The primary goal of this review is to present a clear chemical perspective of borates in order to stimulate and facilitate the discovery of new borate-based optical materials. These materials, whic...

Borates: A Rich Source for Optical Materials.

Owing to their vital role in creating and controlling polarized light, birefringent materials are used extensively in various advanced optical systems which in turn impact a large, rapidly increasing range of applications in science and technology. Currently, the fairly small birefringence of MgF2 and the low transmittance of α-BaB2O4 (α-BBO) hinder their efficient application for wavelength below 200 nm. For example, deep-ultraviolet (DUV) birefringent materials for light polarization are urgently needed for DUV lithography. Here we demonstrate based on computational and experimental results that parallel chains of corner-connected planar sp2-hybridized BO3 groups found in Ca(BO2)2 effectively produce large birefringence. Ca(BO2)2 achieves three vital “best” properties including the shortest UV cutoff edge, the largest birefringence, and the highest laser-induced damage threshold (LIDT) compared to all the reported borate birefringent materials. On the basis of a Ca(BO2)2 single crystal, a DUV Glan polar...

Designing an Excellent Deep-Ultraviolet Birefringent Material for Light Polarization.

Optical anisotropy is a fundamental building block for linear and nonlinear optical components such as polarizers, wave plates, and phase-matching elements1–4. In solid homogeneous materials, the strongest optical anisotropy is found in crystals such as calcite and rutile5,6. Attempts to enhance anisotropic light–matter interaction often rely on artificial anisotropic micro/nanostructures (form birefringence)7–11. Here, we demonstrate rationally designed, giant optical anisotropy in single crystals of barium titanium sulfide (BaTiS3). This material shows an unprecedented, broadband birefringence of up to 0.76 in the mid- to long-wave infrared, as well as a large dichroism window with absorption edges at 1.6 μm and 4.5 μm for light with polarization along two crystallographic axes on an easily accessible cleavage plane. The unusually large anisotropy is a result of the quasi-one-dimensional structure, combined with rational selection of the constituent ions to maximize the polarizability difference along different axes.

Giant optical anisotropy in a quasi-one-dimensional crystal

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...

Rational Design via Synergistic Combination Leads to an Outstanding Deep-Ultraviolet Birefringent Li2Na2B2O5 Material with an Unvalued B2O5 Functional Gene

Birefringent materials are of great importance in optical communication and the laser industry, as they can modulate the polarization of light. Limited by their transparency range, few birefringent materials, except α-BaB2O4 (α-BBO), can be practically used in the deep ultraviolet (UV) region. However, α-BBO suffers from a phase transition and does not have enough transparency in the deep UV region. By introducing the relatively small alkali metal Na+ cation and the F– anion to keep the favorable structural features of α-BBO, we report a new birefringent crystal Na3Ba2(B3O6)2F (NBBF), which has the desirable optical properties. NBBF not only maintains the large birefringence (Δn = no – ne = 0.2554–0.0750 from 175 nm to 3.35 μm) and extends its UV cutoff edge to 175 nm (14 nm shorter than α-BBO) but also eliminates the phase transition and has the lowest growth temperature (820 °C) among birefringent materials. These results demonstrate that NBBF is an attractive candidate for the next generation of deep U...

Na3Ba2(B3O6)2F: Next Generation of Deep-Ultraviolet Birefringent Materials

Growth and spectrum of a novel birefringent α-BaB2O4 crystal

A novel azo derivative, α-(2-azoxyisoxazole)-β-diketone derivative (ADD), and its copper (II) and nickel (II) complex (CuADD and NiADD) films have been prepared respectively by spin-coated method. The absorption spectra of the films on a K9 glass substrate in the 300–800 nm wavelength region have been measured. The optical constants (complex refractive index N = n+ik) and thickness of the complex films on a single-crystal silicon substrate in the 300–600 nm wavelength region have been investigated on an improved rotating analyser-polarizer (RAP) type of scanning ellipsometer, and the dielectric constants e(e = e1+ie2), absorption coefficients α as well as reflectance R of the films were calculated. It is found that the absorption maxima of the ADD, CuADD and NiADD films are at 324 nm, 372 nm and 385 nm, respectively, and small absorption values and steep absorption band edges of the CuADD and NiADD films are observed at the 405 nm side; the CuADD and NiADD films give high n values of 2.08 and 1.98, and low k values of 0.2 and 0.28, respectively, at 405 nm, and their thicknesses are in the range of 130–150 nm; the high reflectivity of 58.5% and 45.5% of the CuADD and NiADD films with Ag as a reflective layer were obtained at the film thicknesses of 70 nm and 80 nm respectively. These results show that the novel CuADD and NiADD films seem to be a very promising organic recording material for the next generation of high density digital versatile disc-recordable (HD-DVD-R) systems that use a high numerical aperture of 0.85 at 405 nm wavelength.

https://iopscience.iop.org/article/10.1088/0256-307X/20/12/049/pdf

Spectroscopy and Optical Properties of Novel Metal(II)-Azo Complex Films in Blue-Violet Light Region

We investigate the optical properties of Nd:YAG crystals grown by temperature gradient technology with different Nd doping levels. The Nd concentrations used are 1.0, 1.5, 2.0, 2.5 and 3.0 at%. It is found that the absorption coefficients of Nd:YAG crystals increase with increasing Nd concentrations. The absorption coefficient of 3.0 at% Nd:YAG is up to 22.1 cm-1. The laser performance of these Nd:YAG crystals is compared with that of the traditional Nd:YAG (1.1 at% Nd) grown by the Czochralski (CZ) method. Although concentration quenching exists in highly doped Nd:YAG, 2.0 at% Nd:YAG shows excellent performance with the slope efficiency of 46.7%, which is higher than that (39%) of 1.1 at% Nd:YAG grown by the CZ method.

https://iopscience.iop.org/article/10.1088/0256-307X/19/9/323/pdf

High Efficient Laser Operation of the High-Doped Nd:YAG Crystal Grown by Temperature Gradient Technology

Silver nanoparticles were precipitated inside an Ag2O-doped glass by femtosecond laser irradiation and successive heat treatment. The influence of heat treatment temperature on the precipitation of silver nanoparticles was investigated. Absorption spectra show that the femtosecond laser irradiation results in an apparent decrease of the treatment temperature for the precipitation of Ag nanoparticles. We demonstrate the control of precipitation, dissolution and growth of silver nanoparticles inside glass by changing the heat treatment temperature or using further femtosecond laser irradiation.

Gan Fuxi

Papers

Growth and spectrum of a novel birefringent α-BaB2O4 crystal

Spectroscopy and Optical Properties of Novel Metal(II)-Azo Complex Films in Blue-Violet Light Region

High Efficient Laser Operation of the High-Doped Nd:YAG Crystal Grown by Temperature Gradient Technology

Influence of Femtosecond Laser Irradiation and Heat Treatment on Precipitation of Silver Nanoparticles in Glass

Photobleaching process of xanthene dyes initiated by N-phenylglycine in the polyvinylalcohol film