Coherent beam combination of seven 1.5 µm fiber amplifiers through up to 1 km atmospheric turbulence: near- and far-field experimental analysis.

A laser testbed based on active coherent beam combination (CBC) of seven 1.5 µm, 3 W fiber amplifiers was developed for applications requiring high power such as power density deposition on targets or free space laser communication. For the first time to our knowledge, the frequency-tagging locking of optical coherence by single-detector electronic-frequency tagging technique was implemented in the field in real atmospheric turbulence conditions in a target-in-the-loop configuration.

Coherent combining of mid-infrared difference frequency generators.

We report what is, to the best of our knowledge, the first experimental demonstration of coherent combining of two mid-infrared difference frequency generators by active phase control in the continuous-wave regime. Using the phase relation that is inherent to the nonlinear process, we are able to phase lock and combine the idler waves by the sole phase control of one of the pump waves. This control is done by an all-fiber electro-optic modulator.

Coherent combining of second-harmonic generators by active phase control of the fundamental waves.

Coherent beam combining by active phase control could be useful for power scaling fiber-laser-pumped optical frequency converters. However, a fast phase modulator operating at the frequency-converted wavelength, a non-standard component, would be necessary. Fortunately, nonlinear conversion processes rely on a phase-matching condition allowing for indirect phase control using standard phase modulators.

Study of filamentation threshold in zinc selenide.

The possibility of creating filaments with laser wavelengths ranging from 800 nm to 2.4 µm was investigated using an OPA laser system. Zinc Selenide's (ZnSe) unique characteristics - small band gap E(gZnSe)=2.