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Spectral Signatures of Exceptional Points and Bifurcations in the Fundamental Active Photonic Dimer
The fundamental active photonic dimer consisting of two coupled quantum well
lasers is investigated in the context of the rate equation model. Spectral
transition properties and exceptional points are shown to occur under general
conditions, not restricted by PT-symmetry as in coupled mode models, suggesting
a paradigm shift in the field of non-Hermitian photonics. The optical spectral
signatures of system bifurcations and exceptional points are manifested in
terms of self-termination effects and observable drastic variations of the
spectral line shape that can be controlled in terms of optical detuning and
inhomogeneous pumping.Comment: 13 pages, 5 figure
Dark state lasers
We propose a new type of laser resonator based on imaginary "energy-level
splitting" (imaginary coupling, or quality factor Q splitting) in a pair of
coupled microcavities. A particularly advantageous arrangement involves two
microring cavities with different free-spectral ranges (FSRs) in a
configuration wherein they are coupled by "far-field" interference in a shared
radiation channel. A novel Vernier-like effect for laser resonators is designed
where only one longitudinal resonant mode has a lower loss than the small
signal gain and can achieve lasing while all other modes are suppressed. This
configuration enables ultra-widely tunable single-frequency lasers based on
either homogeneously or inhomogeneously broadened gain media. The concept is an
alternative to the common external cavity configurations for achieving tunable
single-mode operation in a laser. The proposed laser concept builds on a high-Q
"dark state" that is established by radiative interference coupling and bears a
direct analogy to parity-time (PT) symmetric Hamiltonians in optical systems.
Variants of this concept should be extendable to parametric-gain based
oscillators, enabling use of ultrabroadband parametric gain for widely tunable
single-frequency light sources
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