5,915 research outputs found
Low-threshold bistability of slow light in photonic-crystal waveguides
We analyze the resonant transmission of light through a photonic-crystal
waveguide side coupled to a Kerr nonlinear cavity, and demonstrate how to
design the structure geometry for achieving bistability and all-optical
switching at ultra-low powers in the slow-light regime. We show that the
resonance quality factor in such structures scales inversely proportional to
the group velocity of light at the resonant frequency and thus grows
indefinitely in the slow-light regime. Accordingly, the power threshold
required for all-optical switching in such structures scales as a square of the
group velocity, rapidly vanishing in the slow-light regime.Comment: LaTeX, 6 pages, 4 figure
Purcell Effect in the Stimulated and Spontaneous Emission Rates of Nanoscale Semiconductor Lasers
Nanoscale semiconductor lasers have been developed recently using either
metal, metallo-dielectric or photonic crystal nanocavities. While the
technology of nanolasers is steadily being deployed, their expected performance
for on-chip optical interconnects is still largely unknown due to a limited
understanding of some of their key features. Specifically, as the cavity size
is reduced with respect to the emission wavelength, the stimulated and the
spontaneous emission rates are modified, which is known as the Purcell effect
in the context of cavity quantum electrodynamics. This effect is expected to
have a major impact in the 'threshold-less' behavior of nanolasers and in their
modulation speed, but its role is poorly understood in practical laser
structures, characterized by significant homogeneous and inhomogeneous
broadening and by a complex spatial distribution of the active material and
cavity field. In this work, we investigate the role of Purcell effect in the
stimulated and spontaneous emission rates of semiconductor lasers taking into
account the carriers' spatial distribution in the volume of the active region
over a wide range of cavity dimensions and emitter/cavity linewidths, enabling
the detailed modeling of the static and dynamic characteristics of either
micro- or nano-scale lasers using single-mode rate-equations analysis. The
ultimate limits of scaling down these nanoscale light sources in terms of
Purcell enhancement and modulation speed are also discussed showing that the
ultrafast modulation properties predicted in nanolasers are a direct
consequence of the enhancement of the stimulated emission rate via reduction of
the mode volume.Comment: 12 pages, 5 figure
Vertical-external-cavity surface-emitting lasers and quantum dot lasers
The use of cavity to manipulate photon emission of quantum dots (QDs) has
been opening unprecedented opportunities for realizing quantum functional
nanophotonic devices and also quantum information devices. In particular, in
the field of semiconductor lasers, QDs were introduced as a superior
alternative to quantum wells to suppress the temperature dependence of the
threshold current in vertical-external-cavity surface-emitting lasers
(VECSELs). In this work, a review of properties and development of
semiconductor VECSEL devices and QD laser devices is given. Based on the
features of VECSEL devices, the main emphasis is put on the recent development
of technological approach on semiconductor QD VECSELs. Then, from the viewpoint
of both single QD nanolaser and cavity quantum electrodynamics (QED), a
single-QD-cavity system resulting from the strong coupling of QD cavity is
presented. A difference of this review from the other existing works on
semiconductor VECSEL devices is that we will cover both the fundamental aspects
and technological approaches of QD VECSEL devices. And lastly, the presented
review here has provided a deep insight into useful guideline for the
development of QD VECSEL technology and future quantum functional nanophotonic
devices and monolithic photonic integrated circuits (MPhICs).Comment: 21 pages, 4 figures. arXiv admin note: text overlap with
arXiv:0904.369
Lasing in Single Cadmium Sulfide Nanowire Optical Cavities
The mechanism of lasing in single cadmium sulfide (CdS) nanowire cavities was
elucidated by temperature-dependent and time-resolved photoluminescence (PL)
measurements. Temperature-dependent PL studies reveal rich spectral features
and show that an exciton-exciton interaction is critical to lasing up to 75 K,
while an exciton-phonon process dominates at higher temperatures. These
measurements together with temperature and intensity dependent life-time and
threshold studies suggest that lasing is due to formation of excitons, and
moreover, have implications for the design of efficient, low-threshold nanowire
lasers.Comment: 4 figure
Advances in small lasers
M.T.H was supported by an Australian Research council Future Fellowship research grant for this work. M.C.G. is grateful to the Scottish Funding Council (via SUPA) for financial support.Small lasers have dimensions or modes sizes close to or smaller than the wavelength of emitted light. In recent years there has been significant progress towards reducing the size and improving the characteristics of these devices. This work has been led primarily by the innovative use of new materials and cavity designs. This Review summarizes some of the latest developments, particularly in metallic and plasmonic lasers, improvements in small dielectric lasers, and the emerging area of small bio-compatible or bio-derived lasers. We examine the different approaches employed to reduce size and how they result in significant differences in the final device, particularly between metal- and dielectric-cavity lasers. We also present potential applications for the various forms of small lasers, and indicate where further developments are required.PostprintPeer reviewe
Low-threshold bistability of slow light in photonic-crystal waveguides
We analyze the resonant transmission of light through a
photonic-crystal waveguide side coupled to a Kerr nonlinear cavity, and
demonstrate how to design the structure geometry for achieving bistability
and all-optical switching at ultralow powers in the slow-light regime. We
show that the resonance quality factor in such structures scales inversely
proportional to the group velocity of light at the resonant frequency
and thus grows indefinitely in the slow-light regime. Accordingly, the
power threshold required for all-optical switching in such structures scales
as a square of the group velocity, rapidly vanishing in the slow-light regime
Robust low loss splicing of hollow core photonic bandgap fiber to itself
Robust, low loss (0.16dB) splicing of hollow core photonic band gap fiber to itself is presented. Modal content is negligibly affected by splicing, enabling penalty-free 40Gbit/s data transmission over > 200m of spliced PBGF
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