Laser Power Sensor Using Rayleigh Scattering
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Solution Overview
Problem
Current power sensor units for fiber lasers face challenges in reliably detecting Rayleigh scattered light due to its non-directional nature, leading to inefficient power measurement and increased losses, which affects the reliability and efficiency of the laser system.
Innovation Solution
A power sensor unit with a recessed case and a matte, gilded reflective surface configured to focus Rayleigh radiation onto a photodiode's focal plane, ensuring effective collection and measurement of scattered light, while being hermetically sealed to maintain stability and resist environmental factors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If beam splitters are used to detect optical power, then power measurement is enabled, but power losses increase and heat generation occurs
Solution Approach 1:
The invention extracts only the necessary portion of light for measurement by detecting Rayleigh scattered light in the fiber core, rather than using beam splitters to tap off a predetermined portion of the light beam. This allows power measurement while minimizing power losses in the transmitted light beam.
Solution Approach 2:
The invention uses Rayleigh scattered light as an intermediary to enable power measurement. By detecting the scattered light that naturally occurs in the fiber, the system can measure power without directly intercepting the main beam, thus avoiding the power losses associated with beam splitters.
2Measurement precision
If beam splitters are used to detect optical power, then power measurement is enabled, but heat generation increases and reliability decreases
Solution Approach 1:
The invention extracts only the necessary portion of light for measurement by detecting Rayleigh scattered light in the fiber core, rather than using beam splitters to tap off a predetermined portion of the light beam. This allows power measurement while minimizing power losses in the transmitted light beam.
Solution Approach 2:
The invention uses Rayleigh scattered light as an intermediary to enable power measurement. By detecting the scattered light that naturally occurs in the fiber, the system can measure power without directly intercepting the main beam, thus avoiding the power losses associated with beam splitters.
3Measurement precision
If Rayleigh scattered light is detected using known detectors, then power measurement is attempted, but detection reliability is insufficient due to non-directional scattering
Solution Approach 1:
The invention transitions from attempting to detect scattered light in three-dimensional space around the fiber to detecting light in a two-dimensional cross-sectional plane through the fiber core. By using a detector positioned to receive light transmitted through the fiber core, the system captures the spatial distribution of Rayleigh scattered light in a plane perpendicular to the propagation direction, enabling reliable detection despite the non-directional nature of Rayleigh scattering.
Solution Approach 2:
The invention replaces traditional mechanical beam sampling methods with optical field analysis. Instead of using physical beam splitters or external detectors positioned to catch scattered light, the system uses the fiber core itself as the detection medium by analyzing the spatial distribution of light intensity in a cross-sectional plane, thereby achieving reliable detection of Rayleigh scattered light.
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 solution achieves reliable and repeatable power measurement with a deviation of less than ±3% from certified values, significantly improving the accuracy and stability of fiber laser systems by minimizing additional power losses and enhancing resistance to environmental factors.
Implementation Method 1
light which, while being guided along a fiber by means of a core
Implementation Method 2
The most pronounced type of linear scattering - Rayleigh scattering - can be caused by the existence of tiny dielectric inconsistencies in the glass. Because these perturbations are small with respect to the waves being propagated, light striking a Rayleigh imperfection scatters in all directions.
Implementation Method 3
a photodiode, i.e., a detector configured to sense light which, while being guided along a fiber by means of a core, is scattered in accordance with a Rayleigh mechanism
Data Source
Figure 1A~2
Figure 3A~3B
Figure 4A~4B
AI summary
A sensor unit for detecting Rayleigh scattering of laser light, guided in a fiber along a light path, is configured with a holder. The holder has a U- shaped recess centered along an axis which extends transversely to the light path. The curved bottom of the recess has a matte reflective surface and is configured with such a radius of curvature that Rayleigh scattered light indicated on the bottom is collected in a focal plane of a light input window of a meter coaxial with the recess. The reflected amount of the Rayleigh scattering on the light input window is sufficient to provide a measurement data which deviates from a reference value at no more than about ±3%.