Cover Story

Ultrasonic imaging is versatile, noninvasive, portable, relatively inexpensive, and is second only to X-ray in annual procedural volume. Optical imaging continues to search for an identity in the medical arena. Opto-acoustic tomography... more>>

Features

Therapeutic Lasers and Optical Diagnostic Technology in Dentistry

OPTICAL TECHNOLOGIES PROVIDE PAINLESS PROGRESS IN DENTAL DISEASE PREVENTION, DIAGNOSIS, AND TREATMENT. more>>


Optical Tools Offer Minimally Invasive Medical Diagnostics

Optical imaging and spectroscopy can be applied to a wide variety of medial diagnostic tests, including screening for early signs of cancer. more>>


The van Cittert-Zernike Theorem

Our goal is to present a simple derivation of the van Cittert-Zernike theorem without invoking the theories of probability and stochastic processes. This is possible because most sources of practical interest are ergodic, meaning that time-averaging over a typical waveform emanated by the source yields statistical information about the source's inherently random radiation processes. We shall make exclusive use of time-averaging to derive the degree of coherence of a pair of points within the field of an extended, quasi-monochromatic, incoherent source. more>>


High-NA Pickup Objective for High-Density Media

In 1967 Duguay and Rentzepis suggested the possibility of producing population inversions at short wavelengths by x-ray photoionization of inner-shell p-electrons in atomic species. Instead, the present work uses inner-shell d-electron removal (which has a larger cross section) and improves the pumping efficiency to a specific state by concentrating on species with closed outer shells. The concept of efficient broadband pumping with laser-produced plasmas, as proposed by Harris et al. and demonstrated by Caro et al. at Stanford University, to produce metastable states was also incorporated into this work. more>>

Pulses

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