1,429 research outputs found
Optical frequency synthesis and measurement using fibre-based femtosecond lasers
We report the synthesis and measurement of an ultra-precise and extremely
stable optical frequency in the telecommunications window around 1543 nm. Using
a fibre-based femtosecond frequency comb we have phase-stabilised a fibre laser
at 194 THz to an optical frequency standard at 344 THz, thus transferring the
properties of the optical frequency standard to another spectral region.
Relative to the optical frequency standard, the synthesised frequency at 194
THz is determined to within 1 mHz and its fractional frequency instability is
measured to be less than 2*10^{-15} at 1 s, reaching 5*10^{-18} after 8000 s.
We also measured the synthesised frequency against a caesium fountain clock:
here the frequency comparison itself contributes less than 4 mHz (2*10^{-17})
to the uncertainty. Our results confirm the suitability of fibre based
frequency comb technology for precision measurements and frequency synthesis,
and enable long-distance comparison of optical clocks by using optical fibres
to transmit the frequency information
Spectral Line-by-Line Pulse Shaping of an On-Chip Microresonator Frequency Comb
We report, for the first time to the best of our knowledge, spectral phase
characterization and line-by-line pulse shaping of an optical frequency comb
generated by nonlinear wave mixing in a microring resonator. Through
programmable pulse shaping the comb is compressed into a train of
near-transform-limited pulses of \approx 300 fs duration (intensity full width
half maximum) at 595 GHz repetition rate. An additional, simple example of
optical arbitrary waveform generation is presented. The ability to characterize
and then stably compress the frequency comb provides new data on the stability
of the spectral phase and suggests that random relative frequency shifts due to
uncorrelated variations of frequency dependent phase are at or below the 100
microHertz level.Comment: 18 pages, 4 figure
Cavity-enhanced single frequency synthesis via DFG of mode-locked pulse trains
We show how to synthesize a CW, single-frequency optical field from the
frequency-dispersed, pulsed field of a mode-locked laser. This process, which
relies on difference frequency generation in an optical cavity, is efficient
and can be considered as an optical rectification. Quantitative estimates for
the output power and amplitude noise properties of a realistic system are
given. Possible applications to optical frequency synthesis and optical
metrology are envisaged
Ultrafast electrooptic dual-comb interferometry
The femtosecond laser frequency comb has enabled the 21st century revolution
in optical synthesis and metrology. A particularly compelling technique that
relies on the broadband coherence of two laser frequency combs is dual-comb
interferometry. This method is rapidly advancing the field of optical
spectroscopy and empowering new applications, from nonlinear microscopy to
laser ranging. Up to now, most dual-comb interferometers were based on
modelocked lasers, whose repetition rates have restricted the measurement speed
to ~ kHz. Here we demonstrate a novel dual-comb interferometer that is based on
electrooptic frequency comb technology and measures consecutive complex spectra
at a record-high refresh rate of 25 MHz. These results pave the way for novel
scientific and metrology applications of frequency comb generators beyond the
realm of molecular spectroscopy, where the measurement of ultrabroadband
waveforms is of paramount relevance
Comb-based WDM transmission at 10 Tbit/s using a DC-driven quantum-dash mode-locked laser diode
Chip-scale frequency comb generators have the potential to become key
building blocks of compact wavelength-division multiplexing (WDM) transceivers
in future metropolitan or campus-area networks. Among the various comb
generator concepts, quantum-dash (QD) mode-locked laser diodes (MLLD) stand out
as a particularly promising option, combining small footprint with simple
operation by a DC current and offering flat broadband comb spectra. However,
the data transmission performance achieved with QD-MLLD was so far limited by
strong phase noise of the individual comb tones, restricting experiments to
rather simple modulation formats such as quadrature phase shift keying (QPSK)
or requiring hard-ware-based compensation schemes. Here we demonstrate that
these limitations can be over-come by digital symbol-wise phase tracking
algorithms, avoiding any hardware-based phase-noise compensation. We
demonstrate 16QAM dual-polarization WDM transmission on 38 channels at an
aggregate net data rate of 10.68 Tbit/s over 75 km of standard single-mode
fiber. To the best of our knowledge, this corresponds to the highest data rate
achieved through a DC-driven chip-scale comb generator without any
hardware-based phase-noise reduction schemes
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