Jinghui Xie

Elimination of a zero-order beam induced by a pixelated spatial light modulator for holographic projection

A technique is proposed theoretically and verified experimentally to eliminate a zero-order beam caused by a pixelated phase-only spatial light modulator (SLM) for holographic projection. The formulas for determination of the optical field in the Fourier plane are deduced, and the influence of the pixelated structure of a SLM on the intensity of the zero-order beam is numerically investigated. Two currently existing techniques are studied and a new one is presented. These three techniques are used separately to eliminate the zero-order interruption, and the optical performances of the reconstructed patterns are compared. The new technique results in higher reconstruction quality and diffraction efficiency. A short animated movie is illuminated for holographic projection display. The experimental results show that the zero-order beam can be efficiently eliminated by the new technique. It is believed that this technique can be used in various optical systems that are based on pixelated phase-only SLMs, such as holographic optical tweezers and optical testing systems.

Optical image encryption based on interference of polarized light

We proposed a novel architecture for optical image encryption based on interference between two polarized wavefronts. A polarization-selective diffractive optical element is employed to generate the desired polarized wavefronts by modulating the incident polarized light beam. The encryption algorithm for this new method is simple and does not need iterative encoding. Numerical simulation is performed to demonstrate the validity of this new proposed method.

Chromatic dispersion correction in planar waveguide using one-layer volume holograms based on three-step exposure

We propose a novel method to correct the chromatic dispersion in a planar waveguide with volume holograms fabricated by the three-step exposure technique. The 532 nm green laser is used to illuminate the holographic plate in three groups of different angles for achieving the desired holograms. When it is used in the planar waveguide, the chromatic dispersion of the original display can be corrected and an image with the real color can be obtained. The experiments are performed, and the results are in good agreement with the theory. It is believed that this technique is a good way to correct the chromatic problems in the display systems in the future.

Pushing the resolution of photolithography down to 15nm by surface plasmon interference

A deep ultraviolet plasmonic structure is designed and a surface plasmon interference lithography method using the structure is proposed to generate large-area periodic nanopatterns. By exciting the anti-symmetric coupled surface plasmon polaritons in the structure, ultrahigh resolution periodic patterns can be formed in a photoresist. The resolution of the generated patterns can be tuned by changing the refractive index and thickness of the photoresist. We demonstrate numerically that one-dimensional and two-dimensional patterns with a half-pitch resolution of 14.6 nm can be generated in a 25 nm-thick photoresist by using the structure under 193 nm illumination. Furthermore, the half-pitch resolution of the generated patterns can be down to 13 nm if high refractive index photoresists are used. Our findings open up an avenue to push the half-pitch resolution of photolithography towards 10 nm.

Method for reduction of background artifacts of images in scanning holography with a Fresnel-zone-plate coded aperture

Near-infrared scanning holography with a Fresnel zone plate (FZP) coded aperture has potential applications in imaging through turbid media. However, the nonnegative intensity-distribution function of the FZP coded aperture introduces the background artifacts into the reconstructed images, reducing the contrast and the signal-to-noise ratio (SNR) of the images. A novel method termed as the composite hologram is proposed to reduce the artifacts. The computer simulations showed that the contrast and the SNR of the reconstructed images had improvements of at least 50.2% and 5.58-dB, respectively, compared with the conventional method. The composite hologram of a metal ring with a 6.0-mm diameter made by a wire with a 0.4-mm diameter immersing in 1% intralipid solution was recorded, and the reconstruction was performed numerically. The experimental results demonstrated that the contrast and the SNR of the reconstructed image had improvements of at least 32.3% and 2.51-dB, respectively.

Magnification of three-dimensional optical image without distortion in dynamic holographic projection

We propose a simple technique to enlarge the reconstructed three-dimensional (3D) optical image and shorten the reconstructed distance simultaneously in real time holographic projection using a conventional lens or concave reflecting mirror based on the optical reversibility theorem. The main factors causing the longitudinal and transversal distortions of a 3D enlarged optical image are analyzed, and the 3D optical images are enlarged where severe distortions are precompensated by constructing objects with distortions directly instead of computing the precompensated phase iteratively so that it does not increase the computing time. Numerical simulations and optical experiments are performed for magnifying a simple cubic model. The results show that a 3D enlarged optical image is achieved successfully without any distortion and the reconstructed distance is shortened simultaneously. It is believed that this proposed technique is useful for 3D real time holographic projection in the future.

A Super Lens System for Demagnification Imaging Beyond the Diffraction Limit

A super lens system is proposed to achieve subdiffraction limit demagnification imaging. The super lens system consists of a hyperlens with planar input and output surfaces, a metal superlens, and a plasmonic reflector. By employing the hyperlens to transform evanescent waves into propagating waves and employing the metal superlens and the plasmonic reflector to amplify evanescent waves, the super lens system can produce a subdiffraction limit image with relatively high electric field intensity. The reduction factor of the super lens system depends on the geometric parameters of the hyperlens. Simulation results show that an image with a half-pitch resolution of about one tenth the operating wavelength and a reduction factor of about 2.2 can be produced by the super lens system. The proposed super lens system has potential applications in nanolithography.

Designing and fabricating diffractive optical elements with a complex profile by interference

We demonstrate a novel (to our knowledge) method for the design and the fabrication of diffractive optical elements (DOEs) with an arbitrary complex phase profile based on interference. The DOEs are designed to modulate the complex light wave by the analytical formulas, and an asymmetric holographic DOE with cubic phase modulation is fabricated by a two-step exposure technique. The desired Airy beams are produced experimentally, which demonstrates the validity of this method. It is a simple approach with a low cost for the design and the fabrication of DOEs with a large area and arbitrary phase distribution.

Optical reconstruction of 3D images by use of pure-phase computer-generated holograms

A three-dimensional (3D) object reconstruction technique that uses pure-phase computer-generated holograms (CGHs) and a phase-only spatial light modulator (SLM) is proposed. The full parallax CGHs are generated by the point source method and the wave-oriented method without paraxial approximation. Different from conventional CGHs, the pure-phase information on the hologram plane is loaded on the SLM to reconstruct the 3D diffusive objects without considering the reference wave. This technique is more efficient in its utilization of the space-bandwidth product of the SLMs. Numerical simulations and experiments are performed, and the results show that our proposed method can reconstruct 3D diffusive objects successfully.

Subwavelength light focusing with a single slit lens based on the spatial multiplexing of chirped surface gratings

A lens consisting of a subwavelength slit engraved into a metal film and surrounded by periodic surface gratings and spatial multiplexing chirped surface gratings (SMCSGs) for focusing light is proposed. The focal length of the lens can be accurately designed and tuned by controlling the periods of the local gratings of the SMCSGs. Simulation results show that a subwavelength beam spot can be produced by the lens at a distance of several times the incident wavelength from the slit and the difference between the simulated and designed focal lengths can be reduced to below 3% of the designed focal length.