Abstract
Mode coupling between the whispering-gallery modes (WGMs) is numerically investigated for a two-dimensional microdisk resonator with an output waveguide. The equilateral-polygonal shaped mode patterns can be constructed by mode coupling in the microdisk, and the coupled modes can still keep high quality factors (Q factors). For a microdisk with a diameter of 4.5 microm and a refractive index of 3.2 connected to a 0.6-microm-wide output waveguide, the coupled mode at the wavelength of 1490 nm has a Q factor in the order of 10(4), which is ten times larger than those of the uncoupled WGMs, and the output efficiency defined as the ratio of the energy flux confined in the output waveguide to the total radiation energy flux is about 0.65. The mode coupling can be used to realize high efficiency directional-emission microdisk lasers.
Highlights
Semiconductor microdisk lasers [1] are suitable for realizing ultra-low-threshold operation due to the ultra-small volumes and high Q factors
Mode coupling between the whispering-gallery modes (WGMs)
The equilateral-polygonal shaped mode patterns can be constructed by mode coupling in the microdisk, and the coupled modes can still keep high quality factors (Q factors)
Summary
Semiconductor microdisk lasers [1] are suitable for realizing ultra-low-threshold operation due to the ultra-small volumes and high Q factors. Deformed microdisk resonators were applied to fabricate directional emission semiconductor microlasers [2,3,4,5], and microdisk lasers vertically coupled to a bus waveguide were demonstrated by thermally wafer bonded technique [6,7]. Confined modes with different mode field patterns were investigated theoretically for realizing directional emission in deformed microdisks [8,9], and unidirectional light emission by coupling a low-Q mode to a high-Q mode was simulated for microdisks with a hole [10]. We can connect an output waveguide to the resonator at the position with weak field distribution, and have high Q confined modes for realizing direction emission. The coupled modes have equilateral-polygonal shaped mode patterns, and can have high Q factors with high output coupling efficiency to the output waveguide
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