VCSEL Array On-Chip Capacitor for Fast High-Current Pulse Switching
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing VCSEL chips face challenges in achieving sub-nanosecond pulse mode with fast rise times at high current operation due to parasitic inductance and resistance from external capacitors.
Innovation Solution
Integration of a capacitor within the VCSEL chip, formed by two metal layers with a dielectric layer in between, to reduce parasitic inductance and resistance, enabling sharp and ultra-narrow pulse operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If external capacitors are used to enable pulse mode operation, then capacitance is provided for pulse generation, but parasitic inductance and resistance increase, degrading pulse shape and rise time
Solution Approach 1:
The patent merges the capacitor with the VCSEL chip structure by integrating metal layers and dielectric materials directly into the chip substrate. The first metal layer is formed over the substrate, followed by a dielectric layer, and then a second metal layer, creating an on-chip capacitor that eliminates external connections and reduces parasitic inductance and resistance.
Solution Approach 2:
The patent transitions from external capacitor placement to integrated on-chip capacitor structure by adding vertical layering (metal-dielectric-metal stacks) within the chip substrate. This dimensional integration allows the capacitor to be embedded within the chip footprint, minimizing lead inductance and resistance while maintaining required capacitance for pulse operation.
2Power
If higher electrical current is applied to achieve higher power optical pulses, then optical power increases for greater distance range finding, but pulse rise time and fall time increase, degrading rectangular pulse shape
Solution Approach 1:
The integrated capacitor structure combines the energy storage function directly with the VCSEL driving circuitry, allowing rapid charge discharge cycles that support high current pulses. The on-chip capacitor provides immediate current supplementation during pulse transitions, enabling fast rise and fall times even at high optical power levels.
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 integrated capacitor enhances operating current, switching speed, and driving efficiency, allowing for sub-nanosecond pulse response and faster rise and fall times of optical pulses.
Implementation Method 1
a capacitor integrated with an electrode of the VCSEL array, the capacitor comprising a first portion, a second portion, and a third portion
Implementation Method 2
a VCSEL structure... a higher electrical current across the VCSEL corresponds to a higher power optical pulse
Data Source
AI summary
An optical chip may include a vertical-cavity surface-emitting laser (VCSEL) structure. The optical chip may include a capacitor over at least a portion of an active layer of the VCSEL structure that is outside of an active region of the VCSEL structure. The capacitor may include a first metal layer over the portion of the active layer, a dielectric layer on the first metal layer, and a second metal layer on the dielectric layer. The optical chip may include an isolation region between a substrate of the VCSEL and a portion of the capacitor outside of the VCSEL.