A miniature fiber optic endomicroscope with built-in dynamic focus scanning capability is developed for the first time for 3-D two-photon fluorescence (TPF) imaging of biological samples. Fast 2-D lateral beam scanning is realized by resonantly vibrating a double-clad fiber cantilever with a tubular piezoactuator. Slow axial scanning is achieved by moving the distal end of the imaging probe with an extremely compact electrically driven shape memory alloy (SMA). The 10-mm-long SMA allows 150-μm contractions with a driving voltage varying only from 50 to 100 mV. The response of the SMA contraction with the applied voltage is nonlinear, but repeatable and can be accurately calibrated. Depth-resolved imaging of acriflavine-stained biological tissues and unstained white paper with the endomicroscope is performed, and the results demonstrate the feasibility of 3-D nonlinear optical imaging with the SMA-based scanning fiber-optic endomicroscope.
This paper reviews our recent developments of ultrathin fiber-optic endomicroscopy technologies for transforming high-resolution
noninvasive optical imaging techniques to in vivo and clinical applications such as early disease detection and guidance of
interventions. Specifically we describe an all-fiber-optic scanning endomicroscopy technology, which miniaturizes a conventional
bench-top scanning laser microscope down to a flexible fiber-optic probe of a small footprint (i.e. ~2-2.5 mm in diameter), capable of
performing two-photon fluorescence and second harmonic generation microscopy in real time. This technology aims to enable realtime
visualization of histology in situ without the need for tissue removal. We will also present a balloon OCT endoscopy technology
which permits high-resolution 3D imaging of the entire esophagus for detection of neoplasia, guidance of biopsy and assessment of
therapeutic outcome. In addition we will discuss the development of functional polymeric fluorescent nanocapsules, which use only
FAD approved materials and potentially enable fast track clinical translation of optical molecular imaging and targeted therapy.
A near-field optical virtual probe based on the principle of near-field evanescent wave interference can be used in optical data storage, nano-lithography, near-field imaging and optical manipulation etc. The best choice of evanescent wave interference is evanescent Bessel beams that have the characteristics of both propagating Bessel beams and evanescent wave. It is concluded that evanescent Bessel beams is an evanescent wave with the characteristics of diffraction free and radial polarization. These characteristics lead to several advantages in near-field optics: the focus of radially polarized light can be quite smaller than the one of linear polarized light used commonly and diffraction free can bring in constant intensity distribution in a certain range. Meanwhile, based on the concept of conventional apodization, the idea of apodization of evanescent field is proposed to overcome some disadvantages of evanescent Bessel beams, such as the big side lobe and spread of transversal intensity. In this paper, Finite Difference Time Domain (FDTD) method is adopted to simulate the evanescent Bessel beams. Several parameters are considered as variants changeable to get the different simulation results. The better performance of the side lobe suppression and the narrow spot size are discussed. This work may be important to the application of near-field optical virtual probe in the future.