High-harmonic diffractive lens color compensation.

Large diameter, high-harmonic diffractive lenses could find applications in future space telescopes. Residual chromatic aberrations from these lenses can cause significant blurring. Solutions to reduce chromatic dispersion and other aberrations to diffraction-limited performance are discussed.

Precision glass molding of diffractive optical elements with high surface quality.

Diffractive optical surfaces have attractive properties for use in optical systems, like reducing weight and correcting for chromatic aberrations, but fabrication of high-quality glass diffractive optics is challenging, preventing it from being widely adopted in commercial applications. In this Letter, we report on a fabrication method to address molding challenges for high-surface-quality diffractive glass optics at molding temperatures up to 550°C, including selection of mold material, mold fabrication, precision glass molding, durability, and stability of the mold. To enable optimal mold machining and easy mold release, nickel phosphorous (NiP) is chosen as the plating material for its cutting performance and anti-adhesion properties, and copper-nickel C71500 (CuNi) is selected as the mold substrate because its coefficient of thermal expansion (CTE) is close to NiP.

Multiple-order diffractive engineered surface lenses.

A multiple-order diffractive engineered surface (MODE) lens is introduced, in which focal position change with wavelength exhibits both refractive and diffractive characteristics. Engineering calculations are provided that indicate Strehl ratio and encircled energy performance over a large range of focal length and aperture diameter design space. A prototype lens is designed and constructed for the astronomical R-band (589 nm to 727 nm) wavelength range.

Single-shot phase retrieval with complex diversity.

The concept of complex diversity is introduced that adequately accounts for special considerations in the design of the system and the reconstruction algorithm for single-shot phase retrieval techniques. Complex-number pupil filters containing both amplitude and phase values are extracted by numerical propagation from a computer-generated hologram design, which generates multiple images in a single acquisition. The reconstruction is performed by a Fourier iterative algorithm modified with an area restriction to avoid noise amplification.

Optimization of random phase diversity for adaptive optics using an LCoS spatial light modulator.

Phase retrieval is an attractive approach for sensor-less adaptive optics (AO) because of its relatively simple implementation. Recently, random phase diversity has shown fast convergence for phase retrieval algorithms. In this study, design optimization using random phase diversity is discussed with respect to a sensor-less AO system using a liquid-crystal-on-silicon (LCoS) spatial light modulator.

Hyper-numerical aperture (NA = 2.8) microscope using λ = 1.56 µm femtosecond source for multi-photon imaging.

A new microscope is discussed, where the scanning illumination has a numerical aperture of 2.8 with λ = 1.56 µm femtosecond fiber laser.

Spot distribution measurement using a scanning nanoslit.

A scanning and rotating nanoslit is used to measure submicrometer features in focused spot distributions. Using a filtered backprojection technique, a highly accurate reconstruction is demonstrated. Experimental results are confirmed by simulating the scanning slit technique using a physical optics simulation program.

Microscope system for Blu-ray disc samples.

We introduce a microscope system using a solid immersion lens (SIL) to image Blu-ray disc samples without removing the protective cover layer. The aberration caused by the cover layer is minimized with a truncated SIL. A subsurface imaging simulation is achieved by using the rigorous coupled wave theory, partial coherence, vector diffraction, and the Babinet principle.

Effects of structured mid-spatial frequency surface errors on image performance.

Optical designers are encouraged to adopt aspheric and free-form surfaces into an increasing number of design spaces because of their improved performance. However, residual tooling marks from advanced aspheric fabrication techniques are difficult to remove. These marks, typically in the mid-spatial frequency (MSF) regime, give rise to structured image artifacts.

Illumination artifacts in hyper-NA vector imaging.

Off-axis polarized monopole illumination is applied to a hyper-numerical-aperture (NA) (NA>1) microscopic system. Illumination artifacts due to vector effects are observed, which are asymmetric and depend on illumination conditions. A model based on rigorous coupled wave theory is used to simulate image profiles for dielectric, semiconductor, and metal gratings with different monopole locations and polarization states.

Theory of modulation transfer function artifacts due to mid-spatial-frequency errors and its application to optical tolerancing.

Aspheric and free-form surfaces are powerful surface forms that allow designers to achieve better performance with fewer lenses and smaller packages. Unlike spheres, these surfaces are fabricated with processes that leave a signature, or "structure," that is primarily in the mid-spatial-frequency region. These structured surface errors create ripples in the modulation transfer function (MTF) profile.

Theory of point-spread function artifacts due to structured mid-spatial frequency surface errors.

Optical design and tolerancing of aspheric or free-form surfaces require attention to surface form, structured surface errors, and nonstructured errors. We describe structured surface error profiles and effects on the image point-spread function using harmonic (Fourier) decomposition. Surface errors over the beam footprint map onto the pupil, where multiple structured surface frequencies mix to create sum and difference diffraction orders in the image plane at each field point.

Characteristics of a scanning nano-slit image sensor for line-and-space patterns.

A single scanning nano-slit is used to study aerial image characteristics. Finite-difference time-domain simulations reveal that, in the far field of such a slit, the detected image contrast is very high over a large spatial frequency range regardless of the polarization direction. In the near field, the TM polarization shows a decrease in contrast at larger spatial frequencies.

Effect of optical aberration on Gaussian speckle in a partially coherent imaging system.

Optical aberration effects on Gaussian speckle contrast are theoretically examined in an imaging system exhibiting partial spatial coherence. Analysis includes phase-perturbed random fields from a rough object illuminated by an extended source that generate speckle in the image plane. Results indicate that, unlike coherent illumination, speckle contrast in this partially coherent system depends on odd-functional aberrations, such as coma.

Effect of fractal rough-surface Hurst exponent on speckle in imaging systems.

Speckle image contrasts from a fractal rough-surface object are investigated in simulation, where the image surface is conjugate to the object surface. It is observed that the Hurst exponent H of fractal roughness affects speckle contrast and statistics dramatically. For example, a strong rough surface (sigma(h)>lambda) exhibits Rayleigh statistics over increasing ranges of point spread function widths as H decreases.

Simulation method for non-Gaussian speckle in a partially coherent system.

Non-Gaussian speckle contrast from a phase-perturbed random object field in a spatially partially coherent system is simulated. A quasi-monochromatic extended incoherent source is modeled as a collection of independent point sources distributed on a regular grid. The source illuminates a phase screen object in a Kohler configuration.

Optical force model based on sequential ray tracing.

We discuss how information available from ray-tracing techniques can be used to calculate optical forces and torques on particles. A general ray-trace computer code is augmented with the polarization and irradiance distributions of the illumination and Fresnel surface coefficients to give a reasonably accurate prediction of interaction with large particles out of the focal plane. Calculations of trapping location versus nonuniform illumination conditions are compared with an experiment.

Effect of optical aberration on Gaussian laser speckle.

Optical aberration effects up to the second moment of Gaussian laser speckle are theoretically investigated for both partially and fully developed speckle. In the development, a plane-wave illuminated diffuser generates a phase-perturbed random field in the object plane that creates speckle in the image plane. Theoretical derivations show that image field statistics are generally non-circular Gaussian due to aberrations.

Geometrical analysis of third-order aberrations for a solid immersion lens.

This paper gives a treatment for finding 3rd order aberrations in solid-immersion lenses (SIL) using spherical-aberration as the basis for a polynomial power expansion of the wavefront. Unlike previous work, the treatment is general for any incident and lens media, for any lens thickness, and any chief-ray specification. Using this treatment, a tolerance analysis is given with particular discussion on thickness tolerance and limitations on field of view.

Proposal of three-dimensional phase contrast holographic microscopy.

We propose a three-dimensional phase contrast digital holographic microscopy. The object to be observed is a low-contrast transparent refractive index distribution sample, such as biological tissue. Low contrast phase objects are converted to high contrast images through the microscopy we propose.

Properties of induced polarization evanescent reflection with a solid immersion lens (SIL).

Properties of the induced polarization signal with a solid immersion lens (SIL) are investigated by experiments and simulations. A LaSFN9 SIL (NA=1.5) is used in the experiment.

Evanescent imaging with induced polarization by using a solid immersion lens.

Image contrast enhancement, high lateral resolution, and height information are obtained with induced polarization evanescent imaging using a solid immersion lens. Experiments are conducted by imaging features on a patterned Si substrate. Imaging theory is used to predict optimum orientation of high-spatial-frequency samples, and a topographical image is derived from the induced polarization image through a calibration procedure.

Performance of a write-once multilayer optical disk that uses transparent recording material with an optical switching layer.

A volumetric optical disk that has multiple transparent films with optical switching layers is used as a recording medium to increase the number of recording layers. In the disk the optical switching layer is adapted to reduce decay of laser energy and increase reading and recording sensitivity. Well-defined marks of approximately 100-nm depth can be placed precisely on the transparent films by a focused laser beam.

Interferometric phase reconstruction by nonuniform shifting of the reference beam.

A method for phase measurement in common-path interferometers, believed to be novel, is presented. We use the property of phase reconstruction algorithms, such as the Carré and Hariharan algorithms, that do not require uniform phase across the reference beam. Only the ratio of the phase steps must be the same at each pixel.