A multiwavelength midinfrared quasi-phase-matched (QPM) difference frequency generation (DFG) scheme is proposed based on a segmented temperature controlling technique for the uniform grating periodically poled lithium niobate (PPLN). The QPM DFG output performances have been investigated under the fixed pump and signal wavelength conditions, respectively. Our theoretical results show that when the pump wavelength is fixed at 1.08 μm, three idler QPM bands, located at 3.46, 3.50, and 3.57 μm, have been obtained, where the temperatures of the three PPLN segments with the same length are set at 20°C, 70°C, and 100°C. However, when the signal wavelength is fixed at 1.58 μm, six idler QPM bands, located at 2.95, 3.06, 3.14, 3.63, 3.72, and 3.83 μm, have been achieved with the same crystal temperature distribution of 20°C, 70°C, and 100°C.
A miniature fiber optic pressure sensor based on Fabry-Perot interference fabricated on the tip of a single mode (SM)
fiber is presented. The sensor measures only 125μm in diameter. A Fabry-Perot cavity and a thin silica diaphragm are
fabricated by simple techniques involving only cleaving, wet chemical etching and fusion splicing. Interference pattern of the
sensor is analyzed and issues in sensor design are discussed. The overall chemical reaction of the fiber wet etching is
specifically represented. Pressure testing system is carried out. By tracing a peak point in the interference spectrum, the gap
length of the sensor can be demodulated. Experimental results show the sensor has a good linearity. The sensor is made entirely
of fused silica, whose structure has good stability, cabinet, simple for fabrication and low cost.
This paper presents a miniature fiber optic pressure sensor based on Fabry-Perot interference fabricated on the tip of
a single mode (SM) fiber. The sensor measures only 125μm in diameter. A Fabry-Perot cavity and a thin silica
diaphragm are fabricated by simple techniques involving only fusion splicing, cleaving, and wet chemical etching.
Interference pattern of the sensor is analyzed and issues in sensor design are discussed. The overall chemical
reaction of the fiber wet etching is specifically represented. Pressure testing system is carried out. By tracing a peak
point in the interference spectrum, the gap length of the sensor can be demodulated. The sensor is made entirely of
fused silica, whose structure has good stability, cabinet, simple for fabrication and low cost. It may also find uses in
medical applications.
A new method of fabricating three-dimensional colloidal crystals microstuucture fiber is
proposed. The cladding of single-mode fiber was eroded to 60nm by HF and The eroded cladding was
observed by microscopy and scanning electron microscopy. Colloidal photonic crystal was
self-assembled onto the eroded cladding through isothermal heating evaporation induced self-assembly,
and the colloidal photonic crystals cylindrical annulus embeded in fiber was characterized by scanning
electron microscopy. The results shows the colloidal photonic crystals well-orderedly self-assembled
onto the fiber cladding, and the results also demonstrate a practical means of coating macro- or
micro-curved surfaces with three dimensional photonic crystals.
The growing three-dimensional nanostructures colloidal crystal on the end face of optical fiber by isothermal heating
evaporation induced self-assembly method is presented. The wet chemical etching technique is used to etch single mode
fiber to obtain a shallow circular cavity between the coating and cladding. The optical fiber with the etched cavity was
immersed upside into solution containing polymethylmethacrylate (PMMA). The PMMA spheres used here had an
average diameter of 690nm; it takes one week for the sphere particles to completely settle. The nanostructure
morphology of the colloidal crystal is examined by using the SEM. The colloidal crystal has a face-centered-cubic
(FCC) structure. The optical characterization of the colloidal crystal is also analyzed. The simulation and experiment
result show that the colloidal crystal formed by PMMA spheres has an obvious photonic band gap in the wavelength
1543nm that is typical wavelength of optical communication. The spectra feature of the optical fiber colloidal crystal is
measured by using optical sensing analyzer. The experimental results show the band gap at the 1543nm, consistent with
the simulation results.
A novel pressure sensor with a mesa structure diaphragm based on microelectromechanical systems
(MEMS) techniques is presented. The operating principle of the MEMS pressure sensor is expatiated
by the Fabry-Parot (F-P) cavity model and the relation between pressure and interference light intensity
is deduced in the sensor. The mechanical model of the mesa structure diaphragm is validated by
simulation, which declares that the mesa structure diaphragm is superior to the planar one on the depth
of parallelism. Experimental system is also introduced.
The method of the three-dimensional nanostructures colloidal crystal growth on the end face of optical fiber by gravity
sedimentation method is presented. The end face of optical fiber is lapped by CNFIBERNET optical lapper. The optical
fiber we used is single mode fiber. We found that the cladding and core of optical fiber would be corroded and the
coating of optical fiber would be reserved when the bare optical fiber is taken into the HF buffer solution (HF:NH4F:H2O=3:7:10), and the cavity would be formed by the coating and cladding. This optical fiber is inserted into
the polymethylmethacrylate(PMMA) microspheres colloidal solution from the lower side, and gravity sedimentation
method is used to grow the PMMA colloidal crystal into the cavity. The three-dimensional nanostructures colloidal
crystal onto the end face of optical fiber can be obtained. The nanostructures is face-centered cubic (FCC) by using the
SEM. The RSOFT is used to simulate photonic band gap of FCC structure. Through the theory analysis and simulation,
the PMMA colloidal crystal formed by the diameter 695nm spheres will have an obvious photonic band gap in the
wavelength at 1550nm.
A novel pressure sensor based on Fabry-Perot interferometry and micro-electromechanical system
(MEMS) technology is proposed and demonstrated. Basic micro-electromechanical technique has been
used to fabricate the pressure sensor. Fabrication process and packaging configuration are proposed.
The loaded pressure is gauged by measuring the spectrum shift of the reflected optical signal. The
experimental results show that high linear response in the range of 0.2-1.0 Mpa and a reasonable
sensitivity of 10.07 nm/MPa (spectrum shift/pressure) have been obtained for this sensor.
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