The smallest possible whispering-gallery-like mode in the square lattice photonic-crystal slab single-defect cavity

Abstract

Abstract-The smallest possible whispering-gallery-like mode (WGM) formed in a free-standing square-lattice photonic-crystal slab single-defect cavity is studied by using the three-dimensional finite-difference time-domain method. The WGM is nondegenerate and the only existing resonant mode in the transverse electric mode bandgap of the square lattice. High-quality factors are achieved from this mode by suppressing both the in-plane and the out-of-plane optical losses. By optimizing the structural parameters, the total quality factor 18 000 and the vertical quality factor 40 000 are obtained from the WGM. The quality factor does not decrease significantly in the presence of a current flow path at the center of the cavity due to the null of electromagnetic energy at the cavity center, which means this mode is advantageous to achieve electrically pumped photonic-crystal lasers. In addition, by combining the high-quality factor with wavelength-size small-mode volume, very high Purcell factors 8000 are achieved, the largest value ever reported. The WGM of the square-lattice single-defect cavity is promising for both cavity quantum electrodynamics research and the low-threshold microcavity laser.

Single quantum dot nanolaser

“…With an effective mode volume of only 0:1 (λ =n) 3 the S1 cavity has one of the smallest mode volumes and is on a first glance attractive for making a nanolaser [71]. The corresponding 3D mode profile can be calculated with FDTD simulations by exciting a single mode at its location of maximum field intensity with a spectrally narrow source.…”

High-Q photonic crystal cavities with embedded quantum dots

“…This type of cavity is predicted to support two types of modes, a low-Q dipole resonance and a high-Q whispering-gallery-like mode (WGM) 8 . The dipole mode is doubly-degenerate and unimportant for high Q/V applications.…”

“…In all devices inspected, the RIE sidewalls exhibited significant undercutting resulting in a photonic crystal lattice with r/a ~12% larger at the bottom of the slab than at the top. Since the Q of the WGM is a function of r/a 8 , we anticipated that we were not achieving maximum Q.…”

“…Cavities defined by defects in two-dimensional photonic crystals are relatively easy to fabricate and can support optical modes of very small V. In recent years the sources of loss in this class of devices has become well understood and cavities that also possess high Q have been predicted and experimentally realized [2][3][4][5][6][7][8][9][10][11][12][13] . With this combination of high Q and small V, planar photonic crystal nanocavities are very promising candidates for the observation of strong coupling with a single QD.…”

Lasing Actions of Octagonal Quasi-Periodic Photonic Crystal Microcavities

“…The simulation method used here is quite efficient and reliable for searching for defect modes in a photonic crystal microcavity. 9) We also compare its calculation precision with that of three-dimensional (3D) FDTD simulation on a typical photonic crystal single-defect microcavity. We find that there is only about 3 -5% wavelength red shift of each defect mode in 2D FDTD simulation as compared with 3D FDTD simulation and there is no significant difference observed in mode profile calculation.…”