We experimentally demonstrate a novel grating which only produces reflection with mode conversion in a two-mode waveguide. That characteristic can improve the performance of optical devices that currently use tilted Bragg gratings to provide the mode conversion. Tilted Bragg gratings produce also reflections without mode conversion which increases noise and crosstalk of the optical device.

Juvenile psammomatoid ossifying fibroma (JPOF) is a benign fibroosseous lesion predominantly arising within the paranasal sinuses in children and young adults. Neurocranial occurrence is exceedingly rare and a location within the neurocranial portion of the temporal bone has not been described. The authors report on one case of sinonasal JPOF secondarily extending into the cranial cavity and three cases primarily affecting the neurocranial bones to increase clinical awareness of this uncommon tumor, which may be easily mistaken for meningioma. Moreover, the absence of activating missense mutations of the GNAS1 gene in two cases strongly argues against a relationship between JPOF and fibrous dysplasia.

We have studied the effect of generative-pulse amplitude, spatial profile, and temporal character as well as medium optical thickness on the power of photon and stimulated echoes. Working in atomic Yb vapor, photon echoes are observed that, absent material relaxation, are more powerful than the first generative pulse, thereby exceeding typically expected photon-echo powers by approximately two orders of magnitude. Factors crucial to the generation of powerful echoes identified through Maxwell-Bloch simulation are experimentally confirmed. ͓S1050-2947͑99͒51308-5͔

We report observations of optical superradiant emission and the atomic evolution it drives under conditions closely approximating those originally envisioned in the classic work of Dicke [Phys. Rev. 93, 99 (1954)]. Our experiment involves an optically thin solid sample in a short-lifetime optical cavity whose homogeneous coherence is cryogenically stabilized. Pulsed coherent excitation initiates superradiant emission which subsequently drives the sample to higher or lower states of coherence. Suppression of dephasing via cryogenics and propagation effects through use of an optically thin sample and cavity provides one of the clearest and cleanest examples of Dicke superradiance yet reported.

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