105 research outputs found
Active stabilization of a Michelson interferometer at an arbitrary phase with sub-nm resolution
We report on the active stabilization of a Michelson interferometer at an
arbitrary phase angle with a precision better than one degree at nm, which corresponds to an optical path difference between the two arms
of less than 1 nm. The stabilization method is ditherless and the error signal
is computed from the spatial shift of the interference pattern of a reference
laser, measured in real-time with a CCD array detector. We discuss the
usefulness of this method for nanopositioning, optical interferometry and
quantum optical experiments
Unusual histologic finding in tissue obtained from voluntary pregnancy termination: a case report
BACKGROUND: An unusual histologic finding in tissue obtained from voluntary
pregnancy termination (VPT) is reported to demonstrate the utility of pathologic
examination of this specimen.
METHODS: A 30-year-old woman with a history of depression was referred to the
gynecology clinic for VPT in the eighth week of gestation. Material obtained from
uterine cavity curettage was macroscopically and histologically examined. Based
on the histological findings, a molecular study by polymerase chain reaction
amplification (PCR) was performed to evaluate the presence of human papilloma
virus (HPV) DNA. For DNA extraction, 4-microm-thick histological sections were
stained with hematoxylin and examined under a stereomicroscope. The PCR
amplification was performed with the L1 consensus primers Gp5+/Gp6+, giving an
expected PCR product size of 150 bp: these primers have been developed to allow
the detection of a broad spectrum of mucosotropic HPV genotypes.
RESULTS: Histological examination of tissue obtained from the VPT showed immature
villi with post-abortive hydropic degeneration and the presence of a small
fragment of cervical mucosa with a squamous intraepithelial lesion characterized
by mild to moderate nuclear atypia (SIL). PCR revealed that this lesion was
related to HPV. Subsequently, the pap smear and cervical biopsy revealed a
high-risk squamous intraepithelial lesion due to high-risk HPV.
CONCLUSIONS: This report demonstrates that tissue obtained from VPT cannot be
considered normal "a priori" and that a histological study can be useful to
provide new information regarding a woman's gynecological health
Large second harmonic generation enhancement in SiN waveguides by all-optically induced quasi phase matching
Integrated waveguides exhibiting efficient second-order nonlinearities are
crucial to obtain compact and low power optical signal processing devices.
Silicon nitride (SiN) has shown second harmonic generation (SHG) capabilities
in resonant structures and single-pass devices leveraging intermodal phase
matching, which is defined by waveguide design. Lithium niobate allows
compensating for the phase mismatch using periodically poled waveguides,
however the latter are not reconfigurable and remain difficult to integrate
with SiN or silicon (Si) circuits. Here we show the all-optical enhancement of
SHG in SiN waveguides by more than 30 dB. We demonstrate that a Watt-level
laser causes a periodic modification of the waveguide second-order
susceptibility. The resulting second order nonlinear grating has a periodicity
allowing for quasi phase matching (QPM) between the pump and SH mode. Moreover,
changing the pump wavelength or polarization updates the period, relaxing phase
matching constraints imposed by the waveguide geometry. We show that the
grating is long term inscribed in the waveguides, and we estimate a second
order nonlinearity of the order of 0.3 pm/V, while a maximum conversion
efficiency (CE) of 1.8x10-6 W-1 cm-2 is reached
An integrated source of spectrally filtered correlated photons for large scale quantum photonic systems
We demonstrate the generation of quantum-correlated photon-pairs combined
with the spectral filtering of the pump field by more than 95dB using Bragg
reflectors and electrically tunable ring resonators. Moreover, we perform
demultiplexing and routing of signal and idler photons after transferring them
via a fiber to a second identical chip. Non-classical two-photon temporal
correlations with a coincidence-to-accidental ratio of 50 are measured without
further off-chip filtering. Our system, fabricated with high yield and
reproducibility in a CMOS process, paves the way toward truly large-scale
quantum photonic circuits by allowing sources and detectors of single photons
to be integrated on the same chip.Comment: 4 figure
Energy correlations of photon pairs generated by a silicon microring resonator probed by Stimulated Four Wave Mixing
Compact silicon integrated devices, such as micro-ring resonators, have
recently been demonstrated as efficient sources of quantum correlated photon
pairs. The mass production of integrated devices demands the implementation of
fast and reliable techniques to monitor the device performances. In the case of
time-energy correlations, this is particularly challenging, as it requires high
spectral resolution that is not currently achievable in coincidence
measurements. Here we reconstruct the joint spectral density of photons pairs
generated by spontaneous four-wave mixing in a silicon ring resonator by
studying the corresponding stimulated process, namely stimulated four wave
mixing. We show that this approach, featuring high spectral resolution and
short measurement times, allows one to discriminate between nearly-uncorrelated
and highly-correlated photon pairs.Comment: 7 pages, 4 figure
Micrometer-scale integrated silicon source of time-energy entangled photons
Entanglement is a fundamental resource in quantum information processing. Several studies have explored the integration of sources of entangled states on a silicon chip, but the devices demonstrated so far require millimeter lengths and pump powers of the order of hundreds of milliwatts to produce an appreciable photon flux, hindering their scalability and dense integration. Microring resonators have been shown to be efficient sources of photon pairs, but entangled state emission has never been proven in these devices. Here we report the first demonstration, to the best of our knowledge, of a microring resonator capable of emitting time-energy entangled photons. We use a Franson experiment to show a violation of Bell’s inequality by more than seven standard deviations with an internal pair generation exceeding 107 Hz. The source is integrated on a silicon chip, operates at milliwatt and submilliwatt pump power, emits in the telecom band, and outputs into a photonic waveguide. These are all essential features of an entangled state emitter for a quantum photonic network
Stable 2.1 ÎĽm near 100% polarized Ho-doped all-fiber laser based on a polarizer-free cavity scheme
A highly polarized Ho-doped truly all-fibre laser was demonstrated without in-cavity polarizer. Utilizing PM-FBG and loop mirror, maximum 0.5W output power with 30% slope efficiency, 70dB ASE suppression and 99.997% degree of polarization was recorded at 2.1ÎĽ
All-fibered chalcogenide based continuous-wave parametric amplification in the mid-infrared
We demonstrate parametric amplification around 2 ÎĽm in a dispersion engineered tapered microstructured chalcogenide fiber. Almost 5 dB of signal amplification was achieved by 125 mW coupled power from a thulium-doped fiber pump laser
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