Non-critical phase-matching conditions for fourth harmonic generation of DKDP crystal

The non-critical phase matching (PM) conditions of deuterated dihydrogen phosphate (DKDP) crystal are investigated in this paper for fourth harmonic generation (FHG) of Nd:YAG crystal and Nd:glass lasers, which include exterior angle deviation, deuterium content and PM temperature. DKDP crystals of different deuterium content were grown from aqueous solutions and cut for type-I non-critical phase-matching with the direction at 90° to the crystal Z axis (θ = 90°) and at 45° to the crystal X axis (Ф = 45°). The samples are measured for FHG at 1064 nm and 1053 nm, respectively. The deuterium content of DKDP crystal that supports non-critical phase-matching for FHG experiments is confirmed by measuring the relationship of deuterium content and phase-matching angle. Additionally, the non-critical phase matching temperature is also examined.