Long-range soliton interactions through gain-absorption depletion and recovery.

We report the interpulse dynamics in fiber soliton laser because of depletion and relaxation of gain and absorption. The soliton interaction range is shown to depend largely on the relaxation time of dissipative parameters while the compensation of the dynamical gain and absorption depletion leads to the formation of stationary soliton groups with unequal interpulse distances.

Effect of absorption recovery in bismuth-doped silica glass at 1450 nm on soliton grouping in fiber laser.

Saturable absorption in bismuth-doped glasses was found to have a noticeable influence on soliton interaction and group formation. This phenomenon, observed in 1450 nm mode-locked bismuth-doped fiber laser, shows the distinct feature of the multiple pulse regime, which appears as a stationary pulse group whose length can be spread over the whole cavity length by variation of the pump power and polarization. Pulse positioning within the ensemble depends on the saturation fluence and the relatively fast recovery dynamics of bismuth fiber.

Femtosecond mode-locked holmium fiber laser pumped by semiconductor disk laser.

We report on a 2085 nm holmium-doped silica fiber laser passively mode-locked by semiconductor saturable absorber mirror and carbon nanotube absorber. The laser, pumped by a 1.16 µm semiconductor disk laser, produces 890 femtosecond pulses with the average power of 46 mW and the repetition rate of 15.7 MHz.

Low-noise Raman fiber amplifier pumped by semiconductor disk laser.

A 1.3 µm Raman fiber amplifier pumped by 1.22 µm semiconductor disk laser in co-propagation geometry is demonstrated. Measured relative intensity noise of -148 dB/Hz over frequency range up to 3.5 GHz was measured at 900 mW of pump power. 9 dB gain was achieved with co-propagating pumping geometry with less than 2 dB additional noise induced by amplifier to the signal. Nearly shot-noise-limited operation of semiconductor disk laser combined with the diffraction-limited beam allows for efficient core-pumping of the single-mode fiber Raman amplifiers and represents a highly practical approach which takes full advantage of co-propagating pumping.

1.3 µm Raman-bismuth fiber amplifier pumped by semiconductor disk laser.

A hybrid Raman-bismuth fiber amplifier pumped in co-propagation configuration by a single 1.22 µm semiconductor disk laser is presented. The unique attribute of this dual-gain system is that both amplifiers require the pump source with the same wavelength because pump-Stokes spectral shift in 1.3 µm Raman amplifier and pump-gain bandwidth separation in 1.3 µm bismuth fiber amplifier have the same value. Residual pump power at the output of Raman amplifier in this scheme is efficiently consumed by bismuth-doped fiber thus increasing the overall conversion efficiency. The small-signal gain of 18 dB at 1.3 W of pump power has been achieved for hybrid scheme which is by 9 dB higher as compared with isolated Raman amplifier without bismuth fiber. Low noise performance of pump semiconductor disk laser with RIN of -150 dB/Hz combined with nearly diffraction-limited beam quality and Watt-level output powers allows for efficient core-pumping of a single-mode fiber amplifier systems and opens up new opportunities for amplification in O-band spectral range.

1.38-µm mode-locked Raman fiber laser pumped by semiconductor disk laser.

A mode-locked Raman fiber laser pumped by 1.3 µm semiconductor disk laser is demonstrated. Direct Watt-level core-pumping of the single-mode fiber Raman lasers and amplifiers with low-noise disk lasers is demonstrated to represent a highly practical solution as compared with conventional scheme using pumping by Raman wavelength convertors. Raman laser employing passive mode-locking by nonlinear polarization evolution in normal dispersion regime produces stable pedestal-free 1.97 ps pulses at 1.38 µm. Using semiconductor disk lasers capable of producing high power with diffraction-limited beam allows Raman gain to be obtained at virtually any wavelength of interest owing to spectral versatility of semiconductor gain materials and wafer-fusing technology.

Raman fiber laser pumped by a semiconductor disk laser and mode locked by a semiconductor saturable absorber mirror.

A 1.6µm mode-locked Raman fiber laser pumped by a 1480nm semiconductor disk laser is demonstrated. Watt-level core pumping of the single-mode fiber Raman lasers with low-noise disk lasers together with semiconductor saturable absorber mirror mode locking represents a highly practical solution for short-pulse operation.

High-power quantum-dot-based semiconductor disk laser.

We demonstrate multiwatt cw output power from an optically pumped quantum-dot semiconductor disk laser. Continuous-wave output power of 4.35 W with 22% slope efficiency was demonstrated at a center wavelength of 1,032 nm. This represents an increase in power of 15 times and an increase in slope efficiency of 10 times from the previously published results using Stranski-Krastanow grown quantum dots. An intracavity diamond heat spreader was used for thermal management. The maximum output power was limited by the available pump power, and no sign of thermal rollover was observed.

600 W power scalable single transverse mode tapered double-clad fiber laser.

Pump propagation and absorption in active tapered double-clad fiber has been analyzed based on a ray optics approach. Optimization of the longitudinal shape, absorption and angular distribution of the pump beam allowed for power scaling of a ytterbium fiber laser up to 600 W with high beam quality (M2

Double clad tapered fiber for high power applications.

We report a novel type of active fiber - tapered double clad fiber suitable for pumping by low brightness sources with large beam parameter product of 50/300 mm x mrad. Ytterbium double clad all-silica fiber (core/1(st) clad/2(nd) clad diameters 27/834/890 mum, NA(core)=0.11, NA(clad)=0.21), tapered down by a factor 4.8 for a length of 10.5 m was drawn from a preform fabricated by plasma chemical technologies. At a moderate Yb-ion concentration and 1:31 core/cladding ratio, the tapered double clad fiber demonstrates 0.9 dB/m pump absorption at 976 nm and excellent lasing slope efficiency. An ytterbium fiber laser with 84 W of output power and 92% slope efficiency, a 74 W superfluorescent source with 85% slope efficiency and amplifiers operating both in CW and pulsed regimes have been realized. All devices demonstrated robust single mode operation with a beam quality factor of M(2)=1.07.

All-fiber supercontinuum source based on a mode-locked ytterbium laser with dispersion compensation by linearly chirped Bragg grating.

We demonstrate an all-fiber picosecond soliton laser with dispersion management performed by a chirped Bragg grating that generates ~1.6 ps pulses representing the shortest pulsewidth reported to date using this technology. The large anomalous dispersion provided by the grating allows building of a long-length cavity laser with an extremely low fundamental repetition rate of 2.6 MHz. This source allows us to use an original approach for producing energetic pulses that after boosting in a medium power core-pumped amplifier produce an octave-spanning supercontinuum radiation in a nonlinear photonic crystal fiber.

2.7 W tunable orange-red GaInNAs semiconductor disk laser.

We report on a GaInNAs/GaAs semiconductor disk laser frequency-doubled to produce orange-red radiation. The disk laser operates at a fundamental wavelength of 1224 nm and delivers an output power of 2.68 W in the visible region with an optical-to-optical conversion efficiency of 7.4%. The frequency-converted signal could be launched into a singlemode optical fiber with 70-78% coupling efficiency, demonstrating good beam quality for the visible radiation. Using a Fabry-Pérot glass etalon the emission wavelength could be tuned over an 8 nm spectral range.

All-fiber ytterbium soliton mode-locked laser with dispersion control by solid-core photonic bandgap fiber.

We exploit an anomalous dispersion generated by a solid-core photonic bandgap fiber for dispersion compensation in an ytterbium fiber laser passively mode-locked with a semiconductor saturable absorber. The bandgap-guiding fiber, adequately compatible with standard fiber based on guiding via total internal reflection, allows for an environmentally robust all-fiber subpicosecond soliton oscillator at 1 mum.

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.

Vertical-cavity saturable-absorber intensity modulator.

We propose and demonstrate a reflection-type optical modulator, with surface-normal architecture, that exploits the optical saturation of absorption in semiconductor quantum wells. The modulation section of the modulator, which is composed of quantum wells placed within a Fabry-Perot cavity, is optically controlled by an intensity-modulated beam generated by an in-plane laser integrated monolithically on the same wafer and grown in a single epitaxial step. The modulation section and the in-plane laser share the same medium; therefore, efficient coupling between the control beam and the signal beam is achieved. The device was successfully used for active mode locking of an erbium-doped fiber laser.

Harmonic mode locking by synchronous optical pumping of a saturable absorber with the residual pump.

An actively mode-locked fiber laser is demonstrated, for the first time to our knowledge, by modulation of a saturable-absorber mirror with the light used simultaneously for pumping the gain fiber. Stabilization of a harmonically passive mode-locked fiber laser that generates soliton pulses of 550-fs duration is obtained with this technique. The results indicate a reduction of supermode suppression by more than 55 dB. The timing jitter is improved by 9 dB.

1.5-microm monolithic GaInNAs semiconductor saturable-absorber mode locking of an erbium fiber laser.

We present a new monolithic GaAs-based semiconductor saturable absorber operating at 1.55 microm. An epitaxially grown absorber mirror in a GaInNAs/GaAs material system was successfully used to mode lock an erbium-doped fiber laser. The GaInNAs material system possesses intriguing physical properties and provides great potential for lasers and nonlinear optical devices operating at the 1.3-1.55-microm wavelength range.

Self-starting stretched-pulse fiber laser mode locked and stabilized with slow and fast semiconductor saturable absorbers.

A self-starting stretched-pulse mode-locked erbium-doped fiber laser that uses fast and slow semiconductor saturable absorbers is described. By using two absorbers, we obtained reliable operation at a fundamental repetition rate with 250 pJ of pulse energy without multiple-pulse breakup. External chirp compensation was used to compress the highly chirped pulses to durations of 135 fs.

Stable single- and dual-wavelength fiber laser mode locked and spectrum shaped by a Fabry-Perot saturable absorber.

We show that the spectral response of a Fabry-Perot semiconductor saturable absorber depends on laser beam focusing. We used this effect to achieve stable passive mode-locked operation in a simple and environmentally stable fiber laser by introducing spectral filtering and forcing near-resonant operation. By reducing the free spectral range and increasing the nonlinear response of the Fabry-Perot saturable absorber, we obtained dual-wavelength mode-locked operation.

Multiwavelength picosecond frequency-shifted feedback laser with pulse control by a shaped-gain fiber amplifier.

Stable generation of multiwavelength picosecond pulses by a frequency-shifted laser is demonstrated. Pulses are reliably trapped by gain variations provided by a low-extinction transmission filter. Pulses with close parameters are obtained despite considerable difference in amplifier gain at the pulse train wavelengths owing to a strong gain-equalization mechanism provided by the frequency-shifted feedback.