Growth and property characterization of large-sized Nd:CNGG crystals for high-energy chirped pulse amplification systems

Abstract

Chirped pulse amplification (CPA) technology is the core of ultra-short and ultra-intense pulsed laser systems that are highly dependent on the spectral bandwidth and thermal management ability of the laser medium. However, the traditional laser materials Nd:glass and Nd:YAG are limited by their inherent low thermal conductivity and narrow pulse width, respectively. Hence, exploring large-sized laser crystals with a wide spectral bandwidth and high thermal conductivity becomes more urgent. In this work, a neodymium-doped calcium gallium niobium garnet (Nd:CNGG) was selected as a CPA medium, and a large-sized Nd:CNGG single crystal with a diameter of 80 mm was successfully grown for the first time by optimizing the ratio of raw materials and temperature field, which can be regarded as the largest CNGG single crystal ever reported thus far. X-ray rocking curve and optical uniformity tests showed that the as-grown Nd:CNGG crystal has high optical quality with a small half-peak width (15.48′′) and good optical uniformity (5.47 × 10⁻⁴). Moreover, thermal and spectral tests indicated that the Nd:CNGG crystal has higher thermal conductivity (4.04 W m⁻¹ K⁻¹) and wider emission peak bandwidth (19 nm at 1061 nm) than those of Nd:glass. Therefore, this work provides a large-sized Nd:CNGG crystal with good overall performance as a potential candidate for the high-energy CPA system and further benefits the future development of laser fusion devices.