Cover Story: A dual-cavity master-oscillator power-amplifier (MOPA) offers laser beams with high power and a time-dependent tailored intensity profile
At: 2017/11/27 17:31:41 by admin

Tailoring laser beam profiles is very attractive in material processingapplications since the intensity distribution at the work piece dictates theresultant pattern of the induced damaged zone, and the effects on the zonesurrounding it. Moreover temporal modulation of the laser beam profiles shouldbe very useful for numerous applications in areas, such as sophisticatedmanagement of the laser processing quality, and particle manipulation in thetime and space domains.

Recently Prof. Ji Won Kim’s researchgroup, from Hanyang University ERICA in Korea, proposed an innovative lasersystem, so called a dual-cavity laser configuration. The innovation in thisconfiguration is that it can produce the laser output with the targeted beamprofile from the primary cavity simply by adjusting the round-trip loss of thesecondary cavity independently. This architecture had already proved itsvalidity in generation of the laser outputs with the TEM00 or LG0nmode only, or tailored beam profiles ranging from a pure donut to aquasi-top-hat shape. Despite its simplicity, flexibility, and low cost, powerscaling of the laser output was rather challenging.

Afterwards the authors overcame thisdifficulty and demonstrated efficient power scaling of the laser output from aNd:YAG dual-cavity master-oscillator using a carefully-designed three-stageend-pumped Nd:YVO4 amplifier system. Temporal modulation of thelaser beam profiles in a repetition rate of 1 Hz to 100 Hz was also achieved bymodulating the diffraction loss of the acousto-opticmodulator (AOM). It is reported in Chinese Optics Letters Volume 15, No.12,2017 (S. H. Noh et al., High power generation of adaptive laser beamsin a Nd:YVO4 MOPA system).

“This laser configuration will benefit a range of applications requiringlaser beams with high power and a bespoke intensity profile, or time-dependentspatial intensity distribution because of its simplicity and flexibility alongwith low cost.” said Prof. Ji Won Kim from this group.

The following works will be focused on pulsed modes of operation, suchas Q-switching and mode-locking, to produce high-peak pulsed outputs and the investigationof how fast mode-switching can be achieved.

Graphic description: Schematicdiagram of the three-stage Nd:YVO4 amplifier incorporating a Nd:YAGdual-cavity master-oscillator is shown in the figure. The adaptable beamprofiles were well-maintained in the amplifiers (bottom left) and the outputbeam profiles could be modulated in the temporal domain (bottom right).


Related Picture: