Method for obtaining low-coherence generation in Nd:YVO4 and Nd:YAG lasers

Laser media based on mixtures of particles and liquids are the subject of a significant number of studies since this approach makes possible to obtain low-coherence generation and to provide solutions to heat removal in a laser. The preparation of immersion mixtures with particles of such materials as Nd:YAG or Nd:YVO4 crystals (refraction indices, n≈2) and of other known solid-state laser media meets certain difficulties associated with the use of liquids of high n values. We show that low-coherence lasing in such media can be obtained in conventional bulk samples using a simple intra-cavity cuvette-diffuser with a mixture of microparticles and a liquid of moderate n values. In such a cuvette (similar to a Christiansen filter) parts of the laser beam are randomly deflected at small angles forming independent lasing channels in the resonator. Thus a spatially incoherent radiation is expected in the common laser beam cross section. A cuvette with a mixture of 70–140μm LiF granules and isobutanol (nD=1.39) was installed in compact resonators (L≲2cm) containing Nd:YAG or Nd:YVO4 active elements at 808 nm QCW LD pumping. At the output of Nd:YAG and Nd:YVO4 lasers, 1 ms pulses of 1064 nm radiation with 10–200 mW power at 10 Hz frequency and beam divergence 0.005–0.1 rad were obtained. The reduction of the degree of laser spatial coherence to the values γ≈0.1 and speckles contrast to C≈0.04 by decreasing the level of immersion in the cuvette was demonstrated. Further studies of lasers with immersion diffusers in the visible and near-IR spectral ranges and their possible applications are discussed. •Nd:YAG and Nd:YVO4 low coherent lasers with an immersion diffuser are proposed.•Small-angle immersion diffuser made on a mixture of LiF microparticles and isobutanol.•Cuvette-diffuser in a laser resonator forms small independent lasing channels.•The laser coherence control occurs by changing the level of immersion in a diffuser.•The immersion diffuser works in the visible and near-IR regions of the spectrum.