Rational
Design via Synergistic Combination Leads
to an Outstanding Deep-Ultraviolet Birefringent Li2Na2B2O5 Material with an Unvalued B2O5 Functional Gene
posted on 2019-01-18, 00:00authored byMin Zhang, Donghai An, Cong Hu, Xinglong Chen, Zhihua Yang, Shilie Pan
Birefringent materials,
the key components in modulating the polarization
of light, are of great importance in optical communication and the
laser industry. Limited by their transparency range, few birefringent
materials can be practically used in the deep ultraviolet (DUV, λ
< 200 nm) region. Different from the traditional BO3- or B3O6-based DUV birefringent crystals,
we propose a new functional gene, the B2O5 unit,
for designing birefringent materials. Excitingly, the synergistic
combination of Li4B2O5 and Na4B2O5 generates a new compound, Li2Na2B2O5, with enhanced optical
properties. The Li2Na2B2O5 crystal with a size of up to 35 × 15 × 5 mm3 was grown by the top-seeded solution growth (TSSG) method, and its
physicochemical properties were systematically characterized. Li2Na2B2O5 features a large
amount of birefringence (0.095@532 nm), a short DUV cutoff edge (181
nm) with a high laser-induced damage threshold (LDT, 7.5 GW/cm2 @1064 nm, 10 ns), favorable anisotropic thermal expansion
(αa/αb = 5.6), and the lowest crystal
growth temperature (<609 °C) among the commercial birefringent
crystals. Moreover, the influences of the B2O5 structural configurations on the optical anisotropy were explored.
The fascinating experimental results will provide a prominent DUV
birefringent crystal and an effective synthesis strategy, which can
facilitate the design of DUV birefringent materials.