Substrate-Side VCSEL Emission via Open Region and AR Coating
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional vertical cavity surface emitting lasers (VCSELs) are designed to emit laser light from the second distributed Bragg reflector (DBR), limiting their operation to specific wavelengths and requiring high-resistance substrate inclusion in the electric circuit.
Innovation Solution
The VCSEL is modified to emit laser light from the first DBR on the substrate side by creating an open region through the substrate, applying an anti-reflection coating and a first ohmic contact on the first DBR, and removing substrate material to expose the first DBR, allowing for operation at wavelengths below the nominal cutoff and reducing substrate resistance in the electric circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional VCSEL is designed to emit laser light from the second DBR, then the laser cavity is properly formed, but the operation is limited to specific wavelengths above the nominal cutoff and the substrate introduces high resistance in the electric circuit
Solution Approach 1:
The patent inverts the conventional emission direction by making the first DBR (substrate side) the emission surface instead of the second DBR. This is achieved by removing substrate material to expose the first DBR and applying an anti-reflection coating to enable efficient light extraction at wavelengths below the nominal cutoff, thereby expanding wavelength adaptability while maintaining circuit reliability through direct ohmic contact to the first DBR
Solution Approach 2:
The patent changes the optical parameters of the first DBR by applying an anti-reflection coating specifically tuned for the desired emission wavelength (850 nm or 1550 nm). This parameter modification enables the first DBR to become an effective emission surface at wavelengths that would normally be below the material cutoff, thus expanding the operational wavelength range
2Productivity
If the substrate is included in the electric circuit, then the VCSEL structure is complete, but the substrate introduces relatively high resistance that reduces efficiency
Solution Approach 1:
The patent extracts the high-resistance substrate portion from the electric circuit path by making the first DBR the emission surface and applying ohmic contact directly to it. The substrate is removed or bypassed in the region where light is emitted, eliminating the substrate's harmful resistance effect while preserving its structural support function in other regions
Solution Approach 2:
The first DBR serves as an intermediary element that provides both optical reflection functionality and electrical conduction. By making the first DBR the emission surface and contacting it directly with ohmic contact, it mediates between the electrical circuit and optical emission functions, eliminating the need for current to pass through the high-resistance substrate
3Adaptability or versatility
If an open region is created through the substrate to expose the first DBR, then emission below nominal cutoff wavelength is enabled, but the manufacturing process becomes more complex
Solution Approach 1:
The patent segments the substrate into regions with different functions: an open region where substrate material is removed to expose the first DBR for wavelength operation below cutoff, and surrounding regions where the substrate remains to provide mechanical support and electrical connection. This segmentation enables the dual benefit of extended wavelength capability while maintaining manufacturing feasibility through localized processing
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
Enables operation at optimized wavelengths (e.g., 850 nm and 1550 nm) with reduced substrate resistance, improving efficiency and compatibility with existing system components.
Implementation Method 1
An anti-reflection coating and a first ohmic contact are located on the first DBR in this region
Implementation Method 2
a first distributed Bragg reflector (DBR) on the first major surface of the substrate, an active region on the first DBR, and a second DBR on the active region. The two DBRs form a laser cavity
Data Source
AI summary
A VCSEL is described that provides for emission from the substrate side. The VCSEL comprises a substrate having first and second major surfaces, a first distributed Bragg reflector (DBR) on the first major surface of the substrate, an active region on the first DBR, and a second DBR on the active region. These elements are aligned on a longitudinal axis along which laser radiation is emitted. In an illustrative embodiment of the invention, an open region extends through the substrate along the longitudinal axis between the second major surface of the substrate and the first DBR. An anti-reflection coating and a first ohmic contact are located on the first DBR in this region. Preferably the first ohmic contact extends around all or part of the anti-reflection coating. A second ohmic contact is located on the surface of the second DBR. The two DBRs form a laser cavity; and emission takes place along the longitudinal axis through the anti-reflection coating. A method for forming the VCSEL is also described.