N-Type Bismuth Telluride Nanocomposite Materials Optimization for Thermoelectric Generators in Wearable Applications.

Thermoelectric materials could play a crucial role in the future of wearable electronic devices. They can continuously generate electricity from body heat. For efficient operation in wearable systems, in addition to a high thermoelectric figure of merit, , the thermoelectric material must have low thermal conductivity and a high Seebeck coefficient.

Type VIII Si based clathrates: prospects for a giant thermoelectric power factor.

Although clathrate materials are known for their small thermal conductivity, they have not shown a large thermoelectric power factor so far. We present the band structures of type VIII Si, Ge, and Sn clathrates as well as the alkali and alkaline-earth intercalated type VIII Si clathrates. Our calculations revealed that this group of materials has potentially large power factors due to the existence of a large number of carrier pockets near their band edges.

Trans-rectal ultrasound-coupled spectral optical tomography of total hemoglobin concentration enhances assessment of the laterality and progression of a transmissible venereal tumor in canine prostate.

Objectives: To evaluate whether trans-rectal spectral optical tomography of total hemoglobin concentration (HbT) can image longitudinal and lateral developments of a canine transmissible venereal tumor (TVT) in a canine prostate.

Methods: A near-infrared (NIR) applicator was integrated with a trans-rectal ultrasound (TRUS) transducer to perform ultrasound (US)-coupled optical tomography of the canine prostate. Spectral detection at 785 and 830 nm enabled quantitation of HbT.

Trans-rectal ultrasound-coupled near-infrared optical tomography of the prostate, part II: experimental demonstration.

We demonstrate trans-rectal optical tomography of the prostate using an endo-rectal near-infrared (NIR) applicator integrated with a transrectal ultrasound (TRUS) probe. The endo-rectal NIR applicator incorporated a design presented in our previously reported work. A continuous-wave NIR optical tomography system is combined with a commercial US scanner to form the dual-modality imager.

Endoscopic, rapid near-infrared optical tomography.

This is believed to be the first demonstration of near-infrared (NIR) optical tomography employed at the endoscope scale and at a rapid sampling speed that allows translation to in vivo use. A spread-spectral-encoding technique based on a broadband light source and linear-to-circular fiber bundling was used to provide endoscopic probing of many source-detector fibers for tomography as well as parallel sampling of all source-detector pairs for rapid imaging. Endoscopic NIR tomography at an 8 Hz frame rate was achieved in phantoms and tissue specimens with a 12 mm probe housing eight sources and eight detectors.

Piezo-driven deformable mirror for femtosecond pulse shaping.

We have developed a deformable, gold-coated mirror based on piezoelectric actuators with 15-micros response time. With 20 independent channels we were able to compress 72-fs pulses from a Ti:sapphire oscillator down to 45 fs in a 4f zero-dispersion compressor arrangement. Spectral interference was used to measure the mirror performance, while the spectral phase interferometry for direct electric field reconstruction (SPIDER) technique was used for the laser pulse characterization.

Photography of shock waves during excimer laser ablation of the cornea. Effect of helium gas on propagation velocity.

Shadow photography of shock waves excited by means of a xenon chloride excimer laser was performed to determine the shock wave propagation velocity in air, nitrogen and helium. Energy densities between 500 and 2,000 mJ/cm2 were used to ablate a rotating rubber cylindrical target and porcine corneas. In ablating the rubber cylinder, a shock wave velocity of 3.

Increased efficiency for sum-frequency generation for broadband input fields.

A new method of efficient sum-frequency generation for broadband input fields is theoretically analyzed and experimentally demonstrated. The method involves using an arrangement with two or more nonlinear mixing crystals, with a time-delay line situated between the crystals, for one of the fundamental fields relative to the other. The delay line temporally shifts the fundamental fields, one relative to another, by a time longer than their coherence time.

Theory of mode-locked intracavity second-harmonic generation in a ring laser.

We model the dynamics of a Q-switched mode-locked intracavity second-harmonic-generation (SHG) ring laser. Numerical studies show that a long train of constant-pulse-duration short pulses at the second-harmonic and fundamental frequencies result. The efficiency of the mode-locked intracavity SHG laser is comparable with that of the mode-locked fundamental-frequency laser not containing SHG.

Birefringence of solid-state laser media: broadband tuning discontinuities and application to laser line narrowing.

Spectral consequences that result from using birefringent media with broadband gain inside of laser cavities containing polarizing elements are described. We show that the laser intensity is modulated as a function of the output frequency unless the cavity elements are carefully aligned so that their polarization axis coincides with a principal optical axis of the gain medium. Analysis of the tuning characteristics of a birefringent polarizationdependent gain medium is exploited to provide a simple method for line narrowing the laser output.