Resonant Saturable Absorber Mirror Research Articles

Wiggling instabilities of temporal localized states in passively mode-locked vertical external-cavity surface-emitting lasers.

We analyze the emergence of wiggling temporal localized states in a passively mode-locked vertical external-cavity surface-emitting laser composed by a gain chip and a resonant saturable absorber mirror. We show that the wiggling instability stems from the interplay between the third-order dispersion induced by the micro-cavities and their frequency mismatch. The latter is identified as an experimentally crucial parameter defining the range of existence of stable emission. We reveal the homoclinic scenario underlying the wiggling phenomenon, and we show how it allows us to control the oscillation parameters.

Control and Generation of Localized Pulses in Passively Mode-Locked Semiconductor Lasers

We show experimentally and theoretically that localized pulses can be generated from an electrically biased 200 μm multitransverse-mode vertical-cavity surface-emitting laser. The device is passively mode-locked using optical feedback from a distant resonant saturable absorber mirror and is operated below its threshold. We observe multistability between the nonlasing (off) solution and a large variety of pulsating solutions which have a different number and arrangement of pulses per round trip, thus indicating that the mode-locked pulses are localized, i.e., mutually independent. We show that modulation of the bias current allows control of the number and the location of the pulses traveling within the cavity, thus suggesting that our system can be operated as an arbitrary pattern generator of mode-locked pulses.

Passive Mode-Locking and Tilted Waves in Broad-Area Vertical-Cavity Surface-Emitting Lasers

We show experimentally and theoretically that an electrically biased 200-μm multitransverse mode vertical-cavity surface-emitting laser can be passively mode-locked using optical feedback from a distant resonant saturable absorber mirror. This is achieved when one cavity is placed at the Fourier plane of the other. Such nonconventional optical feedback leads to the formation of two tilted plane waves traveling in the external cavity with opposite transverse components and alternating in time at every round-trip. Each of these plane waves gives birth to a train of mode-locked pulses separated by twice the external cavity round-trip, while the two trains are time shifted by a round-trip. A large portion of the transverse section of the device contributes to mode-locked emission leading to pulses of approximately 1-W peak power and 10-ps width. We discuss how inhomogeneities in the transverse section of the saturable absorber select the emitted tilted waves, thus leading to tunable emission over 4 nm.

1.55-μm wavelength ultrafast fiber oscillators and amplifiers

In this paper, we review our recent developments on ultrafast pulse generation in erbium-doped fiber laser systems operating in the 1550 nm wavelength range. This work concerns the generation of ultrafast pulses from dissipative soliton fiber lasers featuring resonant saturable absorber mirrors, as well as their amplification in highly efficient erbium-doped large-mode-area fibers. Different amplification schemes featuring all-fiber components are studied leading to the achievement of record pulse energy from a high repetition rate laser system.

130 mW average power, 46 nJ pulse energy, 102 ps pulse duration from an Er^3+ fiber oscillator passively mode locked by a resonant saturable absorber mirror

An Er(3+) fiber laser passively mode locked by a resonant saturable absorber mirror achieves more than 130 mW average power at 1560 nm from a Fabry-Perot cavity. The pulsed regime is self-starting from the CW regime without any Q-switch transition. The output pulse has a duration of 10.2 ps and can be extracavity dechirped with 42% efficiency down to 614 fs, which represents 1.2 times the Fourier limit imposed by the spectrum. To date, this corresponds to the highest averaged power directly extracted at such a wavelength from a fiber laser mode locked with a saturable absorber mirror.

Dispersionless saturable absorber mirrors with large modulation depths and low saturation fluences

We show that it is possible to eliminate group delay dispersion over wide bandwidths in low-finesse, resonant saturable absorber mirrors, whilst maintaining a low saturation fluence and a high modulation depth. By modelling the mirror structure we demonstrate that these properties can be produced by capping a resonant device with a single dielectric layer of carefully selected refractive index. We show that a specially capped dispersionless structure minimises the temporal broadening of femtosecond pulses reflected from the mirror. We compare this device against uncapped-resonant and anti-resonant structures. The superior performance of the capped, dispersionless device was verified experimentally by comparing resonant, anti-resonant and dispersionless quantum-dot (QD) saturable absorber mirrors incorporated into a Cr4+:forsterite laser system. We found that a minimum pulse duration of 86 fs could be achieved for the dispersionless structure at 1290 nm with an output power of 55 mW compared to 122 fs in an anti-resonant structure and several-picosecond pulses for a resonant structure.

8 ns fiber laser Q switched by the resonant saturable absorber mirror

We demonstrate that resonant high-modulation-depth saturable absorbers allow efficient pulse shortening in Q-switched lasers. Using a 70% modulation depth resonant saturable absorber mirror we achieved 8 ns pulses that are close to the limit set by the cavity length and are, to our knowledge, the shortest pulses demonstrated to date from passively Q-switched fiber lasers.