Surface Emitting Laser Array Electrode Configuration
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Solution Overview
Problem
Surface emitting laser element arrays face challenges with electrical interference (crosstalk) and high resistance values, which hinder high-speed response due to the arrangement of electrodes, leading to varying ground potentials and increased inductance effects.
Innovation Solution
A surface emitting laser element array configuration with a first electrode on the mesa post, a second electrode on one substrate surface, and a third electrode as a common ground electrode on the opposite substrate surface, reducing electric capacity and resistance, and ensuring constant ground potential across elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrodes are arranged on the same substrate surface for each laser element, then ground potential varies and inductance increases, but if arranged on opposite surfaces, then ground potential becomes constant and inductance decreases
Solution Approach 1:
The patent transitions from a two-dimensional electrode arrangement (all electrodes on the same substrate surface) to a three-dimensional arrangement (electrodes on opposite substrate surfaces). Specifically, the first electrode is placed on the front surface while the second electrode is placed on the back surface of the substrate, utilizing the third dimension (depth/thickness of substrate) to resolve the contradiction between ground potential stability and inductance reduction.
Solution Approach 2:
The patent segments the electrode arrangement by separating the first electrode (on front surface) from the second electrode (on back surface), dividing the electrical connection path through the substrate thickness. This segmentation allows independent optimization of each electrode's position to achieve both stable ground potential and reduced inductance simultaneously.
2Productivity
If conventional electrode arrangement is used, then manufacturing is simpler, but high-speed response is hindered due to high resistance and electric capacity
Solution Approach 1:
By placing electrodes on opposite surfaces of the substrate, the patent reduces the effective path length for current flow through the substrate, thereby reducing both resistance and electric capacity. This three-dimensional arrangement enables high-speed response by minimizing the electrical path while remaining compatible with standard semiconductor manufacturing processes.
3Ease of operation
If p-side and n-side electrodes are both on the top surface, then current injection is straightforward, but electrical interference (crosstalk) occurs between adjacent elements
Solution Approach 1:
The patent eliminates crosstalk by separating the current injection path (first electrode on front surface) from the ground path (second electrode on back surface). This vertical separation in the third dimension prevents lateral electrical interference between adjacent laser elements while maintaining straightforward current injection through the mesa post structure.
Solution Approach 2:
The patent extracts the ground electrode function from the front surface electrode arrangement and places it on the back surface. This separation removes the source of electrical interference from the active region where current injection occurs, eliminating crosstalk while preserving current injection simplicity through the mesa post.
Data Source
AI summary
A surface emitting laser element array comprises a plurality of surface emitting laser elements (15) on a same substrate (1) each comprising a mesa post formed of a laminated structure including an active layer (4) for reducing a crosstalk between the surface emitting laser elements constituting the surface emitting laser element array, and for improving a high speed response, wherein each of the surface emitting laser elements (15) comprises a first electrode (9), a second electrode (10) and a third electrode (11) that have a polarity different from that of the first electrode (9); the first electrode (9) is arranged on the mesa post; the second electrode (10) is arranged on one surface of the substrate (1) same as that of the first electrode (9); the third electrode (11) is arranged on the other surface of the substrate (1) opposite to that of the first electrode and the second electrode (9, 10) and is provided as a common electrode of the surface emitting laser elements (15); and an electric current is applied to the active layer (4) using the first electrode (9) and the second electrode (10).