A diffractive optical element for shaping arbitrary beams

A design method is presented for an optical element that shapes an arbitrary collimated beam. The optical element consists of a pair of diffractive optical elements (DOEs). The outgoing beam is also collimated, and can have any desired intensity profile. The phase functions of the DOEs are computed by minimizing an appropriate cost function under an energy conservation constraint.     

Using diffractive optical element and Zygo interferometer to test large-aperture convex surface

A valid method for measuring the large-aperture convex surface by using a curved diffractive optical element (DOE) and a Zygo interferometer is demonstrated experimentally. In this method, the direct use of source and high-resolution CCD camera of Zygo interferometer represents a major advance in the areas of adjustment. The DOE, fabricated by combining laser direct writing and lithography, results in higher accuracy, efficiency and lower cost for testing aspheric compared with other types of DOE employed. We have fabricated one optical test system and measured a 110-mm-diameter convex surface of errors 44.3 nm rms and 311 nm P–V.     

Silicon-based transmissive diffractive optical element

A silicon nitride (SiNx) membrane diffractive optical element (DOE) designed to exhibit beam-splitting and focusing behavior at visible wavelengths has been fabricated and tested. Since the fabrication process is based on silicon micromachining technology, the DOE is easily integrated with a laser diode chip and a photodiode chip on a silicon substrate to function as the hologram-laser-photodiode unit for use in the pickup head of a CD or DVD system. The SiNx film is deposited with low-pressure chemical-vapor deposition and the free-standing membrane is formed by KOH etching. The transmissive DOE showed a high diffraction efficiency (>20% for a binary-phase-level element). The experimental evaluation was in good agreement with the designed and modeled predictions.     

Multifunctional double-layered diffractive optical element

We propose a novel multifunctional double-layered diffractive optical element (DOE) based on the fractional Talbot effect. This DOE consists of two layers: one is the encoding layer, in which multiple sub-DOEs, i.e., multiple optical functions, are encoded; the other is the decoding layer, which is a properly designed Talbot illuminator. This DOE can perform each of the multiple optical functions one by one by shifting the encoding layer. Experimental results demonstrate that this method is efficient. This device should be highly interesting for integrated optics, optical interconnection, secure optical storage, and dynamic optical fiber communications.     

Simultaneous multicolor image formation with a single diffractive optical element

A design for a novel diffractive optical element (DOE) that can reconstruct three different intensity patterns when it is illuminated by three different wavelengths is presented. If the chosen wavelengths are red, green, and blue, full-color reconstruction capability is obtained. Reconstruction is achieved in the near field (Fresnel domain). Computer simulation results as well as experimental evidence are presented, proving the capabilities of this novel DOE design procedure.     

Wave-front control and aberration correction with a diffractive optical element

A method that permits aberration correction and wave-front reshaping with a diffractive optical element (DOE) is described. Two aligned DOE's made of two different dispersive materials are used. The different dispersions of the two materials in addition to freedom in choosing their thicknesses enables the chromatic aberration and the wave fronts to be manipulated. Design and simulation of such DOE's are described.     

A compact holographic interferometer with a single optical element

A compact holographic interferometer is presented. A key feature of the instrument is the minidiffuser used as a single optical element. Divergent diffuse waves formed on illumination of the minidiffuser by a narrow beam from a continuous wave (CW) laser are shown to be well suited for obtaining high-quality reflection holographic interferograms and holograms.     

Multiphoton multifocal microscopy exploiting a diffractive optical element

Multiphoton multifocal microscopy (MMM) usually has been achieved through a combination of galvo scanners with microlens arrays, with rotating disks of microlens arrays, and cascaded beam splitters with asynchronous rastering of scanning mirrors. Here we describe the achievement of a neat and compact MMM by use of a high-diffraction-efficiency diffractive-optic element that generates a multiple-spot grid of uniform intensity to achieve higher fidelity in imaging of live cells at adequate speeds.     

Polarization converter for higher-order laser beams using a single binary diffractive optical element as beam splitter

We propose a new approach to generating a pair of initial beams for a polarization converter that operates by summing up two opposite-sign circularly polarized beams. The conjugated pairs of vortex beams matched with laser modes are generated using binary diffractive optical elements (DOEs). The same binary element simultaneously serves two functions: a beam shaper and a beam splitter. Two proposed optical arrangements are compared in terms of alignment complexity and energy efficiency. The DOEs in question have been designed and fabricated. Natural experiments that demonstrate the generation of vector higher-order cylindrical beams have been conducted.     

含多层衍射光学元件的折/衍射混合头盔目镜

基于对多层衍射元件的衍射效率的理论分析,设计了用于头盔显示器的含有多层衍射元件的60视场折/衍射混合目镜系统。系统在设计波段和整个视场范围内衍射效率均在90 %以上,提高了光能利用率和像面对比度。目镜的出瞳距离为22 mm,出瞳直径为8 mm。调制传递函数（MTF）在25 lp/mm时全视场均在0.38以上,满足VGA分辨率要求。目镜中畸变为4.8%,垂轴色差最大为10 m。整个系统结构紧凑,镜头总长26.8 mm,最大直径16 mm,全系统质量仅8 g,实现了光学系统的轻小型化     

Optimization of 350× optical zoom lens with diffractive optical element

Through researching and validating, a set of optical designs using a diffractive optical element (DOE) and optimization process has been derived in this paper. We put forward a set of theories to solve the numerous quality issues in imaging and applied it to an optical design. For an optical design to be successful, it must comply with the standards of the optical system. Optical designers must also take into consideration imaging quality, wherein the most influential aspects are chromatic aberration and monochromatic aberration. We complied with systemic standards such as effective focal length and total system length. Diffractive Optical Element, based on the theory of wave phase difference, takes advantage of negative Abbe number, which might significantly eliminate chromatic aberrations of optics. Following the advanced technology applied to micro lens and etching process, precisely made micro DOE element now is possible to be manufactured in a large number. A 350× zoom lens with DOE is demonstrated in the proposal. The results show that regardless of whether chromatic aberration is axial or longitudinal, issues concerning the optical lens's chromatic aberration could be significantly reduced.     

Design of a diffractive optical element for wide spectral bandwidth

A new method for eliminating the chromatic aberration of a diffractive optical element (DOE) for wideband wavelengths is presented. The wideband-wavelength diffractive optical element (WBDOE) consists of two aligned DOE's. The use of different dispersive materials for the two DOE's eliminates chromatic aberration. The design and simulation of a WBDOE for the visible spectrum are presented.     

Dual focus diffractive optical element with extended depth of focus

A dual focus property and an extended depth of focus were verified by a new type of diffractive lens displaying on liquid crystal on silicon (LCoS) devices. This type of lens is useful to read information on multilayer optical discs and tilted discs. The radial undulation of the phase groove on the diffractive lens gave the dual focus nature. The focal extension was performed by combining the dual focus lens with the axilens that was invented for expanding the depth of focus. The number of undulations did not affect the intensity along the optical axis but the central spot of the diffraction pattern.     

衍射光学元件检测及数据处理

衍射光学元件以其优异的光学性能,能够调制出理想的波面,较球面、非球面光学系统在校正色差方面具有较大优势。衍射光学元件的加工难点在于其加工精度不仅要求非球面基底的面形满足精度要求,还需要衍射结构的相位突变点及高度满足要求。由于其面形非连续性,存在相位突变点,传统的检测方式难于满足要求。对轮廓仪检测误差来源进行分析,结合检测数据分析加工误差数据,在此基础上进行数据处理,并将该方法获得的误差数据应用于零件加工,实现口径120 mm衍射面加工面形误差为0.539 μm。     

Optimal design of a multilayer diffractive optical element for dual wavebands

A method for optimal design of a multilayer diffractive optical element (MLDOE) for dual-wide-waveband optical systems is presented with consideration of polychromatic integral diffraction efficiency (PIDE) and the weight factors of PIDE for each waveband. The design process and simulation of a MLDOE in mid-wave and long-wave IR are described, and the comparison of diffraction efficiency of the MLDOEs for different design wavelength pairs determined by different methods is given. This method can make the design process more rational and more reasonable and can give a better design result than that with the conventional design method.     

Low divergent diffractive optical element for remote detection

The low divergent Dammann grating is researched for the potential applications in aerospace. A laserbeam writing system is developed for writing the low divergent Dammann grating. The uniformity and efficiency of the Dammann grating are presented in this letter. The novelty of this letter is to demonstrate a low-cost and effective method to fabricate low divergent Dammann grating.     

Three-dimensional dynamic optical manipulation by combining a diffractive optical element and a spatial light modulator

Since the introduction of computer-controlled spatial light modulators (SLMs), holographic optical tweezers have become an important tool for dynamic parallel optical manipulation. In this paper we clarify the usefulness of a new configuration for optical trapping that creates light patterns using the combination of a diffractive optical element (DOE) and an SLM. This configuration not only enables the use of the higher part of the SLM’s diffraction efficiency curve, because a simple hologram can be chosen for the SLM, but also achieves three-dimensional dynamic optical manipulation over a large spatial range. By switching blaze-like holograms displayed on the SLM, we demonstrated simultaneous transportation of three 6-μm-diameter polystyrene beads over a range of 90 μm in the vertical direction and 37.5 μm in the horizontal direction. Compared with the same manipulation executed using only the SLM, the range of this method is extended four-fold in the vertical direction and three-fold in the horizontal direction.     

Generation of millimeter-wave sub-carrier optical pulse by using a Fabry-Perot interferometer

A novel scheme is proposed to transform a Gaussian optical pulse to a millimeter-wave (mm-wave) frequency modulation pulse by using a Fabry-Perot interferometer (FPI) for radio-over-fiber (ROF) system.It is shown that modulation frequency of mm-wave is determined by the optical path of the Fabry-Perot (F-P) cavity, and amplitude decay time and energy transfer efficiency are related to the reflectivity of the F-P cavity mirror. The effect of pulse train extension on inter-symbol interference is also discussed.