We report a unique technique to generate a liquid periodic structure whose unit volume is as low as a few hundred
femto-liter. Liquids such as water, toluene and ethanol were filled in a hollow optical fiber (hole diameter of 8 and
13μm), which were locally heated by a traversing miniature electric furnace. The periods between droplets could be
varied flexibly in the range from 14 to 100μm and the volume of individual droplet was in the range from 112 to 845
femto-liter. We also fabricated the periodic liquid droplets with quantum dots, whose fluorescence was successfully
measured in each droplet. These periodic liquid droplets could serve as flexible liquid long period fiber grating for the
hollow optical fiber, which can be further applied in various mechanical and bio-chemical sensors
Photoluminescence is one of the methods used for analyzing the optical characteristics of materials. For components
in solid-state lighting such as GaN-based LEDs, the use of an LED structure configuration on a patterned sapphire
substrate has shown to be highly effective in improving light-extraction efficiency. We proposed a compact and simple
photoluminescence measurement system based on fiber-optic probes that can be scanned over a 20 × 20 μm2 area with a
high spatial resolution. We applied the system in morphological study of InGaN/GaN epitaxial layers for LED
applications. With this system, we obtained peak intensity, peak wavelength, and full width at half maximum of the
emission spectrum.
Optical-resolution photoacoustic microscopy (OR-PAM) becomes a premier microscopic imaging tool in biomedicine
because it provides agent-free optical absorption information in tissues. By tightly focusing light to a spot, the fine
lateral resolution can be achieved in OR-PAM. The focal spot size is typically determined by the numerical aperture of
the used objective lens. Here, we demonstrate focus-free OR-PAM using a Bessel beam generator. In this approach, no
objective lens is required. We have photoacoustically imaged a carbon fiber with a diameter of ~6 μm, and the
measured lateral resolution was ~6-7 μm. Beneficially, the complexities of the existing OR-PAM systems can be greatly
relieved.
Optical-resolution photoacoustic microscopy (OR-PAM) becomes a premier microscopic imaging tool in biomedicine because it provides agent-free optical absorption information in tissues. By tightly focusing light to a spot, a significantly improved lateral resolution can be achieved in OR-PAM. The focal spot size is typically determined by the numerical aperture of the used objective lens. Here, we demonstrate objective-free OR-PAM using a fiber optic Bessel beam generator. In this approach, no objective lens is required and, beneficially, the complexities of conventional OR-PAM systems can be greatly relieved. We have obtained photoacoustic images of a carbon fiber with a diameter of ∼6 μm, whose lateral resolution was measured to be better than 6 to 7 μm.
Optical lining of multiple dielectric beads was experimentally demonstrated using two counter- propagating Bessel-like
beam generated by multimode interference in optical fibers embedded in polydimethylsiloxane (PDMS) channel. All
Fiber Bessel-like beam (AFB) generator was composed of a single mode fiber concatenated with a segment of coreless
silica fiber of 1600 μm length and a fiberized focusing lens. A Bessel-like beam was achieved by multimode interference
along the coreless silica fiber, and it maintained an average center beam diameter of 3.7 μm over an axial length of 300
μm, having a nearly uniform output power within a variation of ±0.11%. AFB generator was designed to be compatible
with a continuous wave Yb-doped fiber laser oscillating at the wavelength of 1084nm in order to provide all-fiber
solution. A micro-fluidic system of cross-channel was fabricated using PDMS to embed two counter-propagating fiber probes, which provided an accurate beam alignment and stable delivery of sample. One dimensional optical potential well was generated along the counter propagating beams, where samples were trapped, and then self-optical line of them was formed along longitudinal axis. This results from self-reconstruction, which is property of Bessel beam and it was confirmed in not only dielectric particles but also biological sample. This AFB generator paves the way for novel integration of microfluidic system as optical filter or chromatography.
We present a novel implementation of Fourier optics along a single strand of hybrid optical fiber in a monolithic manner
that can generate a highly efficient pseudo-Bessel beam. The incident fundamental mode of an optical fiber is
adiabatically transformed to multiple ring modes by interference within a coreless silica fiber, which serves as a micro
annulus apertures. A micro polymer lens was formed at the end face to complete the Fourier-transform providing a
pseudo-Bessel beam at the output. Efficient multiple particle trapping experiments for both polystyrene beads were
realized over 1 mm distance along the pseudo-Bessel beam. Furthermore all-optical transport of the trapped particles
along a three dimensional optical route was demonstrated by spatially multiplexing pseudo-Bessel beams via multi mode
interference (MMI) type Bessel beam generators. 1x3 pseudo-Bessel beam multiplexer was installed in the water based
solution with 10mm(micro meter?) polystyrene beads. After a polystyrene particle was trapped by pseudo-Bessel beam,
the initial acceleration was observed as 150μm/s2. The final velocity of the trapped particle maintained about 300μm/s
with 40μm/s undulation due to pseudo-Bessel beam crossing points. The spatial multiplexing of fiber optic pseudo-
Bessel beam arrays could make a new building block to realize reconfigurable all-optical transportation of particles.
A new and flexible method to deliver target particle to sensor through optical trapping with pseudo Bessel
beam is presented. Pseudo Bessel beam generator was based upon a Fourier optical system. Single mode fiber
(SMF) delivered a fundamental mode without loss. SMF was spliced with Hollow optical fiber (HOF) which
served as an annular aperture. A light wave with ring shape was propagated in Coreless Silica Fiber (CSF) and
simultaneously transformed a Bessel shape. A Bessel shape with central peak profile will be maintained by a
tiny polymer lens on the end of CSF. Delicate control of particle position was enabled by 3 pseudo Bessel beam
sources which can be controlled individually. Unique characteristic of Bessel beam allows target particle to have
few hundred micrometer tolerance in propagation length and sudden change of propagating direction was
achieved by applying another Bessel beam source from other direction. Experimental results on Polystyrene
beads which have 4 um diameter are shown. Also, living cell such as Jurkat cell was tested to check practicality.
In this paper, we experimentally demonstrate the potential of quasi-distributed high temperature sensor based on fiber
Bragg grating (FBG) utilizing high thermal conductive sheath, which can be a cost-effective alternative for conventional
distributed temperature sensors based on Raman, Brillouin, and Rayleigh scattering. A unique Fire Sensing Cable (FSC)
used in this experiment is constructed from a 304 stainless steel sheath with 16 optical fibers imbedded in a conductive
fluid. One of the fibers contains FBGs for temperature sensing. Total of seventy seven FBGs were serially inscribed with
the spacing of six meter over the total length of 468 meter. FSC was heated by various hot zones formed by IR furnace
and nitrogen heat nozzle, as the shifts of FBGs were monitored. Although FBGs were 6 meter apart each other, high
thermal conductivity of the stainless steal sheath made it possible to check temperature change in the region between
gratings. These preliminary results clearly show a high potential of FBGs combined with FSC in applications of quasi-distributed
fire sensing cables and monitoring systems.
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