Quantum Cascade Laser Setback Structure for Solder Protection
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Solution Overview
Problem
Quantum cascade lasers have high threshold currents and operation voltages, leading to high power consumption, and existing high reflection coatings on end facets are compromised by soldering materials like indium, degrading lasing characteristics and reliability.
Innovation Solution
A quantum cascade laser design with a set-back structure on the end facet and a metal layer made of gold, where the insulating layer prevents contact with soldering materials, maintaining high reflectance and preventing electrical connection, and a method involving a stacked semiconductor layer with a metal layer on the end facet to enhance reflectance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a metal film is formed on the end facet to increase reflectance, then the mirror loss is reduced and threshold current is lowered, but the soldering material flows to the end facet and reacts with the metal film during mounting, degrading reflectance and lasing characteristics
Solution Approach 1:
An insulating layer is introduced as an intermediary between the soldering material and the metal film on the end facet. This insulating layer prevents the harmful chemical reaction between the soldering material (e.g., indium) and the metal film (e.g., gold), thereby maintaining high reflectance and stable lasing characteristics during the mounting process.
Solution Approach 2:
The end facet of the stacked semiconductor layer is retreated from the end facet of the substrate before the mounting process. This preliminary structural adjustment creates a setback configuration that prevents soldering material from reaching the metal film on the end facet, thereby protecting the reflective surface from degradation during subsequent mounting operations.
2Ease of manufacture
If the quantum cascade laser is mounted on a sub-mount using soldering material, then the device is fixed and electrically connected, but the soldering material contacts the metal film on the end facet and causes chemical reactions that reduce reflectance
Solution Approach 1:
The insulating layer serves as a protective intermediary that allows the mounting process to proceed normally while preventing the soldering material from contacting and reacting with the metal film on the end facet, thus maintaining reflectance stability without compromising manufacturing ease.
Solution Approach 2:
The end facet retreatment is performed in advance during device fabrication, creating a protective setback structure that preserves the metal film integrity during the subsequent mounting process, enabling both easy manufacturing and reliable performance.
3Use of energy by moving object
If the threshold current is reduced by increasing mirror reflectance, then power consumption is lowered, but the metal film on the end facet is vulnerable to soldering material contamination that degrades reflectance
Solution Approach 1:
The insulating layer acts as a protective barrier that preserves the metal film's high reflectance properties by preventing soldering material contamination, thereby maintaining the reduced power consumption benefits achieved through the high-reflectance mirror design.
Solution Approach 2:
The setback structure is prepared in advance to protect the metal film from soldering material exposure, ensuring that the high reflectance and low power consumption characteristics are maintained throughout the device's operational life.
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 reduces power consumption by maintaining high reflectance and preventing solder-induced degradation, enhancing the reliability and lasing characteristics of the quantum cascade laser.
Implementation Method 1
a metal layer disposed on the conductive layer on the first end facet and an upper surface of the stacked semiconductor layer
Implementation Method 2
an insulating layer disposed on the first end facet and an upper surface of the stacked semiconductor layer
Data Source
AI summary
A quantum cascade laser includes a substrate having first and second regions; a stacked semiconductor layer disposed on the second region, the stacked semiconductor layer including an active layer, the stacked semiconductor layer having a first end facet and a second end facet that constitute a laser cavity; an insulating layer disposed on the first end facet and an upper surface of the stacked semiconductor layer, the insulating layer having an opening on the upper surface; a conductive layer disposed on the insulating layer and in the opening, the conductive layer being in contact with the upper surface through the opening; and a metal layer disposed on the conductive layer on the first end facet and the upper surface. The first end facet of the stacked semiconductor layer is retreated from an end facet of the substrate to a boundary between the first and second regions.