There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Nanoscale quantum emitters are key elements in quantum optics and sensing. However, efficient optical excitation and detection of such emitters involves large solid angles because their interaction with freely propagating light is omnidirectional. Here, we present unidirectional emission of a single emitter by coupling to a nanofabricated Yagi-Uda antenna. A quantum dot is placed in the near field of the antenna so that it drives the resonant feed element of the antenna. The resulting quantum-dot luminescence is strongly polarized and highly directed into a narrow forward angular cone. The directionality of the quantum dot can be controlled by tuning the antenna dimensions. Our results show the potential of optical antennas to communicate energy to, from, and between nano-emitters.

http://science.sciencemag.org/content/sci/329/5994/930.full.pdf

Unidirectional emission of a quantum dot coupled to a nanoantenna

Objective: To demonstrate optical coherence tomography for high-resolution, noninvasive imaging of the human retina. Optical coherence tomography is a new imaging technique analogous to ultrasound B scan that can provide cross-sectional images of the retina with micrometer-scale resolution. Design: Survey optical coherence tomographic examination of the retina, including the macula and optic nerve head in normal human subjects. Settings Research laboratory. Participants: Convenience sample of normal human subjects. Main Outcome Measures: Correlation of optical coherence retinal tomographs with known normal retinal anatomy. Results: Optical coherence tomographs can discriminate the cross-sectional morphologic features of the fovea and optic disc, the layered structure of the retina, and normal anatomic variations in retinal and retinal nerve fiber layer thicknesses with 10- μm depth resolution. Conclusion: Optical coherence tomography is a potentially useful technique for high depth resolution, cross-sectional examination of the fundus.

Optical Coherence Tomography of the Human Retina

Course Description This is an advanced course in which we explore the field of Statistical Optics. Topics covered include such subjects as the statistical properties of natural (thermal) and laser light, spatial and temporal coherence, effects of partial coherence on optical imaging instruments, effects on imaging due to randomly inhomogeneous media, and a statistical treatment of the detection of light. Development of this more comprehensive model of the behavior of light draws upon the use of tools traditionally available to the electrical engineer, such as linear system theory and the theory of stochastic processes.

http://ieeexplore.ieee.org/iel5/3/23094/01073023.pdf

Statistical optics

Publisher Summary This chapter describes the phase-measurement interferometry techniques. For all techniques, a temporal phase modulation is introduced to perform the measurement. By measuring the interferogram intensity as the phase is shifted, the phase of the wavefront can be determined with the aid of electronics or a computer. Phase modulation in an interferometer can be induced by moving a mirror, tilting a glass plate, moving a grating, rotating a half-wave plate or analyzer, using an acousto-optic or electro-optic modulator, or using a Zeeman laser. Phase-measurement techniques using analytical means to determine phase all have some common denominators. There are different equations for calculating the phase of a wavefront from interference fringe intensity measurements. The precision of a phase-measuring interferometer system can be determined by taking two measurements, subtracting them, and looking at the root-meansquare of the difference wavefront. The chapter discusses the simulation results. The elimination of the errors that reduce the measurement accuracy depends on the type of measurement being performed. Phase-measurement interferometry (PMI) can be applied to any two-beam interferometer, including holographic interferometers. Applications can be divided into: surface figure, surface roughness, and metrology.

V Phase-Measurement Interferometry Techniques

In vivo confocal scanning laser microscopy of human skin II: advances in instrumentation and comparison with histology.

We demonstrate a new method of determining the three-dimensional dipole orientations of single molecules by direct imaging of the emission patterns in the back focal plane of a high-numerical-aperture objective lens. We compare the reconstructed emission-dipole orientations with a previously established method of absorption-dipole mapping. We find that, for a given number of emitted photons, emission pattern imaging provides better accuracy (1°–2°) than absorption-dipole mapping of single molecules. Compared with some other methods for emission-dipole mapping, the presented method is (1) less sensitive to optical aberrations and adjustment and (2) data analysis is simplified because radiation patterns can be expressed in a simple analytical form.

Single-molecule orientations determined by direct emission pattern imaging

In order to facilitate pathological examination of a lesion in in-vivo tissue, a system and method are provided having a computer system in which both a camera for producing a digital macroscopic picture of the lesion and an imager are coupled to the computer system. The imager is responsive to the computer system and has optics for scanning the lesion to generate images representing microscopic sections of the lesion which provide sufficient information for pathological examination of the lesion. The computer system generates location information, referencing the location in the macroscopic picture of the lesion where the lesion was scanned to the images, and stores data in an electronic file structure which contains at least a representation of the images, a representation of the macroscopic picture, and the location information. The file structure may then be sent to another computer system for viewing the images stored in the file structure to facilitate pathological examination of the lesion by persons trained to interpret such images, adding a diagnostic report about the lesion to the data of the file structure, and sending back the file structure to the computer system that originated it.

System for facilitating pathological examination of a lesion in tissue

A hand held microsurgical instrument for applying laser energy to selected locations (sites) in an area under the skin (or other exposed translucent tissue) to provide localized photothermolysis of underlying tissue at these sites, is described. The laser energy is focused into a spot within the tissue. This spot is of sufficiently small size so that the energy density is sufficient to provide surgical or treatment effects within the tissue without damaging the surface tissue. In dermatology, for example, the technique can be used to destroy endothelial cells in blood vessels which are desired to be removed, such spider veins (nevi) in the skin, hair follicles to prevent hair growth therefrom, or other microsurgical procedures. The area is visualized while the laser beam is steered, using a deflection system, in X and Y coordinates. A telecentric optical system, in which a mirror of the deflection system is located, directs the laser light essentially perpendicular to the area to be treated as the beam is scanned over the area. The optical system also focuses illumination light reflected from the area to a sensor matrix of a CCD video camera. The reflected illumination light is imaged essentially parallel to the optical axis in the object space thereby providing a precise, high resolution image corresponding to the area. The laser beam may be tracked as it is deflected over the area to the selected locations by visualization thereof on a display or monitor associated with the video camera. The locations are then apparent to the treating physician who can then effect an increase of the beam power or turn the beam on so as to treat the tissue in the selected locations.

Dermatological laser treatment system with electronic visualization of the area being treated

The quality of images produced by confocal microscopy, and especially scanning laser confocal microscopy, is enhanced especially for images obtained in turbid mediums such as many biological tissue specimens, by reducing speckle from scatterers that exist outside (above and below) the focal plane region which is being imaged by utilizing sheared beams, both of which are focused to spots in the focal or image plane (region of interest) and polarizing the beams to have opposite senses of circular polarization (right and left handed circular polarization). The return light from the image plane of certain polarization is detected after passing through the confocal aperture of the confocal microscope. Light from scatterers outside the region of interest, which are illuminated by both of the sheared beams, interfere thereby reducing speckle due to such scatterers, and particularly scatters which are adjacent to the image plane. Sheared beams having orthogonal linear polarization, as may be obtained from a Wollaston or Nomarski prism are converted into circularly polarized beams of opposite polarization sense by a quarter wave plate. The optical signals representing reflections from the focal plane are derived by polarizing optics which may either, be a polarizing beamsplitter in the incident beam path or with a retarder and analyzer. The retarder may be selected to provide different polarization phase shift of the return light, and with the analyzer, detects the degree of elliptical polarization representing the optical activity and circular dichroism producing the optical signal representing the image.

James M. Zavislan

Papers

In vivo confocal scanning laser microscopy of human skin II: advances in instrumentation and comparison with histology.

Single-molecule orientations determined by direct emission pattern imaging

System for facilitating pathological examination of a lesion in tissue

Dermatological laser treatment system with electronic visualization of the area being treated

Imaging system using polarization effects to enhance image quality