Yong-Won Song

Carbon nanotube mode lockers with enhanced nonlinearity via evanescent field interaction in D-shaped fibers

We demonstrate a novel passive mode-locking scheme for pulsed lasers enhanced by the interaction of carbon nanotubes (CNTs) with the evanescent field of propagating light in a D-shaped optical fiber. The scheme features all-fiber operation as well as a long lateral interaction length, which guarantees a strong nonlinear effect from the nanotubes. Mode locking is achieved with less than 30% of the CNTs compared with the amount of nanotubes used for conventional schemes. Our method also ensures the preservation of the original morphology of the individual CNTs. The demonstrated pulsed laser with our CNT mode locker has a repetition rate of 5.88 MHz and a temporal pulse width of 470 fs.

Passively mode-locked lasers with 17.2-GHz fundamental-mode repetition rate pulsed by carbon nanotubes.

17.2 GHz, the highest fundamental-mode repetition rate to our knowledge, of a carbon nanotube-based passively mode-locked laser is realized at 1570 nm by employing purified single-walled carbon nanotubes as saturable absorbers. The ultrashort linear laser cavity configured with a approximately 9 mm length is designed and demonstrated with our extremely miniaturized nanotube mode locker and a mirror-coated semiconductor optical amplifier as gain medium. The demonstrated pulsed laser has the inferred temporal pulse width of 14 ps and a 3 dB spectral bandwidth of 0.73 nm.

Polarization insensitive all-fiber mode-lockers functioned by carbon nanotubes deposited onto tapered fibers

The authors demonstrate a nonblocked all-fiber mode locker operated by the interaction of carbon nanotubes with the evanescent field of propagating light in a tapered fiber. Symmetric cross section of the device with the randomly oriented nanotubes guarantees the polarization insensitive operation of the pulse formation. In order to minimize the scattering, the carbon nanotubes are deposited within a designed area around the tapered waist. The demonstrated passively pulsed laser has the repetition rate of 7.3MHz and the pulse width of 829fs.

1300-nm pulsed fiber lasers mode-locked by purified carbon nanotubes

For the first time, we demonstrate a novel passively mode-locked fiber laser operating at 1300 nm using purified single-walled carbon nanotubes (CNTs) as a saturable absorber. The saturable absorber incorporates diameter-controlled CNTs with peak absorption /spl sim/1300 nm, guaranteeing mode-locking over the same wavelength region. The ring laser uses praseodymium-doped fiber as a gain medium. The pulse repetition rate is 3.18 MHz, and the spectral half-width is 0.15 nm. Dual-wavelength mode-locking is also demonstrated with a channel spacing of 1.1 nm.

All-fiber pulsed lasers passively mode locked by transferable vertically aligned carbon nanotube film

An all-fiber passive laser mode locking is realized with a vertically aligned single-walled carbon nanotube film that can be transferred onto an arbitrary substrate using only hot water. A D-shaped fiber is employed as the substrate for the evanescent field interaction of propagating light with the nanotubes. The scheme highlights the efficient interaction achieved by the nanotube alignment as well as the dramatically simplified device preparation process. The demonstrated pulsed laser output has 2.9 nm of spectral full width at half-maximum and a 20.8 MHz repetition rate.

Novel Kerr shutter using Carbon nanotubes deposited onto a 5-cm D-shaped fiber

We experimentally demonstrate a novel Kerr shutter functioned by the interaction of carbon nanotubes with the evanescent-field of propagating light in a D-shaped fiber. The scheme initiates applications of the nanotubes to ultrafast all-optical switches.

Generation of all-fiber optical Manchester code using nonlinear polarization rotation

We experimentally demonstrate all-fiber optical Manchester code generation at 10 Gbit/s using nonlinear polarization rotation in a single 1- km highly-nonlinear fiber with the nonlinearity of 20.4 W-1km-1. 33-dB extinction ratio is achieved in a -4-dBm CW dummy channel by coinjecting orthogonally aligned two 8-dBm pumps into the Kerr medium. Our encoder functions with 10 Gbit/s NRZ data stream and 10 GHz optical clock as the pumps. We present the resultant waveform as well as the optical spectrum of the Manchester-coded output.

Realization of All-fiber Tunable Filter and High Optical Power Blocker Using Thinned Fiber Bragg Gratings Coated with Carbon Nanotubes

Using thinned fiber Bragg gratings coated with carbon nanotubes, we demonstrate that the reflection band can be controlled by the in-line optical power. We use the structure to realize an all-fiber tunable filter and a high optical power blocker.

Ultrashort-cavity passively mode-locked fiber lasers using carbon nanotubes

We review our studies on high-repetition rate, ultrashort-cavity mode-locked fiber Fabry-Perot lasers (FFPLs) using Er:Yb fiber and carbon nanotube (CNT) based mode lockers. We also present our recent results of an ultrashort-cavity SOA-based mode-locked laser.

Enhanced passive mode-locking of fiber lasers using carbon nanotubes deposited onto D-shaped fiber

We demonstrate a novel passive mode-locking enhanced by the interaction of carbon-nanotubes with the evanescent-field of propagating beam in a D-shaped fiber. The scheme featuring long lateral interaction guarantees strong nonlinear effect from the nanotubes.