Photonic Crystal Circular-Defect Microcavity Laser Designed for Wavelength Division Multiplexing

Photonic crystal (PC) lasers with circular-defect (CirD) microcavity offer high-potential application in wavelength division multiplexing (WDM), and therefore, are a suitable candidate to realize intrachips optical communications. In this paper, a CirD laser for the WDM applications is designed for the first time by using the three-dimensional finite-difference time-domain method. For the realization of the WDM applications, it is critical to achieve the adequate high-quality (Q)-factor (>7142) in the bandwidth range over 20 nm, which is estimated from the characteristics of the gain medium and the coupling of the CirD cavity with a PC waveguide. After optimizing the laser structure, we achieved a constant high Q-factor of 15 000 within the bandwidth range of 25 nm. A proof-of-principle experiment of the lasing wavelength tuning was conducted by exploiting the CirD lasers with air/AlGaOx cladding layers under optical pumping conditions. The fabricated laser showed a single-mode lasing operation with the linewidth narrower than 0.07 nm (the resolution-limit of the optical spectrum analyzer) and side mode suppression ratio of ~20 dB. The wavelength tuning of a whispering-gallery mode over 20 nm was confirmed. The present results imply that there is a great potential of CirD laser for larger scale WDM integrated devices.