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Article
Although the residual nonlinearity and slow power modulation of the
comb sidebands during the frequency chirp only weakly influences the
distance and velocity evaluation, we emphasize that both effects can be
avoided entirely if both the laser and cavity are modulated in unison^36.
Similarly, the laser can be self-injection-locked to the modulated cavity,
which can furthermore extend the laser coherence length substan-
tially^37 ,^38. Promising actuation technologies include recently developed
high-bandwidth and energy-efficient integrated electro-optical^39 and
piezoelectrical actuators^36.
Moreover, by virtue of the laser line separations, our concept is com-
patible with nanophotonics-based gratings for beam separation and
could greatly simplify optical phased array systems^12 , wherein one
axis of beam separation is provided by the nanophotonic grating and a
second axis is provided by integrated phase shifters. Furthermore, this
concept alleviates problems with eye safety, as the light is dispersed
over multiple detection pixels at all times, similar to time-of-flight
flash systems, yet avoids the problems associated with the excessive
peak powers of high-energy pulsed light sources. Finally, spectrally
multiplexed detection can also be carried out in a dual-comb approach,
whereby the second comb scans in unison with the first, but has a dif-
ferent repetition rate, which removes the need for demultiplexing
and individual detection of the comb lines. It should be noted that
(resonant) electro-optical frequency combs^39 ,^40 based on LiNbO 3 also
provide a platform in which the approach presented here could be
realized. Hence, we conclude that microcombs, combined with con-
current advances in chip-scale lasers, optical beamforming structures,
and hybrid electro-optical integration provide a path towards rapid,
precise and simultaneously long-range coherent lidar modules suit-
able for industrial, automotive and airborne applications demanding
high-speed 3D imaging in excess of ten megapixels per second.
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