Spectral interferometric implementation with passive polarization optics of coherent anti-Stokes Raman scattering

We have developed an interferometric implementation of coherent anti-Stokes Raman scattering which enables broadband coherent Raman spectroscopy free from the nonresonant background, with a signal strength proportional to concentration. Spectra encode mode symmetry information into the amplitude response, which can be directly compared to polarized spontaneous Raman spectra. The method requires only passive polarization optics and is suitable for a wide range of laser linewidths and pulse durations. The method's application to Raman spectral imaging is demonstrated.

Anomalous power laws of spectral diffusion in quantum dots: a connection to luminescence intermittency

We show that the wandering of transition frequencies in colloidal quantum dots does not follow the statistics expected for ordinary diffusive processes. The trajectory of this anomalous spectral diffusion is characterized by a sqrt[t] dependence of the squared deviation. The behavior is reproduced when the electronic states of quantum dots are assumed to interact with environments such as, for example, an ensemble of two-level systems, where the correlation times are distributed according to a power law similar to the one generally attributed to the dot's luminescence intermittency.

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. We develop a theoretical treatment of this system and perform numerical simulations for a typical CARS system, which indicate that resolutions around 120 nm are obtainable with the present scheme. As an imaging system, this method combines the advantages of sub-diffraction-limited resolution, endogenous contrast generation, and a wide field of view.

Coherent super-resolution microscopy via laterally structured illumination

Theory describing a super-resolution microscopy experiment using temporally and spatially coherent structured illumination was developed, and used to derive a method for processing experimental data. Numerical simulations were performed to verify that the method can, in principle, produce super-resolved images that are exactly equivalent to an image processed by a system with a much larger aperture (that is, the correct weighting between different regions of the image spectrum is maintained). The process was then demonstrated experimentally, showing a factor of two improvement in resolution over a diffraction-limited, coherently illuminated, microscope.