VCSEL Resonator Loss Layer for Reliable Wavelength Tuning
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Solution Overview
Problem
Existing VCSELs with small active diameters exhibit a large wavelength shift but suffer from reduced reliability due to high current densities, which is a challenge for sensor applications relying on self-mixing interference.
Innovation Solution
Introduce a loss layer in the optical resonator of the VCSEL to intentionally increase optical and/or electrical losses, leading to a higher wavelength dependence on driving current without relying on active diameter reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the active diameter of the VCSEL is reduced to increase wavelength shift, then the wavelength dependence on driving current is improved, but the current density increases which reduces reliability
Solution Approach 1:
The patent introduces a loss layer with specific optical and electrical loss properties at a localized position within the VCSEL cavity. This loss layer creates a non-uniform distribution of optical and electrical properties, enabling enhanced wavelength dependence on driving current without requiring reduction of the active diameter. The localized introduction of losses allows the active diameter to remain larger while still achieving the desired wavelength shift characteristics.
2Reliability
If the active diameter is kept fixed to maintain reliability, then the current density is reduced, but the wavelength shift decreases which reduces sensor accuracy
Solution Approach 1:
The patent changes the optical and electrical loss parameters within the VCSEL cavity by introducing a dedicated loss layer. This parameter change enables the VCSEL to exhibit enhanced wavelength dependence on driving current even with a fixed, larger active diameter. The loss layer's optical loss coefficient and electrical resistance are specifically designed to create the desired wavelength shift while maintaining reliable operation at fixed active dimensions.
3Use of energy by moving object
If optical losses are reduced to improve efficiency, then the optical absorption is decreased, but the wavelength dependence on driving current is reduced
Solution Approach 1:
The patent segments the VCSEL structure into distinct functional regions, including a dedicated loss layer that is spatially separated from the active region. This segmentation allows the loss layer to provide the necessary optical and electrical losses for enhanced wavelength dependence without significantly impacting the overall optical efficiency. The loss layer is positioned to interact with the optical field in a controlled manner, creating wavelength dependence while minimizing negative impact on efficiency.
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 loss layer enhances wavelength shift for a given current variation, improving sensor accuracy while maintaining reliability by localized heating and Ohmic heating effects.
Implementation Method 1
the loss layer comprises a material with a fundamental absorption at the emission wavelength of the VCSEL
Implementation Method 2
The loss layer may introduce optical as well as electrical losses
Data Source
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AI summary
The present invention relates to Vertical Cavity Surface Emitting Laser (VCSEL) (10), which comprises an optical resonator (20) with a first distributed Bragg reflector (12), a second distributed Bragg reflector (16), and an active region (14) for light emission arranged between the first distributed Bragg reflector (12) and the second distributed Bragg reflector (16). The VCSEL (10) comprises an electrical contact arrangement (32, 34) which is arranged to provide an electrical drive current to electrically pump the optical resonator (20). An additional loss layer (18) arranged in the optical resonator (20) provides optical and/or electrical losses. These additional losses increase the wavelength shift of the VCSEL (10), which wavelength shift is an important parameter for sensor applications that rely on self-mixing interference. The present invention further relates to an optical sensor comprising such a VCSEL and a fabrication method thereof.