Yunsong Jeong

Highly polarization-dependent periodic coupling in mechanically induced long period grating over air-silica fibers

A very flexible and versatile tunable mechanical grating platform is introduced, with which highly polarization-dependent mode coupling is observed for three types of air-silica microstructured fibers: hollow core fiber, hexagonal-boundary holey fiber (HHF), and circular-boundary holey fiber. The resonances of gratings showed highly polarization-dependent broadband coupling compared with conventional single-mode fibers due to their unique beat-length dispersions between the core and the cladding modes, which could find applications in wideband polarization-dependent loss compensation. We further present significance of the spatial symmetry of HHF in distinct mode coupling for different rotation angles around the fiber axis.

Development of microoptical waveguide on microactuating platform technologies for reconfigurable optical networking

This paper reports on new hybrid optomechanical technology for reconfigurable optical networking applications. Unique and versatile functions in the technology were provided by micrometer-scale fused-taper waveguides mounted on microelectromechanical actuating platforms. The proposed technology can endow new degrees of freedom to control spectral response and port-to-port output power of the throughput of multiport fiber-fused-taper devices. Applications in a reconfigurable optical switch, an interband router, and a high-power optical attenuator for optical networking are discussed.

Fiber-optic color synthesizer

Full-color synthesis was achieved, for what we believe is the first time, utilizing a novel 3x1 hard polymer-clad fiber coupler along with red, green, and blue (RGB) LED primaries. By using RGB LEDs that are coupled to three input ports, the device rendered full color from the output port with a circular emitting pixel of 135 microm in diameter with an extended color gamut. The proposed fiber-optic color synthesizer can provide a compact waveguide solution for the beam scanning display and the tunable pure white source for LED backlighting.

Multiport N x N multimode air-clad holey fiber coupler for high-power combiner and splitter

We report 2 x 2 and 4 x 4 multimode air-clad holey fiber couplers fabricated by a novel fusion and tapering technique. The devices showed excellent port-to-port coupling uniformity over a wide spectral range of 800-1650 nm. The 4 x 4 coupler showed a low insertion loss of 9.9 dB and excess loss of 3.9 dB at 1310 nm. Because of its unique air cladding and the high numerical aperture of the holey fiber structure, the device showed strong potential in high-power applications.

Giga-bit transmission over multimode air-clad holey fiber in a 1×4 PON configuration

We report 1.25 Gbps transmission over a multimode air clad holey fiber(MACHF) using a 1times4 MACHF power splitter that showed a low insertion loss of 9.9 dB and excess loss of 3.9 dB. Eye opening for 20 m transmission at 850 nm was measured.

LED backlight system with fiber-optic red, green, blue to white color combiner

As an application in the backlight system of small LCD display, we realized a pure white light source by mixing red, green, blue (RGB) lights using a 3 X 3 Hard Plastic Cladding Fiber (HPCF) coupler. We also proposed the 0.44 inch LED backlight system with these fiber-optic pure white sources and characterized its illumination characteristics. Using optimized fusion-tapering technique, we fabricated HPCF coupler which combines three input lights over the circularly formed waist. HPCF has the core diameter of 200 μm and clad diameter of 230 μm. The fabricated 3 X 3 HPCF coupler has the perfect uniformity of about 0.3 dB, low insertion loss of 5.5 dB, and low excess loss of 0.8 dB, which shows excellent uniform power splitting ratio. In order to improve the transmission performance, The RGB chip LEDs were butt-coupled directly to the ferruled input ports of the coupler and packaged by TO46-can type. In the produced white color by HPCF coupler, the photometric brightness at the circular endface of outputs of HPCF coupler was in a rage of 10062 ~ 10094 cd/m2. The fiber optic white color combiner provides tunable white sources excluding heat source and having thickness of 200 μm. We also proposed a 0.44 inch LED backlight system with these fiber-optic pure white sources. With the proposed device, we obtain the improved uniformity in luminance distribution and wide color gamut by using the white light mixing red, green and blue lights.

Q-switching of Yb-doped double-clad fiber laser using micro-optical waveguide on micro-actuating platform modulator for marking applications

A Q-switched all-fiber laser application based on a novel micro-optical waveguide (MOW) on micro-actuating platform (MAP) light modulator is presented. A fused biconical taper (FBT) coupler acts as MOW, mounted on an electromechanical system, MAP, where an axial stress over the waist of FBT coupler is precisely controlled. The axial stress induced refractive index changes caused the coupling efficiency to result in modulation of optical power. The light modulator was implemented in a laser cavity as a Q-switching element. Q-switching of Yb3+-doped fiber laser was successfully achieved with the peak power of 192mW at 4.1W pump power and 699mW at 5.2W at the repetition rate of 18.6kHz. Further optimization of switching speed and modulation depth could improve the pulse extraction efficiency and the proposed structure can be readily applied in all-fiber Q-switching laser systems for marking applications.

Cascaded microoptical waveguide on microactuating platform structure for high-power wideband variable optical attenuator applications

We present a novel cascaded two-stage microoptical waveguide (MOW) on microactuating platform (MAP) structure for applications in high-power ultrawideband variable optical attenuator (VOA). The device consists of a fused biconical taper (FBT) fiber coupler, which acts as a MOW, mounted on an electromechanical system MAP, where an axial stress over the waist of FBT coupler is precisely controlled by a piezoelectric transducer actuator. Cascaded two stages with complementary spectral responses were employed to enhance the spectral flatness and optical extinction ratio, which allowed the maximum attenuation over 60 dB at 1450 nm and a low spectral tilt of < 1 dB over 100 nm for 20-dB attenuation, as well as low polarization-dependent loss of < 0.07 dB. These VOA characteristics were maintained for optical power over 1 W.

Highly polarization-dependent periodic mechanical mode coupling in air-silica fibers

We report highly polarization-dependent mode coupling in hexagonal and circular air-silica microstructured fibers under periodic mechanical gratings. Coupling changes in terms of micro-structure spatial symmetry are investigated for PDL compensation.

Acousto-optic polarization dependent mode coupling in a dual mode hollow optical fiber

We report acousto-optic polarization-dependent coupling in two-mode hollow optical fiber. Local deformation of circular symmetry by traveling acoustic wave results in high birefringence making it suitable for polarization control devices.