Influence of laser array performance on spectrally combined beam

Abstract

Incoherent spectral beam combining (SBC) of multiple laser beams is accomplished along the emitters' arraying direction. Considering that the output beams from a laser array (LA) usually have deflection angles, positional displacements and divergence angles even after being collimated, a propagation model of SBC systems based on multilayer dielectric gratings has been built up. On the basis, properties of the spectrally combined beam affected by parameters of the LA have been discussed in detail. Simulation results show that with the increase in the deflection angle, both the power and the beam quality of the combined beam degrade dramatically. The positional displacement has little impact on the intensity distribution and the beam quality of combined beam but change the wavelength composition of the combined beam. The divergence angle strongly affects the intensity distribution and the beam quality of the combined beam. Additionally, the effect of the deflection angle on the output beam quality is more obvious and may shift the beam spot when comparing with that of the divergence angle.

Wavelength selection for spectrally combined laser beams propagating in free space and the atmosphere

“…. , λ G [10][11][12]. The elements may be approximately regarded as GS beams of equal waist widths w 0 , located at the center of a rectangular (x, y) coordinate system.…”

“…In this work, the spectral line width of each element is taken much smaller than the wavelength spacing ∆λ (i.e. the wavelength difference between any two adjacent elements), so the line width can be neglected [12]. Making use of the Collins formula [25,26] for paraxial wave fields, the field distribution of each element at the target plane can be written as…”

“…The output of an SBC system exhibits not only high brightness and high power of several hundred kilowatts but also a good beam quality which is comparable to that of an individual laser [10,11]. Therefore, SBC is viewed as a simple and robust technique for achieving highpower lasers [8,[10][11][12].…”

Dynamic of Grating Thermal Deformation on Beam Quality for Spectral Beam Combining

“…The z 2 -axis is the main optical axis of the lens, and the x 2 -axis lies on the focal plane of the lens in object space. For each individual beam with a waist width of w 0 , the field distribution on the incident plane of the grating can be expressed as a function of grating groove number n [21]: where k q = 2π/λ q and f is the focal length of the transform lens. It is worth noting that the quartic-aberration produced by the transform lens is ignored.…”