Efficient power scaling of laser radiation by spectral beam combining

Abstract

The possibility of achieving multikilowatt laser radiation by spectrally combining beams using volume Bragg gratings (VBGs) is shown. The VBGs recorded in a photothermorefractive glass exhibit long-term stability of all its parameters in high-power laser beams with power density >1 MW/cm2 in the cw beam of total power on a kilowatt level. We consider an architecture-specific beam-combining scheme and address the cross-talk minimization problem based on optimal channel positioning. Five-channel high efficiency spectral beam combining resulted in a >750 W near-diffraction-limited cw beam has been demonstrated experimentally.

16 W output power by high-efficient spectral beam combining of DBR-tapered diode lasers

“…Losses in general can be linked to finite divergences [28] and grating vector non-uniformities across the large aperture. However, the results ranging between 93% and 96% are comparable to the values achieved by others [22][23][24]. The temperature tuning of both lasers for optimum performance results in a wavelength separation of 0.5 nm (Fig.…”

“…This immediately increases the chance of achieving a combined near diffraction limited beam just by choosing the proper lasers. Regarding SBC of individual lasers with smaller wavelength separations, volume Bragg gratings (VBG) have been shown to be a suitable alternative [22,23]. In these experiments five diode lasers as well as five fiber lasers emitting at around 1060 nm and spectrally spaced 0.5 nm were successfully combined.…”

High-Power Continuous-Wave Directly-Diode-Pumped Fiber Raman Lasers

“…We attribute the decrease in reflection efficiency for the higher-power diode to its larger linewidth. In addition, the increased heating at higher power may perturb the VBG [21]. Figure 5 shows the transmitted and the reflected power from the VBG against the input power from the diodes.…”

Polarization changes at Lyot depolarizer output for different types of input beams

“…Spectral beam combining is a recently developed method for efficient power scaling of laser radiation [24,25]. In applications where depolarized light it is necessary or convenient, one wonders if an LD could be useful to depolarize a spectral beam combined superposition of lasers.…”

“…For example, beams with a state of polarization that varies across the transverse section, like radially and azimuthally polarized fields, as well as fields which can be represented as an uncorrelated superposition of beams with the same or different states of polarization have been studied and/or synthesized [18][19][20][21][22][23]. On the other hand, several spectral-beam-combining schemes have been developed in order to obtain an efficient power scaling of laser radiation; see for example [24,25]. This suggests a detailed analysis of the behavior of the LD for input beams with different spectral and polarization properties.…”