The interaction between surface plasmon polariton (SPP) and acousto-optic tunable filter was studied. Acoustic wave was used to induce core mode to cladding mode coupling and eventually resulted in SPP generation at the fiber cladding surface. The interaction between optical fiber core mode, cladding mode and SPP mode is formulated by using mode coupling theory. The dielectric constant of SPP and light reflection coefficient on fiber surface was calculated using Nlayer model. Experimental studies were also carried out to verify the theory and simulation results. The existence of SPP at fiber surface boosted the acoustic assisted optical energy coupling from fiber core mode to TM and HE cladding mode but not to TE cladding mode, which agrees with the theoretical and simulation results. It provides a motion-free, high speed and full-electronic solution for generation and control of SPP with high flexibility and tunability.
As the most abundant protein in the human body, collagen has a very important role in vast numbers of bio-medical applications. The unique second order nonlinear properties of fibrillar collagen make it a very important index in nonlinear optical imaging based disease diagnosis of the brain, skin, liver, colon, kidney, bone, heart and other organs in the human body. The second-order nonlinear susceptibility of collagen has been explored at the macroscopic level and was explained as a volume-averaged molecular hyperpolarizability. However, details about the origin of optical second harmonic signals from collagen fibrils at the molecular level are still not clear. Such information is necessary for accurate interpolation of bio-information from nonlinear optical imaging techniques. The later has shown great potential in collagen based disease diagnosis methodologies. In this paper, we report our work using an atomic force microscope (AFM), near field (SNOM) and nonlinear laser scanning microscope (NLSM) to study the structure of collagen fibrils and other pro-collagen structures.
Two-photon fluorescence (TPE) and second harmonic generation (SHG) can been used to extract biological information
from tissues at the molecular level, which is blind to traditional microscopes. Through these two image contrast
mechanisms, a nonlinear laser scanning endoscope (NLSE) is able to image tissue cells and the extra cellular matrix
(ECM) through a special fiber and miniaturized scanner without the requirement of poisonous chemical staining.
Therefore, NLSE reserves high potential for in-vivo pathological study and disease diagnosis. However, the high cost
and bulky size of a NLSE system has become one of the major issues preventing this technology from practical clinical
operation. In this paper, we report a fiber laser based multi-modality NLSE system with compact size and low cost, ideal
for in-vivo applications in clinical environments. The demonstration of the developed NLSE nonlinear imaging
capability on different bio-structures in liver, retina and skin are also presented.
We demonstrate the first in-fiber light-induced bioactive biotin-functionalization via photobleaching fluorophore-conjugated biotin. Photobleaching the fluorophores generated free radicals that bind to the albumin-passivated inner surface of pure silica photonic crystal fiber. The subsequent attachment of dye-conjugated streptavidin to the bound biotin qualified the photo-immobilization process and demonstrated a potential for the construction of in-fiber macromolecular assemblies or multiplexes. Compared with other in-fiber bioactive coating methods, the proposed light-induced technique requires only a low-power light source, without the need for additional preactivation steps or toxic chemical reagents. This method, hence, enables a simple and compact implementation for potential biomedical applications.