Sigang Yang

Theoretical study and experimental fabrication of high negative dispersion photonic crystal fiber with large area mode field

We present a systematic process of theoretical design and experimental fabrication of the large mode area and large negative dispersion photonic crystal fiber. An easily fabricated fiber structure is proposed. The influence of structure parameters deviations from the design on the chromatic dispersion are evaluated and a design rule is given. Finally our fabricated fiber and test results are demonstrated. The measured effective area of inner core mode is 40.7 mum(2) which is the largest effective area of high negative dispersion photonic crystal fibers that have been experimentally fabricated. The measured peak dispersion is -666.2ps/(nm.km) and the bandwidth is 40nm.

Broadband dispersion-compensating photonic crystal fiber

We present a modified dual-core photonic crystal fiber, based on pure silica, with special grapefruit holes in the inner cladding. The fiber has large, broadband negative dispersion, and the dispersion value varies linearly from -380 t o-420 ps/(nm km) in the C band. To decrease the fabrication difficulty, large air holes are adopted. Furthermore, the chromatic dispersion of the fiber is not sensitive to the structure parameters. So the proposed fiber structure can greatly facilitate fiber drawing and can be used for broadband dispersion compensation.

Widely tunable picosecond optical parametric oscillator using highly nonlinear fiber.

We demonstrated a fully fiber-integrated widely tunable picosecond optical parametric oscillator based on highly nonlinear fiber. The ring cavity with a 50 m highly nonlinear fiber was synchronously pumped with a picosecond mode-locked fiber laser. The tuning range was from 1413 to 1543 nm and from 1573 to 1695 nm, which was as wide as 250 nm. A high-quality pulse was generated with a pulse width narrower than that of the pump.

Actively Mode-Locked Fiber Optical Parametric Oscillator

We demonstrate active mode locking of a fiber optical parametric oscillator (FOPO). By inserting an amplitude modulator (AM) into a continuous-wave pumped FOPO loop, intracavity loss is varied periodically. When the modulation frequency of AM coincides with the harmonics of longitudinal modes spacing of the loop cavity, stable 10-GHz pulse train can be obtained. By adjusting the intracavity filter, the wavelength of the pulse train can be tuned over 21 nm.

Multiwavelength time-stretch imaging system

A high-speed microscopic imaging system based on a multiwavelength source and time-stretch technique is proposed and demonstrated. We realize an imaging system at 1D scan rate of 80 MHz with 20 resolvable points. This scheme breaks the bottleneck of large bandwidth and high repetition rate in mode-lock lasers and has great potential for imaging system integration.

Slow-light delay enhancement in small-core pure silica photonic crystal fiber based on Brillouin scattering

We demonstrate that we realize large-delay slow light based on stimulated Brillouin scattering in a short length of our fabricated small-core photonic crystal fiber (PCF). The cavity effect from the partially reflective splices in the end of the PCF enhances slow-light delay significantly. Our experiments show that large slow-light delay can be easily realized in a very short length of the PCF with a moderate pump power. Up to a one-half pulse-width delay is achieved in only 50 m of PCF in a single pump segment.

Fast and wide tuning wavelength-swept source based on dispersion-tuned fiber optical parametric oscillator

We demonstrate a dispersion-tuned fiber optical parametric oscillator (FOPO)-based swept source with a sweep rate of 40 kHz and a wavelength tuning range of 109 nm around 1550 nm. The cumulative speed exceeds 4,000,000 nm/s. The FOPO is pumped by a sinusoidally modulated pump, which is driven by a clock sweeping linearly from 1 to 1.0006 GHz. A spool of dispersion-compensating fiber is added inside the cavity to perform dispersion tuning. The instantaneous linewidth is 0.8 nm without the use of any wavelength selective element inside the cavity. 1 GHz pulses with pulse width of 150 ps are generated.

All-Fiber-Based Ultrashort Pulse Generation and Chirped Pulse Amplification Through Parametric Processes

We experimentally demonstrate, for the first time to the best of our knowledge, the use of optical fiber for optical parametric chirped pulse amplification to amplify subpicosecond pulses. We use this system to amplify a subpicosecond signal at 1595 nm generated by a fiber-optical parametric oscillator. The 750-fs signal from the oscillator output is stretched to 40 ps, amplified by an all-fiber optical parametric amplifier and then compressed to 808 fs. The peak power of the signal is amplified from 93 mW to 10 W.

60-nm-Wide Tunable Single-Longitudinal-Mode Ytterbium Fiber Laser With Passive Multiple-Ring Cavity

A broadband tunable, single-longitudinal-mode (SLM) ytterbium fiber laser based on a passive multiple-ring cavity (MRC) technique is proposed and demonstrated experimentally for the first time to our knowledge. Two different short ring cavities are inserted into the main ring cavity and serve as wideband mode filters to ensure SLM oscillation. With 1-m ytterbium-doped fiber as the gain medium, the SLM operation is achieved with over 60-nm wavelength tuning range at 100-mW pump power. The laser is very stable with output power of 6 dBm and an optical signal-to-noise ratio of higher than 53 dB in all the 60-nm tuning range.

Tunable single-longitudinal-mode fiber optical parametric oscillator

A tunable single-longitudinal-mode (SLM) fiber optical parametric oscillator is demonstrated by using a subring cavity and a fiber loop mirror incorporated with a saturable absorber. It can provide dual-wavelength SLM output.