Weakly tilted fiber Bragg gratings (W-TFBGs) with a certain tilted angle are inscribed in the Ge-doped cladding rods of
all-solid photonic band-gap fibers (AS-PBGF) by UV illumination. There are couplings not only forward-propagating
LP01 mode to counter-propagating LP01 mode but also the couplings to counter-propagating high order supermodes based
on tilted refractive index modulation. The responses of the W-TFBGs to temperature and bend are investigated. The
results indicate that the resonance peaks will shift red-side with increasing temperatures, and the sensitivities of different
resonance peaks are very close in the same grating. When the bend is applied, the grids of W-TFBG will be compressed
or stretched. Two resonance peaks will shift with increasing curvatures, which is related to the orientation of curvature.
Therefore, it is potential to work as a directional bend sensor. For the fiber grating with high-order supermodes coupling,
it could form fiber grating array by different levels. If every grating has individual response to surrounding, such a single
W-TFBG could be used for one point and multi-parameter measurement. In addition, this work provides some insights
into the mechanisms that contribute to the measured properties of TFBG in the photonic crystal fiber. It is also an
effective method to investigate supermode properties of photonic crystal fiber.
We propose a photonic crystal fiber (PCF) temperature sensor that is based on intensity modulation by
magnetic fluid (MF) filling of air holes with index-guiding PCF. Temperature characteristic of MF-filled PCF is
investigated without magnetic field and with weak magnetic field. The results show that light is still guided by
total internal reflection (TIR) in this device because MF has a smaller refractive index than the material in the
fiber core; the transmission power of the MF-filled PCF is used as the sensor signal to investigate its
temperature properties. The temperature sensitivity of transmission power was experimentally determined to
be 0.06dBm/oC for a 10cm-long PCF without applying magnetic field.
This letter demonstrates that the fluorescence intensity of CdSe-core CdS/ZnS-multishell quantum dots (QDs) in toluene is
related via a power-law of ~1.9 to the input intensity of femtosecond laser at 5~130 GW/cm2. This clearly indicates a broad
range of optical intensity of two-photon excitation (TPE). The two-photon absorption (TPA) cross sections of QDs of
core-size 2.9, 4.0 and 5.3 nm at 800 nm are 1980, 5680 and 14600 GM, respectively. Furthermore, the log-log plot of
CdSe-core diameters versus the TPA cross sections shows the increase with a slope >3, indicating a nonlinear dependent
relationship between TPA cross section and size of CdSe-core. The broad optical range of TPE and large TPA cross section
make these QDs excellent candidates for two-photon fluorescent microscopy and bioimaging. Based on these two-photon
properties of our QDs, we continue to investigate the bioimaging applications with two-photon microscopy. The results of
the fluorescence images of living cells with the QDs demonstrate that QDs could be penetrate into cell membrane, then
steadily and dispersedly distribute at the cytoplasm, which further indicates such QDs could be excellent candidate for
two-photon microscopy applications.
Core-shell semiconductor quantum dot (QD) has been attracting more and more extensive attentions and interests in
biomedicine photonics due to its good stability and high fluorescence quantum efficiency. In this paper, we reported that
the photoluminescence of core-multishell CdSe QDs performed a two-photon action under a femtosecond laser
excitation in wide incident power range. The two-photon absorption cross sections of such QDs were measured by the
intensity-dependent transmittance method and the results demonstrated a very strong two-photon absorption capacity of
QDs. The fluorescent spectra of QDs with an amphiphilic polymer showed that the fluorescent peak wavelength
appeared blue shift obviously and the full width at half maximum (FWHM) broadened to 40 nm. Furthermore, the
intracellular distribution of the QDs probes in cancer cells had been observed under two-photon excitation. The
experimental results indicated that the QDs mainly distribute at cell membrane and selectively gathered on cytoplasm of
cancer cells. The QDs which permeated into cancer cells quickly were very steady binding with cancer cells. Under long
time laser irradiation, the QDs hardly took place photobleaching, which demonstrated a very steady photochemical
performance of these QDs..
Photodynamic therapy (PDT) is a promising new treatment modality for several diseases, most notably cancer. In PDT,
light, O2, and photosensitizer are combined to produce a selective therapeutic effect. Chlorophyll derivative
photosensitizer(CPD) is the class of new photosensitizers for photodynamic therapy ( PDT) . And to date, little is known
about the interaction between the photosensitizer and the inner parts of tumor cell in PDT. A fluorescent microscopy and
imaging study on CPD was performed. To observe the dynamic process of how the photosensitizer (CPD) enters the
tumor cell and intracellular distribution of CPD in tumor cells, we used confocal laser scan microscopy(CLSM) under
one-photon excitation induced by a 488nm Ar+ laser. We also obtained the fluorescence photobleaching of CPD in cells
with varied intensity of excitation laser(488nm). By means of CLSM, we found most of the photosensitize CPD
distribute in on nuclear membrane but few in nuclear.
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