3,512 research outputs found
Evanescent straight tapered-fiber coupling of ultra-high Q optomechanical micro-resonators in a low-vibration helium-4 exchange-gas cryostat
We developed an apparatus to couple a 50-micrometer diameter
whispering-gallery silica microtoroidal resonator in a helium-4 cryostat using
a straight optical tapered-fiber at 1550nm wavelength. On a top-loading probe
specifically adapted for increased mechanical stability, we use a
specifically-developed "cryotaper" to optically probe the cavity, allowing thus
to record the calibrated mechanical spectrum of the optomechanical system at
low temperatures. We then demonstrate excellent thermalization of a 63-MHz
mechanical mode of a toroidal resonator down to the cryostat's base temperature
of 1.65K, thereby proving the viability of the cryogenic refrigeration via heat
conduction through static low-pressure exchange gas. In the context of
optomechanics, we therefore provide a versatile and powerful tool with
state-of-the-art performances in optical coupling efficiency, mechanical
stability and cryogenic cooling.Comment: 8 pages, 6 figure
Demonstration of an erbium doped microdisk laser on a silicon chip
An erbium doped micro-laser is demonstrated utilizing
microdisk resonators on a silicon chip. Passive microdisk resonators exhibit
whispering gallery type (WGM) modes with intrinsic optical quality factors of
up to and were doped with trivalent erbium ions (peak
concentration using MeV ion
implantation. Coupling to the fundamental WGM of the microdisk resonator was
achieved by using a tapered optical fiber. Upon pumping of the erbium transition at 1450 nm, a gradual
transition from spontaneous to stimulated emission was observed in the 1550 nm
band. Analysis of the pump-output power relation yielded a pump threshold of 43
W and allowed measuring the spontaneous emission coupling factor:
A microrod-resonator Brillouin laser with 240 Hz absolute linewidth
We demonstrate an ultralow-noise microrod-resonator based laser that
oscillates on the gain supplied by the stimulated Brillouin scattering optical
nonlinearity. Microresonator Brillouin lasers are known to offer an outstanding
frequency noise floor, which is limited by fundamental thermal fluctuations.
Here, we show experimental evidence that thermal effects also dominate the
close-to-carrier frequency fluctuations. The 6-mm diameter microrod resonator
used in our experiments has a large optical mode area of ~100 {\mu}m, and
hence its 10 ms thermal time constant filters the close-to-carrier optical
frequency noise. The result is an absolute laser linewidth of 240 Hz with a
corresponding white-frequency noise floor of 0.1 Hz/Hz. We explain the
steady-state performance of this laser by measurements of its operation state
and of its mode detuning and lineshape. Our results highlight a mechanism for
noise that is common to many microresonator devices due to the inherent
coupling between intracavity power and mode frequency. We demonstrate the
ability to reduce this noise through a feedback loop that stabilizes the
intracavity power.Comment: 11 pages, 5 figure
Optical Nanofibers: a new platform for quantum optics
The development of optical nanofibers (ONF) and the study and control of
their optical properties when coupling atoms to their electromagnetic modes has
opened new possibilities for their use in quantum optics and quantum
information science. These ONFs offer tight optical mode confinement (less than
the wavelength of light) and diffraction-free propagation. The small cross
section of the transverse field allows probing of linear and non-linear
spectroscopic features of atoms with exquisitely low power. The cooperativity
-- the figure of merit in many quantum optics and quantum information systems
-- tends to be large even for a single atom in the mode of an ONF, as it is
proportional to the ratio of the atomic cross section to the electromagnetic
mode cross section. ONFs offer a natural bus for information and for
inter-atomic coupling through the tightly-confined modes, which opens the
possibility of one-dimensional many-body physics and interesting quantum
interconnection applications. The presence of the ONF modifies the vacuum
field, affecting the spontaneous emission rates of atoms in its vicinity. The
high gradients in the radial intensity naturally provide the potential for
trapping atoms around the ONF, allowing the creation of one-dimensional arrays
of atoms. The same radial gradient in the transverse direction of the field is
responsible for the existence of a large longitudinal component that introduces
the possibility of spin-orbit coupling of the light and the atom, enabling the
exploration of chiral quantum optics.Comment: 65 pages, to appear in Advances in Atomic, Molecular and Optical
Physic
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