共查询到20条相似文献,搜索用时 46 毫秒
1.
An analytic treatment and computer calculations of the spectral properties of novel interference microwave filters are carried out. A filter is represented by a set of plane-parallel polarizing gratings made of linear conductors whose orientation in neighboring gratings is chosen in a special way. The analysis is based on the assumption that the polarization properties of the gratings are perfect. 相似文献
2.
We determined the magnetic field of a bifilar lead with circular cross-section having arbitrary permeabilities and radii of
the conductors. the separation of variables method has been used and field patterns have been mapped. 相似文献
3.
Long-period fiber gratings based on periodic microbends 总被引:6,自引:0,他引:6
We demonstrate a new type of high-performance long-period fiber grating based on arc-induced periodic microbends. The fabrication method is simple and does not require special fibers. Flexibility in controlling the filter parameters makes it possible to produce arbitrary filter profiles by use of a simple apodization technique, which is difficult to do with conventional long-period gratings. 相似文献
4.
The formation of holographic transmission and reflection gratings is examined taking into consideration photoinduced absorption
in photopolymer materials. The holographic gratings are assumed to be formed by light beams with arbitrary amplitude profiles.
The problem is solved analytically in the zero-and first-harmonic approximation of the monomer concentration and refractive
index with allowance for the interference-pattern contrast, an arbitrary degree of photopolymerization nonlinearity, and the
dependence of the diffusion coefficient on the degree of polymerization. The effect of beam-amplitude profiles and light-induced
absorption on the spatial profiles of holographic gratings is studied using numerical simulation. The effect of light-induced
absorption on the diffraction characteristics of holographic gratings is discussed.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 81–89, October, 2006. 相似文献
5.
Transition radiation that arises when a charged particle passes through two consecutive plane gratings is considered. The gratings are made up of parallel metal wires. The planes of the gratings are parallel to each other and perpendicular to the direction of motion of the particle. The conductors of one of the gratings are perpendicular to the conductors of the other. It is shown that the generated transition radiation has elliptic polarization; the ellipticity and the sign of rotation depend on the angle of radiation, the distance between the gratings, and the velocity of the charged particle. 相似文献
6.
Methods for calculating the spectral properties of multilayer anisotropic structures are described. The structures comprise plane-parallel polarizing gratings made of linear conductors. The conductors in adjacent gratings are arbitrarily directed. The methods employ mathematical approaches used in the interference optics of multilayer isotropic structures. 相似文献
7.
Temperature-Insensitive Fibre-Optic Acceleration Sensor Based on Intensity-Referenced Fibre Bragg Gratings
下载免费PDF全文
![点击此处可从《中国物理快报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A temperature-insensitive acceleration sensor using two fibre Bragg gratings (FBGs), based on reflection spectrum intensity modulation and optical power detection, is proposed and demonstrated. A cantilever beam is used to generate acceleration-induced axial strain along two sensing gratings, which are glued on the two opposite surfaces of the beam. Because the two gratings operate within the linear spectral range of a light source, formed by a thermally-tunable extrinsic Fabry-Perot optical filter, the intensity difference of the two reflections from the gratings is proportional to the acceleration applied. This eliminates the need for sophisticated wavelength interrogation of the gratings, and it also endows the sensor with immunity to temperature variation. Compared with a commercial micromachined accelerometer, the sensor is proven to be capable of accurately detecting acceleration. 相似文献
8.
Tiwari U Tripathi SM Thyagarajan K Shenoy MR Mishra V Jain SC Singh N Kapur P 《Optics letters》2011,36(19):3747-3749
We propose and demonstrate a wavelength tunable wavelength division multiplexing channel isolation filter based on two concatenated chirped long-period fiber gratings (LPGs). An intergrating space (IGS), deliberately introduced between the two gratings, provides an extra phase difference between the core and cladding modes. Changing this phase by heating the IGS without affecting the gratings tunes the channels. A theoretical account of the filter action is also presented and the results are found to be in excellent agreement with the experiments. Unlike the filters based on normal concatenated chirped LPGs without an IGS, the current filter shows a linear tuning over an increased spectral range. 相似文献
9.
Xuefeng Yang Dao Hua Zhang Zhengji Xu Yueke Wang Jun Wang 《Applied physics. B, Lasers and optics》2012,109(2):215-219
We report one- and two-dimensional arbitrary patterns which are achieved by nanocavity waveguides made of a quasi-metal?Cdielectric-metal heterostructure with omnidirectional illumination. This proposed heterostructure supports the surface plasmon polaritons whose phase and group velocities have opposite sign for given frequency. Negative refraction and reflection in the waveguide result in imaging nanolithography and the omnidirectional property can be well understood by the dispersive relation of the nanocavity waveguide. Numerical results demonstrate that such an omnidirectional nanolithography scheme is feasible for arbitrary 1D gratings and 2D linearly chirped gratings with TM and circular polarized incidence, respectively, at 365?nm. 相似文献
10.
We report on the time-domain differentiation of light waves by metallic transmission gratings. Time-resolved terahertz experiments show that the first time derivative of an arbitrary waveform can be achieved by use of gratings of subwavelength period. The results are in accord with classical diffraction theory and may permit novel applications for tailoring few-cycle light pulses and ultrahigh-frequency optoelectronics. 相似文献
11.
We show that the strength of long-period gratings recorded in boron-doped fibers by CO2 radiation can be significantly enhanced by a uniform pre-exposure by the same laser. The resultant gratings could be erased by a similar uniform exposure and then recorded again multiple times with no loss of fiber sensitivity. We suggest that such gratings are formed by reversible densification of the fiber core. These densification gratings have higher thermal stability than gratings written with ultraviolet light. 相似文献
12.
13.
Single-longitudinal-mode dual-wavelength fiber ring laser by incorporating variable saturable absorbers and feedback fiber loops 总被引:1,自引:0,他引:1
A single-longitudinal-mode dual-wavelength fiber ring laser is proposed and demonstrated experimentally by introducing feedback fiber loops and a variable saturable absorber in a fiber ring cavity. A dynamic ultra-narrow bandpass filter is formed by the combined interactions of cascaded fiber Bragg gratings, feedback fiber loops and low-pumped erbium-doped fiber. Both ultra-narrow bandpass filter and accurate control for the cavity length are not required for the single-longitudinal-mode performance. The proposed scheme offers a possibility of generating terahertz waves by photomixing the lasing wavelengths in a high-speed photodetector. 相似文献
14.
The filter made up of two gratings performs as a two-dimensional non-spatial filtering. This paper reports that the volume Bragg gratings are fabricated by interfering two collimated coherent laser beams in photopolymer. Diffraction efficiency of a single grating is up to 78% in Bragg's condition, then a two-dimensional non-spatial filter, which consists of two volume Bragg gratings and a half-wave plate, enables the laser beam filtered in two dimensions with the diffraction efficiency of 54%. The Bragg's condition and effect of polarisation on performances of the two-dimension filter are also discussed. 相似文献
15.
Abstract A novel approach to implement high flattened comb filters with precise channel spacing based on DC phase compensation is proposed. Channel wavelength error and peak reflectivity variation are discussed and calculated. A phase compensation method by simply changing the DC refractive index is proposed. Fiber Bragg gratings with different DC phase shifts are fabricated, which indicates that an arbitrary DC phase shift can be introduced precisely. A high flattened comb filter with precise 50-GHz channel spacing is realized with the help of a micrometer-precision translation stage. Then the peak reflectivity variation with and without phase compensation for different chirp coefficients is researched. 相似文献
16.
A modified phase contrast method is described for the fabrication of holographic optical elements with in-line diffraction patterns. In this method, a liquid crystal phase modulator is addressed by computer-generated holograms to achieve variable phase gratings. The phase gratings are imaged onto photosensitive material by a phase contrast method without a Fourier filter. We show the analytical treatment of the modified phase contrast method and demonstrate the application in holographic recording. 相似文献
17.
A comparison of the optical path and differential equation methods for optically thin phase gratings
It is shown that the optical path method may lead to an approximate solution of the wave equation valid under a wide range of conditions for slanted phase gratings of arbitrary profile. Analytic solutions are given for sinusoidal and sawtooth gratings, and the accuracy of the approximations is checked by comparison with numerical solutions. The conditions under which sawtooth gratings may yield 100% efficiency are clarified. 相似文献
18.
Zhao Zhiyong Zhang Shuang Yu Yongsen Zhuo Zhongchang Zhang Jian Zheng Wei Zhang Yushu 《Optical and Quantum Electronics》2004,36(6):499-506
In this letter a simple method for fabricating tunable sampled nonlinearly chirped fiber Bragg gratings (SNCFBGs) is demonstrated
experimentally. A SNCFBG is formed when tension is applied to an etched sampled fiber Bragg grating (SFBG), whose cross-section
area's reciprocal varies along the length of the SFBG. The chirp of the grating period and the sampled period can be tuned
by adjusting the strain gradients, and the dispersion and dispersion slope can also be compensated. 相似文献
19.
20.
R. Alferness 《Applied Physics A: Materials Science & Processing》1975,7(1):29-33
A method of analyzing optical propagation in thick holographic gratings by decomposition of the thick material into thin gratings is discussed. The method is readily applicable to study propagation in multiple gratings of arbitrary spatial frequency and orientation recorded in the same thick emulsion. Applied to the double grating case, the method predicts strong cross-coupling between the two gratings for proper relative slope of the gratings. Results are given. 相似文献