Optical frequency comb based parallel FM LIDAR
In a LIDAR device ( 100 ) a laser light source ( 110 ) generates first laser light having a first laser frequency which is frequency modulated with a first frequency modulation. A non-linear optical element ( 120 ) receives the first laser light and generates therefrom second laser light having a comb-like frequency spectrum with a plurality of second laser frequencies which are each frequency modulated with a second frequency modulation defined by the first frequency modulation. A frequency excursion of the second frequency modulation is smaller than a spacing of the second laser frequencies. A diffractive element ( 140 ) spatially separates the second laser light according to the second laser frequencies and directs the spatially separated second laser light towards a ranging region ( 200 ), with each of the second laser frequencies being directed towards a corresponding spatially distinct target position in the ranging region ( 200 ). A detector ( 150 ) receives reflections of the second laser light from the ranging region ( 200 ) and measures, by simultaneously detecting a frequency modulation of the reflections for each of the second laser frequencies, a distance and/or a velocity at the target position corresponding to the second laser frequency.
1. A device for light detection and ranging (LIDAR), the device comprising:
a laser light source configured to generate first laser light having a first laser frequency which is frequency modulated with a first frequency modulation;
a non-linear optical element configured to receive the first laser light and generate therefrom second laser light having a comb-like frequency spectrum with a plurality of second laser frequencies which are each frequency modulated with a second frequency modulation defined by the first frequency modulation, with a frequency excursion of the second frequency modulation being smaller than a spacing of the second laser frequencies;
a diffractive element configured to spatially separate the second laser light according to the second laser frequencies and direct the spatially separated second laser light towards a ranging region, with each of the second laser frequencies being directed towards a corresponding spatially distinct target position in the ranging region; and
a detector configured to receive reflections of the second laser light from the ranging region and to measure, by simultaneously detecting a frequency modulation of the reflections for each of the second laser frequencies, at least one of a distance and a velocity at the target position corresponding to the second laser frequency.
2. The device according to claim 1 ,
wherein the non-linear optical element comprises at least one photonic resonator.
3. The device according to claim 1 ,
wherein the non-linear optical element is configured to generate the second laser light having the comb-like frequency spectrum based on pumping a dissipative Kerr soliton in the photonic resonator by the first laser light, and
wherein a frequency excursion of the first frequency modulation is within a frequency range selected to support stable generation of the dissipative Kerr soliton.
4. The device according to claim 2 , comprising:
a tuning mechanism configured to modulate tuning of the photonic resonator depending on the first frequency modulation.
5. The device according to claim 2 ,
wherein the non-linear optical element has at least one of a second order non-linear characteristic and a third order non-linear characteristic.
6. The device according to claim 1 ,
wherein the first frequency modulation and the second frequency modulation are of a triangular type.
7. The device according to claim 1 ,
wherein the second frequency modulation is a linear function of the first frequency modulation.
8. The device according to claim 1 ,
wherein the second frequency modulation has a frequency excursion of 500 MHZ to 10 GHz.
9. The device according to claim 1 ,
wherein a frequency spacing of the second laser frequencies is at least 50 GHz.
10. The device according to claim 1 ,
wherein the second frequency modulation has modulation frequency of 1 kHz to 10 MHz.
11. The device according to claim 1 , further comprising:
a further non-linear optical element configured to generate third laser light having a comb-like frequency spectrum with a plurality of third laser frequencies which have a frequency spacing offset with respect to a frequency spacing of the second laser frequencies,
wherein the detector is configured to detect the frequency modulation of the reflections by mixing the third laser light with the reflections of the second laser light and directing the mixed light to a photodetector.
12. The device according to claim 1 ,
wherein the detector is configured to detect the frequency modulation of the reflections by mixing the second laser light with the reflections of the second laser light and directing the mixed light to a photodetector.
13. The device according to claim 1 ,
wherein the detector comprises multiple photodetectors and is configured to direct light corresponding to different ones of the second laser frequencies to different ones of the multiple photodetectors.
14. The device according to claim 1 , comprising:
a scanning mechanism configured to sequentially scan the target positions over different portions of the ranging region.
15. The device according to claim 1 ,
wherein the first frequency modulation is controlled by a control signal, and
wherein the device further comprises an adjustment stage configured to measure a deviation of the first frequency modulation from a desired modulation waveform and to adjust the control signal depending on the measured deviation.
16. A method for light detection and ranging (LIDAR) the method comprising:
generating first laser light having a first laser frequency which is frequency modulated with a first frequency modulation;
receiving the first laser light in a non-linear optical element to generate therefrom second laser light having a comb-like frequency spectrum with a plurality of second laser frequencies which are each frequency modulated with a second frequency modulation defined by the first frequency modulation, with a frequency excursion of the second frequency modulation being smaller than a spacing of the second laser frequencies;
spatially separating the second laser light by a diffractive element;
directing the spatially separated second laser light towards a ranging region, with each of the second laser frequencies being directed towards a corresponding spatially distinct target position in the ranging region;
receiving reflections of the second laser light from the ranging region; and
measuring, by simultaneously detecting a frequency modulation of the reflections for each of the second laser frequencies, at least one of a distance and a velocity at the target position corresponding to the second laser frequency.
17. The method according to claim 16 ,
wherein the non-linear optical element comprises at least one photonic resonator.
18. The method according to claim 17 ,
wherein the non-linear optical element generates the second laser light having the comb-like frequency spectrum based on pumping a dissipative Kerr soliton in the photonic resonator by the first laser light, and
wherein a frequency excursion of the first frequency modulation is within a frequency range selected to support stable generation of the dissipative Kerr soliton.
19. The method according to claim 17 ,
modulating tuning of the photonic resonator depending on the first frequency modulation.
20. The method according to claim 16 ,
wherein the non-linear optical element has at least one of a second order non-linear characteristic and a third order non-linear characteristic.