The Single Longitudinal Mode Laser Emission In The Photonic Molecule Microdisk

Whispering gallery(WG) modes are specific resonances or modes that are confined with total internal reflection inside a given resonator with smooth edges, e.g. microdisk, microsphere, microring, and microtoroid. As the light is confined along the cavity boundary for a long time, the quality(Q) factors of microcavitites are usually ultra-high. Microdisk is one of the prominent examples. Due to its natures on ultrahigh Q factor and on-chip device, microdisk has been considered to play a crucial role in optical modulation, sensors, and on-chip integration. In general, microdisks can support a series of WG modes with different Azimuthal number and finally generate multiple lasing modes. This is contradicting with the basic requirements of lasers on monochromaticity. To improve the monochromaticity, a number of techniques have been developed to generate single-mode laser operation, e.g. shrinking cavity size or inserting dispersive elements. However, most of them are strongly dependent on fabrication technique and will reduce the intrinsic Q factors of microdisks. Here, we take photonic molecule as an example to develop a new approach to generate and control the single-mode laser emission.The photonic molecule consists of two independent microdisks. Therefore, comparing the conventional parameters of microdisk, photonic molecule has additional degrees to control the lasing actions, e.g. the separation distance, the size mismatching et al. In the thesis, based on the unique properties of photonic molecule, we have completed the following works:We have studied the mode coupling theory in photonic molecules and revealed the dependence of inverse Vernier effect on the coupling of two resonances.Based on the theoretical analysis and numerical calculation, we have fabricated the photonic molecule and studied the corresponding lasing actions. We have demonstrated for the first time that inverse Vernier effect exists and can be used to generate single-mode laser emission.By applying the recently developed modal interaction theory, we have experimentally observed that the lasing mode can be easily switched on and off without varying the pumping profiles or cavity parameters. And we also observed that the lasing mode can be easily shifted by changing the temperature of the sample.