Fabrication and packaging of whispering gallery mode rod resonators with adjustable coupling

• Published in: Optics and lasers in engineering 2023-07, Vol.166, p.107583, Article 107583
• Main Authors: Yacoby, E., London, Y., Harari, G.
• Format: Article
• Language: English
• Subjects: Adjustable coupling; Packaging; Q factor; Rod resonators; Tapered fiber; Whispering gallery mode
• ISSN: 0143-8166; 1873-0302
• DOI: 10.1016/j.optlaseng.2023.107583

•A new and simple packaging method of cm-scale Whispering Gallery Mode (WGM) rod resonators, with the ability to tune and adjust the coupling efficiency is presented.•The position of tapered fiber used to couple light into the resonator is easily stabilized and fixed to the tips of two mounting screws.•The ability to control the position of the screws' tips makes it possible to apply this packaging to different rod resonators diameters, and eliminates the sensitivity to the fiber angle.•The coupling is adjusted using an adjusting screw, which when fastened, "pushes" the tapered fiber toward the rod resonator, and therefore change the resonator-tapered fiber contact length.•Detailed description of the fabrication technique of the rod resonators with an ultra-high q factor of ∼ 7.5·108 is presented. Optical Whispering Gallery Mode (WGM) resonators are an ideal platform for high sensitivity sensors. They exhibit extremely high Q factors - on the order of 106–109 – providing a sensing platform with low detection limit. For some sensing applications, the micrometric diameters of microresonators may be undesirable, and resonators of large diameters are required. Here we present the fabrication and packaging of a cm-scale silica rod resonator with a Q factor of ∼ 7.5·108. The demonstrated packaging provides – for the first time to the best of our knowledge – the ability to tune and adjust the coupling efficiency on demand. The coupling adjustment makes it possible to modulate the transmission power of the tapered fiber used to couple light into the rod resonator, as well as to modulate the loaded Q factor of the resonator.