A.B. Grudinin

Passive harmonic mode locking in soliton fiber lasers

We present an experimental and theoretical study of passively mode-locked fiber soliton lasers. Our theoretical analysis based on perturbation theory describes the soliton interactions that occur when pulse bunches form. Our results indicate that the nonsoliton component emitted by the propagating solitons causes small changes of the central frequency of individual solitons, and the strength and the sign of this interaction between the soliton and dispersive waves depend on their mutual phase as well as on the soliton position within the soliton bunch. For a certain phase difference between the solitons and the nonsoliton component the interaction force becomes repulsive for all solitons within a soliton bunch and results in an almost uniform distribution of the pulses inside the laser cavity. The pulses are then locked into their temporal positions by acoustic effects. We also demonstrate that the laser performance could be further improved by the use of a multiple-quantum-well saturable absorber in combination with a nonlinear amplifying loop mirror. In this instance the multiple-quantum-well sample acts not only as a fast saturable absorber but also as a passive phase modulator. We experimentally demonstrate that such a laser is capable of generating 500-fs pulses at repetition rates exceeding 2 GHz.

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. Pulse durations as short as 2 ns have been achieved.

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%. To our knowledge these are the highest powers efficiencies achieved from a single-mode fiber laser at approximately 980 nm and the first demonstrated results on a high-power amplified-spontaneous-emission source in this wavelength range. High power and high slope efficiency are achieved by using a high numerical aperture (> 0.7), a jacketed air-clad fiber, and a high-brightness pump source. Both types of sources exhibit relative intensity noise below -130 dB/Hz and are thus suitable for a wide range of applications.

8- and 16-channel all-fiber DFB laser WDM transmitters with integrated pump redundancy

All-fiber DFB-laser-based 8-channel 100-GHz and 16-channel 50-GHz wavelength-division-multiplexing (WDM) transmitter arrays with integrated pump redundancy are demonstrated for the first time. Each fiber laser WDM channel in the modules remain in operation despite the drop out of several of the pump diodes and the maximum power drop to each channel in an 8/spl times/8 channel 100-GHz system for the drop of seven out of eight pump diodes is just 14 dB.

Compact high-energy Q-switched cladding-pumped fiber laser with a tuning range over 40 nm

We describe a compact Q-switched diode pumped double-clad ytterbium-doped fiber laser. The fiber laser was bidirectionally pumped by two laser diodes (2 W of output power each) via two side-injecting pump-couplers. We used a large multimode core of 15 /spl mu/m diameter to increase the laser gain volume and thus to achieve higher pulse energy. Experimentally this laser produced pulses with energy up to 170 /spl mu/J with a peak power of 2 kW (at a low repetition rate of 500 Hz) and was tunable from 1060 to 1100 nm.

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).

High power fiber lasers: new developments

We assess different power limits of cladding-pumped fiber lasers. Despite recent advances in pump sources, these are still primarily limited by available pump power. We find that it should be possible to reach output powers beyond 1 kW in single-mode ytterbium doped fiber lasers. Experimentally, we have realized an ytterbium-doped fiber laser with 272 W of output power at 1080 nm, with an M2-value of 3.2, as well as an erbium-ytterbium co-doped fiber laser with 103 W of output power at 1565 nm, with an M2-value of 2.0. We believe these are the highest-power ytterbium and erbium-ytterbium fiber lasers ever reported.

Custom design of long chirped Bragg gratings: application to gain-flattening filter with incorporated dispersion compensation

We present and experimentally demonstrate simple relationships between the refractive index modulation, the chirp-rate or dispersion and the transmission loss through, and reflection of, chirped Bragg gratings, and apply them to the design of a new type of gain flattening filter with incorporated dispersion compensation.

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 1.2 kW.

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.