All-precision-machining fabrication of ultrahigh-Q crystalline optical microresonators
Shun Fujii, Yuka Hayama, Kosuke Imamura, Hajime Kumazaki, Yasuhiro Kakinuma, Takasumi Tanabe
Abstract
The development of ultrahigh-quality-factor ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mtext class="MJX-tex-mathit" mathvariant="italic">Q</mml:mtext> </mml:mrow> </mml:math> ) microresonators has been driving such technologies as cavity quantum electrodynamics (QED), high-precision sensing, optomechanics, and optical frequency comb generation. Here we report ultrahigh <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mi>Q</mml:mi> </mml:math> crystalline microresonator fabrication with a <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mtext class="MJX-tex-mathit" mathvariant="italic">Q</mml:mtext> </mml:mrow> </mml:math> exceeding <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:msup> <mml:mn>10</mml:mn> <mml:mn>8</mml:mn> </mml:msup> </mml:mrow> </mml:math> , for the first time to our knowledge, achieved solely by computer-controlled ultraprecision machining. Our machining fabrication method readily achieves the dispersion engineering and size control of manufactured devices via programmed machine motion, both of which were not possible with the conventional manual polishing method. We can achieve an ultrahigh <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi>Q</mml:mi> </mml:mrow> </mml:mrow> </mml:math> without the need for subsequent careful polishing that is generally required to ensure that surface integrity is maintained. We carefully addressed the cutting condition and crystal anisotropy to overcome the large surface roughness that has thus far been the primary cause of the low <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mi>Q</mml:mi> </mml:math> in the machining process. Our result paves the way for a reliable fabrication with a view to various photonic applications utilizing ultrahigh- <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mtext class="MJX-tex-mathit" mathvariant="italic">Q</mml:mtext> </mml:mrow> </mml:math> crystalline microresonators.