947 research outputs found
Kilohertz-resolution spectroscopy of cold atoms with an optical frequency comb
We have performed sub-Doppler spectroscopy on the narrow intercombination
line of cold calcium atoms using the amplified output of a femtosecond laser
frequency comb. Injection locking of a 657-nm diode laser with a femtosecond
comb allows for two regimes of amplification, one in which many lines of the
comb are amplified, and one where a single line is predominantly amplified. The
output of the laser in both regimes was used to perform kilohertz-level
spectroscopy. This experiment demonstrates the potential for high-resolution
absolute-frequency spectroscopy over the entire spectrum of the frequency comb
output using a single high-finesse optical reference cavity.Comment: 4 pages, 4 Figure
Self-referencing a continuous-wave laser with electro-optic modulation
We phase-coherently measure the frequency of continuous-wave (CW) laser light
by use of optical-phase modulation and f-2f nonlinear interferometry. Periodic
electro-optic modulation (EOM) transforms the CW laser into a continuous train
of picosecond optical pulses. Subsequent nonlinear-fiber broadening of this EOM
frequency comb produces a supercontinuum with 160 THz of bandwidth. A critical
intermediate step is optical filtering of the EOM comb to reduce
electronic-noise-induced decoherence of the supercontinuum. Applying f-2f
self-referencing with the supercontinuum yields the carrier-envelope offset
frequency of the EOM comb, which is precisely the difference of the CW laser
frequency and an exact integer multiple of the EOM pulse repetition rate. Here
we demonstrate absolute optical frequency metrology and synthesis applications
of the self-referenced CW laser with <5E-14 fractional accuracy and stability.Comment: 8 pages, 4 figure
An Ultra-Stable Referenced Interrogation System in the Deep Ultraviolet for a Mercury Optical Lattice Clock
We have developed an ultra-stable source in the deep ultraviolet, suitable to
fulfill the interrogation requirements of a future fully-operational lattice
clock based on neutral mercury. At the core of the system is a Fabry-P\'erot
cavity which is highly impervious to temperature and vibrational perturbations.
The mirror substrate is made of fused silica in order to exploit the
comparatively low thermal noise limits associated with this material. By
stabilizing the frequency of a 1062.6 nm Yb-doped fiber laser to the cavity,
and including an additional link to LNE-SYRTE's fountain primary frequency
standards via an optical frequency comb, we produce a signal which is both
stable at the 1E-15 level in fractional terms and referenced to primary
frequency standards. The signal is subsequently amplified and frequency-doubled
twice to produce several milliwatts of interrogation signal at 265.6 nm in the
deep ultraviolet.Comment: 7 pages, 6 figure
Highly tunable repetition-rate multiplication of mode-locked lasers using all-fibre harmonic injection locking
Higher repetition-rate optical pulse trains have been desired for various
applications such as high-bit-rate optical communication, photonic
analogue-to-digital conversion, and multi- photon imaging. Generation of multi
GHz and higher repetition-rate optical pulse trains directly from mode-locked
oscillators is often challenging. As an alternative, harmonic injection locking
can be applied for extra-cavity repetition-rate multiplication (RRM). Here we
have investigated the operation conditions and achievable performances of
all-fibre, highly tunable harmonic injection locking-based pulse RRM. We show
that, with slight tuning of slave laser length, highly tunable RRM is possible
from a multiplication factor of 2 to >100. The resulting maximum SMSR is 41 dB
when multiplied by a factor of two. We further characterize the noise
properties of the multiplied signal in terms of phase noise and relative
intensity noise. The resulting absolute rms timing jitter of the multiplied
signal is in the range of 20 fs to 60 fs (10 kHz - 1 MHz) for different
multiplication factors. With its high tunability, simple and robust all-fibre
implementation, and low excess noise, the demonstrated RRM system may find
diverse applications in microwave photonics, optical communications, photonic
analogue-to-digital conversion, and clock distribution networks.Comment: 25 pages, 9 figure
- …