Note: Improved technique for ultrashort lasers pulse width stabilization.

We have developed an improved pulse width stabilization method based on the second harmonic generation (SHG) technique using the relationship between pulse width, input intensity, and SHG intensity. On the basis of an analysis of the improved method accuracy, we then proposed a novel processing algorithm, which allowed us to increase the accuracy of pulse width stabilization to 1.2%.

Environmentally stable picosecond ytterbium fiber laser with a broad tuning range.

We demonstrate a widely tunable passively mode-locked fiber laser operating at a fundamental frequency of 80 MHz with an output power of 90 mW. The laser is capable of generating 5-ps pulses in the region 1010-1064 nm. A strong mode-locking mechanism promoted by frequency-shifted feedback allows us to operate in simultaneous Q-switched and mode-locked regimes and to obtain peak power in excess of 1.

Ultrafast intensity modulation by Raman gain for all-optical in-fiber processing.

We present experimental results on ultrafast intensity modulation using the Raman effect and demonstrate 10-Gbit/s selective pulse erasure. The technique is both broadband and polarization insensitive and has a potential speed in excess of 500 Gbits/s. In addition to performing pulse erasure, this all-optical modulator can shape pulses as a precise, soft aperture scalpel and create short, dark pulses.

Enhanced Q switching in double-clad fiber lasers.

A novel cladding pumped Nd(3+) fiber laser operating in an enhanced Q-switched regime with a stable repetition rate is described. By exploiting fiber nonlinearities in the laser cavity, we demonstrated a peak power of 3.7 kW enhanced by an order of magnitude greater than that of conventional Q-switched fiber devices.

Slicing the supercontinuum radiation generated in photonic crystal fiber using an all-fiber chirped-pulse amplification system.

We report on an experimental study of supercontinuum broadening in photonic crystal fiber performed by measuring the temporal behavior of spectrally-sliced radiation in different propagation regimes. The study confirms the soliton fission theory by observing the red-shifted fundamental solitons and blue-shifted nonsolitonic radiation.

Mode-locked ytterbium fiber laser tunable in the 980-1070-nm spectral range.

Spectral tuning of a mode-locked Yb-doped fiber laser over a 90-nm range is reported. Using semiconductor saturable absorber mirrors in a fiber laser cavity incorporating a grating-pair dispersive delay line, we obtain reliable self-starting mode locking over the whole tuning range. The wide tuning range is achieved by optimization of reflection characteristics and bandgap energy of the multiple-quantum-well semiconductor saturable absorber and by proper engineering of the laser cavity.

High-power, low-noise, Yb-doped, cladding-pumped, three-level fiber sources at 980 nm.

We present results on a high-power, cladding-pumped, Yb-doped fiber emitting at 977 nm in laser and ampllified-spontaneous-emission source configurations. We obtained up to 1.4 W of fiber-coupled, single-mode output power and slope efficiency as high as 68%.

Soliton fiber laser with a hybrid saturable absorber.

We present an experimental study of a picosecond fiber soliton laser in which mode locking is achieved by the combined action of a multiple-quantum-well saturable absorber and a nonlinear amplifying loop mirror. In this configuration the multiple-quantum-well sample acts not only as a saturable absorber but also as a passive phase modulator, while the inclusion of a nonlinear amplifying loop mirror fixes the energy of the generated pulses. The laser stably operates at a repetition rate of 250 MHz with a timing jitter below 10 ps.

Femtosecond harmonically mode-locked fiber laser with time jitter below 1 ps.

We have made an experimental study of the time jitter in a harmonic passively mode-locked fiber soliton ring laser. We demonstrate that jitter as low as 600 fs (100-550 Hz), which is less than the soliton pulse width, can be achieved at a repetition frequency of 463 MHz. The results support the suggestion that the stability of the laser is dependent on the long-range soliton interaction through the excitation of acoustic waves that is induced by the propagating pulses.

Increased amplifier spacing in a soliton system with quantum-well saturable absorbers and spectral filtering.

The spacing between optical amplifiers in a long-haul soliton system may be increased to 100 km by using only passive quantum-well saturable absorbers and narrow-band filters for soliton control. After transmission over 9000 km at 10 Gbits/s, the effects of soliton-soliton interaction and Gordon-Haus jitter in the proposed systemyield bit error rates of better than 10(-9).

Soliton interaction in the presence of a weak nonsoliton component.

We study both experimentally and theoretically soliton interaction in the presence of a weak nonsoliton component and show that the existence of a frequency-shifted cw wave results in a temporal shift of the soliton.

Amplification of femtosecond pulses in a passive, all-fiber soliton source.

We report a theoretical and experimental study of the amplification of femtosecond soliton pulses generated by a passively mode-locked fiber laser in a high-gain erbium-doped fiber amplifier (EDFA). Results on the spectral and temporal evolution of 450-fs soliton pulses propagating within an EDFA are presented. Power gains as high as 30 dB and the generation of sub-100-fs Raman colored solitons are observed.