Cavity mode manipulation of a bottle microresonator with gold nanoparticles

Microlasers, which reduce at least one lateral dimension of a laser structure down to the order of one wavelength, have promising applications for on-chip optical communication, sensing and information processing. Devices based on bottle microresonators have certain advantages as compared to other types of microlasers, such as favorable tunability and high-Q factor.

Lun et al. report on the successful cavity mode manipulation of a bottle microresonator simply by depositing single gold nanoparticles. Previously, such bottle microresonators usually exhibited multi-mode lasing behavior. To the surprise of the researchers, the precise deposition of gold nanoparticles caused most of the lasing modes to disappear.

Single gold nanoparticles were deposited onto the surface of a bottle cavity fabricated with rhodamine 6G and epoxy resin with a fiber taper. The researchers then investigated the effect of the nanoparticles on lasing by exciting the microresonator with a pump laser and measuring the generated photoluminescence signals with a spectrometer. All the lasing peaks were found to almost disappear as a result.

Theoretical analyses indicated that gold nanoparticles affect cavity modes by introducing significant optical cavity losses. The authors realized they could take advantage of this mechanism to efficiently manipulate cavity modes in a reconfigurable and tunable manner. To demonstrate this simple method, they achieved single mode lasing with a high side-mode suppression factor of approximately 13 dB.

In the future, the researchers plan to extend the controllability of mode manipulation, both in small bottle cavities as well as in microresonators of different sizes and types. They also hope to achieve more flexible manipulation of microlaser modes, such as the free selection of one or several modes in the multi-mode output.

Source: “Cavity mode manipulated by single gold nanoparticles,” by Yipeng Lun, Ziyu Zhan, Fuxing Gu, Pan Wang, Huakang Yu, and Zhi-yuan Li, APL Photonics (2020). The article can be accessed at http://doi.org/10.1063/5.0009272 .