High-power operation of coherently coupled tapered laser diodes in an external cavity

Abstract

We demonstrate a rear-side phase-locking architecture with two high-brightness diode lasers. This technique is based on the passive phase-locking of emitters in an external cavity on their rear facet, and their coherent combination on the front facet. Two high-brightness high-power tapered laser diodes are coherently combined using a Michelson-based cavity. The combining efficiency is above 80% and results in an output power of 6.7 W in a nearly diffraction-limited beam. The rear-side architecture is then used with a laser bar of 5 tapered emitters using an interferometric extended cavity, based on a diffractive optical element. We describe the experimental evaluation of the diffractive optical element, and the phase-locked operation of the laser bar.

Coherent combining architectures for high-brightness laser diodes

“…Overcoming this limitation would deliver a technological breakthrough in cost effective, high-brilliance laser diode sources for industrial applications. The favored approach to scale up the brightness is to use several moderately powerful high-brightness lasers and to combine them in one single beam [1] [2]. The conservation of etendue principle forbids the improvement of spatial brightness through incoherent beam superposition.…”

Coherent combining of high brightness tapered lasers in master oscillator power amplifier configuration

“…We use the ridge current of the amplifiers to correct for the relative phase fluctuations in the multi-arm interferometer to achieve CBC in our experimental setup which is presented later in this proceeding. The relation between the phase piston and the ridge current is close to linear and a current variation of ΔIrw = 35 mA corresponds to a phase piston of ΔΦ ≈ π in the used TPA 10 . We can comfortably use variations of the ridge current in the range of 250 to 400 mA with limited impact on the output power per element as shown earlier in Figure 1.…”