Rapidly swept, ultra-widely-tunable 1060 nm MEMS-VCSELs.

Demonstrated are 1060 nm microelectromechanical-systems-based tunable vertical-cavity surface-emitting lasers (MEMS-VCSELs) with a 100 nm continuous tuning range under repetitively scanned operation at rates beyond 500 kHz and a 90 nm continuous tuning range under static operation. These devices employ a thin strained InGaAs multiple quantum well active region integrated with a fully oxidised GaAs/AlxOy bottom mirror and a suspended dielectric top mirror. The devices are optically pumped via 850 nm light. These ultra-widely tunable lasers represent the first MEMS-VCSELs reported in this wavelength range, and are ideally suited for application in ophthalmic swept-source optical coherence tomography.

High-sweep-rate 1310 nm MEMS-VCSEL with 150 nm continuous tuning range.

Microelectromechanical-systems-based vertical-cavity surface-emitting lasers (MEMS-VCSELs) capable of a 150 nm continuous tuning range near 1310 nm are demonstrated. These devices employ a thin optically pumped active region structure with large free-spectral range, which promotes wide and continuous tuning. To achieve VCSEL emission at 1310 nm, a wide-gain-bandwidth indium phosphide-based multiple quantum well active region is combined with a wide-bandwidth fully oxidised GaAs-based mirror through wafer bonding, with tuning enabled by a suspended dielectric top mirror. These devices are capable of being scanned over the entire tuning range at frequencies up to 500 kHz, making them ideal for applications such as swept source optical coherence tomography and high-speed transient spectroscopy.

High-speed, high-resolution optical coherence tomography retinal imaging with a frequency-swept laser at 850 nm.

High-speed, high-resolution optical coherence tomography (OCT) imaging of the human retina is demonstrated using a frequency-swept laser at 850 nm. A compact external cavity semiconductor laser design, optimized for swept-source ophthalmic OCT, is described. The laser enables an effective 16 kHz sweep rate with >10 mm coherence length and a tuning range of approximately 35 nm full width at half-maximum, yielding an axial resolution of <7 micro m in tissue.

Three-dimensional and C-mode OCT imaging with a compact, frequency swept laser source at 1300 nm.

We demonstrate high resolution, three-dimensional OCT imaging with a high speed, frequency swept 1300 nm laser source. A new external cavity semiconductor laser design, optimized for application to swept source OCT, is discussed. The design of the laser enables adjustment of an internal spectral filter to change the filter bandwidth and provides a robust bulk optics design. The laser generates ~30 mW instantaneous peak power at an effective 16 kHz sweep rate with a tuning range of ~133 nm full width. In frequency domain reflectometry and OCT applications, 109 dB sensitivity and ~10 microm axial resolution in tissue can be achieved with the swept laser. The high imaging speeds enable three-dimensional OCT imaging, including zone focusing or C-mode imaging and image fusion to acquire large depth of field data sets with high resolution. In addition, three-dimensional OCT data provides coherence gated en face images similar to optical coherence microscopy (OCM) and also enables the generation of images similar to confocal microscopy by summing signals in the axial direction. High speed, three-dimensional OCT imaging can provide comprehensive data which combines the advantages of optical coherence tomography and microscopy in a single system.

Validity of leg-to-leg bioelectrical impedance measurement in males.

BACKGROUND: This study determined the validity of the leg-to-leg bioelectrical impedance analysis (BIA) system (Tanita Body Fat Analyzer, TBF 105, Tanita Corporation of America, Inc., Arlington Heights, IL) in estimating body composition in males. EXPERIMENTAL DESIGN: Fat-free mass (FFM) was estimated using BIA and underwater weighing, and compared. SETTING: Subjects were recruited from the community. PARTICIPANTS: Heterogeneous group of males (N=192) was recruited, with a mean+/-SD age of 39.0+/-16.8 yrs; body mass index, 26.0+/-4.0 kg/m2, percent body fat, 18.1+/-8.9 percent. MEASURES: Prior to BIA testing, subjects were required to adhere to standard BIA testing guidelines, and bioelectrical impedance was measured in subjects standing erect with bare feet on the analyzer's footpads, and wearing a swimsuit. Underwater weighing was conducted using standard procedures, with direct measurement of residual volume. RESULTS: A Bland-Altman plot of difference between FFM measured by underwater weighing and BIA versus average FFM by the two methods showed no systematic difference (mean difference, 0.07+/-3.5 kg). FFM was estimated at 66.3+/-8.6 kg with underwater weighing, and 66.2+/-7.7 kg with BIA (r=0.92, p<0.001; SEE 3.5 kg). CONCLUSIONS: These data indicate that the leg-to-leg bioelectrical impedance system accurately assesses FFM in a heterogenous group of males when compared to underwater weighing.

Locus equations derived from compensatory articulation.

Locus equations are linear regressions of the onset of F2 transitions on their offsets. These functions vowel-normalize the F2 transitions such that they are able to characterize consonantal place categories. The purpose of this research was to determine if compensatory articulation due to bite blocks would alter the normally linear relationship between F2 transition onset and offset frequencies or alter the differential slopes and y intercepts of locus equations as a function of stop place. Six speakers, three male and three female, each produced /bVt/, /dVt/, and /gVt/ tokens for ten vowel contexts under normal and bite block conditions. Extremely linear and practically identical scatterplots were obtained in the two speaking conditions. No adaptation to the bite blocks was found when comparing locus equations derived from the initial versus the final bite block trial. Results are discussed in relation to the "orderly output constraint," which postulates a perceptual function for linearly related F2 transition end points within consonantal place categories.

Observations of sodium atoms in a magnetic molasses trap loaded by a continuous uncooled source.

We describe observations of atoms trapped in magnetic molasses made by using a simplified apparatus that is loaded by a continuous uncooled source of atoms. We also measured the cross section for collisions in which trapped sodium atoms are ejected from the trap by thermal sodium atoms and estimate that the cross section is 30 times larger than for collisions with other background thermal atoms.

Atomic-density-dependent losses in an optical trap.

We have observed that two-body collisions between cold sodium atoms confined within a magnetic-molasses optical trap lead to significant atomic-density-dependent trap losses. Such losses set an upper limit to the product of atomic density and confinement time that can be achieved in such a trap.