Soan Kim

Compact three segmented multimode fibre modal interferometer for high sensitivity refractive-index measurement

We experimentally demonstrate a new compact surrounding refractive-index sensor using a MMF-CSF-MMF (MCM) structure. The evanescent waves in the coreless silica fibre (CSF) region can directly interact with the surrounding medium. Due to its distinctive resonant spectral feature, the MCM sensor showed a high sensitivity of 4.37 × 10−4 for a refractive index range of 1.30 to 1.44, suggesting that the proposed device may be suitable for a wide range of biomedical and chemical sensor applications.

Dispersion properties of dual-core photonic-quasicrystal fiber

We propose a photonic quasi-crystal fiber with a dual-core structure. The circular-like outer core caused by the quasi-periodic arrangement gives rise to an interesting dispersion property that is different from that of a photonic crystal fiber with a dual-core structure. The absolute value of negative dispersion for the dual-core photonic quasi-crystal fiber increases as the distance between the nearest holes increases, while the absolute value of negative dispersion for the dual-core photonic crystal fiber decreases. The dispersion property can be useful in reducing the coupling loss between the compensating dispersion fiber and a conventional single mode fiber.

Enhancement of chemical sensing capability in a photonic crystal fiber with a hollow high index ring defect at the center

A new type of index-guided photonic crystal fiber is proposed to enhance chemical sensing capability by introducing a hollow high index ring defect that consists of the central air hole surrounded by a high index GeO2 doped SiO2 glass ring. Optical properties of the fundamental guided mode were numerically analyzed using the full-vector finite element method varying the design parameters of both the defects in the center and the hexagonal air-silica lattice in the cladding. Enhanced evanescent wave interaction in the holey region and lower confinement loss by an order of magnitude were achieved simultaneously, which shows a high potential in hyper sensitive fiber-optic chemical sensing applications.

Novel optical properties of six-fold symmetric photonic quasicrystal fibers.

We have investigated optical properties of an optical fiber having a six-fold symmetric quasiperiodic array of air holes in cladding, a six-fold symmetric photonic quasicrystal fiber. The photonic quasicrystal fiber exhibits larger cutoff ratio for endlessly single mode operation than that of a triangular photonic crystal fiber having six-fold symmetry and almost zero ultra-flattened chromatic dispersion, 0+/-0.05 ps/km/nm, in the range of wavelength from 1490 to 1680 nm. The dispersion value is much less than those of the proposed dispersion flattened PCFs.

Modified rectangular lattice photonic crystal fibers with high birefringence and negative dispersion.

We propose a modified rectangular lattice PCF and numerically investigate its birefringence and dispersion. Based on the plane wave expansion method, it is shown that the proposed structure provides high birefringence and negative dispersion. Numerical results show that the birefringence of the modified PCF reaches 10(-2) and the leakage loss is about 1000 times smaller than that of an original rectangular PCF because the modification gives rise to the strong confinement of guided modes. Dispersion and its slope are also negative over the C band.

Versatile control of geometric birefringence in elliptical hollow optical fiber

A novel optical fiber fabrication technique was developed by converting the symmetry of the silica substrate into the germanosilicate ring core to efficiently introduce geometric birefringence in an elliptical hollow optical fiber. Due to high ellipticity in the hollow ring core, the fiber provides an extremely high group birefringence of 2.35 x 10(-3) at 1550 nm. Single-mode single-polarization guidance was also experimentally confirmed, with a bandwidth of approximately 35 nm. The generic adiabatic mode conversion capability in the taper also provided a stable fusion splice to conventional single-mode fiber with low loss and high tensile strength.

Compact three segmented multimode fiber modal interferometer for high sensitivity refractive-index measurement

We have experimentally demonstrated a new compact surrounding refractive-index sensor using MMF-CSF-MMF structure. For refractive index range of 1.30 to 1.42, resolution of 9.68×10-3 /nm and linear dynamic range of 20.5dB were obtained at λ=1310nm.

Defect and lattice structure for air-silica index-guiding holey fibers

We propose new design parameters for index-guiding holey fiber that can provide flexibility in defect and lattice design and adiabatic mode transformation capability. The new defect consists of a central air hole and a germanosilicate ring surrounding it, which results in a large-area annulus mode profile, low splice losses to standard fiber, 0.7 dB at 1.55 microm, and chromatic dispersion with a low slope, 0.002 ps/km nm2.

Ultrahigh birefringence of elliptic core fibers with irregular air holes

We have investigated experimentally and theoretically the birefringence of the elliptic core fiber with irregular air holes. The wavelength dependence of the beat length and the birefringence was measured by the wavelength scanning method. The fiber exhibits ultrahigh birefringence of 1.12×10−2 at 1550 nm. We also calculated the modal birefringence of the fundamental modes in the fiber by using the plane wave expansion method. The calculated birefringence is in excellent agreement with the measured one.

New defect design in index guiding holey fiber for uniform birefringence and negative flat dispersion over a wide spectral range

A novel silica index guiding holey fiber (IGHF) design is proposed utilizing a new defect structure that is composed of an elliptic high index ring structure and an elliptic air-hole at the center with triangular lattice structure. The proposed IGHF showed unique modal properties such as uniform and high birefringence over a wide spectral range and single polarization single mode (SPSM) guidance along with a flat negative chromatic dispersion. Optical waveguide properties were numerically analyzed using the plane wave expansion method in terms of mode intensity distribution, modal birefringence, chromatic dispersion for the new defect structural parameters.