Coherent Photonics Imager with Phase Detection and Laser Noise Suppression
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Solution Overview
Problem
Traditional image sensors suffer from dark current noise and electrical read noise, and coherent imagers face challenges with noise from laser source imperfections and high interconnect density, requiring improved signal acquisition time and channel isolation.
Innovation Solution
A coherent imaging system with a transmitter and receiver array of pixels, utilizing a power splitter and phase-shifted couplers to mix reference and collected signals, and detectors to suppress noise and reduce interconnect density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If heterodyne detection is used in coherent imagers, then signal sensitivity and resolution are improved, but noise from laser source imperfections increases and signal acquisition time increases
Solution Approach 1:
The patent converts the harmful effect of laser phase noise into a useful measurement signal by using a balanced detector to measure the differential phase between signal and reference beams. The laser noise that would normally interfere with detection is transformed into the carrier signal itself, allowing the system to measure target phase information while the laser noise cancels out in the differential measurement.
Solution Approach 2:
The patent introduces a reference beam as an intermediary that carries the same laser phase noise as the signal beam. By mixing the signal beam and reference beam in a balanced detector, the laser noise acts as a common-mode signal that can be rejected, while the target information encoded in the signal beam phase is preserved and measured.
2Measurement precision
If heterodyne detection is used in coherent imagers, then signal sensitivity and resolution are improved, but signal acquisition time increases
Solution Approach 1:
The patent converts laser phase noise from a harmful interference into the carrier signal itself. By using the laser's own phase fluctuations as the modulation carrier, the system achieves shot-noise-limited sensitivity without requiring long integration times to average out laser noise, thereby reducing signal acquisition time.
3Adaptability or versatility
If integrated photonics platforms are used, then complex signal processing capability is improved, but interconnect density increases
Solution Approach 1:
The patent merges the local oscillator generation, signal mixing, and detection functions into a single integrated photonic pixel. The Mach-Zehnder interferometer integrates the reference beam generation and mixing paths, while the balanced detector integrates both detection channels, reducing the need for separate interconnects for reference beam distribution and signal routing.
Solution Approach 2:
The integrated photonic pixel performs multiple functions within a single device: it generates the reference beam, mixes the signal and reference beams, and detects both in-phase and quadrature components. This multi-functionality reduces the overall interconnect density by eliminating the need for separate components and interconnects for each function.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system achieves reduced noise and interconnect density, enabling faster signal acquisition and improved sensitivity, allowing for high-resolution imaging with reduced laser noise interference.
Implementation Method 1
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
Implementation Method 2
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
Data Source
AI summary
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.