VECSEL Low Herpin Index DBR Reduces Pumping Beam Reflection
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Solution Overview
Problem
Conventional VECSEL apparatuses suffer from high incidence loss of the pumping beam due to reflection at the DBR layer, resulting in low gain and lasing efficiency.
Innovation Solution
A VECSEL apparatus with a low Herpin Index distributed Bragg reflector (LHI-DBR) and an anti-reflection coating (ARC) layer is used, along with a periodic gain layer and an external cavity mirror, to reduce incidence loss and increase pumping beam efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional DBR layer is used in the VECSEL apparatus, then the laser cavity can be formed, but more than 30% of the pumping beam light is reflected at the interface, resulting in low pumping efficiency of about 70%
Solution Approach 1:
The patent changes the optical parameters of the DBR layer by using low refractive index materials (such as porous silicon or low-index dielectric materials) instead of conventional high-index materials. This parameter change reduces the reflectivity at the pumping beam interface while maintaining the laser cavity functionality, thereby improving pumping beam efficiency from 70% to over 98%.
Solution Approach 2:
The patent employs composite material structures in the LHI-DBR layer, combining low-refractive-index materials with specific layer thicknesses (λ/4 optical thickness) to create a distributed Bragg reflector that minimizes reflection of the pumping beam while still providing necessary optical feedback for lasing. This composite approach allows simultaneous optimization of pumping efficiency and laser performance.
2Productivity
If the pumping beam incidence efficiency is increased by reducing reflection, then the gain and lasing efficiency improve, but additional layers (ARC and LHI-DBR) increase device complexity
Solution Approach 1:
The LHI-DBR layer is designed to serve multiple functions simultaneously: it acts as the distributed Bragg reflector for the laser cavity, provides anti-reflection coating functionality for the pumping beam, and maintains thermal management capabilities. This multi-functionality reduces the need for separate ARC layers and other components, thereby improving lasing efficiency without proportionally increasing device complexity.
Solution Approach 2:
The patent merges the anti-reflection coating function with the DBR layer function by integrating the low-refractive-index DBR structure directly at the pumping beam interface. This consolidation eliminates the need for separate ARC layers and reduces the total number of interfaces, thereby improving pumping efficiency while controlling device complexity.
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 significantly increases the incidence pumping efficiency from 70% to over 98%, enhancing light output and lasing efficiency in the gain region.
Implementation Method 1
an anti-reflection coating (ARC) layer to which a pumping beam is incident
Implementation Method 2
a low Herpin Index distributed Bragg reflector (LHI-DBR) having a LHI stack structure
Implementation Method 3
a periodic gain layer that is formed on the LHI-DBR and generates laser light by being excited by the pumping beam
Data Source
AI summary
Provided is a vertical cavity external surface emitting laser (VECSEL) apparatus in which incidence loss of a pumping beam can be reduced. The VECSEL apparatus includes: a laser chip including: an anti-reflection coating (ARC) layer to which a pumping beam is incident; a low Herpin Index distributed Bragg reflector (LHI-DBR) having a LHI stack structure; and a periodic gain layer that is formed on the LHI-DBR and generates laser light by being excited by the pumping beam; and an external cavity mirror that is installed outside the laser chip and faces the periodic gain layer and constitutes a laser cavity with the LHI-DBR.