反射型导模共振滤波器设计

导模共振滤波器由于其高峰值反射率，低旁带反射，窄带以及带宽可控等优良特性引起了人们极大的关注，采用亚波长光栅的导模共振效应可以实现传统基于高低折射率介质的多层膜滤波器所无法实现的特殊功能，在弱调制模式下，其共振带宽可以被压缩到零点几纳米，但是由于介质表面和空气层的菲涅耳反射，使得偏离或者远离共振区时的反射率偏高，根据等效介质理论，亚波长光栅在远离共振区可以被看为均匀的薄膜，本文通过对导模共振光栅进行单层、双层以及三层抗反射设计，有效的降低了导模共振光栅的旁带反射率，从而在可见光波段获得了性能优良的共振滤波     

反射型导模共振滤波器设计

导模共振滤波器由于其高峰值反射率,低旁带反射,窄带以及带宽可控等优良特性引起了人们极大的关注,采用亚波长光栅的导模共振效应可以实现传统基于高低折射率介质的多层膜滤波器所无法实现的特殊功能,在弱调制模式下,其共振带宽可以被压缩到零点几纳米,但是由于介质表面和空气层的菲涅耳反射,使得偏离或者远离共振区时的反射率偏高,根据等效介质理论,亚波长光栅在远离共振区可以被看为均匀的薄膜,本文通过对导模共振光栅进行单层、双层以及三层抗反射设计,有效的降低了导模共振光栅的旁带反射率,从而在可见光波段获得了性能优良的共振滤波 关键词： 导模共振 平面波导 傅里叶模式理论 窄带滤波     

缓冲层对导模共振滤光片反射光谱截止特性的影响

提出将均质多层膜系设计中的缓冲层概念71入到反射导模共振(GMR)滤光片的设计中,通过严格的耦合波理论精确计算,研究了加入缓冲层对改善导模共振滤光片反射峰边带截止深度及截止宽度的作用.双层导模共振滤光片结构中,入射光为TE偏振光时,设计增加97.5 nm缓冲层后,能够明显地展宽反射光谱范围.由原来的192.4 nm展宽到345.6 nm,并且在650～1250 nm波长范围内的边带截止度均比不含缓冲层结构的要深.入射光为TM偏振光,以类似TE结构的滤光片在布儒斯特角入射时,在700~1300 nm波长范围内,较不含缓冲层的结构,也能够获得更宽的截止带反射光谱和更深的截止度.在提出的膜系结构中,经过优化膜系、选择合适的光栅参数等,可以使反射光谱具有更好的截止特性,同时保证设计的共振峰位置不变.     

基于导模共振效应的宽带宽透射型滤波器的设计与优化

基于导模共振理论,设计了一种工作中心波长位于632.8 nm的宽带宽透射型滤波器.根据瑞利异常理论公式,计算得到瑞利波长所在的光谱位置,从而证明异常现象对滤波器的带宽产生了拓宽作用.为了优化宽带宽滤波器的结构参数,利用严格耦合波理论通过计算不同参数条件下的光谱,分析了结构参数和材料对于透射光谱在带宽和峰值效率方面的影响,选取其中最佳的结构参数数值和材料,得到峰值效率为90％、带宽为95 nm的透射光谱.该宽带宽透射型导模共振器件在显示和成像领域有潜在的应用价值.     

基于导模共振效应的宽带宽透射型滤波器的设计与优化（英文）

基于导模共振理论,设计了一种工作中心波长位于632.8nm的宽带宽透射型滤波器.根据瑞利异常理论公式,计算得到瑞利波长所在的光谱位置,从而证明异常现象对滤波器的带宽产生了拓宽作用.为了优化宽带宽滤波器的结构参数,利用严格耦合波理论通过计算不同参数条件下的光谱,分析了结构参数和材料对于透射光谱在带宽和峰值效率方面的影响,选取其中最佳的结构参数数值和材料,得到峰值效率为90%、带宽为95nm的透射光谱.该宽带宽透射型导模共振器件在显示和成像领域有潜在的应用价值.     

基于导模共振效应三基色窄带滤光片的研究

为获得性能优良的三基色窄带滤光片,提出了一种基于减反射薄膜波导光栅结构的导模共振滤光片.该滤光片由亚波长光栅结构、波导层和基底组成.采用严格耦合波理论分析了亚波长光栅结构和波导层厚度对导模共振滤光片反射光谱性能的影响.数值分析表明λ/4-λ/2-λ/4结构能有效提高导模共振滤光片的性能.当光栅结构位于基底侧时,红绿蓝三...     

带缓冲层的导模共振滤光片反射光谱特性

将均质多层膜系设计中的缓冲层概念引入到反射导模共振滤光片的设计中,以研究缓冲层的增加对导模共振滤光片反射光谱特性的影响.设计并通过严格的耦合波理论计算了一、二、三、四通道导模共振反射滤光片光谱特性.在膜系设计中增加缓冲层后.随着其厚度的逐渐增加.反射光谱中依次出现二、三、四个窄带反射峰;缓冲层厚度为796.35 nm时.当滤光片光栅层占空比在0.2～O.9范围内、光栅深度在100～200 nm变化时,共振峰的位置、反射率峰值高度几乎不变,保持了很好的多通道滤光片特性.     

基于导模共振的窄带可调谐滤波器

提出了一种分离的导模共振滤波器.该结构由光栅层和两个被空气薄层隔开的平板介质波导组成.使用时域有限差分法分析了该光栅结构在不同的结构参数下的光谱特性.研究表明,当TM偏振入射时改变空气薄层的厚度可以实现共振波长的可调谐,并且共振波长几乎随着空气薄层厚度线性变化.浅调制光栅被用于实现窄线宽特性.波长可调谐范围为1 515~1 558nm,半高全宽小于0.6nm.     

基于导模共振滤波器的波长可调谐垂直腔面发射激光器的研究

基于光栅层控制光波传播耦合波方程,设计了能够实现共振波长可调谐的亚波长光栅导模共振滤波器.通过调谐空气层的厚度,滤波器可以实现波长75nm的调谐,线宽均小于或等于1nm.将共振波长可调谐滤波器与中心波长为1.55μm的垂直腔面发射激光器(VCSEL)集成,形成了激射波长可调谐VCSEL.研究发现激射波长调谐范围与共振波长可调谐滤波器相同,而且在相同空气层厚度下,激射波长可调谐VCSEL的激射波长和共振波长可调谐滤波器的共振波长相同.该VCSEL不仅可以选择激射波长还可对输出横向模式进行选择.     

基于级联复合光栅的窄带平顶型滤波器设计

导模共振光栅作为一种重要的滤波单元,在光通信中有着广泛的应用.然而,普通的导模共振光栅的传输光谱为洛伦兹型,该类结构在高性能光纤通信系统中的应用受到限制.采用级联导模共振光栅可以实现平顶滤波响应,但是整个器件的体积较大,制作工艺复杂.此外,单一复合光栅结构难以直接实现窄带平顶滤波响应.提出了一种级联双层复合光栅结构以解决这一问题,利用严格耦合波算法和本征模式分析法分析了其输出光谱.仿真结果表明该滤波器的中心波长为1549.9 nm,其平顶光谱的线宽为0.5nm.     

Design of guided-mode resonance filters with an antireflective surface at oblique incidence

A design approach of guided-mode resonance filter (GMRF) with an antireflective surface at oblique incidence is presented. For a given incident angle or grating filling factor, the required grating filling factor or incident angle can be expressed by the analytical forms of the quadratic equations at quarter-wavelength thickness. Long-range, low sidebands are obtainable for a single-layer GMRF under the TM mode wave illumination at oblique incidence. The reflection properties such as the symmetry of the lineshape and the sideband level in the logarithm scale can be further improved by slightly varying both the grating period and the grating thickness. Magnetic field enhancement occurs in these structures due to the coupling between the evanescent diffracted order and the waveguide mode.     

High-efficiency guided-mode resonance filter

A high-efficiency guided-mode resonance reflection filter is reported. The device consists of a surface-relief photoresist grating and an underlying HfO (2) waveguide layer deposited on a fused-silica substrate. The spectral response measured with a dye-laser beam at normal incidence exhibited a peak reflectance of 98% at a wavelength of 860 nm with sideband reflectance below ~5% extending over the wavelength range provided by the dye (800-900 nm). At normal incidence the filter linewidth was 2.2 nm. High-efficiency double-peak resonances occurred at nonnormal incidence, with the spectral locations of the maxima vayring with the incidence angle. The filter response at various angles of incidence agreed well with the theoretically calculated reflectance curves.     

Design of single-material guided-mode resonance filter

In this letter, a guided-mode resonance （GMR） filter with the same material for both the grating layer and the waveguide layer is designed, and its optical properties are investigated. The GMR filter owns almost 100% reflection at the resonance wavelength of 800 nm with the full-width at half-maximum （FWHM） of 20 nm, and its sideband reflection from 700 to 1000 nm is less than 5%. As the resonance wavelength is influenced by more than one parameter during the fabrication process, GMR filter with the same resonance wavelength can be obtained by adjusting other parameters or even one parameter to deviate from the design value.     

Tunable guided-mode resonance filter based on dielectric elastomer actuators

A tunable guided-mode resonant (GMR) reflection filter based on dielectric elastomer actuators (DEA) is designed. Simulating the characteristics of the filter with rigorous coupled wave analysis, it is shown that the resonant wavelength of the kind of GMR filter can be tuned from 1442.8 nm to 1644.6 nm by applying voltage on the dielectric elastomer actuators which changes the period of the grating layer of the GMR filter conveniently. Furthermore, there is an almost perfect linear relationship of resonant wavelength tuned and the period varied with negligible effect on the linewidth.     

Narrow-linewidth bandpass filters with diffractive thin-film layers

Bandpass filters based on guided-mode resonance effects in waveguide-grating structures are obtained by use of a genetic algorithm search-and-optimization routine. Calculated examples show that narrow linewidths, high peaks, and low sideband transmittances can be achieved in thin-film diffractive devices with few layers. A filter with a linewidth of 0.2 nm at a central wavelength of 0.55 microm is demonstrated in a two-layer-two-grating structure. At 10.6-microm wavelength, a filter consisting of a single binary grating is obtained that has a linewidth of 12.7 nm and extended, low sideband transmittance. A three-layer device with a surface relief Si grating and two underlying homogeneous layers of SiO(2) and Si yields a high-efficiency filter centered at 1.55 microm with a linewidth of 0.1 nm.     

Widely tunable monolithic narrowband grating filter for near-infrared radiation

We propose a monolithic narrowband guided-mode grating filter in fused silica that is widely tunable in the near-IR wavelength region. Based on a recently demonstrated approach for a monolithic reflector comprising an encapsulated grating, we theoretically investigate such a device by means of rigorous modeling aimed at a narrow linewidth. It is demonstrated that upon a spatial variation of the filter's grating period its resonance wavelength can be tuned in a remarkably wide range of near-IR radiation with 800 nm<λ(res)< 1600 nm by translating the laser beam relative to the grating area. The filter performance in terms of linewidth and contrast is essentially preserved over the entire tuning interval.     

Tunable intensity of the spectral reflectance of a guided-mode resonance filter with dual channels

Simulating the characteristics of a guided-mode resonance filter with rigorous coupled wave analysis, we find that, by adjusting the azimuthal angle of the grating used as a sub-layer of the guided-mode resonance filter from 0° to 90° under TE-reflectance, the intensity of the spectral reflectance of the guided-mode resonance filter monotonically increases at the wavelength of 684.6 nm, while the spectral reflectance monotonically decreases at the wavelength of 723 nm. Moreover, the spectral reflectance with TE-reflectance at 90° corresponds to the TM-reflectance at 0°. The phenomenon means that the intensity of the spectral reflectance can be easily tuned with different azimuthal angles by choosing appropriate structure parameters of the guided-mode resonance filter.     

A method to accurately control the period of subwavelength planar holographic grating in the fabrication process of guided mode resonance filter

Subwavelength optical element such as guided-mode resonance filter has gained much interest recently due to its properties and applications. It is very hard to fabricate an ideal guided-mode resonance filter with the same parameters as the designed one. The reason is that the resonance wavelength of guided-mode resonance filter is susceptible to the fabrication errors of its parameters, such as the period, the groove depth, the thickness of a guided-wave layer, and the refraction indexes of materials, etc. In this article, a method to accurately control the period of subwavelength planar holographic grating which was used as a sub-layer of the guided mode resonance filter is investigated. Results show that utilizing a convex lens placed in the exposure position can cause the adjusting of the period of subwavelength planar grating more convenient in the holographic optical path during the fabrication process. Accuracy controlling the period of grating which was used as the sub-layer of guided-mode resonance filter has great significance in the fabrication of guided-mode resonance filter.     

Design of internal Brewster guided-mode resonance filter

An internal Brewster guided-mode resonance （GMR） filter is designed. For this kind of GMR filter, the Brewster reflection occurs at the interface of grating/waveguide layers rather than at the interface of air/grating layers. At Brewster angle of 60~, the GMR filter owns almost 100% reflection at the resonance wavelength of 800 nm with the full-width at half-maximum （FWHM） of 0.2 nm. Its angle response changing with the fabrication deviation is also discussed.