Topic
Fresnel zone
About: Fresnel zone is a research topic. Over the lifetime, 2337 publications have been published within this topic receiving 37650 citations.
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TL;DR: A method for aligning a photolithographic mask at the top of a transparent wafer that has a pattern on its bottom side is presented, based on optical self-imaging of special alignment marks and provides submicrometer accuracy.
Abstract: A method for aligning a photolithographic mask at the top of a transparent wafer that has a pattern on its bottom side is presented. The method is based on optical self-imaging of special alignment marks and provides submicrometer accuracy. The method is simple and robust and can conveniently be implemented on laboratory mask aligners for contact or proximity printing.
22 citations
TL;DR: The proposed method implements a time-varying FZP with an in-line optical setup by using only an SLM, which reveals the feasibility of the new motionless holographic 3D imaging technique.
Abstract: Optical scanning holography (OSH) is an attractive technique since 3D information can be obtained with a single pixel detector. However, OSH requires an interferometer, scanning architecture, and a frequency shifter to scan a time-varying Fresnel zone plate (FZP), which makes the optical setup complicated. To reduce the complexity, the polarization sensitivity of a spatial light modulator (SLM) is applied. The proposed method implements a time-varying FZP with an in-line optical setup by using only an SLM. Observing results for a USAF pattern and a fluorescent bead reveals the feasibility of the new motionless holographic 3D imaging technique.
22 citations
TL;DR: In this paper, a velocity anomaly is introduced in a homogeneous medium and the presence of the velocity anomaly breaks the wavefront into two main parts, the first part which travels through the anomaly, corresponds to the specular ray and gives rise to an event which is called the ray event since it can be predicted by standard ray tracing techniques.
Abstract: For impedance, velocity resolution depends on Fresnel zone considerations. A change of velocity can be distinguished only if its size is greater than the Fresnel zone. This is demonstrated on synthesized examples where a single velocity anomaly is introduced in a homogeneous medium. (Although unrealistic, this model was designed to exhibit the physical phenomenon in its simplest configuration.) The presence of the velocity anomaly breaks the wavefront into two main parts. The first part, which travels through the anomaly, corresponds to the specular ray and gives rise to an event which we call the ray event since it can be predicted by standard ray‐tracing techniques. The second, which emanates from outside the anomaly, does not correspond to a ray event. Therefore, we call it the nonray event. It travels at the speed of the background medium. The relative amplitude of the two events depends upon the size of the anomaly compared to the size of the Fresnel zone. When the anomaly is larger than the Fresnel ...
22 citations
20 Jun 1985
TL;DR: In this paper, a VG HB5 STEM has been modified to allow computer controlled contamination writing on thin Carbon substrates, with line widths of 20 nM and height to width aspect ratios of better than 5:1.
Abstract: A VG HB5 STEM has been modified to allow computer controlled contamination writing on thin Carbon substrates. Line widths of 20 nM and height to width aspect ratios of better than 5:1 can be drawn. This writing has been used to fabricate Fresnel zone plates. A patching process is involved with registration to an accuracy of 2.5 nM. Methods and techniques have been developed to compensate for non-linearity of the field scans together with specimen drift. Zone plates of 50 NM diameter and outer zone widths of 40 nM have been con-structed.
22 citations
TL;DR: In this article, a hybrid-level Fresnel Zone Plate (HLFZP) was proposed to maximize the diffraction efficiency under a certain lithography condition, and the diffracted field was derived by establishing a diffraction model.
Abstract: The Fresnel Zone Plate (FZP) is widely used in a variety of applications. However, the most concerning drawback of the FZP is its low diffraction efficiency limited by fabrication capability. The diffraction efficiency of an FZP with a surface-relief profile can reach 100% at a specified diffracted order, however, this is difficult to engineer in a precise manner. In this paper, a hybrid-level FZP (HLFZP) is proposed to maximize the diffraction efficiency under a certain lithography condition. To theoretically verify this enhancement, the diffracted field of the HLFZP is derived by establishing a diffraction model. According to different machining capabilities, the design criteria for the level number distribution on the HLFZP are presented. Simulated results show significant improvement in imaging quality while comparing the diffraction efficiency of the specifically designed 8-4-2 HLFZP to that of the traditional 2-level FZP. Fabrication processes for the 8-4-2 HLFZP are developed, with experimental results indicating that the diffraction efficiency could be improved by 54% using the proposed HLFZP, compared to the traditional 2-level FZP. The root mean square (RMS) of the wavefront error for the 8-4-2 HLFZP is 1/20λ (λ = 632.8 nm), and imaging results are good as the predicted results. It is concluded that the proposed hybrid-level method is also promising for improving the diffraction efficiency of other diffractive optical elements.
22 citations