Qizhong Huang

Decomposition storage of information based on computer-generated hologram interference and its application in optical image encryption.

An information-encryption method based on computer-generated hologram (CGH) interference is presented. In this method the original information is decomposed into two parts, and then each part is encoded on a separate CGH. When these two encoded CGHs are aligned and illuminated, a combined interference pattern is formed. The original information is obtained from this pattern. It is impossible to decrypt the original information from one CGH alone; two matched CGHs must be put together to make it available.

New approaches to optical proximity correction in photolithography

Two new schemes for optical proximity correction (OPC) have been proposed. Based on the analysis of light intensity distribution, one of the schemes uses both clear and opaque assistant features for OPC. These features are located both inside and adjacent to the mask feature to balance the intensity distribution. Another scheme converts the mask design into grey tone at different parts of the feature to re-adjust the aerial image. A deviation factor has been introduced to compare the OPC results. Computer simulation of aerial images indicates that without OPC an aerial image can deviate from its ideal image up to 10%. With the new OPC schemes the deviation can be reduced to below 1%.

Optical proximity correction by grey tone photolithography

A new approach to optical proximity correction in VLSI photolithography has been proposed. Instead of changing feature dimension or adding serifs, the mask feature itself has been coded in different grey tone levels at different parts of the feature, based on the analysis of aerial image. Improvement on proximity effect is demonstrated by computer simulation and confirmed by experiment.

Electron-beam lithography to improve quality of computer-generated hologram

Abstract The quantized errors in computer generated holograms (CGH) have been analysed theoretically. In order to evaluate quantitatively the influence of these errors on the quality of reconstructed image, a signal-to-noise ratio (SNR) is introduced. It is found that the SNR of a reconstructed image is very sensitive to the accuracy of amplitude and phase. Improving the accuracy of amplitude and phase is much more effective for improvement of CGH image quality than simply increasing the sampling cells. The accuracy of amplitude and phase of a sampling cell is represented by the fidelity of sampling cell geometry. CGH plates with the same encoded image have been fabricated by both conventional photoreduction method and e-beam direct write method. The reconstructed images from both plates have been compared. The experimental result has confirmed the theoretical analysis: e-beam direct write can produce CGHs with quality superior to conventional photoreduction technique

New method for optical proximity correction with gray-level serifs

Based on analysis of physical mechanics on optical proximity effect, we present a new method for fine correction of optical proximity effect and point out that the optimum of amplitude distribution on mask can improve distribution of spatial frequency spectrum, so intensity distribution of printed image near ideal distribution can be obtained. The simulation results show that deviation between contour of image after OPC and contour of ideal image is less than 0.009.

Optical proximity correction for submicron lithography by laser direct writing

Generally, a laser direct writing lithography system can only produce feature sizes larger than its beam spot size. When the feature size is comparable to its spot size, corner rounding and line shortening appears. This is caused by optical proximity effect. The effect is mainly due to light intensity spread in a laser beam which causes the spread of photon energy in resist layer. A new pre-compensation method has been developed to correct the optical proximity effect. The method has been implemented in the ISI-2802 laser direct write system. Feature size down to 0.6 micrometers has been produced with the system which normally can only produce 1 micrometers lithography without proximity correction.

Fine OPC approach with gray-tone coding mask

In this paper, a new method has been proposed to realize fine OPC with gray-tone coding mask instead of gray-tone mask. The relationships of the gray-tone coding mask and gray-tone mask have been discussed, and OPC simulation results are given with the gray-tone coding mask.

Interference anticounterfeiting using computer-generated hologram

An anti-counterfeiting method using CGH phase coding is presented in this paper. The phase of a wave-front is coded by means of detour phase coding and then interfere with a reference wave, which is also generated by CGH. The object recorded in the hologram can be read out from the interference patterns. The object can be easily generated by computer, caught by CCD camera or scanner, both black-white and grayscale object can be used in our method. The features of this method lies in that it is flexible in designing, easy to observation and reconstructed by common expanding white light source. The reference wave can be a plane wave or another phase coding wave, then its difficult to duplicate an identical CGH based on the decoding information, this made it enjoy a high anti-counterfeiting ability.

Binary optical element for dividing harmonic waves applied in ICF system

This paper aims at the request of dividing harmonic waves in the high power laser system used to perform Inertial Confinement Fusion. Dividing harmonic waves is realized by introducing binary optical element. Based on scalar diffraction theory, the distribution of its diffraction field was calculated and the fabrication parameters were also optimized. The element is fabricated with RIE. We also measured the relief structure and diffraction efficiency of each harmonic wave and analyze the errors.

Pseudochromatic encoding fractional Fourier transform rainbow hologram

The FRTH is presented in this paper and its properties are discussed. Then we make a pseudo chromatic encoding fractional Fourier transform rainbow hologram, based on its specialty in its reconstruction and that the encoding color has relationship with the order of the reconstruction FRT system, a new type of anti-counterfeiting hologram is introduced.