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Regular version of the site

Article

III–V microdisk/microring resonators and injection microlasers

Semiconductor whispering-gallery-mode (WGM) microresonators are promising candidates for
creating compact, energy-efficient light sources (microlasers) for various applications owing to
their small footprints, high Q factors, planar geometry, in-plane light emission, and high
sensitivity to the environment. In this review we present the most recent advances in III–V
microdisk/microring lasers. We briefly describe basic physics behind photonic WGM resonators
and discuss different designs of III–V microdisk/microring lasers. We focus on the technological
key points of the different approaches to realize efficient optical and carrier confinement in the
laser cavity. Advantages and disadvantages of various types of the laser active region, i.e.
quantum well (QW) and quantum dots, are discussed. We also report on successful fabrication of
microlasers with gain medium of mixed dimensionality, so called QW-dots, which is promising
for low-threshold, temperature insensitive and high output power operation. We summarized
and systematically compare the characteristics of electrically driven microlasers. We address
one major shortcoming for the circular WGM lasers, which is that the lasing emission is
non-directional and non-homogeneous along the cavity rim. High quality factor of the resonator
modes and circular symmetry lead to difficulties in obtaining the directional light output and in
obtaining significant levels of the output optical power. We compared various techniques for
realizing unidirectional emission or coupling to a waveguide. We also discuss high-speed direct
modulation, which is another crucial characteristic for the microlasers. We also address energy
consumption characteristics of the WGM microlasers under direct modulation and possibilities
of energy-to-data ratio minimization. Finally, we summarize the prospects for the WGM lasers
and their role in future applications in communications and sensing.