Yb3+-doped CaF2-LaF3 ceramics laser.

Highly transparent ceramic is an attractive gain medium for high-power lasers due to its high fracture toughness, homogeneity, and size scalability. Here we report the first Yb3+-doped CaF2-LaF3 ceramics laser. Codoping of La3+ ion can reduce the formation of Yb2+ ions and enhance the laser efficiency. In the laser experiment, the maximum output power of 4.36 W and the maximum slope efficiency of 69.5% were obtained with a 3% La, 2% Yb sample and a 2% La, 1% Yb sample, respectively. Due to the combined properties of Yb:CaF2 and a ceramic laser gain medium, Yb:CaF2-LaF3 ceramic is a promising gain medium for a high-power ultrashort pulse laser and amplifier.

High-performance antireflective coatings with a porous nanoparticle layer for visible wavelengths.

Ghosts and flares are well-known problems that are caused by reflections from lens surfaces when we take photographs. It is more difficult to prevent such stray light in a digital camera than in a film camera because of high reflectance from the low-pass filter and diffraction from the image sensor. To prevent such stray light, we introduce an ultralow refractive index layer into the antireflective (AR) coatings. We used the solgel method to form porous fluoride layers with ultralow refractive indices, and we succeeded in developing a unique process to form AR coatings with superior performance.

Preparation of MgF2-SiO2 thin films with a low refractive index by a solgel process.

Porous MgF(2)-SiO(2) thin films consisting of MgF(2) particles connected by an amorphous SiO(2) binder are prepared by a solgel process. The films have a low refractive index of 1.26, sufficient strength to withstand wiping by a cloth, and a high environmental resistance. The refractive index of the film can be controlled by changing the processing conditions. Films can be uniformly formed on curved substrates and at relatively low temperatures, such as 100 degrees C. The low refractive index of the film, which cannot be achieved by conventional dry processes, is effective in improving the performance of antireflective coatings.

Investigation of MgF2 optical thin films with ultralow refractive indices prepared from autoclaved sols.

We have successfully developed a process to form high quality MgF(2) thin films with ultralow refractive indices from autoclaved sols prepared from magnesium acetate and hydrofluoric acid. And we have confirmed that our porous MgF(2) coatings have not only high transmittance in the UV region but also high uniformity of film thickness. They can be uniformly formed on phiv 300 mm substrates as a single coating and as a hybrid coating with sublayers formed by physical vapor deposition. They are expected to be applied to various optics that need high transmittance in the UV region.

Preparation of high-performance optical coatings with fluoride nanoparticle films made from autoclaved sols.

An ultralow refractive index is very advantageous when one designs antireflective coatings. We successfully obtained high-quality MgF2 thin films with ultralow refractive indices from autoclaved sols prepared from magnesium acetate and hydrofluoric acid. The MgF2 films consist of nanosized particles, and they have high laser-exposure durability at 193 nm. The reflectance of the antireflective coating with five layers, of which the top layer is formed by our method, is lower than 0.6% in the incident angle range of 0 degrees - 60 degrees at 193 nm.