Nanophotonics And Integrated Optics Photonic Crystal CavitiesSource: CST of America, Inc.
This whitepaper gives a general overview on different concepts of photonic crystal cavities. Important figures such as the transmission, the mode volume and the quality factor are discussed. The presented information will help the reader to decide which type of photonic crystal cavities will be most suited for the application in view. A design example for a WDM channel filter is given in order to illustrate the design process for a photonic crystal cavity. Furthermore two experimental examples from recent research are shown to demonstrate the wide range of applications in which photonic crystal cavities could be used.
An optical cavity confines light at resonance frequencies and can therefore be regarded as an optical resonator. Optical resonators are characterized by two key parameters reflecting their ability to confine the optical energy temporally and spatially: The former is quantified by the quality factor Q and the latter by the mode volume V. The Q-factor is directly proportional to the decay time, a large value indicating long decay time. The mode volume measures the volume occupied by the optical mode, and a small value represents strong spatial confinement. Resonators are generally frequency selective elements and may serve as spectral analyzers and optical filters. Strong spatial confinement is also beneficial for lasing properties and nonlinear interactions.
Several types of optical cavities have been proposed. In this white paper we will discuss how to form optical cavities by means of photonic crystal lattice defects. This approach results in cavities with very high Q-factors and modal volumes in the order of a cubic wavelength.