Discriminative remote sensing and surface profiling based on superradiant photonic backscattering

Patent metadata

Field	Value
Publication number	US-10535974-B2
Application number	US-201715673666-A
Country	US
Kind code	B2
Filing date	Aug 10, 2017
Priority date	Aug 11, 2016
Publication date	Jan 14, 2020
Grant date	Jan 14, 2020

Abstract

Disclosed is a system and method for remote sensing, surface profiling, object identification, and aiming based on two-photon population inversion and subsequent photon backscattering enhanced by superradiance using two co-propagating pump waves. The present disclosure enables efficient and highly-directional photon backscattering by generating the pump waves in properly pulsed time-frequency modes, proper spatial modes, with proper group-velocity difference in air. The pump waves are relatively delayed in a tunable pulse delay device and launched to free space along a desirable direction using a laser-pointing device. When the pump waves overlap in air, signal photons will be created through two-photon driven superrdiant backscattering if target gas molecules are present. The backscattered signal photons propagate back, picked using optical filters, and detected. By scanning the relative delay and the launching direction while the signal photons are detected, three-dimensional information of target objects is acquired remotely.

First claim

What is claimed is:

1. A method, comprising:
generating co-propagating pulsed pump waves having shaped time-frequency modes, spatial modes, and group-velocity difference;
relatively delaying said pump waves for a predetermined time period;
launching said pump waves to a free space along a predetermined direction;
backscattering a signal wave having backscattered signal photons when said pump waves overlap in said free space;
detecting said backscattered signal photons; and
scanning said predetermined direction of said launched pump waves and said time period of the relative delay of said pump waves to remotely obtain three- dimensional information of a target.

2. A method for remote scanning via detection of superradiant backscattered photons, comprising the steps of:
determining modes for a pair of co-propagating pump pulses in spatial and temporal modalities such that said pair of pump pulses are optimized to cooperate for energizing a population of a specific gaseous molecule into an excited state;
generating said pair of pump pulses having said determined modes;
launching a first pulse of said pair of pump pulses into free space at a first launch angle;
launching a second pulse of said pair of pump pulses into free space at a second launch angle, said first and second launch angles being selected such that said first and second pulses meet at a predetermined intersection point around which said population of said specific gaseous molecule exist, thereby producing from said population a first plurality of excited molecules, at least some of said first plurality of excited molecules emitting photons, at least some of said emitted photons traveling along a backscattering path and inducing further emission of photons from a second plurality of excited molecules on said backscattering path to create a superradiant photonic signal, said second plurality of excited molecules being produced from said population of said specific gaseous molecule in response to said first and second pulses meeting at said predetermined intersection point;
detecting said superradiant photonic signal; and
analyzing said superradiant photonic signal to obtain data regarding the presence, concentration and/or distribution of said specific gaseous molecule.

3. The method of claim 2 , wherein said second pulse is launched after said first pulse is launched to thereby create a time delay between the launches of said first and second pulses.

4. The method of claim 3 , further comprising the step of varying said predetermined intersection point by varying said time delay between the launches of said first and second pulses.

5. The method of claim 2 , further comprising the step of scanning along a target direction by varying said predetermined intersection point, modulating said pair of co- propagating pump pulses and/or varying at least one of said first and second launch angles.

6. The method of claim 5 , wherein said scanning step is conducted utilizing the chromatic dispersion of Earth's atmosphere.

7. The method of claim 2 , further comprising the step of storing said data regarding the presence, concentration and/or distribution of said specific gaseous molecule.

8. The method of claim 2 , wherein the steps of claim 2 are repeated with a different pair of pump pulses for a different specific gaseous molecule, thereby obtaining multi-faceted data on various specific gaseous molecules.

9. The method of claim 8 , further comprising the step of generating a 3 D tomogram based on said multi-faceted data.

10. The method of claim 2 , wherein said analyzing step further comprises the steps of monitoring said superradiant photonic signal for sudden decreases; determining, through negative imaging, coordinates of a detected object; and creating a corresponding surface profile of said detected object.

11. The method of claim 10 , wherein said detected object is a stealth object.

12. The method of claim 2 , wherein said first and second pulses are self-deflecting, thereby propagating in a curved trajectory.

13. The method of claim 12 , wherein said first and second pulses are Airy beams.

14. The method of claim 13 , further comprising the step of simulating the trajectory of a bullet by modulating said Airy beams such that said Airy beams follow a parabolic propagation that is coincident with that of bullets in air due to gravitation.

15. The method of claim 12 , wherein said backscattering path follows said curved trajectory.

16. The method of claim 12 , wherein said backscattering path is different from said curved trajectory.

17. The method of claim 2 , wherein said determining step further comprises the step of modulating said pair of pump pulses to enhance said superradiant backscattering by minimization of out-of-phase interactions between said second plurality of excited molecules and said at least some of said emitted photons.

18. The method of claim 2 , wherein said first pulse and said second pulse have different wave numbers.

19. The method of claim 18 , wherein said second pulse has an intensity of from about 10 KW/m∧2 to about 100 MW/m∧2, such that Rabi oscillations are effected in said first plurality of excited molecules and/or said second plurality of excited molecules.

20. The method of claim 18 , wherein said first pulse has more energy than said superradiant photonic signal.

21. The method of claim 2 , wherein at least one pulse of said pair of pulses has a spectral band of from about 0.1 THz to about 10 THz.

22. The method of claim 2 , wherein said determining step further comprises the steps of formulating proposed waveforms and testing said proposed waveforms.

23. The method of claim 22 , wherein said generating step is performed through line- by-line modulation of comb lines via a Global Searching Algorithm.

24. The method of claim 22 , wherein said formulating step is performed via recursive steps, starting with initial waveforms and randomly changing the amplitude and phase of comb lines, said comb lines constituting said proposed waveforms.

25. The method of claim 22 , wherein said testing step is performed via real-time evaluation of said proposed waveforms, said evaluation comprising the steps of generating a test laser having said proposed waveforms, passing said test laser through a reference gas sample and measuring the excitation of said reference gas sample.

26. The method of claim 22 , wherein said testing step is performed numerically by solving level transition dynamics.

27. The method of claim 22 , wherein said formulating step and said testing step are conducted using global numeric optimization.

28. The method of claim 2 , wherein said first pulse and said second pulse have the same propagation speed but launch at angles to meet at a predetermined point in space.

29. The method of claim 2 , wherein said first pulse and said second pulse have the same launch angle, whereby said first launch angle equals said second launch angle.

30. The method of claim 2 , wherein said detecting step is performed by a mode- resolving photon detector.

31. The method of claim 2 , wherein said detecting step is performed by a sensitive photon detector.

Assignees

• Stevens Institute Of Technology

Inventors

• Huang Yuping

Classifications

• H01S3/305

  in a gas · CPC title

• H01S3/06758

  Tandem amplifiers · CPC title

• H01S3/0057

  Temporal shaping, e.g. pulse compression, frequency chirping (soliton generation and propagation G02F1/3513, H01S3/063 and H01S3/108) · CPC title

• G01S17/95

  for meteorological use · CPC title

• H01S3/1608

  erbium · CPC title