共查询到20条相似文献,搜索用时 15 毫秒
1.
Holographic blazed diffraction grating is analysed as a periodic relief of an inclined sinusoidal curve in the shallow profile approximation. Under the condition that the rate of the development is a linear function of the development dose the evolution of the relief during the development is discussed. Theoretical curves of diffraction efficiency are compared with measurements on gratings made by direct holographic method for uv spectral region. 相似文献
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The diffraction efficiency of Ag coated holographic gratings was measured as a function of the grating amplitude, H, for a He-Ne laser incident at 30° and 70° in the plane perpendicular to the grating grooves. The grating amplitude was determined using a scanning electron microscope. It was found that the diffraction efficiency of s polarized light increased monotonically with increasing H for H < 250 nm. In contrast, for the same amplitude range, the diffraction efficiency of p polarized light oscillated through two maxima at H = 90 nmand 220 nm. These results were compared to the theoretical calculations of Heitmann and found to agree within 10% for H < 60 nm in the s polarization case and for H < 15 nm in the p polarization case. For larger H, the data deviated significantly, presumably due to a breakdown of the small amplitude assumption on which the calculations were based. 相似文献
3.
T. Jaaskelainen 《Optical and Quantum Electronics》1983,15(5):441-446
The diffraction efficiency of absorption gratings is investigated using a coupled multiwave analysis. For the four-wave case the analytical expressions for the signal amplitudes are given. The applicability of the four-wave approximation is also included. 相似文献
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T. Jääskeläien 《Optics Communications》1983,45(3):145-148
Efficiencies of thick photochromic absorption gratings are theoretically investigated. The treatment is based on a realistic photochromic grating model, which includes both spatial and temporal variations of the absorption coefficient. Simple analytic solutions for dynamic diffraction characteristics are derived. This nonlinear model shows that the maximum diffraction efficiency of photochromic absorption gratings may exceed 10%. 相似文献
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The diffraction efficiency curves of multicoated dielectric gratings are measured as a function of wavelength and angle of incidence for S and P polarization in the visible region. Strong anomalies are observed, due to the excitation of guided waves in the grating. 相似文献
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In As-Se-(S)-Ge amorphous films, the chemical etching rate between the heat treated and the light irradiated states differs as well as the optical properties do. A relief-type grating made by the etching has a high diffraction efficiency (∽15%). The diffraction efficiency of the relief-type grating is analyzed by a Fourier expansion method under some assumptions and good agreement is obtained between the calculated and the experimental values. 相似文献
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R. Kowarschik 《Optical and Quantum Electronics》1978,10(2):171-178
On the basis of the theory of coupled waves the amplitudes of the first-order diffracted waves and the diffraction efficiency is calculated for sequentially superposed phase gratings stored in dielectric reflection holograms. The investigations are restricted to the case of a fixed reference wave during recording and Bragg-angle incidence.By analogy to the transmission volume grating the coupling effects which appear between incident beams and diffracted waves give the possibility of building up beam-couplers and -splitters with certain coupling parameters determined by the recording process. Moreover, reflection gratings allow a favourable combination between coupling and reflecting properties and avoid the diffraction efficiency oscillations that are characteristic of transmission gratings. The performance of the reconstruction process with several waves simultaneously allows the tuning of the intensities of diffracted waves with dependence on amplitude or phase differences between incident beams. 相似文献
9.
In this paper volume hologram reconstruction is considered as an electromagnetic scattering problem that leads to a characteristic integral equation. Our main attempt is the calculation of diffraction efficiency for attenuated gratings, that is compared with those of unattenuated gratings, to point out the influence of grating attenuation. In this respect the solution in the first Born approximation is found to be sufficient for diffraction efficiency calculations of attenuated gratings. 相似文献
10.
L. Nedelchev D. Ivanov N. Berberova V. Strijkova D. Nazarova 《Optical and Quantum Electronics》2018,50(5):212
Azopolymers are one of the most efficient materials able to record the polarization state of light. They have numerous applications, such as data storage and diffractive optical elements with unique polarization properties. An essential parameter for each diffractive element is its diffraction efficiency η. In order to optimize the recording conditions and obtain high-efficient polarization holographic gratings, in the present work we study the dependence of the diffraction efficiency on the recording angle and thickness of a series of azopolymer layers. Three recording angles are used ??10°, 20° and 30° and three series of thin films with thicknesses 470, 850 and 2400 nm from the water-soluble azopolymer PAZO. The gratings are inscribed by two plain waves with left and right circular polarization from a He-Cd gas laser (442 nm). The diffraction efficiency of the gratings is probed with a right hand circularly polarized beam from a probe laser with wavelength 635 nm. The kinetics of diffraction efficiency η(t) in the +?1 diffraction order are presented and compared. Our experimental results indicate that highest diffraction efficiency (more than 40%) is obtained for the sample with thickness 2400 nm and for recording angle 10°. As the holographic recording in azopolymers is usually accompanied by formation of surface relief gratings, the surface topography of the recorded samples is also investigated by atomic force microscopy. 相似文献
11.
Based on the modified Kogelnik diffraction efficiency equation, the diffraction intensity spectrum and the total diffraction efficiency of volume gratings in photorefractive media are studied systematically. Taking photorefractive InP:Fe crystal as an example, the effect of the grating parameters and the pulse width on the diffraction properties are presented, in particular under the influence of crystal material dispersion. Under the combined effects, the diffraction pulse profiles and the total diffraction efficiency are shown. Also, the diffraction properties with and without crystal material dispersion are compared. These studies indicate that the properties of the diffraction beams can be controlled by the holographic grating parameters; this property can be used for pulse shaping applications. 相似文献
12.
The diffraction efficiency of gratings in chalcogenide glass thin films during the chemical etching process is described. The experiment is performed by a simultaneous etching and detection technique, and two absolute maxima with intermittent interference maxima and minima are observed. Theoretical analysis including interference effect is presented, and excellent agreement with experimental curve is obtained. Application of this technique to lithographic process for etching control is briefly discussed. 相似文献
13.
Various methods for the recording of blazed holographic diffraction gratings are presented and the regions in the wavelength-groove density plane for which they can be used are shown. The gratings are made in the positive photoresist Shipley AZ-1350. The diffraction efficiency for s and p polarization was measured as a function of wavelength and angle of incidence. An absolute efficiency of 80% was achieved. 相似文献
14.
The diffraction properties of a system of multi-layer volume holographic gratings under an ultrashort pulsed beam with arbitrary temporal profiles are investigated using the multi-layer coupled wave theory. The dependence of the pulse profiles of the diffracted beams, diffraction bandwidth and the total diffraction efficiency of the multi-layer system on the temporal profiles of the input ultrashort pulse are investigated. The calculated results indicate that the temporal shape of the input pulsed beams is an important factor in the analysis of the propagation characteristics. The analysis of this paper will be valuable for the applications of pulse shaping, processing and filter. 相似文献
15.
《Optics Communications》1987,64(1):19-22
The occurrence of Raman-Nath regime and Bragg regime diffraction by planar phase gratings is rigorously analyzed. It is shown that the published indicators for a Raman-Nath regime are unsatisfactory. An attempt to redefine the Raman-Nath region is given in this paper. 相似文献
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Diffraction gratings: aberrations and applications 总被引:1,自引:0,他引:1
Diffraction grating is an optical instrument, which is advantageously used for scientific research in spectroscopy and spatial filtering. It has many other applications in science and technology such as wavelength selectors for tuneable lasers, selective surfaces for solar energy, masks for photolithography, beam sampling mirrors for high power lasers, spectrometers in extreme UV and X-ray regions for space optics, metrology, phase measuring interferometry and pattern recognition, etc. Although the holographic gratings have many advantages over the ruled gratings but they have not yet eliminated completely the classical ruled gratings as the ruled gratings have their own importance in many applications. Therefore, in this article, both the ruled and holographic gratings will be discussed, in particular, their focusing properties, aberrations, and their applications. 相似文献
19.
Holographic gratings recorded in photochromic media often do not obtain the maximally achievable diffraction efficiency because of diminishing the fringe contrast caused, e.g., by a photochemically active readout beam or unequal intensities of object and reference waves. For nonreversible materials this problem causes a decrease in diffraction efficiency that is proportional to the signal-to-noise ratio (SNR). However, in nonlinear materials such as photochromic media, for which saturation effects need to be considered, an out-of-proportion decrease in the SNR results. It is shown that an overshooting peak during hologram growth, which then decays to a lower permanent level of diffraction, is an indicator for such a situation. Even a weak readout beam may cause such effects, which significantly affect the hologram kinetics. The observed overshooting diffraction efficiency may even be misinterpreted to be dependent on material properties. Experimental and theoretical proof that with low levels of auxiliary light this type of problem can be eliminated completely is presented. Throughout this research bacteriorhodopsin films were used, but the results are valid for photochromic media in general. 相似文献
20.
The mode-hop behavior and the power characteristics of a laser diode with wavelength-selective optical feedback are experimentally
investigated. The feedback is provided by external volume holographic gratings, also called ‘Bragg mirrors’, at normal incidence.
We demonstrate that a Bragg mirror forces a laser diode to operate only within a narrow wavelength range, and that the emission
wavelength of the laser diode is stabilized against variations of the injection current. Moreover, we present periodic undulations
of the power characteristics of the laser, depending on the driving current. They can be qualitatively explained with a simple
model which takes into account that the threshold gain in the laser system strongly depends on the wavelength. 相似文献