# US 9,329,381 B1 · Target feature integrated laser field and amplifier compensation system

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- Number: US 9,329,381 B1
- Document ID: US9329381B1
- Status: Granted
- Kind: B1
- Application number: 14/069,024
- Filed: 2013-10-31
- Granted: 2016-05-03
- Earliest claimed: 2009-12-10
- Assignees: Nutronics, Inc.
- Applicants: Jeffrey D Barchers
- Inventors: Jeffrey D Barchers
- Web page: https://patentgrep.com/patent/US9329381B1

## CPC

- G02B 23/12: with means for image conversion or intensification
- G01B 9/02: Interferometers
- G01B 11/02: for measuring length, width or thickness (G01B11/08 takes precedence)
- G01B 11/24: for measuring contours or curvatures
- G01J 1/20: intensity of the measured or reference value being varied to equalise their effects at the detectors, e.g. by varying incidence angle
- G01J 9/00: Measuring optical phase difference (devices or arrangements for controlling the phase of light beams G02F1/01); Determining degree of coherence; Measuring optical wavelength (spectrometry G01J3/00)
- G01J 9/02: by interferometric methods (using interferometers for measuring optically the linear dimensions of objects G01B9/02)
- G01J 9/0246: {Measuring optical wavelength}
- G01S 7/4814: {of transmitters alone}
- G01S 7/497: Means for monitoring or calibrating
- G01S 17/66: Tracking systems using electromagnetic waves other than radio waves
- G02B 26/06: for controlling the phase of light (G02B26/08 takes precedence {, measuring optical phase difference G01J9/00})
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01J: MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources F21, H01J, H01K, H05B; investigating properties of materials by optical means G01N)
- G01S: RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES

## Abstract

An Integrated Laser Field and Amplifier Compensation System (ILFACS) for end-to-end compensation of high-energy laser for propagation through turbulence with non-cooperative target are described. ILFACS using interferometric slaving technique and stand-alone adaptive optical systems to effect pre-compensation of amplitude and phase aberrations in turbulent medium, providing pre-compensation for aberrations in a laser amplifier is presented. ILFACS enables integration with a short pulse mode locked laser for use in Target Feature Adaptive Optics (TFAO) or with a mode locked ultra short pulse laser with carrier envelope phase stabilization for use in Broadband Coherent Adaptive Optics (BCAO).

## Claims

### Claim 1

An electro-optical system for projection of laser beams through a turbulent medium to a non-cooperative target, the system comprising:
a) a master oscillator beam having an optical path to an amplifier means;
b) said amplifier means forming a high energy laser (HEL) beam to a target via an optical path;
c) said optical path including a steering mirror and a telescope;
d) a mode locked beacon master oscillator that produces a majority beacon beam comprising a high repetition rate (ranging from about 100 to 100000 Hz) sequence of transform limited pulsed laser beams and producing a minority reference beam that has a repetition rate defined by the cavity length of the mode locked beacon master oscillator (ranging typically from MHz to GHz);
e) wherein a timing delay circuit receives the minority reference beam and produces a delayed reference beam that is delayed to coincide with the arrival of a return beacon beam from a target aimpoint along a propagation path axis;
f) said majority beacon beam transmitted via an optical path to a medium power amplifier which sends the majority beacon beam via an optical path to the target;
g) wherein a return beacon beam comprising a high repetition rate pulse train beam returns from the target through the turbulent medium, telescope, optical path, and a quarter waveplate in the optical path, then passes through a first polarizing wave splitter optic;
h) wherein the return beacon beam is then directed to a first beacon wave front sensor (WFS) where it is combined with the minority reference beam to form a composite beam for phase measurement;
i) said first WFS controlling a first phase correction and steering device pair which (1) corrects the majority beacon beam with respect to phase aberrations caused by propagation through the turbulent medium and (2) provides phase commands to the first phase correction and steering device pair that will result in correction of amplitude aberrations in the beacon beam caused by propagation through the turbulent medium;
j) a tracker and aim point controller which receives an image of the target from an illumination source, thereby generating a control signal to control the steering mirror;
k) a third WFS (no second WFS is named) receives a sample beam from the minority master oscillator beam after it passes through a spatial filter optic and the fourth correction and steering device pair to compare to a sample of the majority master oscillator beam after it passes through an optical path including a propagation optics and the third correction and steering device pair (no second correction and steering device par is named);
l) said third WFS controlling a fourth correction and steering device pair to correct for aberrations induced by propagation through the third phase correction and steering device pair and propagation optics;
m) a fifth WFS receiving a HEL amplifier probe beam after it passes through the amplifier means; and
n) said fifth WFS controlling a fifth correction and steering device pair.

### Claim 2 (depends on 1)

The system of claim 1, wherein the first and fourth pair of phase correction and steering device pairs are optically conjugate to one another.

### Claim 3 (depends on 1)

The system of claim 1, wherein the third pair of phase correction and steering device pairs have a free space propagation distance (from the conjugate plane of the first and fourth phase correction and steering device pairs) of approximately:
−D2/λN
where D is the beam size, X is the wavelength and N is the number of phase correction device actuator spacings across the beam.

### Claim 4 (depends on 1)

The system of claim 1, wherein the beacon beam is formed as a cooperative beacon located at the target and pointed toward the transmitting HEL optical path.

### Claim 5 (depends on 1)

The system of claim 1, wherein the beacon beam is formed as an illuminator beam launched from an auxiliary telescope to illuminate the target, and the reflection from the target serves as the beacon beam.

### Claim 6 (depends on 1)

The system of claim 1, wherein the beacon beam is a solar illumination of the target.

### Claim 7 (depends on 1)

The system of claim 1, wherein the beacon beam is a thermal emission of the target.

### Claim 8 (depends on 1)

The system of claim 1, wherein the amplifier means is an injection locked laser resonator.

### Claim 9 (depends on 1)

The system of claim 1, wherein the image of the target is formed as a cooperative beacon located at the target and pointed toward the transmitting HEL optical path.

### Claim 10 (depends on 1)

The system of claim 1, wherein the image of the target received by the aim point controller is either a passive or active illumination of the target.

### Claim 11 (depends on 1)

The system of claim 1, wherein a sixth WFS receives a beacon amplifier probe beam after it passes through a beacon medium power amplifier and also receives a sample beam from the beacon amplifier probe beam.

### Claim 12 (depends on 11)

The system of claim 11, wherein the sixth WFS controls a sixth correction and steering device pair.

### Claim 13 (depends on 1)

The system of claim 1, wherein the amplifier means is a high power laser amplifier.

### Claim 14 (depends on 1)

The system of claim 1, wherein the amplifier means is an injection locked laser amplifier.

### Claim 15 (depends on 1)

The electro-optical system of claim 1, wherein a first part of the composite beam is directed to a half waveplate that rotates the polarization of the composite beam by 45 degrees and then to a polarizing beam splitter that directs the resultant interference patterns to a first and second camera with the resulting measurements being used to compute an estimate of a real part of a measured complex field of the return beacon beam.

### Claim 16 (depends on 1)

The electro-optical system of claim 1, wherein a second part of the composite beam is directed first to a quarter waveplate with its crystal axis aligned to the polarization axis of the minority reference beam and then to a half waveplate that rotates the polarization of the composite beam by 45 degrees and then to a polarizing beam splitter that directs the resultant interference patterns to a third and fourth camera with the resulting measurements being used to compute an estimate of an imaginary part of a measured complex field of the return beacon beam.

### Claim 17 (depends on 1)

The electro-optical system of claim 1, wherein the minority reference beam and the return beacon beam are at orthogonal polarizations to one another.

### Claim 18 (depends on 1)

The electro-optical system of claim 1, wherein the first and second WFS consists of a π/3 waveplate, a 5/3π waveplate, and a π waveplate each associated with a separate camera and can be aligned to the axis of polarization of the minority reference beam.

### Claim 19

An electro-optical system for projection of laser beams through a turbulent medium to a non-cooperative target, the system comprising:
a) a mode locked beacon master oscillator that produces a majority beacon beam comprising a high repetition rate (ranging from about 100 to 100000 Hz) sequence of transform limited pulsed laser beams (a beacon beam) and producing a minority reference beam that has a repetition rate defined by the cavity length of the mode locked beacon master oscillator (ranging typically from MHz to GHz);
b) said mode locked beacon master oscillator beam having an optical path to an amplifier means;
c) said amplifier means forming a high energy laser (HEL) beam to a target via an optical path;
d) said optical path including a steering mirror and a telescope;
e) wherein a timing delay circuit receives the minority reference beam and produces a delayed reference beam that is delayed to coincide with the arrival of a return beacon beam from a target aimpoint along a propagation path axis;
f) said majority beacon beam transmitted via an optical path to a medium power amplifier which sends the majority beacon beam via an optical path to the target;
g) wherein a return beacon beam comprising a high repetition rate pulse train beam returns from the target through the turbulent medium, telescope, optical path, and a quarter waveplate in the optical path, then passes through a first polarizing wave splitter optic;
h) wherein the return beacon beam is then directed to a first beacon wave front sensor (WFS) where it is combined with the minority reference beam to form a composite beam for phase measurement;
i) said first WFS controlling a first phase correction and steering device pair which (1) corrects the beacon beam with respect to phase aberrations caused by propagation through the turbulent medium and (2) provides phase commands to the first phase correction and steering device pair that will result in correction of amplitude aberrations in the beacon beam caused by propagation through the turbulent medium;
j) a tracker and aim point controller which receives an image of the target from an illumination source, thereby generating a control signal to control the steering mirror;
k) a third WFS (no second WFS is named) receives a sample beam from the minority reference beam after it passes through a spatial filter optic and the fourth correction and steering device pair to compare to a sample of the majority beacon beam after it passes through an optical path including a propagation optics and the third correction and steering device pair (no second correction and steering device par is named);
l) said third WFS controlling a fourth correction and steering device pair to correct for aberrations induced by propagation through the third phase correction and steering device pair and propagation optics;
m) a fifth WFS receiving a HEL amplifier probe beam after it passes through the amplifier means; and
n) said fifth WFS controlling a fifth correction and steering device pair.

### Claim 20 (depends on 19)

The system of claim 19, wherein the first and fourth pair of phase correction and steering device pairs are optically conjugate to one another;
wherein the third pair of phase correction and steering device pairs have a free space propagation distance (from the conjugate plane of the first and fourth phase correction and steering device pairs) of approximately:
−D2/λN
where D is the beam size, λ is the wavelength and N is the number of phase correction device actuator spacings across the beam;
wherein the image of the target is formed as a cooperative beacon located at the target and pointed toward the transmitting HEL optical path; and
wherein the image of the target received by the aim point controller is either a passive or active illumination of the target.

### Claim 21 (depends on 19)

The system of claim 19, wherein the amplifier means is a high power laser amplifier.

### Claim 22 (depends on 19)

The system of claim 19, wherein the amplifier means is an injection locked laser amplifier.

### Claim 23 (depends on 19)

The system of claim 19, wherein a first part of the composite beam is directed to a half waveplate that rotates the polarization of the composite beam by 45 degrees and then to a polarizing beam splitter that directs the resultant interference patterns to a first and second camera with the resulting measurements being used to compute an estimate of a real part of a measured complex field of the return beacon beam;
wherein a second part of the composite beam is directed first to a quarter waveplate with its crystal axis aligned to the polarization axis of the minority reference beam and then to a half waveplate that rotates the polarization of the composite beam by 45 degrees and then to a polarizing beam splitter that directs the resultant interference patterns to a third and fourth camera with the resulting measurements being used to compute an estimate of an imaginary part of a measured complex field of the return beacon beam;
wherein the minority reference beam and the return beacon beam are at orthogonal polarizations to one another; and
wherein the first and second WFS consists of a π/3 waveplate, a 5/3π waveplate, and a π waveplate each associated with a separate camera and can be aligned to the axis of polarization of the minority reference beam.