Method and apparatus for long-range lidar and active imaging with optical output from a photonic-crystal rod
View Patent ↗A method and apparatus use a photonic-crystal fiber having a very large core while maintaining a single transverse mode. In some fiber lasers and amplifiers having large cores problems exist related to energy being generated at multiple-modes (i.e., polygamy), and of mode hopping (i.e., promiscuity) due to limited control of energy levels and fluctuations. The problems of multiple-modes and mode hopping result from the use of large-diameter waveguides, and are addressed by the invention. This is especially true in lasers using large amounts of energy (i.e., lasers in the one-megawatt or more range). By using multiple small waveguides in parallel, large amounts of energy can be passed through a laser, but with better control such that the aforementioned problems can be reduced. An additional advantage is that the polarization of the light can be maintained better than by using a single fiber core.
1. An apparatus comprising:
an optical transmitter component configured for use in a long-range optical measuring device, the component including:
a signal laser that emits a laser signal; and
a photonic-crystal optical amplifier device operatively coupled to receive the signal laser signal, the photonic-crystal optical amplifier device having a first signal waveguide that has a diameter of at least about 40 microns, maintains a single transverse mode, and is operable to directly generate an output signal of optical pulses having a peak power of at least 500 kW, a spectral linewidth of 1 nm or less, a pulse-to-CW-background ratio of at least 20 dB, and a beam-quality M 2 value of less than 2 at a wavelength of 1.5 microns or longer.
2. The apparatus of claim 1 , further comprising:
a scanning component that scans at least a portion of the output signal across an area;
an imager component that obtains an image signal representing at least a part of the scanned area; and
a display component that displays an image based on the image signal.
3. The apparatus of claim 1 , further comprising:
a scanning component that scans at least a portion of the output signal across an area;
an imager component that obtains an image signal representing at least a portion of the scanned area;
a distance-determining component that determines a distance based on a time-of-flight measurement of at least one of the optical pulses; and
a display component that displays an image based on the image signal, wherein the image also provides an indication of the distance determined by the distance-determining component.
4. The apparatus of claim 1 , further comprising:
a distance-determining component that determines a distance based on a measurement of at least one of the optical pulses; and
a display component that displays an indication of the distance determined by the distance-determining component.
5. The apparatus of claim 1 , further comprising:
a beam-expanding component that expands at least a portion of the output signal to illuminate an area;
a shuttered imager component that obtains an image signal representing at least a portion of the illuminated area during a pulse; and
a display component that displays an image based on the image signal.
6. The apparatus of claim 1 , further comprising:
a scanning component that scans at least a portion of the output signal across an area, wherein temporally different pulses illuminate various portions of the area;
an imager component having a two-dimensional array of pixels that obtain an image signal representing at least a portion of the scanned area, and wherein different subsets of the array of pixels, each having fewer than all the pixels, obtain image information from different pulses; and
a display component that displays an image based on the image information.
7. The apparatus of claim 1 , wherein the photonic-crystal optical amplifier device is an optical fiber, and the first signal waveguide is a core of the fiber, the core exhibiting a numerical aperture defined by photonic-crystal structures.
8. A method comprising:
obtaining a laser signal having pulses;
coupling the pulsed laser signal to a first photonic-crystal optical amplifier device having a first signal waveguide that has a diameter of at least about 40 microns, and which maintains a single transverse mode; and
amplifying the pulsed laser signal to generate an output signal of optical pulses having a peak power of at least 500 kW, a spectral linewidth of 1 nm or less, a pulse-to-CW-background ratio of at least 20 dB, and a beam-quality M 2 value of less than 2 at a signal wavelength of 1.5 microns or longer.
9. The method of claim 8 , further comprising:
scanning at least a portion of the output signal across an area;
generating an image signal representing at least a portion of the scanned area; and
displaying an image based on the image signal.
10. The method of claim 8 , further comprising:
scanning at least a portion of the output signal across an area;
generating an obtains an image signal representing at least a portion of the scanned area;
determining a distance based on a time-of-flight measurement of at least one of the optical pulses; and
displaying an image based on the image signal, wherein the image also provides an indication of the distance determined by the distance-determining component.
11. The method of claim 8 , further comprising:
determining a distance based on a measurement of at least one of the optical pulses; and
displaying an indication of the distance determined by the distance-determining component.
12. The method of claim 8 , further comprising:
expanding at least a portion of the output signal to illuminate an area;
shuttered-imaging the area to obtain an image signal representing at least a portion of the illuminated area during a pulse; and
displaying an image based on the image signal.
13. The method of claim 8 , further comprising:
scanning at least a portion of the output signal across an area, wherein temporally different pulses illuminate various portions of the area;
generating an image signal representing a two-dimensional array of pixels of at least a portion of the scanned area, and wherein different subsets of the array of pixels, each having fewer than all the pixels, represent image information from different pulses; and
displaying an image based on the image information.
14. An apparatus comprising:
an optical transmitter component configured for use in a long-range optical measuring device, the component including:
a signal laser that emits a pulsed laser signal; and
photonic-crystal means for amplifying the pulsed laser signal while maintaining a single transverse mode to generate an output signal of optical pulses having a peak power of at least 500 kW, a spectral linewidth of 1 nm or less, a pulse-to-CW-background ratio of at least 20 dB, and a beam-quality M 2 value of less than 2 at a signal wavelength of 1.5 microns or longer.
15. The apparatus of claim 14 , further comprising:
means for scanning at least a portion of the output signal across an area;
means for generating an image signal representing at least a portion of the scanned area; and
means for displaying an image based on the image signal.
16. The apparatus of claim 14 , further comprising:
means for scanning at least a portion of the output signal across an area;
means for generating an obtains an image signal representing at least a portion of the scanned area;
means for determining a distance based on a time-of-flight measurement of at least one of the optical pulses; and
means for displaying an image based on the image signal, wherein the image also provides an indication of the distance determined by the distance-determining component.
17. The apparatus of claim 14 , further comprising:
means for determining a distance based on a measurement of at least one of the optical pulses; and
means for displaying an indication of the distance determined by the distance-determining component.
18. The apparatus of claim 14 , further comprising: means for expanding at least a portion of the output signal to illuminate an area;
means for shuttered-imaging the area to obtain an image signal representing at least a portion of the illuminated area during a pulse; and
means for displaying an image based on the image signal.
19. The apparatus of claim 14 , further comprising: means for scanning at least a portion of the output signal across an area, wherein temporally different pulses illuminate various portions of the area;
means for generating an image signal representing a two-dimensional array of pixels of at least a portion of the scanned area, and wherein different subsets of the array of pixels, each having fewer than all the pixels, represent image information from different pulses; and
means for displaying an image based on the image information.
20. The apparatus of claim 14 , wherein the photonic-crystal means for amplifying includes an optical fiber having a core exhibiting a numerical aperture defined by photonic-crystal structures.
21. The apparatus of claim 14 , wherein the photonic-crystal means for amplifying includes a photonic crystal fiber having a core diameter larger than 40 microns.
22. The apparatus of claim 14 , wherein the photonic-crystal means for amplifying includes a photonic crystal rod having a core diameter larger than 60 microns.
23. The apparatus of claim 14 , wherein the photonic-crystal means for amplifying includes a photonic crystal rod having a core is doped with Erbium.
24. The apparatus of claim 14 , wherein the photonic-crystal means for amplifying includes a photonic crystal rod having a core is codoped with Erbium and Ytterbium.
25. The apparatus of claim 14 , wherein the photonic-crystal means for amplifying includes a photonic crystal rod having a core is doped with Thulium.
26. The apparatus of claim 14 , wherein the photonic-crystal means for amplifying includes a photonic crystal rod having a core is codoped with Thulium and Holmium.
27. The apparatus of claim 14 , further comprising:
at least one other signal laser that each emits a pulsed laser signal;
at least one other photonic-crystal means for amplifying the at least one other pulsed laser; and
means for spectral-beam combining output signals from the plurality of means for amplifying into a single optical beam.