High-Brightness Wavelength-Beam-Combined Eyesafe Diode Laser Stacks
At 1450 nm, we have demonstrated 20-W wavelength-beam-combined output from a 25- element single bar (M<sup>2</sup> ~ 1.9 times 10), and 80-W cw from a 6-bar diode stack (M<sup>2</sup> ~ 36 times 68).
Coherent (phased array) and wavelength (spectral) beam combining compared (Invited Paper)
Significant progress has been recently reported on beam combining of arrays of fiber and semiconductor lasers using both coherent (phased array) and wavelength (spectral) techniques. The choice between these two classes of beam-combining techniques has implications for the degree of control required on the array elements and on the optical system that is using the beam-combined array. Coherent beam combining imposes more stringent requirements on array-element control (spectrum, phase, amplitude, and polarization) than wavelength combining. Also, wavelength-combined systems should degrade more gracefully than coherent systems and require fewer changes to optical systems as the number of elements is varied.
Coherent beam combining and phase noise measurements of ytterbium fiber amplifiers.
Phase noise characterization of a 10-W Yb fiber amplifier is presented, and we demonstrate phase locking of two fiber amplifiers with near-perfect fringe contrast at power levels of as much as 10 W per fiber. Coherent beam combining is maintained during the turn-on transient as well as in thermal steady-state operation.