ABSTRACT
High-efficiency dynamic holography at 1.55 µm is demonstrated in a broad-area InGaAs/InP multiple-quantum-well vertical microcavity. The design places single quantum wells at the cavity antinodes, reducing mode-pulling and enabling a higher Q-factor. The device is pumped by interference fringes through an amorphous mirror that is transparent to a high-energy hologram writing pulse at a wavelength of 1.06 µm. Optically pumped free carrier gratings are probed by a tunable 1.5 µm laser in a four-wave mixing configuration. Diffraction efficiency into both m=±1 diffraction orders of 35% (70% total) has been obtained with a phase grating contribution approaching the maximum π phase shift by combining absorption bleaching with asymmetric Fabry-Perot reflectivity. The diffracted signal exhibits rise/fall times of 5 ns, demonstrating the high speed capabilities of this device.
ABSTRACT
OBJECTIVE: To evaluate systematic differences in landmark position between cone-beam computed tomography (CBCT)-generated cephalograms and conventional digital cephalograms and to estimate how much variability should be taken into account when both modalities are used within the same longitudinal study. MATERIALS AND METHODS: Landmarks on homologous cone-beam computed tomographic-generated cephalograms and conventional digital cephalograms of 46 patients were digitized, registered, and compared via the Hotelling T(2) test. RESULTS: There were no systematic differences between modalities in the position of most landmarks. Three landmarks showed statistically significant differences but did not reach clinical significance. A method for error calculation while combining both modalities in the same individual is presented. CONCLUSION: In a longitudinal follow-up for assessment of treatment outcomes and growth of one individual, the error due to the combination of the two modalities might be larger than previously estimated.
