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The emerging technique of mid-infrared optical coherence tomography (MIR-OCT) takes advantage of the reduced scattering of MIR light in various materials and devices, enabling tomographic imaging at deeper penetration depths. Because of challenges in MIR detection technology, the image acquisition time is, however, significantly longer than for tomographic imaging methods in the visible/near-infrared. Here we demonstrate an alternative approach to MIR tomography with high-speed imaging capabilities. Through femtosecond nondegenerate two-photon absorption of MIR light in a conventional Si-based CCD camera, we achieve wide-field, high-definition tomographic imaging with chemical selectivity of structured materials and biological samples in mere seconds.

A comprehensive theoretical analysis of photoinduced forces in an illuminated nanojunction, formed between an atomic force microscopy tip and a sample, is presented. The formalism is valid within the dipolar approximation and includes multiple scattering effects between the tip, sample, and a planar substrate through a dyadic Green's function approach. This physically intuitive description allows a detailed look at the quantitative contribution of multiple scattering effects to the measured photoinduced force, effects that are typically unaccounted for in simpler analytical models. Our findings show that the presence of the planar substrate and anisotropy of the tip have a substantial effect on the magnitude and the spectral response of the photoinduced force exerted on the tip. Unlike previous models, our calculations predict photoinduced forces that are within range of experimentally measured values in photoinduced force microscopy (PiFM) experiments.

We examine the mechanical eigenmodes of a quartz tuning fork (QTF) for the purpose of facilitating its use as a probe for multifrequency atomic force microscopy (AFM). We perform simulations based on the three-dimensional finite element method and compare the observed motions of the beams with experimentally measured resonance frequencies of two QTF systems. The comparison enabled us to assign the first seven asymmetric eigenmodes of the QTF. We also find that a modified version of single beam theory can be used to guide the assignment of mechanical eigenmodes of QTFs. The usefulness of the QTF for multifrequency AFM measurements is demonstrated through photoinduced force microscopy measurements. By using the QTF in different configurations, we show that the vectorial components of the photoinduced force can be independently assessed and that lateral forces can be probed in true noncontact mode.

We perform time-resolved pump-probe microscopy measurements by recording the local force between a sharp tip and the photo-excited sample as a readout mechanism for the material's nonlinear polarization. We show that the photo-induced force is sensitive to the same excited state dynamics as measured in an optical pump-probe experiment. Ultrafast pump-probe force microscopy constitutes a non-optical detection technique with nanoscale resolution that pushes pump-probe sensitivities close to the realm of single molecule studies.

We demonstrate the utility of picosecond spectral coherent anti-Stokes Raman scattering imaging with principal component analysis to rapidly map lipophilic components in cardiovascular tissues, facilitating the interrogation of atherosclerosis. © 2011 OSA: BODA/NTM/OMP/OTA.

We demonstrate the utility of picosecond spectral coherent anti-Stokes Raman scattering imaging with principal component analysis to rapidly map lipophilic components in cardiovascular tissues, facilitating the interrogation of atherosclerosis. © 2011 OSA: BODA/NTM/OMP/OTA.

An overview is presented of recent trends in coherent anti-Stokes Raman scattering (CARS) microscopy. We briefly discuss the influence of tissue scattering on the CARS signal, methods for controlling the CARS emission and prospects for surface-enhancement of the CARS radiation.

CARS microscopy is used to quantitatively investigate the process of skin optical clearing. Using glycerol and dimethyl-sulfoxide as the clearing agents, we find that tissue scattering is a highly nonlinear function of agent concentration. © 2007 Optical Society of America.