Chee Seong Goh

Widely tunable optical filters based on fiber Bragg gratings

The authors design and demonstrate a widely tunable wavelength filter, which is realized by lateral bending of a fiber Bragg grating mounted on a substrate. The 40-nm tunable range of the device covers the entire C-band of erbium-doped fiber amplifiers with very small changes in a spectral width and a reflectivity across the operation bandwidth. Furthermore, employment of a hybrid material as a substrate alleviates the stringent requirement for the bending radius. With this hybrid substrate structure, a tuning range as wide as 50 nm is achieved.

Planar waveguide-type saturable absorber based on carbon nanotubes

The authors propose and demonstrate a planar waveguide-type optical device based on carbon nanotubes (CNTs). They realize saturable absorbers utilizing the interaction between the evanescent field of guiding mode and the CNTs. Saturable absorption characteristics are observed and insertion loss decreases ∼3% by high power pulsed laser. The device shows that polarization dependence originated from the asymmetric structure of their device and over 15dB polarization dependent loss. The saturable absorption is observed only in the polarization state that shows a maximum loss caused by the CNTs.

Adjustable dispersion-compensation devices with wavelength tunability based on enhanced thermal chirping of fiber Bragg gratings

We demonstrate a dispersion compensation device based on thermal chirping of a glued fiber Bragg grating. The device can change the group velocity dispersion (GVD) while maintaining a center wavelength or change the center wavelength while preserving a GVD value. The GVD can be tuned from -122.5 to -57 ps/nm with a center wavelength at 1552.9 nm. On the other hand, the center wavelength can be shifted by 2.2 nm with a GVD value around -105 ps/nm.

A widely tunable fiber Bragg grating with a wavelength tunability over 40 nm

We have fabricated and demonstrated a 40 nm widely tunable fiber Bragg grating designed for operation over erbium band. This device is simple, low-cost and will have great potential for applications in optical communication and sensing.

A net normal dispersion all-fiber laser using a hybrid mode-locking mechanism

We propose and demonstrate an all-fiber, dispersion-mapped, erbium-doped fiber laser with net normal dispersion generating dissipative solitons. The laser is mode-locked by a hybrid mode-locking mechanism consisting of a nonlinear amplifying loop mirror and a carbon nanotube saturable absorber. We achieve self-starting, mode-locked operation generating 2.75?nJ pulses at a fundamental repetition rate of 10.22?MHz with remarkable long term stability.

Non-synchronous Optical Sampling and Data-Pattern Recovery Using a Repetition-Rate-Tunable Carbon-Nanotube Pulsed Laser

We demonstrate a non-synchronous all-optical sampling system using a carbon-nanotube mode-locked laser with a tunable repetition-rate. This allows a stable and unambiguous waveform reconstruction without the inherent limitation encountered in conventional non-synchronous optical sampling such as the time-direction ambiguity and the frequency-hole or sparse-sampling phenomena. Real-time eye-diagram reconstruction of 160 Gbit/s return-to-zero (RZ) signals with sub-picosecond resolution and data-pattern recovery with sequence length up to 217 - 4 has be realized.

All optical switching using carbon nanotubes loaded planar waveguide

We realized, for the first time, NOLM-type all optical switching with carbon nanotubes loaded planar waveguide. ~20% splitting ratio contrast has been achieved using just 1 cm-long carbon nanotubes loaded planar waveguide.

Rapid amplitude and group-delay measurement system based on intra-cavity-modulated swept-lasers

In this paper, we present a high-speed wavelength-swept laser for application in a real-time optical device characterization system. The system is capable of simultaneous measurement of both the spectral amplitude and group-delay responses of the device-under-test, at a scan rate of 22 Hz over a wide wavelength range of 50 nm. This corresponds to a record sweep rate of >1000 nm/s.

Polarization Maintaining, Nanotube-Based Mode-Locked Lasing From Figure of Eight Fiber Laser

We propose and demonstrate an all-fiber, polarization maintaining (PM) ultrafast fiber laser using a hybrid mode-locking mechanism consisting of a nonlinear amplifying loop mirror and carbon nanotube saturable absorber (CNT-SA). By incorporating the CNT-SA, the threshold for mode-locked operation is reduced by approximately a factor of 3, from 330 to 120 mW. Moreover, the all-PM fiber design provides excellent stability and turnkey operation.

Greater than 90nm continuously wavelength-tunable fibre Bragg gratings

In this paper silica-based fibre Bragg grating filters with wavelength tuning-spans well over 90nm using a simple set-and-forget beam bending tuning-package is reported. The key operational parameters of the filters are maintained over the entire tuning-window.