Cryogenic solid-state laser materials offer many improvements in thermal, optical, structural, and lasing properties over
their room temperature counterparts. As the temperature of Yb:YAG decreases from room to 80K it transitions from
quasi-three-level lasing to a 4-level laser. In this study, we compare Yb:YAG thin-disk laser performance at room 293K
and 80K. To achieve this direct comparison we have built two cooling systems based on R134A refrigerant and also on
liquid nitrogen (LN2). We have made an analytical calculation of the small signal laser gain that takes into account the
spurious amplified spontaneous emission and photon re-absorption. The cold thin-disk laser clearly outperforms room
temperature operation, and the theoretical results shows room temperature gain flattening.
A ceramic ytterbium:yttrium aluminum garnet (Yb:YAG) thin-disk laser is investigated at 15°C (288 K) and also at 80 K, where it behaves as a four-level laser. We introduce a new two-phase spray cooling method to cool the Yb:YAG. One system relies on R134a refrigerant while the other uses liquid nitrogen (LN2). The use of two systems allows the same disk to be tested at the two temperatures. When the Yb:YAG is cooled from room to cryogenic temperatures, the lasing threshold drops from 155 W to near 10 W, while the slope efficiency increases from 54% to a 63%. A 277 W laser with 520 W of pump is demonstrated. We also model the thermal and structural properties at these two temperatures and estimate the beam quality.
The main goal of this paper is the study of the stimulated Brillouin scattering (SBS) in multimode fibers, at 1550 nm wavelength, cw operation, in order to build high power IR fiber lasers. Two theoretical models are considered, the usual plane wave model and a modal model, developed in this paper. The theoretical results for SBS threshold and SBS reflectivity are compared with the experimentally determined values. Good agreement was obtained when using the mode structure analysis.
We present the time dependence, steady state behavior and spectra of a dual fiber-laser compound cavity. This particular cavity is formed with two Er-doped fiber amplifiers, each terminated with a fiber Bragg grating, and coupled through a 50/50 coupler to a common feedback and output coupling element. The experiment and theory show that a low Q, high gain symmetric compound cavity extracts nearly all the incoherent power in a coherent mode when the two fiber polarizations are aligned. This extraction is maintained even when there is significant difference in the optical pathlengths of the two component elements.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.