Thermal-driven orthogonally polarized eye-safe dual-wavelength Er,Yb:YAl₃(BO₃)₄ microchip laser

We present a thermal-driven, orthogonally polarized, eye-safe dual-wavelength microchip laser based on an a-cut Er,Yb:YAl₃(BO₃)₄ (Er,Yb:YAB) crystal, operating without the need for additional intracavity elements. Two thermal management schemes were investigated, revealing that additional end-face cooling effectively reduces internal temperature gradients within the crystal. As a result, the laser achieved a total output power of 1.04 W at the polarization intersection point (PIP) and an extended polarization coexistence range (PCR) of up to 11 W, with dual-wavelength emission at 1551.9 nm and 1556.5 nm, corresponding to a frequency difference of 0.57 THz. Furthermore, by adjusting the cooling temperature, both the PIP output power and PCR exhibited an approximately linear dependence, offering a practical means of thermally controlling polarization dynamics. Theoretical simulations showed good agreement with experimental results, confirming the validity of the thermal-driving mechanism. This compact, alignment-free laser architecture holds strong potential for applications in laser interferometry, precision metrology, coherent THz radiation, and eye-safe differential absorption lidar.