AgGaS2- and Al-doped GaSe Crystals for IR Applications

We report a systematic study of AgGaS2- and Al-doped GaSe crystals in comparison with pure GaSe and S-doped GaSe crystals. AgGaS2-doped GaSe (GaSe:AgGaS2) crystal was grown by Bridgman technique from the melt of GaSe:AgGaS2 (10.6 wt.%). Its real composition was identified as GaSe:S (2 wt.%). Al-doped GaSe (GaSe:Al) crystals were grown from the melt of GaSe and 0.01, 0.05, 0.1, 0.5, 1, 2 mass % of aluminium. Al content in the grown crystals is too small to be measured. The hardness of GaSe:S (2 wt.%) crystal grown from the melt of GaSe:AgGaS2 is 25% higher than that of GaSe:S (2 wt.%) crystal grown by a conventional S-doping technique and 1.5- to 1.9-times higher than that of pure GaSe. GaSe:Al crystals are characterized by 2.5- to 3-times higher hardness than that of pure GaSe and by extremely low conductivity of ≤ 10− 7 Om− 1 cm− 1. A comparative experiment on SHG in AgGaS2-, Al-, S-doped GaSe and pure GaSe is carried out under the pumps of 2.12–2.9 μm fs OPA and 9.2−10.8 μm ns CO2 laser. It was found that GaSe:S crystals possess the best physical properties for mid-IR applications among these doped GaSe crystals. GaSe:Al crystals have relatively low conductivity which have strong potential for THz application.

Research highlights
► GaSe crystals doped by AgGaS2, Al, and S were used as nonlinear optical elements.
► GaSe:Al crystal is characterized by 3-times higher hardness than that of pure GaSe.
► GaSe:Al crystal is characterized by extremely low conductivity of ≤ 10− 7 Om− 1 cm− 1.
► S-doped GaSe crystals possess higher efficient nonlinearity than that of pure GaSe.
► S and Al-doped GaSe crystals can be cut and polished at arbitrary direction.