- 1State Key Laboratory of Laser Interaction with Matter, Changchun Institute of Optics, Fine Mechanics and Physics, CAS, Changchun 130033, China
- 2Innovation Laboratory of Electro-Optical Countermeasures Technology, Changchun Institute of Optics, Fine Mechanics and Physics, CAS, Changchun 130033, China
- 3Laboratory of Geosphere-Biosphere Interactions, Institute of Monitoring of Climatic and Ecological Systems, SB RAS, Tomsk 634055, Russia
- 4Laboratory of Advanced Materials and Technologies, Siberian Physical-Technical Institute of Tomsk State University, Tomsk 634050, Russia
- 5Crystal Growth Laboratory, Institute of Geology and Mineralogy, SB RAS, Novosibirsk 630090, Russia
- 6Novosibirsk State University, Novosibirsk 630090, Russia
In this review, we introduce the current state of the art of the growth technology of pure, lightly doped, and heavily doped (solid solution) nonlinear gallium selenide (GaSe) crystals that are able to generate broadband emission from the near infrared (IR) (0.8 μm) through the mid- and far-IR (terahertz (THz)) ranges and further into the millimeter wave (5.64 mm) range. For the first time, we show that appropriate doping is an efficient method controlling a range of the physical properties of GaSe crystals that are responsible for frequency conversion efficiency and exploitation parameters. After appropriate doping, uniform crystals grown by a modified technology with heat field rotation possess up to 3 times lower absorption coefficient in the main transparency window and THz range. Moreover, doping provides the following benefits: raises by up to 5 times the optical damage threshold; almost eliminates two-photon absorption; allows for dispersion control in the THz range independent of the mid-IR dispersion; and enables crystal processing in arbitrary directions due to the strengthened lattice. Finally, doped GaSe demonstrated better usefulness for processing compared with GaSe grown by the conventional technology and up to 15 times higher frequency conversion efficiency.