Surface Emitting Laser Stepped Structure Far Field Control
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Solution Overview
Problem
Surface emitting lasers used in image forming apparatuses face challenges in achieving stable oscillation in a single transverse mode due to uneven reflectance and phase differences in stepped structures, leading to undesirable far field light intensity distributions and increased alignment requirements.
Innovation Solution
A surface emitting laser with a laminated structure incorporating a first stepped structure for reflectance control and a second stepped structure for phase difference manipulation, both on the upper mirror, to enhance the divergence angle of far field light intensity distribution by creating reflectance and phase differences between regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a stepped structure is provided to control transverse mode oscillation, then single mode stability is improved, but far field light intensity distribution deteriorates
Solution Approach 1:
The light outgoing surface is divided into multiple regions with different reflectances through the stepped structure. The first region has higher reflectance and the second region has lower reflectance, allowing independent control of light intensity in each region to achieve both single mode stability and improved far field distribution
Solution Approach 2:
Different regions of the light outgoing surface are given different local optical properties (reflectance values). The center region has higher reflectance while the peripheral region has lower reflectance, creating the appropriate intensity distribution for both mode control and far field characteristics
2Reliability
If reflectance of the center portion is increased, then transverse mode control is improved, but half value width of far field distribution is thinned
Solution Approach 1:
The reflectance parameter is changed across different regions of the light outgoing surface. By setting the center region reflectance higher than the peripheral region, the patent achieves both transverse mode control and maintains an appropriate half value width in the far field distribution
3Reliability
If stepped structure is provided for mode control, then oscillation stability is improved, but alignment accuracy requirement increases
Solution Approach 1:
The stepped structure creates an asymmetric reflectance distribution across the light outgoing surface. This asymmetric design with higher center reflectance and lower peripheral reflectance provides inherent mode control that reduces sensitivity to alignment variations, thereby improving oscillation stability without excessively increasing alignment accuracy requirements
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 improves the far field light intensity distribution by thinning the half value width and achieving better axial alignment, making the surface emitting laser more suitable for image forming applications.
Implementation Method 1
the reflectance of the center portion of a light emitting region is higher than that of the peripheral portion
Implementation Method 2
A light path length difference in the center portion of the light emitting region is different from that in the peripheral portion thereof
Data Source
AI summary
A first stepped structure configured to apply a reflectance difference and a second stepped structure configured to change a far field light intensity distribution are provided. A region in which a level difference of the first stepped structure is formed has a predetermined relationship with a region in which a level difference of the second stepped structure is formed.