Growth and property characterization of large-size Nd:CNGG crystal for high-energy chirped pulse amplification system

Abstract

Chirped pulse amplification (CPA) technology is the core of ultra-short and ultra-intense pulsed laser system that is highly dependent on the spectral bandwidth and thermal management ability of laser medium. However, traditional laser materials including Nd:glass or Nd:YAG were limited by the inherent low thermal conductivity or narrow pulse width, respectively. For that reason, exploring large-size laser crystal with wide spectral bandwidth and high thermal conductivity becomes more urgent. In this work, neodymium-doped calcium gallium niobium garnet (Nd:CNGG) was selected as CPA medium and a large-size 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 so far. X-ray rocking curve and optical uniformity tests show that as-grown Nd:CNGG crystal has the high optical quality with small half-peak width (21.6") and good optical uniformity (3.85 × 10-4). Moreover, thermal and spectral tests also indicate that Nd:CNGG crystal has the higher thermal conductivity (3.98 W·m-¹·K-¹) and wider emission peak bandwidth (14.7 nm @1064 nm) than those of Nd:glass. Therefore, this work provides a large-size Nd:CNGG crystal with good overall performances as potential candidate for the high-energy CPA system and further benefits for the future development of laser fusion device.