Fiber ASE Source Speckle Suppression via Large Core Multimode Design
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Solution Overview
Problem
Conventional amplified spontaneous emission (ASE) sources with high spatial coherence introduce undesirable artifacts like speckle in full-field imaging applications, while low spatial coherence sources lack the required power per mode for high-speed imaging, and existing low spatial coherence lasers have narrow bandwidth emission, precluding use in OCT or LiDAR applications.
Innovation Solution
A fiber-based ASE source with low spatial and temporal coherence is achieved by optically pumping a large gain core multimode fiber to minimize optical feedback, resulting in a source that emits radiation distributed among many spatial modes, providing high power per mode and efficient speckle suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional ASE sources with high spatial coherence are used, then high power per mode is achieved, but speckle artifacts are introduced in full-field imaging
Solution Approach 1:
The patent changes the spatial coherence parameter of the ASE source by using a large core multimode fiber (e.g., 100 μm core diameter) to support many transverse modes. This parameter change distributes the optical power across multiple spatial modes, reducing the coherence area and eliminating speckle artifacts while maintaining high total power output suitable for full-field imaging
2Object-generated harmful factors
If low spatial coherence sources such as LEDs are used, then speckle is suppressed, but power per mode is insufficient for high-speed imaging
Solution Approach 1:
The patent merges the advantages of two different light sources: the low spatial coherence and speckle suppression characteristics of LED sources are combined with the high power per mode capability of laser sources. This is achieved by using a large core multimode fiber ASE source that distributes power across many transverse modes, achieving both speckle-free operation and high total power output
3Object-generated harmful factors
If existing low spatial coherence lasers are used, then speckle-free imaging is achieved, but bandwidth is narrow precluding use in OCT or LiDAR
Solution Approach 1:
The patent changes the bandwidth parameter by using broadband pump sources (such as supercontinuum lasers or broad-LEDs) to pump the large core multimode fiber. This enables the ASE source to emit over a broad spectral range (e.g., 800-1600 nm), providing both low spatial coherence for speckle-free imaging and sufficient bandwidth for OCT and LiDAR applications
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 fiber ASE source offers speckle-free full-field imaging and is suitable for both high-speed imaging and ranging applications, combining high power per mode with low spatial and temporal coherence, outperforming traditional sources in terms of speckle suppression and imaging quality.
Implementation Method 1
amplified spontaneous emission (ASE) sources
Implementation Method 2
the gain core being configured to emit radiation at at least a peak wavelength emitted wavelength when pumped with pump radiation
Implementation Method 3
the pump core being configured to substantially confine radiation of the peak emitted wavelength within the gain core
Implementation Method 4
the cladding being configured to substantially confine radiation of the pump wavelength within the pump core and the gain core
Implementation Method 5
the gain core being doped with a rare earth element
Data Source
AI summary
The present disclosure relates more particularly to active optical fibers, amplified spontaneous emission (ASE) sources using such active optical fibers, and imaging and detection systems and methods using such ASE sources. In one aspect, the disclosure provides an active optical fiber that includes a rare earth-doped gain core configured to emit radiation at at least a peak wavelength emitted wavelength when pumped with pump radiation having a pump wavelength; a pump core surrounding the gain core; and a cladding surrounding the pump core, wherein the value M=16R2(NA)2/λ2 in which R is the gain core radius, NA is the active optical fiber numerical aperture, and λ is the peak emitted wavelength, is at least 50, or at least 100. The present disclosure also provides an optical source that includes the optical fiber coupled to a pump source.