Influence of the Surface Roughness of a Silicon Disk Resonator on Its Q-Factor

This article presents a silicon disk resonator of the whispering-gallery-mode (WGM) type. The calculated Q-factor of the silicon WGM resonator was 107. Two methods of studying the surface roughness of a silicon WGM resonator with a nonlinear profile by means of Helios 650 scanning electron microscope and Bruker atomic force microscope (AFM) are presented. The results obtained by the two methods agreed well with each other. A comparison of the surface roughness values of WGM resonators manufactured using different technological approaches is presented. Based on the obtained data, a preliminary estimated Q-factor calculation of the resonators was performed, which was refined by numerical calculation using the finite-difference time-domain (FDTD) method. The effect of the surface roughness of the resonator on its Q-factor was found. Reducing the surface roughness of the resonator from 30 nm to 1–2 nm led to an increase in its Q-factor from 104 to 107.

Review of biosensing with whispering-gallery mode lasers

Lasers are the pillars of modern optics and sensing. Microlasers based on whispering-gallery modes (WGMs) are miniature in size and have excellent lasing characteristics suitable for biosensing. WGM lasers have been used for label-free detection of single virus particles, detection of molecular electrostatic changes at biointerfaces, and barcode-type live-cell tagging and tracking. The most recent advances in biosensing with WGM microlasers are described in this review. We cover the basic concepts of WGM resonators, the integration of gain media into various active WGM sensors and devices, and the cutting-edge advances in photonic devices for micro- and nanoprobing of biological samples that can be integrated with WGM lasers.

A Novel Microlaser-Based Plasmonic-Polymer Hybrid Resonator for Multiplexed Biosensing Applications

Whispering gallery mode (WGM) resonators exhibit a high quality factor Q and a small mode volume; they usually exhibit high resolution when used as sensors. The light trapped inside a polymeric microcavity travels through total internal reflection generating the WGMs. A laser or a lamp is used to power the microlaser by using a laser dye embedded within the resonator. The excited fluorescence of the dye couples with the optical modes. The optical modes (laser modes) are seen as sharp peaks in the emission spectrum with the aid of an optical interferometer. The position of these optical modes is sensitive to any change in the morphology of the resonator. However, the laser threshold of these microlasers is of few hundreds of microjoules per square centimeter (fluence) usually. In addition, the excitation wavelength's light powering the device must be smaller than the microlasers size. When metallic nanoparticles are added to the microlaser, the excited surface plasmon couples with the emission spectrum of the laser dye. Therefore, the fluorescence of the dye can be enhanced by this coupling; this in turn, lowers the power threshold of the microlaser. Also, due to a plasmonic effect, it is possible to use smaller microlasers. In addition, a new sensing modality is enabled based on the variation of the optical modes' amplitude with the change in the morphology's microlaser. This opens a new avenue of low power consumption microlasers and photonics multiplexed biosensors.

Active whispering-gallery-mode optical microcavity based on self-assembled organic microspheres

The self-assembled organic microspheres of (E)-3-(4-(dip-tolylamino)phenyl)-1-(4-fluoro-2-hydroxyphenyl)prop-2-en-1-one (DTPHP) function as active whispering-gallery-mode (WGM) resonators with high group refractive index.

A Novel Microlaser Based Plasmonic-Polymer Hybrid Resonator

Whispering gallery mode (WGM) resonators exhibit high quality factor Q and a small mode volume; they usually exhibit high resolution when used as sensors. The light trapped inside a polymeric micro-cavity travels through total internal reflection generating the whispering gallery modes (WGMs). A laser or a lamp is used to power the microlaser by using a laser dye embedded within the resonator. The excited fluorescence of the dye couples with the optical modes. The optical modes (laser modes) are seen as sharp peaks in the emission spectrum with the aid of an optical interferometer. The position of these optical modes is sensitive to any change in the morphology of the resonator. However, the laser threshold of these microlasers is of few hundreds of microjoules per square centimeter (fluence) usually. In addition, the excitation wavelength’s light powering the device must be smaller than the microlasers size. When metallic nanoparticles are added to the microlaser, the excited surface plasmon couples with the emission spectrum of the laser dye. Therefore, the fluorescence of the dye can be enhanced by this coupling; this in turn, lowers the power threshold of the microlaser. Also, due to a plasmonic effect, it is possible to use smaller microlasers. In addition, a new sensing modality is enabled based on the variation of the optical modes’ amplitude with the change in the morphology’s microlaser. This opens a new avenue of low power consumption microlasers and photonics multiplexed biosensors.