Biomedical subjects

Steve Blair

Publications and source records attributed to Steve Blair.

4 recordsLinked to original sources

PubMed2005

Engineering the nonlinear phase shift with multistage autoregressive moving-average optical filters.

We propose and demonstrate the application of concepts from digital filter design in order to optimize artificial optical resonant structures to produce a nearly ideal nonlinear phase shift response. Multistage autoregressive moving average (ARMA) optical filters (ring-resonator-based Mach-Zehnder interferometer lattices) are designed and studied. The filter group delay is used as a measure instead of finesse or quality factor to study the nonlinear sensitivity for multiple resonances. The nonlinearity of a four-stage ARMA filter is 17 times higher than that of the intrinsic material of the same group delay. We demonstrate that the nonlinear sensitivity can be increased within constant bandwidth by allocating more in-band phase or by using higher-order filter structures and that the nonlinear sensitivity enhancement improves with increasing group delay. We also investigate methods to precompensate the nonlinear response to reduce the occurrence of optical bistabilities. The effect of optical loss, including linear absorption and two-photon absorption, is discussed in postanalysis. In addition, we discuss how the improvement in nonlinear response scales with respect to various filter parameters.

Journal Article↗

PubMed2003

Engineering the nonlinear phase shift.

We treat the nonlinear phase shift response in the weak perturbation limit as a linear digital filter that can be synthesized into the values of its poles and zeros and mapped onto an optical architecture. This procedure results in a significant enhancement in the nonlinear sensitivity with a response that is robust to frequency changes within the filter passband. A precompensation technique can be used to reduce distortions under strongly driven nonlinear operation to achieve a larger phase shift. We also show that nonlinear sensitivity improves with increasing filter group delay and can be increased within constant linear bandwidth by use of higher-order filters.

Journal Article↗

PubMed2003

Fluorescence enhancement from an array of subwavelength metal apertures.

We report the resonant excitation of a fluorescing molecular monolayer applied to a periodic array of subwavelength apertures in a metal film. The peak fluorescence occurs under conditions of maximum transmission of the excitation light, which indicates strong enhancement of the incident light within the apertures under resonant conditions. Fluorescence output normalized to the aperture fill fraction is enhanced by nearly 40 times, and the rate of photobleaching is increased by approximately a factor of 2, suggesting an increase in the fluorescence yield.

Fluorescence↗

PubMed2000

Nonparaxial one-dimensional spatial solitons.

Scalar and vector nonlinear nonparaxial evolution equations are developed for propagation in two-dimensions. Using standard soliton scalings, it is found that nonparaxial propagation is accompanied by higher-order linear and nonlinear terms and an effective quintic nonlinear index. The presence of an intrinsic quintic nonlinearity arising from chi((5)) must also be considered at the order of the analysis. These terms represent corrections to the well-known nonlinear Schrodinger equation. Exact and approximate solutions to these higher-order evolution equations are obtained and are shown to exhibit quasi-soliton behavior based on propagation and collision studies. (c) 2000 American Institute of Physics.

Journal Article↗