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We report the fabrication and characterization of a highly sensitive refractive-index sensor based on a long-period grating (LPG) pair with a fiber-taper section in between. Two LPGs with /spl sim/3-dB transmissivity form an in-fiber Mach-Zehnder interferometer. A fiber taper is made between the two LPGs to improve and tailor the sensitivity of the sensor.(More)
A bilevel mode converter is analyzed for providing low-loss coupling between the small fundamental mode of a silicon nanowire waveguide and the larger mode of a conventional silicon-on-insulator (SOI) rib waveguide. The bilevel converter can also be used to improve the coupling efficiency between a lensed fiber and a silicon nanowire waveguide. The mode(More)
A simultaneous measurement of external refractive-index (RI) and temperature is presented by using a sandwiched structure of long-period gratings (LPGs). An LPG pair with codirectional coupling between the guided mode and a low-order cladding mode acts as a temperature sensor with low RI sensitivity, whereas another in-between LPG which couples the guided(More)
An arrayed waveguide grating (AWG)-based multiplexer has many advantages, including small size, high reliability, and low cost. The commonly used wavelengths for triplexers in fiber access networks are 1310, 1490, and 1550 nm. Because of the wide spectral range and very unequal wavelength spacings, it is difficult to produce satisfactory results with a(More)
The dispersion properties of the guided modes propagating along a dielectric slab waveguide with a left-handed material substrate are studied. It is shown that both the oscillating and surface modes can propagate very slowly along such a waveguide if the thickness of the core layer is chosen appropriately. The propagation speed of the guided waves can even(More)
We present a low-coherent interferometric system of multiplexed sensors based on pairs of long-period gratings (LPGs). The LPGs in each pair have approximately 3-dB transitivity and form an in-fiber Mach-Zehnder interferometer. By using a dual-beam Michelson interferometer with two reflective mirrors, the interferometric signature of the LPG pair is(More)
Compact microracetrack resonator (MRR) devices are presented with small SU-8 polymer strip waveguides. The SU-8 strip waveguide has an SU-8 polymer core (n~1.573) , a SiO<sub>2</sub> buffer (n~1.445), and an air cladding. The fabricated straight waveguide has a low propagation loss of about 0.1 dB/mm. With such a high index-contrast optical waveguide, a(More)
In this paper, an optimal design of a small polymeric ridge waveguide with a high index contrast is presented. In order to reduce the leakage to the substrate and pure bending losses, the buffer layer of the present waveguide is etched partially. The single-mode condition, the bending characteristics, and the birefringence of the present small polymeric(More)
  • Jun Song, Jian-Jun He, Sailing He
  • IEEE Journal of Selected Topics in Quantum…
  • 2005
The polarization-dependent characteristics of an etched diffraction grating demultiplexer are analyzed using the boundary element method. Comparisons are made between an echelle grating coated with a metal and a dielectric grating with retro-reflecting facets. The results indicate that an echelle grating coated with a metal can be approximated as a grating(More)