We demonstrate a novel technique to determine the size of Mie scatterers with high sensitivity. Our technique is based on spectral domain optical coherence tomography measurements of the dispersion that is induced by the scattering process. We use both Mie scattering predictions and dispersion measurements of phantoms to show that the scattering dispersion is very sensitive to small changes in the size and/or refractive index of the scatterer. We also show the light scattered from a single sphere is, in some cases, non-minimum phase, and therefore the phase of the scattered light is independent of the intensity. Phase dispersion measurements may have application to distinguishing the size and refractive index of scattering particles in biological tissue samples.

The design, operation, and application of a novel solar simulator based on a high-power supercontinuum fiber laser are described. The simulator features a multisun irradiance with continuous spectral coverage from the visible to the infrared. By use of a prism-based spectral shaper, the simulator can be matched to any desired spectral profile, including the ASTM G-173-03 airmass 1.5 reference spectrum. The simulator was used to measure the efficiency of gallium arsenide (GaAs), crystalline silicon (Si), amorphous Si, and copper-indium-gallium-selenide (CIGS) thinfilm solar cells, showing agreement with independent measurements. The pulsed temporal characteristic of the simulator was studied and would appear to have a negligible influence on measured cell efficiency. The simulator light was focused to a spot of approximately 8 μm in diameter and used to create micrometerscale spatial maps of full spectrum optical-beam-induced current. Microscopic details such as grid lines, damage spots, and material variations were selectively excited and resolved on GaAs and CIGS cells. The spectral shaping capabilities were used to create output spectra appropriate for selectively light-biasing multijunction cell layers. The simulator was used to create variable blue-rich and red-rich spectra that were applied to a GaInP/GaAs tandem solar cell to illustrate the current-limiting behavior.

A frequency comb is generated with a chromium-doped forsterite femtosecond laser, spectrally broadened in a dispersion-shifted highly nonlinear fiber, and stabilized. The resultant evenly spaced comb of frequencies ranges from 1.1 to beyond 1.8 microm. The frequency comb was referenced simultaneously to the National Institute of Standards and Technology's optical frequency standard based on neutral calcium and to a hydrogen maser that is calibrated by a cesium atomic fountain clock. With this comb we measured two frequency references in the telecommunications band: one half of the frequency of the d/f crossover transition in 87Rb at 780 nm, and the methane v2 + 2v3 R(8) line at 1315 nm.

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