This book provides a systematic introduction to the principles of microscopic imaging through tissue-like turbid media in terms of Monte-Carlo simulation. It describes various gating mechanisms based on the physical differences between the un scattered and scattered photons and method for microscopic image reconstruction, using the concept of the effective point spread function. Imaging an object embedded in a turbid medium is a challenging problem in physics as well as in bio photonics. A turbid medium surrounding an object under inspection causes multiple scattering, which degrades the contrast, resolution and signal-to-noise ratio. Biological tissues are typically turbid media. Microscopic imaging through a tissue-like turbid medium can provide higher resolution than transillumination imaging in which no objective is used. This book serves as a valuable reference for engineers and scientists working on microscopy of tissue turbid media.

This book reports new findings in the fields of nonlinear optics, quantum optics and optical microscopy. It presents the first experimental device able to transform an input Gaussian beam into a non-diffracting Bessel-like beam. The modulation mechanism, i.e. electro-optic effect, allows the device to be fast, miniaturizable and integrable into solid state arrays. Also presented is an extensive study of the superposition of Bessel beams and their propagation in turbid media, with the aim of realizing field that is both localized and non-diffracting. These findings have been implemented in a light-sheet microscope to improve the optical sectioning. From a more theoretical point of view this work also tackles the problem of whether and how a single particle is able to entangle two distant systems. The results obtained introduce fundamental limitations on the use of linear optics for quantum technology. Other chapters are dedicated to a number of experiments carried out on disordered ferroelectrics including negative intrinsic mass dynamics, ferroelectric supercrystals, rogue wave dynamics driven by enhanced disorder and first evidence of spatial optical turbulence.

Optical imaging through biological tissues and other scattering media is challenging, as the scattered light creates an extremely high background noise level that makes it difficult to detect objects that are embedded within the media. This thesis examines a relatively unexplored method of separating scattered light from unscattered light that has application to optical imaging through turbid media. The method creates an optical filter that blocks photons based upon their exit trajectory direction. Such a trajectory filter can be used with a collimated beam that transmissively illuminates a scattering medium to create an imaging system in which a shadowgram is formed from those photons that pass through the filter and have a trajectory close to that of the collimated beam. Experiments have shown that such a system is effective up to measured optical depths of 18 to 21 and scattering ratios of 108 to 109 using both coherent and incoherent sources. A micromachined linear array of 50 m x 10 mm collimating holes was developed earlier as a photon trajectory filter and was used to successfully image through media in which the ratio of scattered to unscattered light is extremely high (>107). These results are much better than simple theory would predict. This thesis provides a theoretical basis for the trajectory filter system to allow its performance to be characterized and compared against other optical imaging methods, such as time-domain imaging. Using Monte Carlo simulations, it is found that the trajectory filter method is more effective than pathlength-based methods for imaging through turbid media with moderate levels of scattering, up to ̃optical depths, and that it can be combined with other imaging methods to further improve contrast. Advantages of the trajectory filter method include coherence and wavelength invariance and the ability to perform either wide beam, full-field or narrow beam, scanned imaging. Experimental results are presented for laser and incoherent beams using two types of trajectory filters: spatiofrequency and linear collimating hole array. It is found that the trajectory filter method offers a viable means of transmissively imaging through moderately scattering media at optical and near infrared wavelengths.

Light scattering review (vol 8) is aimed at the presentation of recent advances in radiative transfer and light scattering optics. The topics to be covered include: scattering of light by irregularly shaped particles suspended in atmosphere (dust, ice crystals), light scattering by particles much larger as compared the wavelength of incident radiation, atmospheric radiative forcing, astrophysical radiative transfer, radiative transfer and optical imaging in biological media, radiative transfer of polarized light, numerical aspects of radiative transfer.

This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The authors have demonstrated the use of a degenerate-four-wave-mixing time gate to allow imaging through turbid media, with potential application to tissue imaging. A near infrared (NIR), long-pulse Cr{sup +3}:Li2SrAlF6 laser was used as the light source (during most the project) for imaging through clear and turbid media. Preliminary experiments were also carried out with a continuous diode laser.

Covering key techniques for optical microscopy and micro-fabrication, this book provides the first detailed treatment of femtosecond laser-based biophotonics. After a review of the techniques for nonlinear and multiphoton imaging, applications for laser-based manipulation of micro-particles are introduced. The final chapter focuses on the burgeoning field of femtosecond micro-engineering.