### Abstract

In Part I, we showed that the radiation loss that is intrinsic loss of micro-resonator laser can be accurately computed by conformal-transformation method. However, estimating the scattering loss with analytical method is difficult because of the complicated boundary roughness pattern. In Part II here, we propose a numerical method to accurately calculate the radiation loss and scattering loss of microdisk laser with our MLME Finite-Difference Time-Domain (FDTD) method. The radiation loss and scattering loss are competing factors affecting the cavity Q factor. The radiation loss is the major loss in small disk (diameter <∼2 μm) while the scattering loss is the more significant loss in large disk (diameter >∼2 μm). We discuss how to compute the cavity Q factors of planar microdisk using our active-lasing FDTD method and study the correlation between the cavity Q factor and the size and edge roughness of the microdisk laser. We show that although the cavity Q factor of smaller microdisk (diameter <∼2 μm) increases exponentially with the disk diameter due to radiation loss, the cavity Q factor of larger-diameter microdisks (diameter >∼2 μm) approaches a constant value that is limited by the optical scattering loss due to the etched sidewall roughness. The cavity Q factors obtained from these simulations that include the surface scattering losses are in good agreement with the typical cavity Q factors obtained in experiment.

Original language | English (US) |
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Pages (from-to) | 447-454 |

Number of pages | 8 |

Journal | Optics Communications |

Volume | 291 |

DOIs | |

State | Published - Mar 15 2013 |

### Keywords

- Cavity Q factor
- Finite-Difference Time-Domain (FDTD)
- Loss mechanism
- Microdisk laser
- Radiation loss
- Scattering loss

### ASJC Scopus subject areas

- Electronic, Optical and Magnetic Materials
- Atomic and Molecular Physics, and Optics
- Physical and Theoretical Chemistry
- Electrical and Electronic Engineering

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## Cite this

*Optics Communications*,

*291*, 447-454. https://doi.org/10.1016/j.optcom.2012.08.012