Tunable VCSEL With Piezo-Actuated Cavity for High Sweep Frequency
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Solution Overview
Problem
Current tuneable laser sources for optical coherence tomography, particularly Fabry-Perot tuneable filters, are limited by low sweep frequency due to mechanical design limitations, leading to restricted high-frequency operation and stability issues in MEMS-based VCSELs.
Innovation Solution
A tuneable VCSEL design with a resonator cavity devoid of light guiding media, featuring a concave recess in one reflecting element and a piezo-electric actuator for modulating the optical path length, allowing for higher sweep frequencies and improved stability through coupled oscillating elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If Fabry-Perot tuneable filters are used for OCT, then wavelength tuning is achieved, but sweep frequency is limited due to mechanical design limitations
Solution Approach 1:
The patent replaces the traditional mechanical Fabry-Perot filter tuning system with a VCSEL-based system using piezo-electric actuators to modulate the optical path length directly within the laser cavity. This substitution eliminates the need for complex mechanical filter assemblies and enables higher sweep frequencies through direct electro-optic control.
Solution Approach 2:
The invention changes the operating parameters by using piezo-electric actuators to dynamically adjust the optical path length in the VCSEL cavity, enabling rapid wavelength sweeping at frequencies exceeding 100 kHz. This parameter modulation approach replaces slow mechanical filter tuning with fast electro-mechanical actuation.
2Adaptability or versatility
If MEMS-based VCSELs are used, then tuneability is achieved, but stability issues occur
Solution Approach 1:
The patent segments the VCSEL structure into distinct functional components: separate piezo-electric actuators for optical path length control, independent dielectric mirrors for wavelength selection, and a dedicated gain medium. This segmentation allows each component to be optimized independently, improving overall stability while maintaining tuneability.
Solution Approach 2:
The invention introduces piezo-electric actuators as intermediary elements between the control system and the optical cavity. These actuators provide stable, precise control of the optical path length without the mechanical contact and wear issues that plague direct MEMS implementations, thereby enhancing operational reliability.
3Stability of the object's composition
If light guiding media are present in the resonator cavity, then light confinement is improved, but manufacturing complexity increases
Solution Approach 1:
The patent extracts and removes light guiding media from the resonator cavity, relying instead on the natural resonant modes of the Fabry-Perot cavity formed by the dielectric mirrors. This extraction simplifies the device structure and manufacturing process while maintaining adequate light confinement through the cavity's geometric and optical properties.
4Measurement precision
If conventional Fabry-Perot filters are used, then wavelength selection is achieved, but modulation amplitude is limited
Solution Approach 1:
The invention implements dynamic modulation of the optical path length using piezo-electric actuators that can rapidly change the cavity length with large modulation amplitudes. This dynamic control enables both precise wavelength selection and large sweep ranges, overcoming the static limitations of conventional Fabry-Perot filters.
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 design achieves higher sweep frequencies and improved reliability and reproducibility, overcoming the limitations of existing technologies by enabling larger modulation amplitudes and a larger free spectral range, while simplifying manufacturing and reducing thermal noise.
Implementation Method 1
a piezo-electric actuator for modulating the optical path length
Implementation Method 2
a resonator cavity having a gain medium provided therein
Data Source
Figure 1~2
Figure 3~4
Figure 5(a)~5(b)
AI summary
Disclosed is a VCSEL (128) comprising a first and a second reflecting element separated by an optical path length to form an optical resonator cavity, a first actuator means mechanically coupled with one or both of said first and second reflecting elements, said first actuator means being configured to modulate the optical path length between said first and second reflecting elements by a modulation amplitude, and a waveguide, in particular an optical fiber, coupled with one of the reflecting elements for coupling light out of the resonator cavity, wherein the surface of at least one of the first and second reflecting elements has a concave recess (118) formed therein.