A method for achieving super-resolved widefield CARS microscopy.

We propose a scheme for achieving widefield coherent anti-Stokes Raman scattering (CARS) microscopy images with sub-diffraction-limited resolution. This approach adds structured illumination to the widefield CARS configuration [Applied Physics Letters 84, 816 (2004)]. By capturing a number of images at different phases of the standing wave pattern, an image with up to three times the resolution of the original can be constructed.

Quantitative SLM-based Differential Interference Contrast imaging.

We describe the implementation of quantitative Differential Interference Contrast (DIC) Microscopy using a spatial light modulator (SLM) as a flexible Fourier filter in the optical path. The experimental arrangement allows for the all-electronic acquisition of multiple phase shifted DIC-images at video rates which are analyzed to yield the optical path length variation of the sample. The resolution of the technique is analyzed by retrieving the phase profiles of polystyrene spheres in immersion oil, and the method is then applied for quantitative imaging of biological samples.

Differential interference contrast imaging using a spatial light modulator.

Differential interference contrast microscopy, imaging by interferometric superposition of two displaced beams passed through a transparent sample, is one of the most sophisticated methods in classical microscopy. Here we demonstrate a versatile electronically controlled variant using a liquid-crystal spatial light modulator that displays a diffractive optical element and steers the beam separation. The orientation and magnitude of the shear angle and the relative phase of the two interfering beams can all be varied at video rates.

OH concentration and temperature measurements by use of near-resonant holographic interferometry.

Near-resonant holographic interferometry is demonstrated to measure temperature and species concentration in a two-dimensional steady premixed air-acetylene flame. A peak temperature of (2600 +/- 100) K and a peak OH number density of (9.6 +/- 0.

Near-resonant holographic interferometry and absorption measurements of seeded atomic species in a flame.

The development of near-resonant holographic interferometry techniques for use on flows seeded with atomic species is described. A theoretical model for the refractivity that is due to the seed species is outlined, and an approximation to this model is also described that is shown to be valid for practical regimes of interest and allows the number density of the species to be determined without knowledge of line-broadening effects. The details of quantitative number density experiments performed on an air-acetylene flame are given, and a comparison with an alternative absorption-based experiment is made.

Enhanced flow visualization with near-resonant holographic interferometry.

Holographic interferometry measurements have been performed on high-speed, high-temperature gas flows with a laser output tuned near a resonant sodium transition. The technique allows the detection and quantification of the sodium concentration in the flow. By controlling the laser detuning and seeded sodium concentration, we performed flow visualization in low-density flows that are not normally detectable with standard interferometry.