Coherent photonics imager with optical carrier suppression and phase detection capability

Patent metadata

Field	Value
Publication number	US-12392873-B2
Application number	US-202217726867-A
Country	US
Kind code	B2
Filing date	Apr 22, 2022
Priority date	Apr 22, 2021
Publication date	Aug 19, 2025
Grant date	Aug 19, 2025

Abstract

A coherent imaging system including a transmitter and a receiver. The transmitter includes a coherent source and a power splitter for splitting the electromagnetic radiation into a reference and a signal beam. The receiver includes an image forming device and an array of pixels. Each of the pixels include means for collecting at least a portion of the signal beam imaged on the pixel by an image forming device, as a collected signal; means for splitting the collected signal into a plurality of collected signals each having different phase shifts; means for mixing each of the collected signals with the reference beam so as to form a plurality of mixed signals; and means for detecting the mixed signals and outputting a plurality of output electrical signals in response to the mixed signals.

First claim

What is claimed is:

1. A coherent imaging system, comprising:
a transmitter comprising:
a coherent source of electromagnetic radiation;
a power splitter for splitting the electromagnetic radiation into a reference and a signal beam transmitted to a target; and

a receiver positioned to receive the signal beam reflected from, or transmitted through, the target, the receiver comprising:
an image forming device; and
an array of pixels, each of the pixels comprising:
a capture area for collecting a portion of the signal beam imaged on the capture area by the image forming device, as a collected signal;
a plurality of waveguides distributing the reference and the collected signal, along a plurality of paths, to a plurality of couplers, wherein:
the collected signals in different paths have different phase shifts; and
each of the couplers mix the reference with a different one of the collected signals having a different one of the phase shifts so as to form a plurality of mixed signals; and

a plurality of detectors coupled to outputs of the couplers so as to detect each of the mixed signals and output a plurality of output signals in response thereto.

2. The coherent imaging system of claim 1 , wherein:
the couplers comprise a first coupler and a second coupler;
the collected signals comprise a first signal and a second signal having the phase shift of 90 degrees relative the first signal;
the mixed signals comprise a first mixed signal and a second mixed signal;
the first coupler mixes the first signal with the reference to form the first mixed signal comprising an in-phase signal;
the second coupler mixes the second signal with the reference to form the second mixed signal comprising a quadrature signal; and
the detectors comprise a first detector detecting the in-phase signal and a second detector detecting the quadrature signal.

3. The coherent imaging system of claim 2 , further comprising a circuit summing the squares of the output signals.

4. The coherent imaging system of claim 1 , wherein:
the collected signals comprise a first signal, a second signal having the phase shift of a first angle relative to the first signal; a third signal having the phase shift of a second angle relative to the first signal; and a fourth signal having the phase shift of a third angle relative to the first signal;
the couplers comprise a first coupler, a second coupler, a third coupler, and a fourth coupler outputting the mixed signals comprising a first mixed signal, a second mixed signal, a third mixed signal, and a fourth mixed signal; and
the detectors comprise a first detector detecting the first mixed signal, a second detector detecting the second mixed signal, a third detector detecting the third mixed signal, and a fourth detector detecting the fourth mixed signal.

5. The coherent imaging system of claim 1 , wherein the transmitter and the receiver share an aperture, so that:
the signal beam is transmitted to the target from the transmitter through the aperture, and
the signal beam is received in the receiver through the aperture.

6. The coherent imaging system of claim 5 , wherein the transmitter and the receiver comprise the aperture sharing optical antennas, so that the optical antennas transmit the signal beam to the target and the optical antennas receive the signal beam from the target.

7. The coherent imaging system of claim 5 , wherein the transmitter and receiver comprise the aperture sharing an optical beamforming system, so that the optical beamforming system forms:
the signal beam transmitted from the transmitter onto the target, and
the signal beam received from the target onto the pixels.

8. The coherent imaging system of claim 1 , wherein:
the receiver further comprises an electrical control circuit, the electrical control circuit biasing the pixels so as to:
select readout of the output signals from one or more selected rows of the pixels, and
de-activate the readout from the remaining rows of the pixels.

9. The system of claim 8 , wherein:
the pixels are disposed in rows and columns;
the electrical control circuit comprises:
a plurality of common row bias lines coupled to each of the pixels in one or more of the rows; and
a plurality of common column bias lines coupled to each of the pixels in one or more of the columns;

each of the pixels further comprise:
each of the detectors comprising two balanced photodiodes connected in series between a pair of the common row bias lines;
protection resistors in parallel with the photodiodes and between the pair of the common row bias lines;

at least one diode, comprising an anode and a cathode, connected in series with an output from the photodiodes; and
wherein:
the pair of common row bias lines bias the photodiodes in reverse bias and set a voltage of the anode; and
the common column bias lines bias the cathode;
so that:
the diodes in the selected rows are forward biased for the readout of the output signals from the one or more selected rows; and
the diodes in the remaining rows are reverse biased.

10. The system of claim 1 , wherein the receiver further comprises a splitter only distributing the reference to one or more selected rows of the pixels so as to select readout of the output signals from the one or more selected rows of the pixels and de-activate readout from the remaining rows of the pixels.

11. The system of claim 10 , wherein the splitter comprises one or more interferometers, each of the interferometers comprising:
a first branch having a first output and an input for receiving the reference;
a second branch having a second output;
a first coupler coupling the first branch and the second branch;
a second coupler coupling the first branch and the second branch, wherein the second branch is positioned in series with the first branch; and
a voltage tunable modulator coupled to the first branch or the second branch, the voltage tunable modulator controlling a relative phase of the reference in at least one of the first branch or the second branch, in response to a voltage signal inputted to the voltage tunable modulator, so as to control a relative power of the reference outputted at the first output and the second output.

12. The system of claim 11 , wherein:
the splitter further comprises a reference detector coupled to the interferometer, the reference detector outputting a current signal monitoring a fraction of the relative power of the reference at the first output or the second output; and
the system further comprising a power distribution circuit controlling the voltage signal using the current signal as feedback.

13. The system of claim 12 , wherein:
the splitter comprises a plurality of the interferometers comprising cascaded interferometers,
the interferometers are distributed in M layers, such that the first output and the second output of the one or more interferometers, in a previous one of the layers, are each fed to the input of a different one of the interferometers in a next one of the layers, allowing splitting of the reference, inputted to the input of the interferometer in a first one of the layers, to N outputs comprising the first outputs and second outputs of the interferometers in the last one of the layers; and
the voltage signals required for allocating the power to the N=2 M outputs are calibrated for M layers, by the power distribution circuit, for each of the interferometers in the j layers 1≤j≤M, starting with j=1:
(a) recording the voltage signals applied to each of the interferometers in the j th layer, and the sum of the current signals outputted from all the interferometers in t

Assignees

• California Inst Of Techn

Inventors

• Khachaturian Aroutin
• Abiri Behrooz
• Fatemi Seyed Mohammadreza
• Hajimiri Seyed Ali

Classifications

• H10F39/813

  Electronic components shared by multiple pixels, e.g. one amplifier shared by two pixels · CPC title

• H10F39/806

  Optical elements or arrangements associated with the image sensors · CPC title

• H10F39/18

  Complementary metal-oxide-semiconductor [CMOS] image sensors; Photodiode array image sensors · CPC title

• H04N23/56

  provided with illuminating means · CPC title

• H01S3/0007

  Applications not otherwise provided for (working metals or other materials by laser beam B23K26/00; using photons to produce a reactive propulsive thrust F03H3/00; optical recording of measured values in general G01D15/14; optics in general G02B; holographic processes or apparatus G03H; optical marking or sensing of data record carriers G06K7/10 - G06K7/14, G06K15/12; injection heating of plasma by laser H05H1/22; acceleration of neutral particles by electromagnetic wave pressure H05H3/04) · CPC title