Room temperature 90° phase-matching in zirconium and magnesium co-doped lithium niobate crystals.

Laser has been widely used in many aspects, by now it is difficult to get each frequency that we want, and frequency conversion is an effective way to obtain different frequency laser through a nonlinear optical crystal. MgO-doped LiNbO (Mg:LN) crystal has usually been used for second harmonic generation (SHG) through temperature-matching configuration with a stove, till now a room temperature 90° phase-matching is still lacking. Here we find that the SHG of Nd:YAG laser is achieved at 26.1 °C while the optical damage resistance is higher than 6.5 MW/cm in the ZrO and MgO co-doped LiNbO (Zr,Mg:LN) crystal. Moreover, the monotonic decrease of phase-matching temperature is firstly found with the increase of doping concentration. These unusual properties may be attributed to the formation of  +  defect pairs. Our work suggests that Zr,Mg:LN crystal may be an attractive candidate for nonlinear optical applications.