Surface-Emitting Laser Module Feedback Light Reduction
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Solution Overview
Problem
Existing surface-emitting laser modules face challenges in minimizing laser light fluctuation caused by feedback light, which affects the quality of multi-color image forming apparatuses, particularly in high-resolution printing systems where precise control of laser light is crucial.
Innovation Solution
A surface-emitting laser module design featuring a substrate with a high reflectance region and a low reflectance region formed within an electrode-enclosed mesa, where the transparent substrate is slanted in the polarization direction of the emitted light to reduce feedback light interference, and the glass cover is angled to minimize feedback reflections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If surface-emitting lasers are used in multi-color image forming apparatuses to achieve high-resolution printing, then printing speed and image quality are improved, but laser light fluctuation occurs due to feedback light from lenses and glass covers
Solution Approach 1:
The patent applies local quality by creating an asymmetric reflectance distribution on the laser element surface. Specifically, a low reflectance region is formed at a specific position (off-center location) while other regions maintain high reflectance. This localized modification targets the specific problem of feedback light entering the laser cavity from particular directions, thereby stabilizing laser output without compromising overall laser performance or printing speed.
Solution Approach 2:
The patent implements asymmetry by intentionally creating an asymmetric reflectance pattern on the laser element surface. The low reflectance region is positioned asymmetrically relative to the laser cavity, and the glass cover is slanted at a specific angle (5-15 degrees) rather than being perpendicular. This asymmetric configuration prevents feedback light from symmetrically returning to the laser cavity, effectively reducing laser light fluctuation while maintaining high printing speed and image quality.
2Reliability
If feedback light resistance is increased by conventional methods (slanting optical fibers or glass cover), then laser light fluctuation is reduced, but the design configuration becomes more complex and the effect is limited
Solution Approach 1:
Rather than uniformly modifying the entire optical system, the patent applies local quality by creating a specific low reflectance region at a precise location on the laser element surface. This localized approach selectively addresses feedback light paths without requiring complex global modifications to the optical system, thereby reducing laser light fluctuation while maintaining relatively simple device configuration.
Solution Approach 2:
The patent employs parameter changes by modifying the reflectance parameter at a specific location on the laser element surface. By changing the reflectance from high to low in a specific region (through physical or chemical treatment), the patent effectively alters the optical path of feedback light without requiring major structural changes, thus improving feedback light resistance with minimal increase in device complexity.
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 reduces laser light fluctuation, enhancing the stability and quality of the laser output, enabling the production of high-resolution images with reduced variability in droop values, thus improving the performance of multi-color image forming apparatuses.
Implementation Method 1
a high reflectance region having a high reflectance of the light emitted from the surface-emitting laser and a low reflectance region having a low reflectance of the light emitted therefrom are formed within a region enclosed by an electrode formed on an upper part of a mesa of the surface-emitting laser
Implementation Method 2
the transparent substrate is slanted to the surface of the substrate having the surface-emitting laser formed thereon in a polarization direction of the light emitted from the surface-emitting laser
Data Source
AI summary
A disclosed surface-emitting laser module includes a surface-emitting laser formed on a substrate to emit light perpendicular to its surface, a package including a recess portion in which the substrate having the surface-emitting laser is arranged, and a transparent substrate arranged to cover the recess portion of the package and the substrate having the surface-emitting laser such that the transparent substrate and the package are connected on a light emitting side of the surface-emitting laser. In the surface-emitting laser module, a high reflectance region and a low reflectance region are formed within a region enclosed by an electrode on an upper part of a mesa of the surface-emitting laser, and the transparent substrate is slanted to the surface of the substrate having the surface-emitting laser in a polarization direction of the light emitted from the surface-emitting laser determined by the high reflectance region and the low reflectance region.