ISSN:0950-0340    

DOI:10.1080/09500340008230513

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The standard design for phase-only diffractive optical elements comprises a transformation of the continuous phase function into a surface relief by means of wrapping the phase into regular intervals ofM2π. This results in a structure with diffractive zones aligned in a horizontal plane. We present an alternative design concept with modulated zone sizes leading to non-periodic boundary positions and non-aligned surface structures. The diffractive properties are compared to those of conventional diffractive optical elements. It can be shown that they are fully equivalent for the design wavelength, but exhibit a different spectral behaviour for deviating wavelengths. These properties are exploited for the improvement of the optical performance of blazed gratings and diffractive lenses under conditions of deviating wavelengths. Special emphasis is put on the optimization of the ratio between diffractive efficiencies of the design order and other orders for blazed gratings and focusing diffractive lenses, as well as the suppression of interference effects within Gaussian beams collimated with diffractive lenses.

ISSN:0950-0340    

DOI:10.1080/09500340008230514

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The design of optical systems capable of transforming one given input field into an output field which maximizes one prescribed merit function is discussed in the functional embodiment of the system, that is by dealing with transmission functions instead of structured matter. Customary beam shaping techniques are identified as a special case of a more general strategy which is called amplitude matching. This strategy makes use of the field quantities amplitude and phase and therefore it is a wave-optical design approach. The flexibility of the technique is demonstrated by various examples. Parameters like conversion efficiency, signal-to-noise ratio, distances between transmission functions, and the number of transmission functions necessary for the implementation of wave transformations are discussed.

ISSN:0950-0340    

DOI:10.1080/09500340008230515

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Following an analysis of the modes inside a perfectly conducting rectangular grid, we design diffractive elements that can split an incident beam into four beams with equal intensities. This property is obtained under Bragg mounting for a wide domain of grating parameters (dimensions of the through-holes, height, period). Extension to finite conductivity is also addressed.

ISSN:0950-0340    

DOI:10.1080/09500340008230516

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The design of an optical element profile with specified transmission function for a given incident wave is of fundamental concern in optical design. A well-known example is the design of an aspherical surface in order to realize a spherical phase-only transmission. Various wave-optical system design methods lead to transmission functions as a first step. Then, often the thin-element approximation is applied in a second step to obtain an element structure with the desired transmission. However, if the refraction at the optical interface cannot be neglected, the thin-element approximation is not valid. In this case, a higher version of the local plane-interface approximation can be used for the element structure design. An algorithm for this model is introduced and its characteristics are discussed for the example of a non-paraxial Gaussian-to-tophat beam shaping element.

ISSN:0950-0340    

DOI:10.1080/09500340008230517

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Fourier-type spot-array illuminators are designed for electromagnetic fields in the paraxial domain of diffractive optics. An analytical construction of the periodic, spatially variable Jones matrix is presented, which produces 100% conversion efficiency from an arbitrarily polarized incident plane wave intoM×N=2P× 2Q(PandQare integers) diffraction orders. Such perfect performance is not possible within the scalar theory of paraxial diffractive optics.

ISSN:0950-0340    

DOI:10.1080/09500340008230518

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A diffraction grating in the resonance domain is known to exhibit significant change in diffraction efficiencies with a small change of the grating parameters. It is proposed that this property can be utilized for frequency filtering, when polychromatic light illuminates the grating. As an example, compression of a femtosecond optical pulse is numerically demonstrated with the concept of superresolution. Suppression of zeroth diffraction order by suitably optimized grating structure induces the pulse width to narrow. This scheme considerably simplifies existing optical pulse shaping systems.

ISSN:0950-0340    

DOI:10.1080/09500340008230519

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Aberration properties of gratings for a number of flat-field spectrometers, recorded in different optical mountings are discussed. Spot diagrams and spread functions achieved using mathematical models of spectrometers with different gratings are presented.

ISSN:0950-0340    

DOI:10.1080/09500340008230520

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

We report on the fabrication and characterization of replicated hybrid elements for low-cost micro-spectrometer array applications. An array of hybrid elements, where one surface combines the fairly large dimensions of refractive microlenses with the submicron features of a diffraction grating, was successfully replicated by hot embossing. The parameters are: lens diameter=990 μm, height=60 μm, grating period=1 μm, linewidth=300 nm and grating depth=2 μm. These replicated spectrometer elements showed a maximum resolution of 2.25 nm and a stray-light suppression better than 30 dB.

ISSN:0950-0340    

DOI:10.1080/09500340008230521

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The spectrally selective optical properties of wavelength selective radiation emitters and filters based on periodically microstructured metal surfaces were investigated. Metal surfaces were structured by the use of a holographic mask and subsequent etching processes. Due to the microstructure, thermally excited surface plasmons couple to electromagnetic radiation. Therefore a structured tungsten surface can act as a selective radiation emitter. The calculation of the absorptance by a rigorous diffraction theory allows the prediction of the emissivity of such structures. The angle dependent emissivity of tungsten gratings with periods of 1.4 μm and 2.0 μm was measured. A peak emissivity of 70% at a wavelength of 1.6 μm was achieved. Band pass filters for the near infrared spectral range based on perforated metal films were investigated theoretically and experimentally. Filters with a grating period of 2.0 μm were produced. A peak transmittance of 80% at a wavelength 2.9 μm was achieved. The optical properties of the diffractive elements described partly show a strong angle dependence

ISSN:0950-0340    

DOI:10.1080/09500340008230522

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor