80 research outputs found
Transient Regime of Kerr Frequency Comb Formation
Temporal growth of an optical Kerr frequency comb generated in a
microresonator is studied both experimentally and numerically. We find that the
comb emerges from vacuum fluctuations of the electromagnetic field on
timescales significantly exceeding the ringdown time of the resonator modes.
The frequency harmonics of the comb spread starting from the optically pumped
mode if the microresonator is characterized with anomalous group velocity
dispersion. The harmonics have different growth rates resulting from sequential
four-wave mixing process that explains intrinsic modelocking of the comb.Comment: 4 pages, 5 figure
Miniature Optical Atomic Clock: Stabilization of a Kerr Comb Oscillator
Mechanical clocks consist of a pendulum and a clockwork that translates the
pendulum period to displayed time. The most advanced clocks utilize optical
transitions in atoms in place of the pendulum and an optical frequency comb
generated by a femtosecond laser as the clockwork. The comb must be stabilized
at two points along its frequency spectrum: one with a laser to lock a comb
line to a transition in the atom, and another through self referencing to
stabilize the frequency interval between the comb lines. This approach requires
advanced techniques, so optical atomic clocks are currently laboratory devices
in specialized labs. In this paper we leverage unique properties of Kerr comb
oscillators for realization of optical atomic clocks in miniature form factors.
In particular, we describe a clock based on D1 transition of 87Rb that fits in
the palm of the hand, and can be further miniaturized to chip scale.Comment: 4 pages, 4 figure
Hard and Soft Excitation Regimes of Kerr Frequency Combs
We theoretically study the stability conditions and excitation regimes of
hyper-parametric oscillation and Kerr frequency comb generation in continuously
pumped nonlinear optical resonators possessing anomalous group velocity
dispersion. We show that both hard and soft excitation regimes are possible in
the resonators. Selection between the regimes is achieved via change in the
parameters of the pumping light.Comment: 4 pages, 7 figure
The Laser-only Single-event Effects Test Method for Spacecraft Electronics Based on Ultrashort-pulsed-laser Local Irradiation
The substantive laser method for studying the radiation hardness of semiconductor devices, not requiring calibration by ions, called ”local irradiation”, is described. The essence of the local approach is in irradiating the sample sensitive volume with the ultrashort-pulsed laser beam at some distance from its focus plane, where the beam becomes rather wide and divergent. Assuming the single-photon absorption, the relationship between the laser pulse energy and the excess charge actually generated in irradiated sensitive volume is obtained by accurate measurement of the electrical response, that makes possible to take into account non-uniform optical losses and avoid additional calibration by ions. Some results, obtained using both the front-side and the backside local irradiation of devices, are presented. Comparison with results obtained by traditional methods using focused laser radiation with subsequent calibration by ions showed that laser-only measurements, based on described local irradiation, give the correct estimates of radiation hardness parameters.
Keywords: Ultrashort laser pulse, single-event effect, local laser irradiation, semiconductor device, integrated circuit
Passively mode locked Raman laser
We report on the observation of a novel mode locked optical comb generated at
the Raman offset (Raman comb) in an optically pumped crystalline whispering
gallery mode resonator. Mode locking is confirmed via measurement of the
radio-frequency beat note produced by the optical comb on a fast photodiode.
Neither the conventional Kerr comb nor hyper-parametric oscillation is observed
when the Raman comb is present
Whispering gallery mode resonator based ultra-narrow linewidth external cavity semiconductor laser
We demonstrate a miniature self-injection locked DFB laser using resonant
optical feedback from a high-Q crystalline whispering gallery mode resonator.
The linewidth reduction factor is greater than 10,000, with resultant
instantaneous linewidth less than 200 Hz. The minimal value of the Allan
deviation for the laser frequency stability is 3x10^(-12) at the integration
time of 20 us. The laser possesses excellent spectral purity and good long term
stability.Comment: To be published in Optics Letter
Efficient upconversion of sub-THz radiation in a high-Q whispering gallery resonator
We demonstrate efficient upconversion of sub-THz radiation into the optical
domain in a high-Q whispering gallery mode resonator with quadratic optical
nonlinearity. The 5x10^{-3} power conversion efficiency of continuous wave
100GHz signal is achieved with only 16 mW of optical pump.Comment: This revision is limited to discussion of only optical WGMs coupled
with the external Rf field. Discussion of RF WGMs is now posted separatel
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