A novel ring fiber laser based on Er-doped photonic crystal fiber (EDPCF) is demonstrated. EDPCF is used as gain
medium to implement stable CW operation. The laser output wavelength can be continuously tuned over the range from
1529 to 1535 nm by adjusting the polarization state of the light inside the cavity. Stable dual-wavelength CW operation
is also observed with proper settings of the intracavity polarization controllers. The laser stability in terms of the output
power and the operation wavelength is characterized, and less than ±0.05 dB power fluctuation as well as 18 pm
wavelength perturbation are obtained.
Thermochromism vanadium dioxide thin films were fabricated by quick thermal oxidation annealing of direct
current facing targets reactive magnetron sputtered vanadium oxide thin films at 300-360°C for 1-3h. X-ray
diffraction shows the vanadium dioxide thin film was obtained annealed at 300°C for 1h, and the structure
changed from monoclinic to tetragonal rutile VO2 at around 54°C. X-ray photoelectron spectroscopy and Fourier
transform infrared spectroscopy show that the structure of VOx film underwent the following transformation:
amorphous structure = VO2 (B) + VO2 (M) - VO2 (M)+VO2 (R).
We demonstrate a passively mode-locked all fiber ring laser based on all-solid Yb-doped Photonic Bandgap fiber (AS-Yb-
PBGF) which is designed to simultaneously provide laser gain and anomalous dispersion. The laser is comprised of
0.42m AS-Yb-PBGF and a segment of single mode fiber (SMF). By varying the length of the SMF from 0.8m to 3.2m,
three operation schemes, namely soliton operation, gain-guided soliton operation, and self-similarity operation, have
been obtained by means of numerical simulations in split-step Fourier method in the ring laser. In the case of net
anomalous cavity group-velocity dispersion (GVD) when the SMF is 0.8m, we obtain soliton pulse with the balance
between the nonlinear self-phase modulation (SPM) and the anomalous GVD. The soliton pulse has the pulse duration of
355fs and the bandwidth of 1.9nm, corresponding to the time-bandwidth product of 0.33, nearly a transform-limited
pulse. As the length of the SMF is changed to 2m, self-similar propagation is generated with the net cavity GVD of
+0.014ps2. The pulse has strong frequency chirp and high pulse energy up to 4nJ. The pulse duration is 2.5ps with the
bandwidth of 2.1THz. To obtain gain-guided soliton, we change the SMF to 3.2m leading to a large net positive cavity
GVD of +0.04 ps2 and enforce the spectral limit of the gain fiber. A chirped gain-guided soliton pulse is observed with
pulse energy of ~1nJ, the pulse duration of 2.5ps and the bandwidth of 2.5 THz.
Porous silicon has been extensively researched as an interesting photoluminescent material for photoelectric device
integration. Residual stress often occurs due to capillary force during drying and results in warp, fracture and failure of
the devices. Micro-Raman spectroscopy (MRS) has many special advantages of nondestructive, non-contact, high spatial
resolution (1μm), broad spectrum range, Raman shift unaffected by the frequency of laser source, and ability to focus on
a specific layer of sample. Furthermore, Raman spectrum is a powerful tool for the study of residual stress for its
sensitivity to strain in the sample, which make it possible to measure residual stress directly. The underlying basis of
micro-Raman spectroscopy for strain measurement is that Raman shift reflects the atomic spacing change, namely the
strain information. The residual stress was measured during drying using Micro-Raman spectrum technology, the maxim
is 3.6GPa. The relation of residual stress and Raman shift, drying times and FWHM were analysed, the capillary effect
and the residual stress evolution from wetting to drying stages of porous silicon were investigated using phonon
confinement model.
WO3 sensing films (1500 Å) were deposited using dc reactive magnetron sputtering method on alumina substrate on
which patterned interdigital Pt electrodes were previously formed. The additive Ti was sputtered with different thickness
(100-500 Å) onto WO3 thin films and then the films as-deposited were annealed at 400°C in air for 3h. The crystal
structure and chemical composition of the films were characterized by XRD and XPS analysis. The effect of Ti addition
on sensitive properties of WO3 thin film to the NH3 gas was then discussed. WO3 thin films added Ti revealed excellent
sensitivity and response characteristics in the presence of low concentration of NH3 (5-400 ppm) gas in air at
200°C operating temperature. Especially,in case 300 Å thickness of additive Ti, WO3 thin films have a promotional effect
on the response speed to NH3 and selectivity enhanced with respect to other gases (CO, C2H5OH, CH4). The influence of
different substrates, including alumina, silicon and glass, on sensitivity to NH3 gas has also been investigated.
Using a plane wave expansion method, we numerically show that the bandgaps of honeycomb photonic bandgap fibers can be effectively tuned by interstitial air holes. It is shown that the number of bands varies with the filling fraction of interstitial air holes, and also that the width of the bands can be substantially increased by interstitial air holes. For a honeycomb photonic bandgap fiber with a large air filling fraction, the widths of the primary and secondary bandgaps are increased twice by interstitial air holes. In the case of a small air filling fraction, the relative sizes of the two gaps can reach up to 11.7% and 6.4% using interstitial air holes. Therefore, using interstitial air holes proves to be an effective way to tune the bandgaps of honeycomb photonic bandgap fibers.
In this article, a metallographic microscopy, an atomic force microscopy and a field emitting scanning electronic microscopy was used to investigate the surface and the cross-sectional morphology of porous silicon films, respectively. Simple micro-structure and micro-mechanical models are established to explain the origin mechanism of residual stresses in the porous silicon. Experimental results reveal that the residual stresses have close relation with the micro-structure of the porous silicon and consist of the lattice mismatch stress, capillary stress, oxidation stress, Van der Walls force and so on. Combining micro-Raman spectroscopy with x-ray diffraction measurements, we get the total residual stress of 900MPa, and its components of the lattice mismatch stress is about of 815.8MPa, the capillary stress of 13.2MPa and the oxidation stress of 71MPa for a chemical etched porous silicon sample with a certain porosity. It can be seen that the lattice mismatch between the porous layer and the Si substrate is a major source (about 91%) for the total residual stress of the porous silicon.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.