Coherent Beam Combining Using Calibration Laser Phase Control
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Solution Overview
Problem
High-power fiber lasers face challenges in achieving coherent superposition of laser beams due to phase fluctuations during switching on and environmental factors like turbulence, which complicates measurement and control, especially when irradiating distant targets.
Innovation Solution
A laser beam apparatus using a calibration laser source with a different wavelength from the effective laser source, allowing phase determination and adjustment through calibration laser radiation, enabling coherent superposition by controlling phase shifters based on calibration laser light phases, even before switching on the effective laser.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high-power fiber lasers are used to achieve high output power, then the laser can irradiate distant targets effectively, but phase fluctuations occur during switching on which cause large fluctuations in performance and require very high dynamics in measurement and control
Solution Approach 1:
The patent applies preliminary action by performing phase measurement and control using a calibration laser source before switching on the high-power effective laser. The system measures phase changes in the amplifier paths and adjusts phase shifters in advance, so that when the effective laser is activated, the coherent superposition is already established, avoiding performance fluctuations during switching.
2Length of stationary object
If high-power fiber lasers are used to irradiate distant targets, then the effective laser radiation can reach the target, but phase changes along the propagation path caused by turbulence add to the phase changes in the apparatus, complicating control
Solution Approach 1:
The patent uses a calibration laser source as an intermediary to measure phase changes in the amplifier paths. This calibration laser operates at a different wavelength and allows indirect measurement of phase changes without being affected by the high power and luminous phenomena of the effective laser. The measured phase changes are then used to adjust phase shifters, compensating for both apparatus-induced and turbulence-induced phase changes.
3Measurement precision
If the effective laser is switched on to measure phase on target, then phase information can be obtained, but a luminous phenomenon occurs on the target due to high intensity which negatively influences the evaluation of intensity on target
Solution Approach 1:
The calibration laser source serves as an intermediary measurement tool that operates at a different wavelength from the effective laser. It allows phase measurement on the target without producing the intense luminous phenomenon that interferes with evaluation. The calibration laser's lower power and different wavelength enable clean phase evaluation while the effective laser remains off during measurement.
4Measurement precision
If indirect measurements are performed to determine phase by evaluating intensity of superposition, then phase information can be obtained, but when using high-power fiber lasers the output power varies greatly placing very high demands on the dynamics of evaluation
Solution Approach 1:
The calibration laser source acts as an intermediary that enables phase determination without the complications of high-power laser operation. By using the calibration laser to measure phase changes in the amplifier paths, the system avoids the great output power variations and luminous phenomena associated with the effective laser, thereby reducing the demands on evaluation dynamics while maintaining measurement precision.
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 coherent superposition of laser beams with reduced control dynamics demands, compensating for phase changes caused by turbulence and luminous phenomena, ensuring precise laser irradiation on both nearby and distant targets.
Implementation Method 1
a calibration laser source (20) for producing calibration laser radiation, wherein the wavelength of the calibration laser radiation deviates from the wavelength of the effective laser radiation
Implementation Method 2
the laser beam apparatus is designed in such a way that at least a portion of the calibration laser radiation produced by the calibration laser source can be divided and/or deflected into the first and second amplifier paths at the beam directing and/or beam splitting device
Implementation Method 3
a particular amplifier path comprises a wavelength-dependent coupling-out element for coupling out at least a portion of the calibration laser light
Implementation Method 4
at least one amplifier path comprises at least one shifter for shifting the phase of laser radiation, and the at least one shifter for shifting the phase can be controlled as a function of the phase of the calibration laser light of the first amplifier path and/or the calibration laser light of the second amplifier path
Data Source
AI summary
A laser beam apparatus for irradiating a target object and a method for operating such a laser beam apparatus. According to an example, at least two laser beams are made coherent.