VCSEL Array Parasitic Impedance Reduction
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Solution Overview
Problem
Existing VCSEL arrays face challenges in achieving high frequency modulation and high power due to heating complexities, parasitic impedances, and frequency response limitations from wire bonds, which hinder their performance in applications requiring both high power and frequency.
Innovation Solution
The design incorporates a monolithic array of VCSELs with short-circuited mesa devices and a thick metal heat sink structure, reducing parasitic impedance by minimizing the common p contact area and eliminating wire bonds, and using a coplanar waveguide configuration for improved heat dissipation and frequency response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If VCSEL arrays are designed for high power output, then power output increases, but heating complexities and parasitic impedances increase, degrading frequency response
Solution Approach 1:
The device is segmented into multiple independent VCSEL elements arranged in an array, each contributing to the total power output while maintaining individual thermal and electrical characteristics. This segmentation allows high aggregate power without proportionally increasing parasitic impedance, as each element has its own contact path to ground.
Solution Approach 2:
The invention transitions from planar wire bond connections to a three-dimensional vertical contact structure where p-type contacts extend through the substrate to reach the n-type contact plane. This dimensional change eliminates the need for lateral wire bonds, reducing parasitic inductance and improving frequency response while maintaining high power capability.
2Ease of manufacture
If wire bonds are used for electrical connections, then ease of manufacture is improved, but parasitic impedance increases, limiting high frequency response
Solution Approach 1:
The invention merges the electrical connection function with the substrate structure itself by extending p-type contact regions through the substrate to form vertical conductive paths. This eliminates the need for separate wire bond components while maintaining electrical connectivity, thereby reducing parasitic impedance without significantly complicating manufacturing.
Solution Approach 2:
The wire bond component is extracted and removed from the design entirely. The electrical connection function is achieved through the integrated vertical contact structure formed by the extended p-type regions, eliminating the source of parasitic inductance while keeping the manufacturing process relatively simple.
3Ease of operation
If common p contact area is increased, then ease of operation is improved, but parasitic impedance increases, reducing frequency response
Solution Approach 1:
The contact geometry transitions from a large lateral common p contact area to a vertical configuration where multiple small p-type contact regions extend through the substrate to reach the n-type contact plane. This dimensional change maintains ease of operation through the contact plane while minimizing parasitic impedance by reducing the lateral common area.
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 approach enhances the high frequency response and power output of VCSEL arrays by reducing parasitic impedance and heat generation, leading to increased reliability and efficiency in high-power, high-frequency applications.
Implementation Method 1
Each VCSEL of the VCSEL array is encompassed by a metal heat sink structure, which increases the height of each VCSEL mesa, the heat sink structure and the solder.
Implementation Method 2
The VCSEL array and short-circuit mesa device array can also be positioned to form a coplanar waveguide lead in a ground-signal-ground configuration in the bonded optoelectronic device.
Data Source
AI summary
A VCSEL array device formed of a monolithic array of raised VCSELs on an electrical contact and raised inactive regions connected to the electrical contact. The VCSELs can be spaced symmetrically or asymmetrically, in a manner to improve power or speed, or in phase and in parallel. The VCSELs include an active region positioned between two mirrors generating a pulsed light operating at a frequency of at least 1 GHz. The VCSELs having an output power of at least 120 mW. The raised VCSELs and raised inactive regions are positioned between the electrical contact and an electrical waveguide.