Eye-safe coherent laser radar

Claim 2

In a method for coherently detecting returned eye-safe laser radiation, the steps of: optically pumping a solid state laser gain medium with optical pumping radiation emanating from a semiconductive diode; resonating lasant radiation emanating from the optically pumped laser gain medium to produce coherent output lasant radiation of an eye-safe wavelength in excess of 1.5 μm; amplifying the coherent output lasant radiation in an optical amplifier to produce amplified coherent eye-safe output lasant radiation; transmitting the amplified output eye-safe lasant radiation from a transmitter station; receiving at a receiving station the lasant radiation returned from a target intercepted by the transmitted lasant radiation; collecting the received eye-safe lasant radiation and propagating the same over a single mode fiber-optic waveguide; and mixing the received lasant radiation as propagated over the single mode fiber-optic waveguide with reference coherent lasant radiation to derive a difference frequency output signal representative of parameters associated with the target.

Claim 3

The method of claim 1 wherein the step of resonating the eye-safe lasant radiation includes the step of: internally reflecting the lasant radiation from a plurality of facets of the solid state laser gain medium and around in a closed path to define a ring resonator.

Claim 4

The method of claim 1 wherein the step of amplifying the lasant radiation includes the step of: directing the lasant radiation to be amplified into a slab of optically pumped laser gain material and amplifying the lasant radiation within the slab of optically pumped laser gain material.

Claim 5

The method of claim 3 including the step of: passing the lasant radiation being amplified through the slab of optically pumped lasant material a plurality of times and over a plurality of different optical paths.

Claim 6

The method of claim 1 wherein the step of amplifying the lasant radiation includes the step of: directing the lasant radiation to be amplified into an optically pumped laser gain medium contained within an optical resonator for seeding and initiating amplified lasant transitions of the gain medium at the wavelength of the lasant radiation being amplified.

Claim 7

The method of claim 1 wherein the step of mixing the received lasant radiation with reference coherent lasant radiation includes the steps of: optically coupling a second fiber-optic waveguide containing the reference radiation together with the first fiber-optic waveguide containing the received radiation such that both radiations are combined and propagated together in a common fiber-optic waveguide; and applying both radiations as propagated over said common fiber optic waveguide to a photodetector for detecting the difference frequency output.

Claim 10

The method of claim 1 wherein the laser gain medium includes a host material doped with a lasant ion selected from the group consisting of Er, Nd, Tm, Ho, Dy, Yb and U.

Claim 11

The method of claim 9 wherein the host material is co-doped with an absorber ion selected from the group consisting of Tm, Er, Nd and U.

Claim 12

The method of claim 9 wherein the host material is selected from the group consisting of transparent oxide crystals, transparent fluoride crystals, transparent garnets, yttrium aluminum garnet, YAlO 3 and LiYF 4 .

Claim 13

The method of claim 1 wherein the laser gain medium is Ho:Tm:YAG lasing at a wavelength in excess of 1.5 μm.

Claim 14

The method of claim 1 including the step of: passing the lasant radiation emanating from the laser gain medium through an optical isolator and thence to the optical amplifier to reduce optical feedback from the optical amplifier to the diode pumped laser gain medium.

Claim 15

In an eye-safe coherent laser radar: a solid state laser gain medium; optical pumping means for optically pumping said laser gain medium with optical pumping radiation emanating from a semiconductive diode; optical resonator means optically coupled to said laser gain medium for resonating lasant radiation emanating from said optically pumped laser gain medium to produce coherent output laser radiation of an eye-safe wavelength in excess of 1.5 μm; optical amplifier means optically coupled to said laser gain medium for amplifying the coherent eye-safe output lasant radiation; transmitter station means optically coupled to said optical amplifier means for transmitting the amplified output eye-safe lasant radiation over a path to illuminate a target; receiver means for receiving the output lasant radiation returned from the illuminated target; a single transverse mode fiber-optic waveguide optically coupled to said receiver means and disposed to receive and propagate therein as a single transverse mode returned and received output lasant radiation; combining means for combining the returned and received output lasant radiation as propagated over said single mode fiber-optic waveguide with reference coherent lasant optical radiation; and detecting means optically coupled to the combined optical radiation for detecting a difference frequency output signal therebetween representative of parameters associated with the illuminated target.

Claim 16

In an eye-safe coherent laser radar: a solid state laser gain medium; optical pumping means for optically pumping said laser gain medium with optical pumping radiation emanating from a semiconductive diode; optical resonator means optically coupled to said laser gain medium for resonating lasant radiation emanating from said optically pumped laser gain medium to produce coherent output laser radiation of an eye-safe wavelength in excess of 1.5 μm; optical amplifier means optically coupled to said laser gain medium for amplifying the coherent eye-safe output lasant radiation; transmitter station means optically coupled to said optical amplifier means for transmitting the amplified output eye-safe lasant radiation over a path to illuminate a target; receiver means for receiving the output lasant radiation returned from the illuminated target; a single transverse mode fiber-optic waveguide optically coupled to said receiver means and disposed to receive and propagate therein as a single transverse mode returned and received output lasant radiation; combining means for combining the returned and received output lasant radiation as propagated over said single mode fiber-optic waveguide with reference coherent lasant optical radiation; and detecting means optically coupled to the combined optical radiation for detecting a difference frequency output signal therebetween representative of parameters associated with the illuminated target.

Claim 17

The laser radar of claim 14 wherein said optical resonator means includes a plurality of optically reflective facets of said solid state laser gain medium for internally reflecting the lasant radiation therefrom around a closed path to define a ring optical resonator.

Claim 18

The laser radar of claim 14 wherein said optical amplifier means includes a slab of solid state laser gain material having a pair of mutually opposed broad side walls between which the lasant radiation to be amplified is reflected back-and-forth in a zig-zag path; and optical pumping means for directing optical pumping radiation through at least one of said broad side walls into said slab of laser gain medium for optically pumping same.

Claim 19

The laser radar of claim 16 including means for directing the lasant radiation through said slab of optically pumped laser gain medium a plurality of times and over a plurality of side-by-side separate zig-zag optical paths for providing a plurality of stages of optical amplification, one stage for each of the separate optical paths.

Claim 20

The laser radar of claim 14 wherein said optical amplifier means includes an amplifying member of solid state laser gain material; optical pumping means for directing optical pumping radiation into said amplifying member of solid state laser gain material for optically pumping same; amplifying optical resonator means optically coupled to said amplifier gain member for resonating optical lasant radiation emanating from lasant energy transitions within said amplifier gain member and for coupling the resonated radiation into said amplifier laser gain member; and seeding means for coupling the output lasant radiation to be amplified into said optically pumped amplifier laser gain member for initiating amplification of said output lasant radiation.

Claim 21

The laser radar of claim 14 wherein said combining means includes a fiber-optic directional coupler for optically coupling the reference laser optical radiation into said single mode fiber-optic waveguide containing said returned output laser radiation such that both said reference and returned lasant radiation are propagated together in a common fiber-optic waveguide.

Claim 22

The laser radar of claim 14 including means for sampling the coherent output lasant radiation to derive the reference lasant radiation for being combined with the received lasant radiation.

Claim 23

The laser radar of claim 14 wherein said solid state laser gain medium includes a lasant ion selected from the group consisting of Er, Nd, Tm, Ho, Dy, Yb and U.

Claim 24

The laser radar of claim 14 wherein said laser gain medium includes an absorber ion selected from the group consisting of Tm, Er, Nd and U.

Claim 25

The laser radar of claim 14 wherein said solid state laser gain medium includes a host material selected from the group consisting of transparent oxide crystals, transparent fluoride crystals, transparent garnets, yttrium aluminum garnet, YAlO 3 and LiYF 4 .

Claim 26

The laser radar of claim 14 including: optical isolator means disposed to receive and pass the output lasant radiation emanating from said optically pumped laser gain medium onto said optical amplifier means and for attenuating output lasant radiation emanating from said optical amplifier means and travelling back toward said solid state laser gain medium.

Claim 27

The laser of claim 14 including a reference source of laser radiation.

Claim 28

The laser radar of claim 25 wherein said reference source of laser radiation is a semiconductive diode ring laser.

Claim 29

In a coherent laser radar: a solid state laser gain medium; optical pumping means for optically pumping said laser gain medium with optical pumping radiation emanating from a semiconductive diode; optical resonator means optically coupled to said laser gain medium for resonating lasant radiation emanating from said optically pumped laser gain medium to produce coherent output lasant radiation; optical amplifier means optically coupled to said laser gain medium for amplifying the coherent output lasant radiation; transmitter station means optically coupled to said optical amplifier means for transmitting the amplified output lasant radiation over a path to illuminate a target; receiver means for receiving the output lasant radiation return from the illuminated target; a single transverse mode fiber-optic waveguide optically coupled to said receiver means and disposed to receive and propagate therein as a single transverse mode the returned and received output lasant radiation; combining means for combining the returned and received output lasant radiation as propagated over said single mode fiber-optic waveguide with reference coherent lasant radiation; and detecting means optically coupled to the combined optical radiation for detecting a difference frequency output signal therebetween representative of parameters associated with the target.

Claim 30

In a coherent laser radar: a solid state laser gain medium; optical pumping means for optically pumping said laser gain medium with optical pumping radiation emanating from a semiconductive diode; optical resonator means optically coupled to said laser gain medium for resonating lasant radiation emanating from said optically pumped laser gain medium to produce coherent output lasant radiation; optical amplifier means optically coupled to said laser gain medium for amplifying the coherent output lasant radiation; transmitter station means optically coupled to said optical amplifier means for transmitting the amplified output lasant radiation over a path to illuminate a target; receiver means for receiving the output lasant radiation return from the illuminated target; a single transverse mode fiber-optic waveguide optically coupled to said receiver means and disposed to receive and propagate therein as a single transverse mode the returned and received output lasant radiation; combining means for combining the returned and received output lasant radiation as propagated over said single mode fiber-optic waveguide with reference coherent lasant radiation; and detecting means optically coupled to the combined optical radiation for detecting a difference frequency output signal therebetween representative of parameters associated with the target.