Transparent non-cubic laser ceramics with fine microstructure

Abstract

Transparent polycrystalline ceramics with cubic crystal structure have played important roles in a wide variety of solid-state laser applications, whereas for non-cubic structures, single crystal only has been used. For further progress in optical technologies, effective materials beyond the current limitations are necessary. Here we report a new type of non-cubic ceramic laser material that overturns conventional common sense. It is hexagonal Nd-doped fluorapatite (Nd:FAP) ceramics with an optical quality comparable to single crystal while having random crystal orientation. It is composed of ultrafine grains with a loss coefficient of 0.18 cm −1 at a lasing wavelength of 1063 nm, and its laser oscillation was demonstrated. This is the first verification of lasing in randomly oriented non-cubic ceramics. Laser oscillation in the non-cubic ceramics was realized through both advanced liquid-phase nano-powder synthesis technology and highly controlled pulsed-current sintering techniques. Our findings should open new avenues for future solid-state laser and optical applications.

A roadmap for laser optimization of Yb:Ca3(NbGa)5O12-CNGG-type single crystal garnets

“…Although the newer transparent ceramics technology [8][9][10] is gradually replacing the above hosts, there are still many applications which benefit from the use of single crystals, for instance in TW-PW short pulsed lasers the depolarization losses are minimized by crystal orientation 11,12 which cannot be achieved in ceramics, when UV Xe lamp pumping is required permanent solarisation of the presently developed YAG ceramics may appear, 13 or the larger Rayleigh light scattering of ceramics in the visible region may limit laser implementation in this spectral range. Furthermore, despite grain-oriented anisotropic fluorapatite ceramics being produced with limited optical transmittance for laser applications, 14,15 large cross section laser ceramics are basically restricted to optically isotropic media, i.e. cubic materials, which limits host options for optical bandwidth engineering.…”

The effect of Nd3+ concentration on fabrication, microstructure, and luminescent properties of anisotropic S‐FAP ceramics

“…𝑅 s describes the reflection losses at the two sample surfaces, and it depends on the refractive index (n) of the material itself; 𝜆 0 is the wavelength of the incident light; 𝑑 is the thickness of ceramics; 2𝑟 is the mean grain size. The transmittance of ceramics decreases with the grain size increase from Equation (9). It can be seen that the grain size increases first and then decreases from Figure 7, and the grain size reaches the minimal value of 5 μm at 2% Nd 3+ content.…”

“…5,6 The main laser medium of transparent ceramics was a regular structure with a cubic crystal structure such as CaF 2 , YAG, 7,8 but the rare-earth elements exhibit the better luminescent property in the lower symmetric crystal field environment. [9][10][11] The energy level transitions of rare-earth ions include electric dipole transition, magnetic dipole transition, and electric quadrupole transition. The electric dipole transition is much stronger than the others and can only occur between different parity (such as 4f to 5d), which are prohibited between the same parity.…”

Synthesis of bulk silicon oxynitride glass through nitridation of SiO2 aerogels and determination of Tg

“…Recognized advantages of oxide glasses over ordinary oxide ceramics include light transparency and a capacity to be shaped/machined owing to the isotropic nature of glasses. Indeed, realizing transparent ceramics is not easy because of the light scattering that occurs at grain boundaries, 1,2 while the fabrication of highly flat ceramic surfaces is challenging because of the appearance of crystalline facets associated with crystalline symmetry 3‐5 . Casting of complicated shapes is another advantage of glasses compared to ceramics which require sintering for densification.…”