We report on an hybrid fiber/crystal ultra-short pulsed laser delivering high pulse energy and high peak power in the picosecond regime. The laser is composed of a mode-lock fiber oscillator, a pulse picker and subsequent fiber amplifiers. The last stage of the laser is a single pass Nd:YVO<sub>4</sub> solid-state amplifier. We believe that this combination of both technologies is a very promising approach for making efficient, compact and low cost lasers compatible with industrial requirements.
In this study, a polarization maintaining (PM) all-fiber laser oscillator passively mode locked at 1.03 μm is presented. The mode locking is achieved by nonlinear polarization evolution occurring along a long span of standard PM fiber (26 m) spliced between an off-axis polarizer and a Faraday rotator mirror. The influence of the total chromatic dispersion and intra-cavity spectral filtering on pulsed operation is studied. Two experimental configurations have been tested. The first configuration is an all normal dispersion cavity using a looped fibered circulator combined to a 1.5 nm filter used as an end cavity mirror. The second configuration used highly reflective chirped Fiber Bragg Grating (FBG) exhibiting different bandwidths (0.7 nm, 1.1 nm and 1.83 nm). The chromatic dispersion induced is +7.2 ps/nm for each FBG. Stable single-pulse mode locked operation has been demonstrated for each configuration. The study highlights however different mode-locking operations according to the intra-cavity spectral filtering and total chromatic dispersion of the cavity. For the first configuration, pulse duration is about 7 ps. According to the optical spectrum which has a FWHM of 2.2 nm, pulses may be compressed to subpicosecond durations with the help of a suited compressor like bulk gratings. Shortest pulses of 2.2 ps have been obtained at a repetition rate of 3.3 MHz with the second experimental configuration. To our knowledge, this is the smallest pulse duration delivered by a fully fibered mode locked laser operating at a repetition rate lower than 10 MHz without any external pulse compressor.
We present in this study a PM all-fiber laser oscillator passively mode-locked (ML) at 1.03 μm. The laser is based on
Nonlinear Polarization Evolution (NPE) in polarization maintaining (PM) fibers. In order to obtain the mode-locking
regime, a nonlinear reflective mirror including a fibered polarizer, a long fiber span and a fibered Faraday mirror (FM) is
inserted in a Fabry-Perot laser cavity.
In this work we explain the principles of operation of this original laser design that permits to generate ultrashort pulses
at low repetition (lower that 1MHz) rate with a cavity length of 100 m of fiber. In this experiment, the measured pulse
duration is about 6 ps. To our knowledge this is the first all-PM mode-locked laser based on the NPE with a cavity of
100m length fiber and a delivered pulse duration of few picosecondes.
Furthermore, the different mode-locked regimes of the laser, i.e. multi-pulse, noise-like mode-locked and single pulse,
are presented together with the ways of controlling the apparition of these regimes. When the single pulse mode-locking
regime is achieved, the laser delivers linearly polarized pulses in a very stable way.
Finally, this study includes numerical results which are obtained with the resolution of the NonLinear Schrodinger
Equations (NLSE) with the Split-Step Fourier (SSF) algorithm. This modeling has led to the understanding of the
different modes of operation of the laser. In particular, the influence of the peak power on the reflection of the nonlinear
mirror and its operation are studied.
We present a theoretical and experimental study on PM ultra-short fiber laser cavities operating at low repetition rate.
The mode-locking operation in this study always relies on SEmicondutor Saturable Absorber Mirror (SESAM) and intracavity
spectral filtering. Several experimental configurations have been tested and modeled. Repetition rates as low as
7.7 MHz with sub-picosecond pulse duration have been obtained. A longer cavity has also been modeled in order to
determine if stable ultra-short pulsed operation would also possible at lower repetition rates.