Dong Hoon Son

Visible to infrared photoluminescence from gold nanoparticles embedded in germano-silicate glass fiber

Germano-silicate glass fiber containing gold nanoparticles was developed by modified chemical vapor deposition and solution doping processes. Pumping with 488 nm Argon ion laser, we firstly report on the visible to infrared photoluminescence of the gold nanoparticles embedded in the core of the germano-silicate fibers. The surface plasmon resonance absorption peak at 498.4 nm and the visible to infrared photoluminescence over the range of 600 nm approximately 1560 nm were found and explained according to the interband and intraband electronic transitions of Au atoms. The averaged quantum efficiencies of the photoluminescence at 833 nm and 1536 nm were estimated to be 5.75 x 10(-8) and 2.01 x 10(-9), respectively.

Optical properties of the fiber-optic temperature sensor based on the side-hole fiber filled with indium

A highly sensitive temperature sensor was made by use of a side-hole glass fiber filled with indium metal, and its optical properties were investigated. The temperature sensitivity of the fiber-optic temperature sensor was dλ/dT=-7.38 nm/K. The temperature sensitivity was also examined in sensors made by different lengths of the side-hole fiber and the indium-filled fiber region. The temperature sensitivity could be varied in the range of -1.83 to -7.38 nm/K by changing the relative length between the side-hole fiber and the indium-filled fiber region.

Radial-firing optical fiber tip containing conical-shaped air-pocket for biomedical applications

We report a novel radial-firing optical fiber tip containing a conical-shaped air-pocket fabricated by deforming a hollow optical fiber using electric arc-discharge process. The hollow optical fiber was fusion spliced with a conventional optical fiber, simultaneously deforming into the intagliated conical-shaped region along the longitudinal fiber-axis of the fiber due to the gradual collapse of the cavity of the hollow optical fiber. Then the distal-end of the hollow optical fiber was sealed by the additional arc-discharge in order to obstruct the inflow of an external bio-substance or liquid to the inner air surface during the surgical operations, resulting in the formation of encased air-pocket in the silica glass fiber. Due to the total internal reflection of the laser beam at the conical-shaped air surface, the laser beam (λ = 632.8 nm) was deflected to the circumferential direction up to 87 degree with respect to the fiber-axis.

Effect of infiltration pressure on the birefringent properties of a side-hole fiber filled with indium

The effect of the infiltration pressure on the birefringent properties of a side-hole fiber filled with indium was investigated by the fiber-optic Sagnac loop interferometry. The fiber was made at the various gas pressures during the metal infiltration process. It was found that the birefringence of the fiber strongly decreased from 5.55×10(-4) to 1.68×10(-4) with the increase of the pressure from 15 to 45 bars, due to the compensation effect of the pressure applied during the infiltration. The temperature dependence of the birefringence, dB(m)/dT, was found to be constant of ∼-3.06×10(-6)/K regardless of the magnitude of the pressure.

Effect of Cross-Sectional Structure on Optical Properties of Metal-Filled Side-Hole Fiber

The effect of the cross-sectional structure of metal-filled side-hole fiber on the birefringence and thermooptic properties was investigated by the fiber-optic Sagnac loop interferometry. The optical fibers having different cross-sectional structures filled with indium metal were fabricated by drawing a fiber preform with two side holes at different temperatures followed by metal infiltration. The original circular core and two identical holes in the fiber preform were deformed into the fiber core with various core ellipticities and different hole diameters after the drawing. It was found that the fiber birefringence (B} and the temperature dependence were strongly influenced by the deformation of the fiber cross section, the birefringence increased from 5.68 × 10-5 to 1.16 × 10-4 with the increase of the core ellipticity from 0.273 to 0.412. Additional birefringence was found to be induced after the infiltration of indium into holes due to the large thermal expansion mismatch between indium and silica glass of the fiber. The temperature sensitivities of the unfilled side-hole fibers (d(δλn)/dT) were almost the same and found to be constant of ~-0.60 nm/K regardless of the fiber cross sections. On the other hand, the sensitivities of the indium-filled side-hole fibers (d( δλm)/dT) were enhanced 10-15 times larger than those of the unfilled side-hole fibers, increased from -5.98 to -11.03 nm/K with the increase of the filler indium diameter from ~18.5 to 24.1 μm, respectively.

Resonant nonlinear refractive index measurement of optical fiber based on mode coupling using cascaded fiber tapers

Measurement of resonant nonlinear refractive index (n2) of optical fiber based on core/cladding mode coupling using cascaded fiber tapers was demonstrated.