Laser action along and near the optic axis of a holmium-doped KY(WO_4)_2 crystal

Abstract

We demonstrate the first (to our knowledge) quasi-three-level conical refraction laser operating at 2 μm, with 1.6 W of output power at 2074 nm, using a holmium-doped KY(WO4)2 crystal. A maximum slope efficiency of 52% has been achieved, along the optic axis with respect to the absorbed pump power. Furthermore, lasing operation around the optic axis has been performed. In this case, a maximum output power of 3 W has been reached, with a slope efficiency better than 70%, which are the best performances ever reported on this material.

In-band pumped conical refraction Nd:KGW laser

“…Fig 1(b) shows the output power versus the absorbed power for both regimes with the slope efficiencies of 46% and 32% for 1067 nm and 1069 nm lasers, respectively. Lower output power in the CR regime can be explained by the laser beam walk-off and agrees with the previous report [11]. The output beam did not produce the CR ring pattern in the current setup due to a big mode size in the crystal.…”

Variable two-crystal cascade for conical refraction

“…This modification adds an extreme versatility to the effect and allows one to tune continuously the actual cascade parameters. As a result, practically any pattern of two-crystal cascade conical refraction can be obtained for any pair of biaxial crystals.In recent years, the internal conical refraction (CR) of light in biaxial crystals has attracted a renewed interest because of several demonstrated possibilities of the effect in manipulations with the amplitude, polarization, and phase of light beams (see, for instance, [1][2][3][4][5][6][7][8]). Under the CR effect, a collimated light beam propagating along one of the optic axes of a biaxial crystal spreads inside the crystal into a hollow slanted cone and exits the crystal as a hollow light cylinder with a characteristic geometrical radius R 0 .…”

Orientation and polarization dependence of both the absorption and the laser efficiency around the optic axis in monoclinic $$\hbox {Ho}^{3+}$$ Ho 3 + :KYW

“…3. Some of those results have already been published in [16]. The pump in these experiments was the same laser as in the previous section.…”

“…It has been studied sporadically during the twentieth century [2][3][4]. Nowadays, some applications, trying to take advantage of this effect, are under investigation as beam transformation [5-9], optical tweezers [10,11], microscopy [12] and laser sources [13][14][15][16]. This recent increase in publications on this effect can be explained by the availability of biaxial crystals with good optical quality needed to observe the conical refraction (CR).…”