Biomedical subjects

Robert R McLeod

Publications and source records attributed to Robert R McLeod.

5 recordsLinked to original sources

PubMed2007

Three-dimensional direct-write lithography into photopolymer.

We demonstrate a three-dimensional direct-write lithography system capable of writing deeply buried, localized index structures into diffusion-mediated photopolymer. The system is similar to that used for femtosecond writing in glass, but has a number of advantages including greater flexibility in the writing media and the ability to use low power, inexpensive, continuous-wave lasers. This system writes index structures both parallel and perpendicular to the writing beam in different types of photopolymers, providing control over the feature size and shape. We demonstrate that this system can be used to create single-mode waveguides that are deeply embedded in the photopolymer medium.

Journal Article↗

PubMed2006

Scanning transmission microscopy using a position-sensitive detector.

Optical data manipulation technologies increasingly employ densely aperiodic optical 3D phase elements. Refinement of such technologies will require the capability to quantitatively characterize the volumetric dielectric modulation of an optical sample to a high level of precision and spatial resolution. We present a scanning transmission microscopy system that uses a position-sensitive detector to impart sensitivity to both the phase and absorption components. We describe the layout of the instrument and then derive its phase and absorption transfer functions. Simulations and experiments are presented to validate the analysis. For phase detection, the instrument possesses depth-sectioning properties similar to those of a confocal microscope without the use of a pinhole, enabling full 3D object reconstruction.

Computer-Aided Design↗

PubMed2006

Acousto-optic parallel read/write head for optical disk data storage.

Parallel read and write of optical disks has traditionally used a static grating for read or a linear array of independent lasers for read and write. Depending on the implementation, these systems suffer from coherent cross talk, excessive space between spots, and an inability to independently track. We show that a dynamic acousto-optic grating can generate multiple parallel read/write spots on the disk, each of which can be independently modulated and tracked and all of which are incoherent in less that a bit period. The resulting disk pickup can potentially reach gigabit per second transfer rates with only a modest increase in the drive complexity.

Journal Article↗

PubMed2005

Improving the spectral resolution of wedged etalons and linear variable filters with incidence angle.

Compact spectrometers fabricated by placing a wedged etalon or a linear variable filter in front of a linear photodiode array typically do not exhibit the spectral resolution of a parallel filter of the same finesse. A theoretical analysis of the beam emerging from a wedged etalon is shown to predict a comalike aberration, explaining the loss in resolution. This analysis also predicts a focused beam waist whose axial position depends on the incidence angle, indicating that resolution can be improved by placing this waist on the detector. These results are experimentally confirmed in a multicavity linear variable filter to achieve 0.09 nm spectral resolution at 1550 nm.

Journal Article↗

PubMed2005

Microholographic multilayer optical disk data storage.

Micrometer-sized reflection holograms can be written into a rapidly rotating homogeneous photopolymer disk at the focus of a high-numerical-aperture beam and its retroreflection to implement high-capacity multilayer digital data storage. This retroreflection is generated by an optical system with positive unity magnification to ensure passive alignment of the counterpropagating beam. Analysis reveals that the storage capacity and transfer rate of this bit-based holographic storage system compare favorably with traditional page-based systems but at a fraction of the system complexity and cost. The analysis is experimentally validated at 532 nm by writing and reading 12 layers of microholograms in a 125-microm photopolymer disk continuously rotating at 3600 rpm. The experimental results predict a capacity limit of 140 Gbytes in a millimeter-thick disk or over 1 Tbyte with the wavelength and numerical aperture of Blu-Ray.

Journal Article↗