Multiple-port directional emission microlasers are potential light sources and optical signal processing units in photonic
integrated circuits. Connecting bus waveguides to a microresonator is a simple method to realize directional emission
microlasers. In this paper, we investigate square and circular resonator microlasers connected with multiple bus
waveguides. The mode characteristics of the microresonators connected with multiple bus waveguides are simulated by
finite-difference time-domain technique, and the numerical results of mode Q factors and output coupling efficiencies
show that high efficiency directional emission microresonator lasers can be realized. Furthermore, the microcylinder
laser connected with a bus waveguide fabricated by planar technology processes is reported, and the lasing spectra of
square microlasers with four vertices connected to bus waveguides are analyzed.
Square microresonators with circular corners and a center air hole are simulated by the finite-difference time-domain
(FDTD) technology and Padé approximation method. The results show that the deformed square resonators can increase
mode Q factor at certain conditions. Furthermore, the hole in the square resonator can not only enhance the Q factor and
the output coupling efficiency, but also have the ability to select the lasing mode.
Microcavity lasers with whispering-gallery modes (WGMs) are potential light sources for photonic integrated circuits.
However, the direction emission and output power are greatly limited for microdisks with the WGMs confined by total
internal reflection. Deformed microdisk with chaos mode light rays or evanescently coupled waveguide were used to
realize directional emission microlasers. Different from the microdisk with traveling wave WGMs, confined modes in
triangle and square microcavities are standing wave WGMs. So the confined modes can still have high Q-factors if an
output waveguide is directly connected to triangle and square microcavities at the position with weak mode field
distribution. Based on theoretical analysis and numerical simulation of the mode characteristics, we fabricate directional
emission triangle and square InGaAsP/InP microcavity lasers with an output waveguide directly connected to the
resonators by standard photolithography and inductively coupled plasma etching technique. Continuous-wave (CW)
electrically injected InGaAsP triangle and square microlasers are realized at room temperature for the triangle
microlasers with side length from 10 to 30 μm and the square microlaser with the side length of 20 μm.
Directional emission semiconductor microcavity lasers integrated with semiconductor planar technique are potential light
sources for photonic integrated circuits. In this article, we investigate mode characteristics for equilateral triangle and
square microcavities for realizing directional emission microcavity lasers. The analytical mode field distributions and
mode wavelengths are presented for two-dimensional (2D) triangle and square resonators, and directional emission are
simulated by finite-difference time-domain (FDTD) technique. The numerical results of mode Q-factors and output
coupling efficiencies for the triangle and square resonators show that high efficiency directional emission microcavity
lasers can be realized by directly connected an output waveguide to the resonators, because the mode field patterns are
standing distributions in the triangle and square resonator. Laser output spectra of fabricated InGaAsP/InP triangle lasers
are compared with the analytical results.