Tatsuya Suetsugu

Optical Waveguides Fabricated by Classical Staining Process

Optical waveguides were prepared by the incorporation of silver or copper ions into soda-lime silicate and borosilicate glass substrates using a classical staining process. The waveguides were colorless and optically clear, indicating that silver and copper metal nanoparticles and Cu2O nanoparticles that cause coloration of glasses were not formed. The increase in the refractive index at 633 nm reached 4×10-2 and 1×10-2 for the silver-doped and copper-doped waveguide layers, respectively. The ion distribution measured by energy dispersion X-ray analysis showed that the silver and copper ions reached depths of 5 and 20 µm, respectively, in the substrates. Single-mode propagations at 633 nm and 1.54 µm were observed for both silver-doped and copper-doped waveguides.

Effect of glass composition on silver-incorporation into aluminoborosilicate glasses through a staining process

To fabricate graded-index optical elements by silver staining, we investigated the behavior of ion incorporation in aluminoborosilicate glasses, in which the contents of Al 2 O 3 and Na 2 O were the same (in mol%). The amount of silver incorporated into the aluminoborosilicate glasses by the staining at 320 °C for 12 h was 5 to 10 times larger than that incorporated into the soda-lime silicate and borosilicate glasses. The diffusion depth of the incorporated silver ions was approximately 80 μm, which was also much deeper than that of the soda-lime silicate and borosilicate glasses. The coloration of the glasses was suppressed, particularly for the glass with the low content of Na 2 O. The concentration of the incorporated silver ions at the glass surface was 2 × 10 21 atom/cm 3 for the 37.5SiO 2 ·25Al 2 O 3 ·25Na 2 O·12.5B 2 O 3 glass, corresponding to the replacement of sodium ions (20%). The refractive indices near the stained surfaces increased by 0.04 to 0.06. These values were comparable with those of the soda-lime silicate and borosilicate glasses.

Optical waveguide fabricated by ion-exchange using stain method

Optical waveguides were prepared by the incorporation of silver or copper ions using the classical staining. We used commercially available soda-lime silicate and borosilicate glasses as substrates. Silver or copper stain was applied on a side of the glass substrates. The substrates were heat-treated at elevated temperature for various times. The treated glasses were optically clear and almost colorless except for a few samples stained for longer time. This indicates that silver and copper metal nanoparticles and Cu2O nanoparticles causing coloration of glasses were not formed in the glass substrates. The ion-incorporation process was approximately controlled by the diffusion of ions. We observed the propagation of 633 nm laser radiation by a prism coupling method showing that the glass surface region plays a role of waveguide. Refractive index change more than 0.01 at 633 nm was achieved in the waveguide layers.