性。     

矩形空心介质波导激光谱振腔的理论分析

本文发展了一种矩形空心介质波导激光腔的理论分析方法并给出其数值计算结果。这种方法采用多模近似理论,并以一个变换矩阵来表示腔内复杂的传输过程,使复杂的谐振腔模的特性得以简单而准确的描述。 通过对CO_2波导激光腔典型结构的计算,着重讨论了波导入口光斑尺寸对耦合效率的影响,球面反射镜参数与腔模特性的关系,最低损耗模的模式组成与模式选择性,平镜腔的近区特性以及波导结构、介质材料光学常数对腔模损耗特性的影响等;并对其中某些问题提出一些新的见解,为波导激光器的研究和设计提供了一系列有益的数据和结论。     

基于微环谐振腔的耦合谐振光波导反射镜

研究了一种基于微环谐振腔的耦合共振光波导反射镜.基于耦合模理论,对这种新型波导反射镜的反射光谱进行了数值分析,详细讨论了直波导与微环谐振腔之间的耦合系数和相邻微环谐振腔之间的耦合系数对反射光谱的影响.计算结果表明这种反射镜的反射光谱存在多峰结构,在弱耦合的情况下可以实现波长选择性反射滤波,并且发现在这种波导反射镜中存在类似于原子系统中电磁诱导透明现象的耦合共振诱导透明现象.     

CO_2波导激光器的最佳化

计算了内腔封离型CO_2波导激光器的EH_11波导模的传输和耦合损耗,设计并制造了内腔封离型CO_2波导激光器.器件的最高输出功率为3.57W,单位激活长度和体积的输出功率分别为0.27W/cm、17.3W/cm~3.     

医用波导CO2激光器

本文报导一种符合医用要求的新型玻璃波导CO2激光器。该器件采用大孔径玻璃波导（d=3～4mm）。提出近场非匹配凹面镜选模的新方法和整体冷却管体的新结构。激光器全长310mm时，能得到输出功率8W左右的稳定基模。连续工作寿命大于1000小时。     

基于表面等离子波导的面发射分布反馈量子级联激光器的分析

分析了基于表面等离子波导的面发射分布反馈量子级联激光器。通过在金属层上刻蚀二级光栅,实现了强的反馈。光的模式性质用耦合模理论来描述,其中,耦合系数从无限周期性结构的Floquet-Bloch解推导而来。基于此理论,获得了优化的面发射二级分布反馈量子级联激光器结构,其中,面耦合效率高达43%,而阈值为12 cm-1。这些结果表明,相对于基于传统介质波导的面发射分布反馈量子级联激光器（典型的值为面耦合效率17.5%,阈值增益20 cm-1）,基于表面等离子波导的面发射分布反馈量子级联激光器的性能有很大的改进。     

Optimized overmoded TE01-to-TM11 mode converters for high-power millimeter wave applications at 70 and 140 GHz

Mode coupling in bent, oversized, smooth-wall circular waveguides was studied by means of numerical integration of coupled-mode differential equations in order to optimize high-power TE01-to-TM11 mode transducers at 70 GHz and 140 GHz. Such mode transformers are used in the mode conversion sequence TEOn to TE01 to TM11 to HE11 for generating the almost perfectly linearly polarized Gaussian-like HE11 mode from circular electric TEOn gyrotron modes. This quasi-optical HE11 hybrid mode is in many respects ideal for electron cyclotron resonance heating (ECRH) of magnetically confined plasmas in thermonuclear fusion research and for other technical applications. Curvature and ellipticity coupling as well as ohmic attenuation of 6 coupled modes (TE01, TM11, TE11, TE12, TE21, TM21) are included in the coupling matrices. Integral expressions were used for deriving the coupling coefficients for arbitrary modes in bent, smooth-wall waveguide. Lowest level of unwanted spurious modes together with highest transmission efficiency (shortest arc length) is achieved with sinusoidal curvature distribution instaed of constant curvature. The calculated conversion efficiencies of 98.0% at 70 GHz and 95.2% at 140 GHz (interior waveguide diameter D=27.8 mm for 200 kW transmission lines) are in excellent agreement with the measured values of (97.6±0.4)% and (95±1)%, respectively.     

Light Out‐Coupling Management in Perovskite LEDs—What Can We Learn from the Past?

The research on perovskite light‐emitting diodes (PeLEDs) has experienced an exponential growth in the past six years. The highest external quantum efficiencies (EQEs) have surpassed 20%, 20%, and 10% for red, green, and blue colored LEDs, respectively. Considering the internal quantum efficiency is already approaching unity owing to the high material quality, the limiting factor for further improving the EQE is mainly the poor light out‐coupling efficiencies. Here, by reviewing the progress on the light out‐coupling studies for PeLEDs, organic LEDs (OLEDs), conventional semiconductor LEDs, and other special LEDs, the rational design guidelines are summarized for enhancing PeLED out‐coupling. Briefly, these design guidelines include: 1) introducing nanostructures into the active layer or tuning the thickness of it to couple out the waveguide modes, 2) adding nanostructures between the active layer and transparent electrodes to couple the waveguide modes to substrate modes, 3) adding nanostructures such as nanowires to the glass substrate to couple the substrate mode to air. Essentially, these guidelines indicate that implementing nanophotonic engineering on PeLEDs is a highly promising direction to explore, so as to substantially enhance the device performance.     

同轴TE_(11)~⊙模与矩波导TE_(10)模的耦合计算

首先建立同轴 TE1 1 ⊙ 模与圆波导 TE1 1 o 模的等效关系。进而将同轴 TE1 1 ⊙ 模与矩波导 TE1 0 模的耦合问题转化为其等效圆波导 TE1 1 o 模与矩波导 TE1 0 模的耦合问题。实验证明 ,理论计算与实测结果吻合     

用波导激光理论讨论自由电子激光辐射的传输

本文提出新的建议,用波导激光理论来处理自由电子激光辐射的传输问题。研究表明,存在特定的低损耗传输模。介质波导中电磁场为EH_(11)模。讨论了模的耦合损耗。     

On the Mode and Square Correspondence Between Circular Multimode Tapered Waveguides

In an axially straight multimode circular waveguide taper excited with a pure TE/sup /spl circle// /sub 11/ dominant mode, the first and only converted mode at and near cutoff is the TM/sup/spl circle// /sub 11/ mode. It is shown that in an axially straight multimode square waveguide taper excited with a pure TE/sup/spl square// /sub 10/ dominant mode, the TM/sup/spl square// /sub 12/ mode corresponding to the TM/sup/spl circle// /sub 11/ mode in circular case is not the only first converted mode at and near cutoff. The overall behavior or coupling mechanism of waveguides is similar whether the waveguide is rectangular, square, circular, or elliptical: i.e., the overall coupling coefficient at cutoff of a converted mode or modes approaches an ininfinity of the order 0/sup -1/4/.     

Finite-aperture waveguide-laser resonators

A general theory of finite-aperture waveguide-laser resonators is developed which represents the external reflectors by matrices which couple linearly polarized waveguide modes having the same azimuthal symmetry. The theory allows the determination of resonator efficiency, resonator frequencies, and laser near- and far-field patterns. Computations of the coupling loss for the fundamental waveguide mode as a function of mirror curvature, separation, and aperture are in good agreement with recent infinite-aperture calculations in the limit of large apertures and indicate three low-loss configurations: 1) large radius of curvature mirrors close to the guide; 2) "large" radius of curvature mirrors centered at the guide entrance: and 3) generally smaller curvature mirrors separated by half their curvature from the guide entrance. The importance of higher order waveguide modes in determining laser output power and far-field patterns is demonstrated experimentally and compared to theoretical predictions. Design guidelines for the construction of high-efficiency CO2, CO, and He-Ne waveguide-laser resonators are summarized in tabular form.     

Coupling losses in hollow waveguide laser resonators

Hollow waveguide gas lasers of the type described by Smith have some inherent loss in coupling radiation from the guide into free space and back into the guide. This paper calculates that loss for the EH11lowest order waveguide mode as a function of mirror position and mirror radius. It is shown that some mirror positions and radii are optimum, in that they provide low coupling loss and are relatively insensitive to mirror position.     

Non-polarization and high-coupling-efficiency coupler using multilevel grating structure

A multilevel grating coupler based on silicon-on-insulator (SOI) material structure is proposed to realize the coupling between waveguide and waveguide or waveguide and fiber. This coupler is compatible with the current fabrication facilities for complementary metal oxide semiconductor (CMOS) technology with vertical coupling. This structure can realize coupling when the beams with transverse electric (TE) polarization and transverse magnetic (TM) polarization are incident at the same time. The influences of the grating coupler parameters including wavelength, the thickness of waveguide layer, the thickness of SiO₂ layer and the number of steps on the TE mode and TM mode coupling efficiencies are discussed. Theory researches and simulation results indicate that the wavelength range is from 1533 nm to 1580 nm when the TE mode and TM mode coupling efficiencies are both more than 40% as the grating period is 0.99 μm. The coupling efficiencies of the incident TE and TM modes are 49.9% and 49.5% at the wavelength of 1565 nm, respectively, and the difference between them is only 0.4%.     

射频激励增益波导CO2激光器的光强分布

提出了一种新的射频(RF)激励增益波导阵列CO2激光器技术。为了提高输出激光光束质量,增强多个波导通道之间模式的耦合,通过在上电极刻上等距离的凹槽,形成一个个并列的子电极,使增益在电极横向具有周期分布特征。同时使用表面刻有周期性凹槽的相移全反射镜,实现了远场光束的极强相干叠加。研究了其近场和远场的光强分布情况。在气压为10.0 kPa,10.7 kPa的情况下,近场为长20 mm的若干个尖峰分布,远场为中心压窄的极锐尖峰。随着时间变化,只有光强峰值变化,相对强度分布保持不变。