MMI-type RGB coupler with 100-mW blue light input using ZrO2-doped silica-based planar lightwave circuit

We developed an MMI-type RGB coupler with 100-mW blue light input using a ZrO2-doped silica-based planar lightwave circuit (ZrO2-doped PLC) for a compact RGB laser light source. The fabricated coupler was about 7.5 µm wide and 900 μm long without fan-in/fan-out and had the transmittance of approximately –1.0 dB at R, G, and B wavelengths. Moreover, its transmittance did not change after a 445-nm, 100-mW, 1000-h light input test.