Planar Waveguide Amplifier Layout for ASE Suppression
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Solution Overview
Problem
Conventional planar waveguide amplifiers suffer from reduced signal-to-noise ratio due to amplified spontaneous emission (ASE) caused by excitation of portions within the waveguide that do not pass signal light, leading to inefficient energy conversion and parasitic oscillations.
Innovation Solution
A planar waveguide amplifier design where signal and pumping light propagate in opposite directions within the core, allowing the core to absorb scattered light and ASE in areas not traversed by the signal, using rare-earth elements as active ions in a three-level system to enhance amplification efficiency and suppress ASE.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the entire core in the planar waveguide is excited by pumping light, then the signal light can be amplified, but the efficiency of converting pumping light energy to useful amplification energy decreases
Solution Approach 1:
The patent applies local quality by creating different excitation states in different regions of the core. The signal light path region is excited to provide amplification, while the non-signal light path region remains unexcited or less excited to avoid ASE generation. This spatial differentiation of excitation quality resolves the contradiction by concentrating pumping energy only where needed for signal amplification.
Solution Approach 2:
The core is effectively segmented into two functional regions: a signal light path region that is excited for amplification and a non-signal light path region that is not excited. This segmentation allows the pumping light to be converted to useful amplification energy only in the necessary region, improving overall energy conversion efficiency while maintaining amplification power.
2Power
If the entire core is excited by pumping light, then gain is available throughout the core, but amplified spontaneous emission (ASE) and parasitic oscillation occur in regions where signal light does not pass
Solution Approach 1:
The patent creates local quality differentiation by exciting only the signal light path region while leaving the non-signal light path region unexcited. This ensures that gain is available only where signal light passes, preventing ASE and parasitic oscillation from occurring in unexcited regions, thus eliminating harmful factors while maintaining necessary amplification gain.
Solution Approach 2:
The patent converts the potential harm of having an unexcited non-signal region into a benefit. By intentionally leaving this region unexcited, the design prevents ASE and parasitic oscillation, transforming what could be a source of harmful emissions into a region that actively suppresses noise and instability, thereby improving overall signal quality.
3Power
If intense ASE is present in the planar waveguide amplifier, then the amplification function is maintained, but the signal-to-noise ratio (S/N ratio) of the laser radar device deteriorates
Solution Approach 1:
The patent applies local quality by restricting excitation to only the signal light path region. This spatially selective excitation maintains amplification function in the necessary region while eliminating ASE generation in other regions, thereby preserving high signal-to-noise ratio for laser radar device operation without sacrificing amplification capability.
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
This design effectively suppresses ASE and parasitic oscillations, achieving a higher amplification factor and improved signal-to-noise ratio by ensuring that only the necessary portions of the waveguide are excited, leading to enhanced performance in laser radar devices.
Implementation Method 1
a core (71) to amplify signal light (A), with the core (71) excited by pumping light (B)
Implementation Method 2
a first cladding (72) to reflect light having propagated from the core (71) back to the core (71), and a second cladding (73) to reflect light having propagated from the core (71) back to the core (71)
Implementation Method 3
the core (71) is an amplification medium that contains a rare-earth element serving as an active ion of a three-level system, and absorbs scattered light of the signal light (A) and amplified spontaneous emission in a portion through which the pumping light (B) does not pass
Data Source
Figure 1~2
Figure 3
Figure 4
AI summary
A planar waveguide amplifier (1) includes a planar waveguide (7) including a flat plate-like core (71); a first cladding (72) provided on a first principal face of the core (71); and a second cladding (72) provided on a second principal face of the core (71), and signal light (A) and pumping light (B) travel into the planar waveguide (7) so that the signal light (A) and the pumping light (B) propagate inside the core (71) in such a manner that optical paths of the signal light (A) and the pumping light (B) overlap each other, and in a zig-zag manner, and the core (71) is an amplification medium containing a rare-earth element serving as an active ion of a three-level system, and absorbs the signal light (A) on the basis of a reduction in intensity of the pumping light (B).