The Bridge - Issue 1, 2023 - 8

Feature
Ultrafast Lidar Experimental Setup at Missouri S&T
Ultrafast Lidar Based on Signal Time Stretch
and Various Transduction Techniques
Behzad Boroomandisorkhabi and Mina Esmaeelpour, Department of Electrical and Computer Engineering,
Missouri University of Science and Technology
Abstract
This article discusses light detection and ranging (Lidar)
techniques based on time-to-wavelength mapping
and real-time fast Fourier transformation, as well as its
application in spectroscopy. Different signal transduction
techniques for Lidar data acquisition and processing are
also discussed, including direct optical detection, detection
of the microwave signals extracted from the interferometric
measurements, and imaging based on the spectrotemporal
encoding of various optical bands of the
input signal.
I. Introduction
Light detection and ranging, known as Lidar, use the
transmission and return of light as a remote sensing
technology. A variety of wavelengths and pulse lengths are
used. The use of ultrafast lasers with pulse lengths less
than a nanosecond has been a topic of interest for scientific
and commercial applications. Ultrafast Lidar technology has
the advantages of noncontact and remote operation and
immunity to electromagnetic interference. Optical ranging
and Doppler Lidars, as well as composition analysis of
complex materials and molecular evolution in chemistry
and biomedicine, are some of the applications of this
THE BRIDGE
technology [1,2]. Ultrafast range detection is possible on
a large dynamic range with nanometer accuracy by using
dispersive Fourier transformation known as " Time-stretch "
[1,3]. It requires an analog-to-digital conversion with a high
sampling rate where short-time data storage and timeconsuming
post-processing may cause issues. These issues
can be addressed through continuous detection and realtime
feedback. Microwave photonics can also be applied
to overcome these problems and realize real-time signal
processing with integrated functionality [4].
The " Time-stretch " ultrafast Lidar technique has applications
in ultrafast single-shot spectroscopy, imaging, ranging, ultrawideband,
and chirped microwave pulse generation for
high-speed communications and radars. However, because
of the high insertion loss of the adopted dispersion device,
it has the disadvantage of a low signal-to-noise (SNR)
ratio, which can be improved by incorporating heterodyne
detection by mixing the weak signal with a strong local
oscillator. However, the spectral information encoded in the
envelope is hard to acquire because of the narrow-band
radio-frequency (RF) spectrum. The amplitude-modulated
interferometry (AMI), frequency-modulated interferometry
(FMI), and spectrally resolved interferometry (SRI) are
the most notable interferometric techniques for high

The Bridge - Issue 1, 2023

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