Laser Diode Structure with Movable Optical Element for Noise Reduction
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Solution Overview
Problem
Existing laser diode structures for gas detection suffer from optical noise due to self-mixing and etalons caused by back-reflections, which reduce signal resolution in high-resolution testing devices.
Innovation Solution
A laser diode structure with a movable optical element that continuously varies the optical path length for back-reflected laser light, using an electrically controllable power device to alter the position and alignment of optical elements, effectively averaging out interference effects by changing the optical path length in synchronization with the laser current modulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a laser diode structure with fixed optical elements is used, then the device complexity is low, but optical noise due to self-mixing and etalons reduces measurement precision
Solution Approach 1:
The patent applies the dynamics principle by making the optical element movable instead of fixed. The optical element is positioned on a movable carrier that can change its position relative to the laser diode, thereby dynamically varying the optical path length. This dynamic adjustment prevents stable interference patterns (etalons and self-mixing) from forming, eliminating optical noise while maintaining manageable device complexity through a relatively simple movable carrier mechanism.
2Measurement precision
If the optical path length is varied to reduce interference, then measurement precision improves, but the device complexity increases due to additional movable components
Solution Approach 1:
The patent implements dynamics by introducing a movable optical element whose position can be varied to change the optical path length. This dynamic configuration allows the system to eliminate interference patterns by preventing stable resonance conditions, thereby improving signal resolution while adding only minimal complexity through a straightforward movable carrier mechanism.
Solution Approach 2:
The patent applies periodic action by continuously or cyclically varying the position of the optical element, which periodically changes the optical path length. This periodic movement ensures that any potential interference patterns are continuously disrupted and averaged out over time, effectively eliminating etalons and self-mixing effects. The periodic motion can be achieved through simple oscillating mechanisms, maintaining device simplicity while achieving high measurement precision.
3Measurement precision
If back-reflections are eliminated by fixed optical design, then device complexity remains low, but optical noise from etalons and self-mixing reduces measurement precision
Solution Approach 1:
The patent resolves this contradiction by making the optical element movable rather than fixed. The movable carrier allows continuous adjustment of the optical path length, which prevents the formation of stable feedback loops that cause etalons and self-mixing. This dynamic approach eliminates back-reflection interference without requiring complex fixed optical designs, achieving high measurement precision with acceptable device complexity.
Solution Approach 2:
The patent applies continuity of useful action by continuously varying the optical path length through the movable optical element. This continuous variation ensures that back-reflections are constantly changing in phase and path length, preventing any single interference pattern from stabilizing and causing noise. The continuous motion maintains measurement precision while avoiding the need for complex intermittent adjustment mechanisms.
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
Significantly reduces or eliminates etalons and self-mixing effects, enhancing the resolution of test signals and improving detection sensitivity in gas sensors by minimizing optical noise.
Implementation Method 1
slightly varying, continuously and cyclically, the optical path length for the laser beam between the reflecting surfaces and the laser aperture by means of a movable optical element
Implementation Method 2
a laser beam that is generated by the laser diode structure and tuned in its wavelength to the gas to be detected is directed through the gas mixture. The wavelength of the laser light is selected so that the laser light is strongly absorbed by the gas.
Implementation Method 3
The operating temperature of the laser diode is usually selected and kept constant by means of a thermo-electric temperature control device, for example a cooling Peltier element
Data Source
AI summary
A laser diode structure for generating a collimated or divergent laser beam, preferably for application in gas detection, with a laser diode arranged in a closed housing, with the housing comprising a housing bottom, an exit window, electrical connections, a temperature control device for the laser diode, and an optical element for influencing the laser beam. The temperature control device carrying the laser diode is arranged on the housing bottom and the optical element is positioned at a distance from the laser diode. The invention proposes an electrically controllable power device for the cyclic alteration of the position and/or alignment of the optical element in relation to the laser diode so that the optical path length for the laser beam in the housing changes periodically. The oscillating motion of the optical element has the effect of time-averaging the etalon and/or self-mixing effects caused by the back-reflections of the laser beam in the housing, thereby reducing the optical noise of the laser diode structure.