This review takes a look at the historical development of the dielectric planar waveguide laser leading to key state-of-the-art technologies which fall within this broad subject area. Discussed herein are many of the advantages offered by the waveguide geometry such as; high optical-gain and thus low threshold-power requirements, suitability for quasi-three-level laser transitions, integration with functional devices on single substrates, guided spatial-mode control, and its considerable immunity to thermal effects and external environmental conditions. A detailed snapshot is made of many active host media for which there has been reported laser action in the planar waveguide geometry, covering many of the major rare-earth-ion transitions. Several fabrication techniques are highlighted and appraised for their applicability to different host media, touching on their benefits and drawbacks. Challenges and future prospects for these lasers are considered.
The advantages and potential hazards of using a planar waveguide
as the host in a high-power diode-pumped laser system are described. The
techniques discussed include the use of proximity-coupled diodes,
double-clad waveguides, unstable resonators, tapers, and integrated passive
Q switches. Laser devices are described based on Yb3+-, Nd3+-, and
Tm3+-doped YAG, and monolithic and highly compact waveguide lasers
with outputs greater than 10 W are demonstrated. The prospects for scaling
to the 100 W level and for further integration of devices for added
functionality in a monolithic laser system are discussed.
Samarium, europium, and ytterbium displace the alkali metals from their molten chlorides, forming the divalent species Sm(II), Eu(II), and Yb (II) in solution. Progressive coulometric reduction of solutions of SmCI3, EuCI3, and YbCI3 in LiCI-KCI at 450~ enabled the redox potentials to be measured vs. im Pt(II)-Pt(0): Sm(III)-Sm(II) --1.729 ~ 0.006V; Eu(III)-Eu(II) --0.554 ___ 0.007V; Yb(III)-Yb(II) --1.375 • 0.003V. Potentials of ytterbium systems starting from both YbC13 and YbC12 were followed over a ~200~ interval and from OE~ --OE~ = 0.66 x 10-3V deg -1, ~S ~ and ~H ~ for the reaction YbC13 ~ YbCI.~ + 1/2C12 in LiC1-KC1 at 450~ were found to be 22 cal/deg -1 mole-1 and 54.5 kcal/mole -1, respectively, close to the values for pure YbC13 decomposition. No evidence of disproportionation of Sm(II), Eu(II), and Yb (II) was found but scrupulous precautions were needed to keep the solvent free from impurities which readily react with the highly reducing ions, especially Sm (II). Considerable experimental details are included.
We theoretically investigated the effect of the spatial distribution of the active-ion concentration in multimode step-index waveguides on transverse-mode selection for continuous-wave laser operation. We found that uniform doping of a central portion of as much as 60% of the full waveguide core width is highly effective for the selection of fundamental-mode operation, even under highly saturated, high-power conditions. Profiling the dopant distribution to match that of the particular mode desired was also found to be effective, especially if it is the saturated inversion profile that is matched to the shape of the mode.
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