Laser Diode Structure with Inclined Window for Gas Detection
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Solution Overview
Problem
Existing gas sensors face reduced detection sensitivity due to interference phenomena caused by reflections within the laser diode structure, which are influenced by temperature changes and optical path variations, leading to increased noise and decreased resolution.
Innovation Solution
A laser diode structure with a window inclined relative to the laser beam's center axis, combined with a temperature-controlled optical beam shaping element, such as a lens or microlens, that maintains a uniform temperature with the laser diode chip, minimizing reflections and interference patterns by aligning the polarization vector with the plane of incidence and using an adhesive or surface-to-surface contact for reduced refractive index transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a microlens is provided in the laser diode structure to shape the laser beam, then the beam quality is improved, but interference patterns are generated due to reflections at the microlens boundary surfaces, worsening the detection sensitivity
Solution Approach 1:
The patent converts the harmful reflections at the microlens boundary surfaces into beneficial effects by tilting the window at the Brewster angle. This orientation causes the reflected light to be polarized perpendicular to the plane of incidence, which can be filtered out, while the transmitted light maintains its intensity. The harmful interference patterns are thus converted into manageable reflected beams that can be excluded from the detection path.
Solution Approach 2:
The patent changes the orientation parameter of the window relative to the laser beam by tilting it at a specific angle (Brewster angle). This parameter change transforms the reflection characteristics at the window-microlens interface, reducing the intensity of reflected beams that could cause interference patterns and improving overall beam quality without sacrificing detection sensitivity.
2Device complexity
If the window is oriented perpendicular to the laser beam to simplify the structure, then the device complexity is reduced, but interference patterns occur due to reflections, worsening the measurement precision
Solution Approach 1:
The patent modifies the orientation parameter of the window from perpendicular to tilted at the Brewster angle relative to the laser beam. This single parameter change fundamentally alters the reflection characteristics, reducing interference patterns while maintaining structural simplicity. The tilted orientation causes reflected light to follow a different path that can be excluded from the detection system.
Solution Approach 2:
The patent introduces asymmetry by tilting the window at a specific angle rather than orienting it perpendicular to the laser beam. This asymmetric orientation breaks the symmetry of reflection paths, causing reflected light to diverge from the main beam path and reducing interference patterns that would otherwise degrade measurement precision.
3Stability of the object's composition
If temperature control is applied to the laser diode chip to maintain stable operation, then the operating stability is improved, but temperature-induced interference patterns persist, worsening the detection sensitivity
Solution Approach 1:
The patent converts temperature-induced expansion and the resulting interference patterns into a beneficial configuration by tilting the window at the Brewster angle. This orientation ensures that even when the optical path length changes due to thermal expansion, the reflected light maintains a polarization state and trajectory that can be excluded from the detection path, thus maintaining detection sensitivity despite temperature variations.
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
This configuration significantly reduces interference patterns, enhancing the detection sensitivity and reliability of gas sensors by minimizing reflections and maintaining a consistent temperature, thereby improving the resolution and cost-efficiency of the laser diode structure.
Implementation Method 1
an optical beam shaping element that collimates a laser beam emerging from a laser aperture of the laser diode chip
Implementation Method 2
The beam shaping element and the laser diode chip are in a defined temperature condition in relation to one another, in particular the same temperature
Implementation Method 3
The azimuth angle of the window inclination has a fixed relation to the polarization vector of the laser beam in that the polarization vector is in the plane of incidence of the window
Data Source
AI summary
The invention relates to a laser diode structure, specifically for use in gas detection, with a hermetically sealed housing with electrical connections having a bottom and a window. A laser diode chip and a temperature control system for the laser diode chip are provided in the housing. A thermo element in the form of a Peltier element forms the temperature control system, and is connected via a lower flat surface to the bottom of the housing and via an upper flat surface to the laser diode chip, with a temperature-controlled beam shaping element as collimator provided between the laser diode chip and the window of the housing that acts on a laser beam emerging from a laser aperture of the laser diode chip before it passes through the window. The beam shaping element is in contact with the laser diode chip and is preferably connected via a boundary surface to the laser aperture with surface-to-surface contact or adhesively, or is made in one piece together with the laser aperture.