Fabrication and characterization of large-core Yb/Al-codoped fused silica waveguides using dry etching

• Yb/Al-codoped fused-silica (FS) waveguides for high-power integrated-optics are developed.
• No process reported for simultaneous dry-etching of silica matrix and Al constituent.
• Inductively-coupled plasma (ICP) deep-etching by alternating BCl3 and CF4 is reported.
• Heat buildup during high-density ICP etching of thermally isolating FS was mitigated.
• Preliminary optical measurements show 1 dB/cm loss for 20 × 33 μm waveguide at 1030 nm.

A deep inductively coupled plasma etching process was developed as a part of a continuous effort to develop an all-silica on-chip platform for high-power optical devices. Combined F and Cl based etching chemistry was found most suitable since silica matrix and Al doping are generally etched using different chemistries. First large-core (∼20 × 20 μm) Yb/Al-codoped fused silica waveguides on pure silica substrate were successfully fabricated, featuring ∼1 dB/cm optical propagation loss.