Pulsed laser for lidar system
A lidar system comprising with a light source, an optical link, and a sensor head. The light source can include a seed laser to produce pulses of light and an optical preamplifier to amplify the pulses of light. The optical link can convey amplified pulses of light to the sensor head remotely located from the light source. The sensor head can include an optical booster amplifier, a scanner to scan amplified output pulses of light across a field of regard, and a receiver to detect pulses of light scattered by a target located a distance from the sensor head.
1. A lidar system comprising:
a light source comprising:
a seed laser configured to produce pulses of light; and
an optical preamplifier configured to amplify the pulses of light to produce amplified pulses of light;
an optical link configured to convey at least a portion of the amplified pulses of light to a sensor head remotely located from the light source, wherein the optical link comprises a fiber-optic cable terminated at the sensor head by an output collimator configured to produce a free-space optical beam comprising the portion of the amplified pulses of light; and
the sensor head, wherein the sensor head comprises:
an optical booster amplifier configured to receive the free-space optical beam comprising the portion of the amplified pulses of light and amplify the free-space optical beam to produce amplified output pulses of light, wherein the optical booster amplifier comprises a free-space optical amplifier comprising a pump laser and a gain crystal configured to provide gain to the free-space optical beam;
a scanner configured to scan the amplified output pulses of light across a field of regard; and
a receiver configured to detect at least a portion of the scanned pulses of light scattered by a target located a distance from the sensor head.
2. The lidar system of claim 1 , wherein:
the pump laser has an operating wavelength of approximately 908 nm, 915 nm, 940 nm, 960 nm, 976 nm, 980 nm, 1050 nm, 1064 nm, 1450 nm, or 1480 nm; and
the pump laser produces a free-space pump beam that is directed into the gain crystal.
3. The lidar system of claim 1 , wherein the gain crystal comprises neodymium-doped yttrium aluminum garnet (Nd:YAG), neodymium-doped yttrium aluminum borate (Nd:YAB), erbium-doped glass, glass doped with erbium and ytterbium, YAB doped with erbium (Er:YAB), or YAB doped with erbium and ytterbium (Er:Yb:YAB).
4. The lidar system of claim 1 , wherein the optical preamplifier comprises a single-pass amplifier comprising a gain fiber with erbium dopants or erbium and ytterbium dopants.
5. The lidar system of claim 1 , wherein the light source further comprises an optical amplifier configured to:
receive the amplified pulses of light from the optical preamplifier; and
amplify the pulses of light received from the optical preamplifier.
6. The lidar system of claim 1 , wherein the sensor head further comprises an optical amplifier configured to amplify the portion of the amplified pulses of light prior to the portion of the amplified pulses of light being amplified by the optical booster amplifier.
7. The lidar system of claim 1 , wherein the amplified output pulses have output-pulse characteristics comprising:
a wavelength between 1400 nm and 1600 nm;
a pulse repetition frequency of less than or equal to 10 MHz;
a pulse duration of less than or equal to 10 nanoseconds;
a duty cycle of less than or equal to 1%; and
a pulse energy of greater than or equal to 100 nanojoules.
8. The lidar system of claim 1 , wherein the fiber-optic cable has a length between 1 meter and 20 meters.
9. The lidar system of claim 1 , wherein the optical preamplifier comprises an optical filter configured to transmit light at one or more operating wavelengths of the seed laser and attenuate amplified spontaneous emission (ASE) produced by the optical preamplifier.
10. The lidar system of claim 1 , wherein the optical booster amplifier further comprises an optical filter configured to transmit light at one or more operating wavelengths of the seed laser and attenuate amplified spontaneous emission (ASE) produced by the optical preamplifier or the optical booster amplifier.
11. The lidar system of claim 1 , wherein the seed laser comprises a laser diode configured to be electrically driven by a pulse generator to produce the pulses of light.
12. The lidar system of claim 1 , wherein the seed laser comprises:
a plurality of laser diodes, wherein each laser diode is configured to produce light at a different wavelength; and
an optical multiplexer configured to combine the light produced by each laser diode into a single optical fiber.
13. The lidar system of claim 1 , wherein the seed laser comprises a wavelength-tunable laser configured to produce light at a plurality of wavelengths.
14. The lidar system of claim 1 , wherein the fiber-optic cable of the optical link comprises a gain fiber distributed along a length of the optical link.
15. A lidar system comprising:
a light source comprising:
a seed laser configured to produce pulses of light; and
an optical preamplifier configured to amplify the pulses of light to produce amplified pulses of light, wherein the optical preamplifier comprises a double-pass amplifier comprising:
a circulator;
an erbium-doped or erbium/ytterbium-doped gain fiber comprising a first end and a second end, wherein the first end is coupled to the circulator; and
a fiber Bragg grating (FBG) coupled to the second end of the gain fiber, wherein the FBG is configured to reflect light corresponding to one or more operating wavelengths of the light source and transmit or attenuate light that is away from the reflected wavelengths;
an optical link configured to convey at least a portion of the amplified pulses of light to a sensor head remotely located from the light source; and
the sensor head, wherein the sensor head comprises:
an optical booster amplifier configured to receive the portion of the amplified pulses of light and amplify the received pulses of light to produce amplified output pulses of light;
a scanner configured to scan the amplified output pulses of light across a field of regard; and
a receiver configured to detect at least a portion of the scanned pulses of light scattered by a target located a distance from the sensor head.
16. A lidar system comprising:
a light source comprising:
a seed laser configured to produce pulses of light;
an optical preamplifier configured to amplify the pulses of light to produce amplified pulses of light; and
an optical demultiplexer configured to receive the amplified pulses of light from the optical preamplifier and distribute the amplified pulses of light to a plurality of optical links of the lidar system, wherein the optical links are coupled to a respective plurality of sensor heads of the lidar system;
an optical link of the plurality of optical links, the optical link configured to convey at least a portion of the amplified pulses of light to a sensor head of the plurality of sensor heads, the sensor head remotely located from the light source; and
the sensor head, wherein the sensor head comprises:
an optical booster amplifier configured to receive the portion of the amplified pulses of light and amplify the received pulses of light to produce amplified output pulses of light;
a scanner configured to scan the amplified output pulses of light across a field of regard; and
a receiver configured to detect at least a portion of the scanned pulses of light scattered by a target located a distance from the sensor head.
17. The lidar system of claim 16 , wherein the optical booster amplifier comprises a double-clad gain fiber comprising erbium dopants or erbium and ytterbium dopants.
18. The lidar system of claim 17 , wherein the optical booster amplifier further comprises a cladding mode stripper configured to remove residual pump-laser light from the double-clad gain fiber.
19. The lidar system of claim 16 , wherein the sensor head further comprises an output collimator configured to:
receive the amplified output pulses of light from the booster amplifier;
produce a free-space optical beam comprising the amplified output pulses of light; and
send the free-space optical beam to the scanner.