Laser Phasing System Using Diffractive Optical Element
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current coherent recombination techniques for high-power and high-energy laser sources face limitations due to resistance issues in gain media, requiring complex phase-locking and calibration processes, which are costly and inefficient, especially when dealing with a large number of laser beams.
Innovation Solution
A system using a diffractive optical element (DOE) for spatial recombination of laser beams, generating a vector error signal from higher-order diffraction intensities to optimize phase locking without RF components and calibration, allowing for a simple feedback signal calculation using a matrix product of detected intensities and Fourier series expansion coefficients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional coherent recombination techniques are used with a large number of laser beams, then phase-locking can be achieved, but the system complexity and calibration requirements increase significantly
Solution Approach 1:
The system uses the recombined beams themselves to generate the error signal through diffractive ordering, eliminating the need for external reference beams and complex calibration procedures. The higher-order diffracted beams automatically provide feedback about phase alignment quality.
Solution Approach 2:
The error signal is extracted from the higher-order diffracted beams produced by the diffractive optical element, rather than requiring separate measurement systems or reference beams. This extracts useful phase information directly from the recombination process itself.
2Measurement precision
If RF components are used for phase measurement in each channel, then phase information can be obtained, but the cost per channel increases
Solution Approach 1:
Multiple phase measurements are combined into a single spatial pattern through the diffractive optical element. Instead of requiring separate RF measurement systems for each channel, the phases are merged into the spatial distribution of diffracted orders, which can be measured more simply.
Solution Approach 2:
The patent replaces complex RF measurement systems with an optical diffractive system. The phase information is obtained through optical diffraction patterns rather than electrical RF measurements, eliminating the need for expensive RF components in each channel.
3Measurement precision
If sequential time modulation is used to modulate each beam, then phase information can be obtained, but the system bandwidth is reduced
Solution Approach 1:
The system uses periodic diffractive ordering with a frequency of several kHz to encode phase information from multiple beams simultaneously. This periodic optical action replaces sequential time modulation, maintaining high bandwidth while capturing phase data from all channels.
4Shape
If far-field recombination is used, then beam parallel propagation is achieved, but secondary lobes are generated reducing efficiency
Solution Approach 1:
The diffractive optical element acts as an intermediary between the individual beams and the final recombined output. It mediates the interference pattern to concentrate energy in the desired central lobe while suppressing secondary lobes, achieving both proper beam shaping and high efficiency.
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
Enables efficient coherent recombination of multiple laser beams with a bandwidth greater than 1kHz, supporting up to 1000 or more beams without calibration, at a lower cost and with improved beam quality, by directly optimizing recombined intensity in the recombination plane.
Implementation Method 1
a recombination diffractive optical element (DOE) with a phase grating of predetermined spatial period... Each beam arrives on the DOE with a specific angle of incidence defined by the spatial period of the DOE
Implementation Method 2
Once phase-locked, the M emerging laser beams interfere constructively and thus constitute a source of luminance M times greater than that of an elementary amplifier
Implementation Method 3
a Fourier lens having an object plane in which the exit plane of the laser sources is located and an image plane in which the recombination diffractive optical element is located
Data Source
Figure 1~3a
Figure 2
Figure 3b
AI summary
The invention relates to a system for phasing laser sources with a periodic configuration, the system comprising: means for collimating and directing the beams coming from sources onto a recombination diffractive optical element (1) having a periodic phase network, with an angle of incidence which differs from one beam to another, these angles of incidence being determined on the basis of the network period; means of controlling the phases of the sources on the basis of a counter-reaction signal coming from the recombined beams; means (5) for sampling a fraction (12) of the recombined beams; on the path of this beam fraction, a Fourier lens (6), with the recombination diffractive optical element (1) disposed in its object plane; a detector matrix (7) in the image plane of the Fourier lens (6), capable of detecting intensity distribution; and means (8) for calculating the counter-reaction signal on the basis of these intensity distributions.