Multi-core Photonic Crystal Fiber Laser Research Articles

Phase-locked and mode-locked multicore photonic crystal fiber laser with a saturable absorber.

Multicore photonic crystal fiber (MC-PCF) can scale the output power with the number of cores by spatial beam combining if the in-phase mode is selected. We demonstrated simultaneous realization of phase-locked and mode-locked laser using Yb-doped 7-core MC-PCF by a semiconductor saturable absorber placed in the near-field inside a resonator. High energy 333 nJ pulses were obtained directly from a mode-locked fiber laser oscillator at a 42.4 MHz repetition rate with an average power of 14.1 W at 24 W excitation. We observed the direct output pulse width of 52 ps assuming a sech2 profile. However, it might be noise-like pulses because of no variation when we performed pulse compression. Single-pulse operation was achieved by increasing the bandwidth of the intracavity filter. In this case, 137 nJ, 42.4 MHz pulses were generated with a 5.8 W average power and the compressed output pulse width was 8.6 ps.

Seven-core photonic liquid crystal fibers for simultaneous mode shaping and temperature sensing

Through doping liquid crystals into the core region, we propose a kind of seven-core photonic crystal fiber (PCF) which can achieve mode shaping and temperature sensing simultaneously in the communication window of 1.1–1.7 μm. To the best of our knowledge, this is the first time that the function of seven-core PCFs as temperature sensors is investigated. By using the full vectorial finite element method, the characteristics of the fiber with the temperature, such as the effective mode area, the waveguide dispersion, and the confinement loss, are analyzed. This kind of PCF can be competitive in providing temperature sensing in multi-core PCF lasers.

Thermal distribution analysis of multi-core photonic crystal fiber laser

The thermal properties of photonic crystal fiber (PCF) laser with 18 circularly distributed cores are investigated by using full-vector finite element method (FEM). The results show that the 18-core PCF has a more effective thermal dispersion construction compared with the single core PCF and 19-core PCF. In addition, the temperature distribution of 18-core PCF laser with different thermal loads is simulated. The results show that the core temperature approaches the fiber drawing value of 1800 K approximately when the thermal load is above 80 W/m which corresponds to the pumping power of 600 W approximately, while the coating temperature approaches the damage value of about 550 K when the thermal load is above 15 W/m which corresponds to the pumping power of 110 W approximately. Therefore the fiber cooling is necessary to achieve power scaling. Compared with other different cooling systems, the copper cooling scheme is found to be an effective method to reduce the thermal effects.

Mode locked multi-core photonic crystal fiber laser

A mode locked fiber laser based on Yb-doped large mode area photonic crystal fiber operating in the all-normal dispersion regime is experimentally studied. The eighteen cores of the gain fiber are arranged in array-type geometry with an equivalent mode diameter of about 52 μm. A sigma laser cavity is used without using any elements for dispersion compensation. Reliable self-starting mode-locking is achieved using a fast semiconductor saturable absorber mirror. The laser directly produces 4.92 ps chirped pulses at a 44.68 MHz repetition rate for an average power of 3.3 W corresponding to a pulse energy of 74 nJ. The pulses are compressed to 780 fs with a grating pair outside the cavity.

Numerical analysis of mode locking in multi-core photonic crystal fiber

With linearly coupled nonlinear Schrodinger equations, numerical analysis has been performed on the mode locking forming procedure of a fiber laser in the linear cavity configuration. The fiber is Yb-doped multi-core photonic crystal fiber and semiconductor saturable absorber mirror (SESAM) is adopted as the nonlinear transmission element to start mode locking. Because of the noise randomness, initial pulse would be picked out by SESAM in one or more cores which makes the multi-core mode locking quite different from single-core one. The two situations are compared and fully discussed. Mode locking in multi-core photonic crystal fiber laser can be realized only if the couple coefficient between the cores and the temporal overlap between the pulses in different cores are large enough.

Numerical analysis mode locking multi-core photonic crystal fiber laser

Numerical analysis was performed on the mode locking forming procedure of a fiber laser in the linear cavity configuration. The fiber is a doped multi-core photonic crystal fiber. The SESAM is adopted as the nonlinear transmission element to start mode locking. Because of the noise randomness, initial pulse would be picked out by the SESAM in one or more cores which makes the multi-core mode locking quite different from single-core one. The two situations are compared and fully discussed. The mode locking in multi-core photonic crystal fiber laser can be realized only if the couple coefficient between the cores is large enough and the overlap between the beams in different cores is also necessary.

Multicore Photonic Crystal Fiber Lasers for High Power/Energy Applications

In this paper, the authors discuss the modal and lasing properties of multicore photonic crystal fiber lasers in the context of high power/energy production from fiber cores with very large mode area. Supermode selection methods like Talbot imaging or far-field aperturing are tested using 6-, 7-, and 18-core fibers. It is shown that in-phase mode selection is achieved efficiently by using either method. The fibers have been tested in continuous-wave (CW) and Q-switched laser operation. The mode field area is as large as 4240 mum <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> for one of the fibers, providing up to 2 mJ of pulse energy in Q-switched operations with 30 ns pulse duration.

Characteristics of a Q-switched multicore photonic crystal fiber laser with a very large mode field area

We model and characterize the behavior of a Q-switched fiber laser. The fiber is a doped multicore photonic crystal fiber having six cores in a ring-type geometry. The fiber laser is Q-switched using an intracavity acousto-optic modulator. Using a mode filtering technique in the far field, a mode very close to the fundamental in-phase supermode is obtained with a mode field area of 4200 microm(2) and a divergence of 9 mrad. Pulses with energies of up to 2.2 mJ and durations of 26 ns (limited by end facet damage) at a repetition rate of 10 kHz are obtained.

Phase locking and supermode selection in multicore photonic crystal fiber lasers with a large doped area

We report on the laser properties of multicore photonic crystal fiber lasers. A stable phase locking of six- and seven-core structures through evanescent coupling is observed. Effective supermode selection is obtained by using both diffraction losses and the Talbot effect. A pure in-phase supermode is obtained (1.1 times diffraction limited). The laser operating in this mode has a slope efficiency of 70% with up to 44 W of output power. The modal area of the in-phase supermode multicore fiber is 1150 microm2, which makes it, to our knowledge, the single-mode fiber laser with the largest mode field area. In-phase laser action is stable when the fiber is bent.