Abstract
Frequency-modulated continuous-wave LIDAR (FMCW LIDAR) has been widely used for both scientific and industrial tools. Here, in this report, a new class of LIDAR technique based on an optical frequency comb, named frequency-modulated comb LIDAR (FMcomb LIDAR), is proposed. Instead of using one carrier such as FMCW LIDAR, the multiple carriers from an optical frequency comb are used in FMcomb LIDAR. Because of the correlation between comb modes, each frequency-scanned comb mode can be coherently stitched, thus allowing for a resolution equivalent to scanning by many comb modes while scanning only by the comb mode spacing. In a proof-of-concept experiment, three comb modes from an electro-optic frequency comb (EO comb) are coherently stitched, showing Fourier-transform limited resolution (defined as FWHM linewidth) of 10 ps (i.e., 1.5 mm in air) for about 65 ns delay. The obtained resolution is three-times higher than that of conventional FMCW LIDAR when the same scan range is considered.
Highlights
LIDAR systems are ubiquitous in ranging, autonomous navigation, and surface profilometry.1 One of the most powerful methods is based on the use of dual fiber frequency combs, enabling high resolution, high precision, and fast refresh rate.2–4 the method requires two mutually phase locked frequency combs, making a system very complicated
In frequency-modulated continuous-wave (FMCW) LIDAR, since the nonambiguous range (NAR) can be extremely large, an actual limit for the measurable range is set by the coherence length of the used cw laser, which is proportional to the inverse of the cw laser linewidth
We propose frequency-modulated comb LIDAR (FMcomb LIDAR), in which the comb modes of a frequency comb, generated from a single cw laser, are coherently stitched
Summary
LIDAR systems are ubiquitous in ranging, autonomous navigation, and surface profilometry. One of the most powerful methods is based on the use of dual fiber frequency combs, enabling high resolution, high precision, and fast refresh rate. the method requires two mutually phase locked frequency combs, making a system very complicated. In FMCW LIDAR, since the NAR can be extremely large, an actual limit for the measurable range is set by the coherence length of the used cw laser, which is proportional to the inverse of the cw laser linewidth. The more the DFB lasers are required, the more complicated the system becomes Since both the knowledge of the chirp rate (=scan range/scan time) and the instantaneous frequency (from an offset frequency). In a proof-of-concept demonstration, three comb modes from an EO comb are coherently stitched, resulting in three times higher Fourier-transform limited resolution (10 ps, i.e., 1.5 mm in the air, defined as FWHM linewidth) than that of the conventional FMCW LIDAR for about 65 ns delay
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