Design guidelines for normal-dispersion fiber optical parametric chirped-pulse amplifiers.

We theoretically investigate methods of controlling pulse generation in normal-dispersion fiber optical parametric chirped-pulse amplifiers. We focus on high-energy, ultrashort pulses at wavelengths widely separated from that of the pump, and find that within this regime, a number of simple properties describe the essential phase and gain dynamics. Of primary importance are the relationships between the chirps of the pump, seed, and parametric gain, which we theoretically predict and then experimentally validate. By properly arranging these parameters, the signal and idler waves can be widely customized to fulfill a remarkable range of application requirements, spanning from narrowband to few-cycle.

Fiber four-wave mixing source for coherent anti-Stokes Raman scattering microscopy.

We present a fiber-format picosecond light source for coherent anti-Stokes Raman scattering microscopy. Pulses from a Yb-doped fiber amplifier are frequency converted by four-wave mixing (FWM) in normal-dispersion photonic crystal fiber to produce a synchronized two-color picosecond pulse train. We show that seeding the FWM process overcomes the deleterious effects of group-velocity mismatch and allows efficient conversion into narrow frequency bands. The source generates more than 160 mW of nearly transform-limited pulses tunable from 775 to 815 nm. High-quality coherent Raman images of animal tissues and cells acquired with this source are presented.

Pulse dynamics of a passively mode-locked Bi-doped fiber laser.

The pulse evolution in Bi-doped soliton fiber laser with slow and fast saturable absorber has been studied both experimentally and numerically. Semiconductor saturable absorbers with balanced slow and fast absorption recovery mechanisms exhibit a bi-temporal recovery dynamics which permits both reliable start-up of passive mode-locking and short pulse generation and stabilization. The pulse dynamics within the Bi fiber laser cavity have been investigated.

Mode-locked Yb-doped fiber laser with external compression to 89 fs in normal dispersion fiber.

A practical ytterbium-doped mode-locked fiber source producing 89 fs pulses without an external bulk compensator was developed by investigating the pulse propagation dynamics in a mode-locked fiber laser with small average dispersion. Negatively chirped pulses are taken from the cavity and compressed in a standard output fiber resulting in high-quality pulses.

Effect of post-epitaxial-growth processing on the nonlinear response of saturable absorber.

The nonlinear response of an ion-irradiated saturable Bragg reflector, further modified by thermal annealing, has been studied. We demonstrate that the absorption recovery time and the effective saturation fluence dependent on the pulse duration can be tailored over a wide range after epitaxial growth by the proper combination of ion irradiation and subsequent annealing. Thermal treatment is also an efficient means for the reduction of the unbleachable losses and the stabilization of the absorber parameters.

Dynamic gain induced pulse shortening in Q-switched lasers.

We describe a novel mechanism of pulse shortening in a Q-switched laser induced by the gain compression effect under strong pumping conditions. The pulse shortening requires a large variation of the gain excursion during the saturation process and benefits from the large volume of the gain medium. The effect has been experimentally demonstrated using a passive Q-switched Tm/Ho-doped fiber laser that shows gain-induced pulse compression from 800 ns down to 160 ns when the pump threshold is exceeded by 15 times.

Harmonically mode-locked VECSELs for multi-GHz pulse train generation.

We report on optically-pumped vertical-external-cavity surface-emitting lasers passively mode-locked with a semiconductor saturable-absorber mirror. The potential of harmonic mode-locking in producing pulse trains at multigigahertz repetition rates has been explored. The results present first systematic study of multiple pulse formation in passively mode-locked VECSELs.

Fiber taper for dispersion management in a mode-locked ytterbium fiber laser.

We exploit the large anomalous dispersion in the waist of a fiber taper to offset the intracavity normal chromatic dispersion of an Yb-doped fiber laser. The fiber taper provides sufficient anomalous dispersion to ensure soliton operation of the mode-locked laser. With the taper removed from the cavity, the laser operates in a net normal dispersion regime.

Passively synchronized erbium (1550-nm) and ytterbium (1040-nm) mode-locked fiber lasers sharing a cavity.

Erbium and ytterbium fiber lasers were firmly synchronized by nonlinear interaction in active media placed in the same cavity. A two-color femtosecond-picosecond pulse train at largely separate wavelengths of 1.55 and 1.04 microm was generated. Optimizing the laser cavity to enhance the cross-phase modulation in the gain materials has yielded a large mismatch of 20 microm between the two laser cavities.

Passively synchronized two-color mode-locked fiber system based on master-slave lasers geometry.

Using a master - slave configuration, a robust synchronization was achieved for two-color Erbium and Ytterbium mode-locked fiber lasers. Due to enhanced nonlinear interaction in the fiber, noise-free pulse-locking was achieved allowing for a cavity mismatch tolerance of 140 microm. This is the highest tolerable cavity-length difference ever been obtained for synchronized mode-locked oscillators.

1.05-microm mode-locked Ytterbium fiber laser stabilized with the pulse train from a 1.54-microm laser diode.

Using cross-phase modulation in an optical fiber, we synchronized the pulse train from a mode-locked ytterbium fiber laser operating at 1.05 microm to an external optical master signal. The optical master source based on a 1.54 microm distributed feedback (DFB) diode laser was driven by the clock signal and was used as a seed source. The amplified seed pulses are launched into the fiber cavity and synchronize the mode-locked pulses through cross-phase modulation. The master clock signal is electronically generated, benefiting from inherent stability and repeatability. Due to its simplicity, this technique provides an attractive alternative to the traditional scheme that uses an independent mode-locked laser as source of seed signal. Since the approach is flexible and generally applicable, we expect this stabilization method to have a good potential for use in metrology and optical communications.

1.05-microm mode-locked Ytterbium fiber laser stabilized with the pulse train from a 1.54-microm laser diode: errata.

Figures 2 and 4 have been altered during publication. Their correct version is presented herein.