Ultra-narrow bandwidth resonant reflection grating filters using the second diffracted orders

In this paper, we design resonant reflection grating filters employing the second diffracted orders as the leaky modes, then analyze the bandwidth of the reflection peak and the electric field distributions inside the wavegude under resonance. The numeric calculation confirms that ultra-narrow resonant reflection peaks can be observed in these structures. At the same time, strong electric field enhancement appears under resonance. It provides a new approach to diversify the resonant reflection filters and may open a new way to the realization of ultra-narrow bandwidth filters. (C) 2008 Elsevier B.V. All rights reserved.

Wideband tuneable fibre Bragg grating filters

A fibre Bragg grating filter device, tunable over 45 nm, is reported. The device has a wavelength setting time below 1.5 ms and a maximum tuning speed of 21 nm/ns.

Polarizing fibre Bragg grating filters and its fibre laser application

Poster

Direct design of high channel-count fiber Bragg grating filters with low index modulation

A novel method for designing high channel-count fiber Bragg gratings (FBGs) is proposed. For the first time, tailored group delay is introduced into the target reflection spectra to obtain a more even distribution of the refractive index modulation. This approach results in the reduction of the maximum refractive index modulation to physically realizable levels. The maximum index modulation reduction factors are all greater than 5.5. This is a significant improvement compared with previously reported results. Numerical results show that the thus designed high channel-count FBG filters exhibit superior characteristics including 30 dB channel isolation, a flat-top and near 100% reflectivity in each channel. © 2012 Optical Society of America.

Fibre grating filters for suppression of near infrared OH emission lines

Here we present the design and fabrication of multi-notch optical fibre Bragg gratings for suppressing OH emission lines in the near infrared spectra of the night sky for astrophysical applications. We demonstrate a novel approach of fabricating 2, 3 and 5-notch filters using the phase mask technology, which show a good match with the model.

Electric field enhancement in guided-mode resonance filters

Electric fields inside guided-mode resonance filters (GMRFs) may be intensified by resonance effects. The electric field enhancement is investigated in two GMRFs: one is resonant at normal incidence, the other at oblique incidence. It is shown that the two GMRFs exhibit different behaviors in their electric enhancement. Differences between the electric field distributions of the two GMRFs arise because coupling between counter-propagating modes occurs in the first case. It is also shown that the order of the electric field of maximum amplitude can be controlled by modulation of the dielectric constant of the grating. (c) 2006 Optical Society of America.

Compensation of reflectance response deviations of guided-mode resonant filters induced by overetching fabrication

Unless the fabrication error control is well treated, it easily causes overetched fabrication errors, which causes the resonant peak value deviation during the fabrication process of guided-mode resonant filters (GMRFs). Hence, the fabrication error control becomes a key point for improving the performance of GMRF. We find that, within the range of the groove depth from 93 to 105 nm, the relationship between the overetched error and the resonant peak value deviation is nearly linear, which means that we can compensate the reflectance response deviation and reduce the resonant peak value deviation by the method of covering the layer film on the GMRF. Simulation results show that the deviation is compensated perfectly by this way. (C) 2008 Optical Society of America

Wideband trapezoidal strip grating for elimination of specular reflection

A trapezoidal strip grating surface that eliminates specular reflections almost over the entire X -band frequency range for TM polarization is reported This new grating structure overcomes the bandwidth limitation of conventional rectangular strip grating surfaces

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器.

可见光波段双层浮雕型导模共振滤波器设计与分析

基于傅里叶模式理论分析了双层浮雕型导模共振光栅的共振效应,分别讨论了光栅的槽深、剩余厚度、周期以及填充系数对峰值反射率、带宽、旁带反射率的影响.数据计算表明,欠刻蚀情形的误差宽容度远远优于过刻蚀情形,两者在光栅槽深相对误差小于15%的范围内,都能保证共振峰的衍射效率高于99.5%,在相同的误差范围内,共振峰线宽的相对误差将分别达到7%和60%,因此厚度误差集中反映在对共振线宽的改变上.另外,光栅周期和填充系数的变化将明显改变共振峰中心波长和线宽.

Surface plasmon resonance transmission filters at 1053 nm based on metallic grating with narrow slit

Metallic gratings with narrow slits can lead to special optical properties such as strongly enhancing the transmission and considerably strengthening the polarized effect. A narrow-band filter suitable for application in optical communication is designed by sandwiching a metallic grating between two identical dielectric films. The maximum transmission can reach 96% after optimizing the parameters of films and grating at a central wavelength of 1053 nm. It is the first time, to our knowledge, that such high transmission has been reported since the discovery of the extraordinarily high transmission through periodic holes or slits; moreover, the extremely polarized effect is also found in P mode of this symmetric grating.

Optically tunable fiber grating transmission filters

We propose and demonstrate single- and multiple-passband fiber grating transmission filters that are remotely tunable by exploitation of the optical pump-induced thermal effects in Er Yb-codoped fiber sections. A repeatable, wavelength-independent induced phase shift of 0.1p mW is obtained without hysteresis and anisotropic effects. A transmission extinction ratio of .23 dB with a 3-mW change in pump power is achieved.

Near-constant time delay response of fibre grating Sagnac loop filters

A theoretical and experimental investigation of the time delay characteristics of fiber Bragg grating-based Sagnac loops (FBGSLs) is presented. Analytic expressions for the phase and time delay of the FBGSL have been derived and excellent agreement is found between their predictions and experimental results for configurations incorporating uniform-period and chirped-period gratings. For symmetrical grating structures, it is found that the FBGSL time delay response is similar to that of the incorporated grating; with asymmetrical gratings, the FBGSL response is quite different. It is shown that wavelength-division-multiplexing filters exhibiting near-zero dispersion characteristics can be implemented using FBGSLs.

Optically tunable fiber grating transmission filters

We propose and demonstrate single- and multiple-passband fiber grating transmission filters that are remotely tunable by exploitation of the optical pump-induced thermal effects in Er Yb-codoped fiber sections. A repeatable, wavelength-independent induced phase shift of 0.1p mW is obtained without hysteresis and anisotropic effects. A transmission extinction ratio of .23 dB with a 3-mW change in pump power is achieved.