Narrow-line coherently combined tapered laser diodes in a Talbot external cavity with a volume Bragg grating

Abstract

We present the phase locking of an array of index-guided tapered laser diodes. An external cavity based on the self-imaging Talbot effect has been built. A volume Bragg grating is used as the output coupler to stabilize and narrow the spectrum at 976 nm. A power of 1.7 W is achieved in the in-phase single main lobe mode with a high visibility. We have checked that each emitter is locked to the Bragg wavelength with a 100 pm spectrum linewidth. The experimental results compare well with numerical simulations performed with two-dimensional wide-angle finite difference beam propagation method

Spectral beam combining of a 980 nm tapered diode laser bar

“…Recently, Paboeuf et al [10], coherently combined an array of ten index guided tapered laser diodes in a Talbot cavity and achieved 1.7 W of output power. Additionally, experiments on off-axis feedback to an index guided tapered laser bar has shown promising results with single-lobe output [11].…”

Volume Bragg grating external cavities for the passive phase locking of high-brightness diode laser arrays: theoretical and experimental study

“…This also permits the laser array to reach high operating currents (more than four times the threshold) with no significant degradation of the phase locking. Even better results have been already demonstrated with a VBG and the 16]. This makes VBGs a promising tool for increasing the output power from coherent diode laser arrays in external Talbot cavity configurations and makes it possible to overcome the usual limitation related to the incoherent background at high operating currents.…”

“…Conversely, the in-phase mode was forced by angling the VBG by λ=2pð5 mradÞ. A maximum output power of 1:7 W was obtained for an operating current of 3:9 A [16]. The output power was only limited by the thermal rollover of the array, which appeared at 4 A under our experimental conditions.…”

“…A few papers have demonstrated spatial beam improvement by taking benefit of their angular-filtering properties [10,15]. We have recently demonstrated experimentally that these components can also be used for the phase locking of an array of diode lasers [16]. Because of the intrinsic angular selectivity of a VBG, the use of this component inside an external cavity may modify the beam propagation and reduce the effective coupling coefficient.…”

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

“…CBC consists in the superposition of individual laser beams by constructive interference, providing a single high-power laser beam with excellent spectral and spatial properties 4 . Over the years, different approaches were investigated 5 : either active phaselocking of amplifiers 6,7 or passive self-organization of emitters in a common laser cavity [8][9][10][11][12] . For simplicity and industrial purposes, passive techniques are here favored to improve the building block performance.…”