Technical Information

Fianium employees are still active in the research field and get their papers published in journals and introduced at major conferences around the world. This section contains all their recent published papers.

August 2005

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.

May 2005

High Power Ultrafast Fibre Laser in the 920 nm Spectral Range

We describe an ultrafast Nd-doped fibre laser capable of generating 170 fs pulses in the 920 nm spectral range with output power of 0.8 W.

May 2005

The rising power in ultrafast technology

High-power ultrafast fiber lasers are challenging the dominance of the bulk solid-state laser, outperforming solid-state systems in many applications; their potential is far from being exhausted.

April 2004

Femtosecond Neodymium-Doped Fiber Laser Operating in the 894-909-nm Spectral Range

We demonstrate a practical ultrafast Nd-doped fiber laser operating in the 894-909-nm spectral range. Using purposely designed semiconductor saturable absorbers, a truly self-started mode-locking regime of operation with clean transform-limited 360-fs pulses was achieved.

November 2003

980-nm Picosecond Fiber Laser

A mode-locked Yb3+ fiber laser operating at 980 nm is reported. Using a semiconductor saturable-absorber mirror in a laser incorporating a grating-pair dispersive delay line, we obtain reliable self-starting 1.6-ps pulse operation.

November 2003

Mode-Locked, Tunable Fiber Laser Is Alternative to Ti:Sapphire

Fiber lasers are being developed in laboratories around the world as alternatives to traditional solid-state lasers. The Ti:sapphire laser, however, has remained largely unchallenged as a source of broadly tunable, ultrashort pulses. But now a collaboration of engineers in Europe has produced a mode-locked, wavelength-tunable fiber laser that can give a Ti:sapphire laser a run for its money in terms of tunability and short-pulse generation.

September 2003

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 ref lection characteristics and bandgap energy of the multiple-quantum-well semiconductor saturable absorber and by proper engineering of the laser cavity.

July 2003

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-modeoutput power and slope efficiency as high as 68%. To our knowledge these are the highest powers and efficienciesachieved from a single-mode fiber laser at ~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 pumpsource. Both types of sources exhibit relative intensity noise below 2130 dB/Hz and are thus suitable for awide range of applications.

July 2003

Low-Noise Intelligent Cladding-Pumped L-Band EDFA

We present results on a low-cost cladding-pumped -band amplifier based on side pumping (GTWave) fiber technology and pumped by a single 980-nm multimode diode.We show that simultaneous noise reduction and transient suppression can be achieved by using gain clamping by a seed signal ( λ = 1564nm). In the gain-clamping regime, the amplifier exhibits 30-dB gain over 1570-1605-nm spectral band with noise figure below 7 dB. The noise figure can be further reduced to below 5 dB by utilizing a low power single-mode pump at 980 nm. The erbium-doped fiber amplifier is relatively insensitive to input signal variations with power excursions below 0.15 dB for a 10-dB channel add-drop.

May 2003

High Power 980 nm Yb-doped Picosecond Fibre System Pumped by a Cladding Pumped 925 nm Nd-doped Fibre Laser

Picosecond pulses from a 980 nm passively mode-locked fibre laser are amplified up to energies of 50 nJ in a short length core-pumped fibre amplifier pumped by single mode cladding pumped 925 nm fibre lasers.

May 2003

Fiber-DFB Laser Array Pumped With a Single 1-W CW Yb-Fiber Laser

A 50-GHz grid fiber distributed feedback laser wavelength-division-multiplexing transmitter source is demonstrated pumped by a single continuous-wave Yb-fiber laser source at 977 nm. Up to 21mWof output power is achieved per channel with maintenance of key operational parameters. The performance of this single Yb-fiber laser pump configuration is also compared with that of a semiconductor pump configuration which shows no degradation for all the important parameters.

February 2003

Performance Limitations of High-Power DFB Fiber Lasers

In this letter, we experimentally study several different configurations of high-power single-frequency sources based on distributed-feedback fiber laser (DFB FL). In particular, we have compared two schemes in terms of pumping efficiency, relative intensity noise (RIN) and optical signal-to-noise ratio (OSNR): directly pumped DFB FLs pumped by a high-power fiber-based pump source (stand-alone DFB FL) and a combination of a DFB FL and a power amplifier (amplified DFB FL). At the output powers below 40 mW, a stand-alone DFB FL has the highest OSNR ( > 63 dB) and the lowest RIN ( < -165 dB Hz). The net efficiency of a stand-alone DFB FL can be doubled by using an amplified DFB FL at the expense of degraded OSNR and RIN. It is also shown that RIN below - 160 dB Hz and OSNR > 60 dB can be achieved by an amplified DFB with output power greater than 1 W.

May 2000

Advanced Pulsed and CW High-Power Fibre Lasers

Part of the CLEO2000 presentation.

August 1999

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 μm diameter to increase the laser gain volume and thus to achieve higher pulse energy. Experimentally this laser produced pulses with energy up to 170 μJ with a peak power of 2 kW (at a low repetition rate of 500 Hz) and was tunable from 1060 to 1100 nm.

January 1999

Broad-Band Diode-Pumped Ytterbium-Doped Fiber Amplifier with 34-dBm Output Power

We investigate a high-power diode-pumped doubleclad ytterbium-doped fiber amplifier with 34-dBm average output power and 1050-1095-nm bandwidth. A multidiode concentrator pumps the amplifier at 980 nm, with ~6 W of power launched into the inner cladding. Besides CW-signals, we amplify pulses from a mode-locked laser to 1 kW of peak power with only minor nonlinear distortions as well as pulses from a Q-switched laser to 50 μJ of energy. Reflections and backscatter limit the gain of the amplifier to 40 dB for a pump power of 2.5 W. For higher pumppowers than this, the amplifier started to self-Q-switch. The results are important for the development of cladding-pumped high-power fiber amplifiers.

April 1998

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.

January 1997

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.

February 1996

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.