Wavelength tuning of the soft-approached whispering gallery mode microlasers for display and sensing
Date of Issue2017-06-09
School of Physical and Mathematical Sciences
Photonics Research Centre
Whispering gallery mode (WGM) microcavities and microlasers have attracted enormous research attentions in recent years due to the high quality factors, small mode volumes, enhanced light-matter interactions, and abundant applications in various fields such as optoelectronics, biological and chemical sensing, high-quality lasers, nonlinear studies, etc. Although the mature but sophisticated top-down and bottom-up approaches for semiconductor processing can provide WGM microcavities and microlasers with high quality and ultra-compact integration, the intrinsic rigid nature of the materials hinders the development of flexible applications like display and sensing, which require the tuning of the wavelengths within the cavity. As the confined resonances are ultra-sensitive to the gain medium, the refractive index and the cavity size, doping-flexible, elastic and cost-efficient soft-approached WGM microlasers are competitive in wavelength tuning and promising in application broadening. However, though the reported soft candidates based on polymer materials have shown outstanding optical performances and improved flexibility, the lack of controllable fabrication techniques dramatically decreases the practical values of such microlasers. Therefore, engineering soft-approached WGM microlasers with controllable approaches and enhanced flexibilities in wavelength tuning for practical applications remains challenging. In this thesis, three works that emphasize the challenges are introduced. By employing a commercially available microplotter, the proposed fabrication processes for the hemispheres and microfibers are wellx controlled. In addition, wavelength tuning for new applications in display and sensing are demonstrated by manipulating the gain medium and the cavity geometry of the two configurations, respectively. Furthermore, a novel floating quasi-disk microlaser, which is bi-directionally and reconfigurably tunable, is proposed and exploited as a sensitive sensor for water-soluble chemicals in microfluidics. The proposed works not only broaden the applications for the tunable microlasers but are also significant in the spread of the soft-approached WGM microcavities for industrialization and commercialization.