Cryogenic performance of Ho:YAP: spectroscopy and lasing at 2.1 $$\upmu$$m

Abstract The holmium-doped yttrium aluminum perovskite (Ho:YAP, $$\hbox {Ho:YAlO}_{3}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mtext>Ho:YAlO</mml:mtext> <mml:mn>3</mml:mn> </mml:msub> </mml:math> ) is a promising material for high-power mid-infrared solid-state lasers. This study presents detailed temperature-dependent spectroscopic properties of Ho:YAP, including 2 $$\upmu$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>μ</mml:mi> </mml:math> m polarisation-resolved absorption and emission spectra, as well as the upper-laser-level lifetime, measured across a wide temperature range (4–300 K). For experimental validation, three Ho:YAP crystals with different orientations ( $$\mathbf {{a}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>a</mml:mi> </mml:math> -, $$\mathbf {{b}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>b</mml:mi> </mml:math> -, and $$\mathbf {{c}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>c</mml:mi> </mml:math> -cut) were employed as the gain medium in cryogenically cooled (78–300 K), multi-watt, resonantly pumped microchip lasers operating near 2.1 $$\upmu$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>μ</mml:mi> </mml:math> m. Similarly to other quasi-three-level laser media, Ho:YAP demonstrated a significant reduction in the laser threshold with decreasing temperature, alongside a simultaneous drop in effective absorption. The maximum output power was achieved at approximately 200 K. The orientation of the crystal primarily influenced the emission wavelength, while the lasers consistently exhibited linearly polarised output and fundamental-mode beam profiles. These findings confirm Ho:YAP as a versatile material for efficient laser operation in the mid-infrared region, even under cryogenic conditions.