The Experimental Research On Solid State Optical Microcavities

Quantum information and computation is a new computation model based on principle of coherent superposition and quantum entanglement, which can solve certain problems that are hard for conventional classical computer and is of great importance. For decades, many physical implementations have been put forward, among which quantum electrodynamics(QED) is thought to be a very promising physical system. How to fabricate cavity with high quality factor seems of vital importance. With the development of micro-fabrication, optical microcavities are available. Whispering gallery(WG) mode microcavities such as microsphere are already used to study the interaction of matter and light field and cavity QED phenomena as Purcell effect and strong coupling are observed due to their Ultrahigh-Q and small mode volume. This gives rise to the implementation of quantum logic gate. Practically, it has many technical difficulties toward realizing a quantum logic gate, and even the preparation of optical microresonator itself is a challenge.We have set up our own experimental platform to study on microcavity after referring to several projects already carried out by some famous groups in the world. With this setup, microsphere with controllable size and ultrahigh quality factor can be fabricated. By coupling with low loss fiber taper under nanometer scale, the mode structure and quality factor can be measured, critical coupling is also achieved. To the date, this coupling skill is the main method used in our low threshold microlaser, and . will be of greater use in our future implementation of quantum logic gate.In the research on active cavity, modulated photon emission from Eu³⁺ -microsphere has been observed, which is proved to reveal Purcell effect. This experimental result is our first step in achieving strong coupling between rare earth ions and microcavities and fufure applications in quantum information science.In the research on optical property of microcavities, fiber taper coupling is introduced into the study of zeolite cylinder with natural hexagonal cross section. It is for the first time that we directly observed WG-like modes in hexagonal microcavities similar to microsphere. And the result seems to support the BEM and geometry optics theory brought forward by others. With a low-loss fiber taper coupling and a broadband EDFA as light source, the measured fiber transmission spectrum directly shows several mode distributions, which agrees well with the theoretical prediction. This result shows that the fiber taper provides a powerful tool for coupling WGMs of a zeolite cylinder, and this taper-coupled zeolite can be a potential microcavity system for the cavity quantum electrodynamics and the microlaser.The current results show that our experimental setup has a variety of usage in the research on microcavities. Besides microspheres, other WG mode cavity such as microdisks, microrings, microtoroids and even crystals can be measured with this testing platform. This should be a basic technique for many applications, especially in the development of quantum logic devices.