Light Emitting Element With Segmented Resonator Lengths
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Solution Overview
Problem
Surface emitting laser elements with high reflectance suffer from speckle noise due to narrow spectral width, which is problematic for image display devices as it causes interference patterns from uneven screens.
Innovation Solution
A light emitting element with varying resonator lengths in each unit, achieved by adjusting the thickness of the laminated structural body units, allowing for multiple vertical modes and a widened spectral width to reduce speckle noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the reflectance of the reflecting mirror is set to about 99% or higher to obtain net gain with short resonator length and small active layer volume, then the laser oscillation efficiency is improved, but the spectral width of laser light becomes narrower and speckle noise occurs
Solution Approach 1:
The invention divides the uniform resonator into multiple sections with different thicknesses (first resonator section with thickness L1, second resonator section with thickness L2, third resonator section with thickness L3 where L1 < L2 < L3). This segmentation creates multiple vertical modes with different spectral widths, and when these modes are combined, the overall spectral width is widened while maintaining high oscillation efficiency, thereby suppressing speckle noise.
Solution Approach 2:
Different regions of the resonator are given different local properties by varying the thickness of the laminated structural body in each section. The first section has the thinnest structure (L1), the second section has intermediate thickness (L2), and the third section has the greatest thickness (L3). This local variation in thickness creates distinct vertical modes in each region that, when combined, produce a widened overall spectral width without sacrificing the high reflectance benefit.
2Object-affected harmful factors
If the spectral width of laser light is widened to suppress speckle noise, then the coherence of light decreases and interference patterns are reduced, but the laser oscillation efficiency and net gain are reduced
Solution Approach 1:
The resonator is segmented into multiple thickness sections (L1, L2, L3) that each support different vertical modes. By carefully designing the thickness differences, the invention ensures that each segment contributes to the overall lasing action while the combined effect widens the spectral width. The high reflectance mirrors maintain oscillation efficiency for each mode, and the superposition of these modes achieves speckle noise suppression without significant efficiency loss.
Solution Approach 2:
The invention changes the physical parameter of resonator thickness across different sections (from L1 to L2 to L3, with L1 < L2 < L3). This parameter variation creates distinct vertical modes with different resonant frequencies and spectral characteristics. The controlled change in thickness parameter allows the system to achieve widened spectral width while maintaining the high Q-factor necessary for efficient laser oscillation in each mode.
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 effectively suppresses speckle noise by increasing the spectral width of emitted light, improving coherence and reducing interference patterns, enhancing the performance of light emitting elements in image display devices.
Implementation Method 1
laser oscillation occurs by causing light to resonate between two light reflecting layers (distributed bragg reflector layers (DBR layers))
Implementation Method 2
reflectance of a reflecting mirror is sometimes set to about 99%, or set to be higher than 99%
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
A light emitting element includes at least a first light reflecting layer 41 formed on a surface of a substrate 11, a laminated structural body 20 made of a first compound semiconductor layer 21, an active layer 23 and a second compound semiconductor layer 22 formed on the first light reflecting layer 41, and a second electrode 32 and a second light reflecting layer 42 formed on the second compound semiconductor layer 22, the laminated structural body 20 is configured from a plurality of laminated structural body units 20A, a light emitting element unit 10A is configured from each of the laminated structural body units 20A, and a resonator length in the light emitting element unit 10A is different in every light emitting element unit.