Author:  Jingsong Xia     2014-04-29

Photonic crystals are periodic optical nanostructure that have a photonic bandgap and can control the light propagation effectively. Photonic crystal (PhC) cavities are formed by introducing various defects in photonic crystals. PhC cavities have become a promising platform for realizing photonic integrated circuits. Photonic crystal ring resonator (PCRR) is formed by introducing defects in shape of an equilateral hexagon based on two dimensional photonic crystals. PCRR has some advantages, including scalability in size, flexibility in mode design due to their multimode nature, adaptability in structure design because of numerous design parameters and flexibility design of backward and forward dropping for channel drop filters. The concept of PCRR was introduced in a hexagonal waveguide ring laser for the first time in 2002, and a Q factor around 2000 for lasing mode was observed [8]. So far, the applications of PCRR, such as filters, wavelength division demultiplexers, lasers, bends, splitters and sensors have been reported. Most works focused on PCRR structures based on photonic crystals of dielectric rods and only theoretical simulations. Experimental demonstration of PCRR based on photonic crystal of air holes was recently reported by X. Ren et al.. However, the Q factor of their reported PCRR was only three hundred.

Zhang yong and Xia jinsong et al. present a design for enhancing the Q factor of PCRR. A simulated Q factor of 121000 is achieved by a slight decrease of the radius of the six holes at the corners. The analysis of momentum space distributions shows that, the higher Q factor can be attributed to the reduction of tangential k-vector component inside the leaky region. The improvement of the Q factor is experimentally demonstrated, and a record Q factor about 75200 is obtained for the modified PCRR with Δr =-14 nm. The high Q factor PCRR demonstrated here has potential for channel drop filters, wavelength-division multiplexing applications, lasers or light-emitting devices, all-optical switching, nonlinear devices and so on.

This work was published in OSA Optics Letters (Vol. 39, Issue 5, 1282-1285, 2014) and was partly supported by the Major State Basic Research Development Program of China (grant 2013CB632104, 2013CB933303 and 2012CB922103), National Natural Science Foundation of China (grant 61177049 and 61335002).