Biomedical subjects

Andrew M Weiner

Publications and source records attributed to Andrew M Weiner.

3 recordsLinked to original sources

PubMed2004

400-photon-per-pulse ultrashort pulse autocorrelation measurement with aperiodically poled lithium niobate waveguides at 1.55 microm.

We demonstrate ultrasensitive intensity autocorrelation measurements of subpicosecond optical pulses in the telecommunication band by using aperiodically poled lithium niobate (A-PPLN) waveguides. The tightly confined optical beam in the waveguides and the chirped poling period facilitate simultaneous high second-harmonic generation (SHG) efficiency and broad phase-matching (PM) bandwidth. The resulting measurement sensitivity is 3.2 x 10(-7) mW2, approximately 500 times better than the previous record for intensity autocorrelations. We also show that chirped A-PPLN waveguides retain nearly the same SHG efficiency as the unchirped guide as long as the PM bandwidth is not significantly broader than the input spectrum.

Journal Article↗

PubMed2003

Generalized grating equation for virtually-imaged phased-array spectral dispersers.

The virtually-imaged phased array (VIPA) is a side-entrance etalon with potential application as a high-resolution spectral disperser for wavelength division multiplexing. Here we present an approximate analytical spectral dispersion law for the VIPA, which we confirm experimentally.

Journal Article↗

PubMed2003

Temporal response of a random medium from speckle intensity frequency correlations.

We reconstruct the temporal response of a random medium by using speckle intensity frequency correlations. When the scattered field from a random medium is described by circular complex Gaussian statistics, we show that third-order correlations permit retrieval of the Fourier phase of the temporal response with bispectral techniques. Our experimental results for random media samples in the diffusion regime are in excellent agreement with the intensity temporal response measured directly with an ultrafast pulse laser and a streak camera. Our speckle correlation measurements also demonstrate sensitivity to inhomogeneous samples, highlighting the potential application for imaging within a scattering medium.

Journal Article↗