891 research outputs found
Towards milli-Hertz laser frequency noise on a chip
Narrow-linewidth lasers are important to many applications spanning precision metrology to sensing systems. Their miniaturization in the form of on-chip lasers is receiving increasing attention. Here, a noise level that is consistent with a fundamental frequency noise of 9 mHz⋅Hz/Hz linewidth (60 mHz linewidth) is measured in a Brillouin laser. The results leverage ultra-high-Q silica-on-silicon resonators and point towards a new performance target for chip-based laser platforms
Towards milli-Hertz laser frequency noise on a chip
Narrow-linewidth lasers are important to many applications spanning precision metrology to sensing systems. Their miniaturization in the form of on-chip lasers is receiving increasing attention. Here, a noise level that is consistent with a fundamental frequency noise of 9 mHz⋅Hz/Hz linewidth (60 mHz linewidth) is measured in a Brillouin laser. The results leverage ultra-high-Q silica-on-silicon resonators and point towards a new performance target for chip-based laser platforms
Linewidth enhancement factor in a microcavity Brillouin laser
The linewidth of regenerative oscillators is enhanced by amplitude–phase coupling of the oscillator field [Phys. Rev. 160, 290 (1967)]. In laser oscillators, this effect is well known for its impact on semiconductor laser performance. Here, this coupling is studied in Brillouin lasers. Because their gain is parametric, the coupling and linewidth enhancement are shown to originate from phase mismatch. The theory is confirmed by measurement of linewidth in a microcavity Brillouin laser, and enhancements as large as 50× are measured. The results show that pump wavelength and device temperature should be carefully selected and controlled to minimize linewidth. More generally, this work provides a new perspective on the linewidth enhancement effect
The stability of Einstein static universe in the DGP braneworld
The stability of an Einstein static universe in the DGP braneworld scenario
is studied in this paper. Two separate branches denoted by of
the DGP model are analyzed. Assuming the existence of a perfect fluid with a
constant equation of state, , in the universe, we find that, for the branch
with , there is no a stable Einstein static solution, while, for
the case with , the Einstein static universe exists and it is
stable when . Thus, the universe can stay at this stable state
past-eternally and may undergo a series of infinite, non-singular oscillations.
Therefore, the big bang singularity problem in the standard cosmological model
can be resolved.Comment: 10 pages, 2 figures, to appear in PL
Vernier spectrometer using counter-propagating soliton microcombs
Acquisition of laser frequency with high resolution under continuous and
abrupt tuning conditions is important for sensing, spectroscopy and
communications. Here, a single microresonator provides rapid and broad-band
measurement of frequencies across the optical C-band with a relative frequency
precision comparable to conventional dual frequency comb systems. Dual-locked
counter-propagating solitons having slightly different repetition rates are
used to implement a Vernier spectrometer. Laser tuning rates as high as 10
THz/s, broadly step-tuned lasers, multi-line laser spectra and also molecular
absorption lines are characterized using the device. Besides providing a
considerable technical simplification through the dual-locked solitons and
enhanced capability for measurement of arbitrarily tuned sources, this work
reveals possibilities for chip-scale spectrometers that greatly exceed the
performance of table-top grating and interferometer-based devices
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