Semiconductor Laser Beam Combining for Speckle Reduction
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Solution Overview
Problem
Laser components used in visible wavelengths often exhibit undesirable interference effects such as speckles and are hindered by large coherence lengths when combined with diffractive optics, leading to uneven illumination and pattern disturbances.
Innovation Solution
A semiconductor laser component that generates electromagnetic radiation with an increased spectral bandwidth by superposing primary radiations from multiple semiconductor lasers, reducing coherence length and enhancing beam quality, using a beam combiner and various structural and operational adjustments to achieve a secondary spectral bandwidth at least twice the primary bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If laser components are used in visible wavelength range, then good beam quality and small emission range extension are achieved, but undesirable interference effects such as speckles and large coherence length occur
Solution Approach 1:
The invention divides a single laser source into multiple semiconductor lasers (at least two) with different main emission wavelengths. By segmenting the light source into multiple wavelengths, the coherence length is reduced, which eliminates interference effects and speckles while preserving good beam quality. Each laser emits at a slightly different wavelength, and their superposition creates the desired effect.
Solution Approach 2:
The invention changes the spectral parameter by using multiple semiconductor lasers with different main emission wavelengths (differing by 0.5 nm to 3 nm, particularly 1 nm to 2 nm). This parameter change in the emission wavelength directly reduces the coherence length from the original single-wavelength value to a reduced coherence length, eliminating interference effects while maintaining beam quality.
2Reliability
If single wavelength laser is used, then coherent radiation is achieved, but coherence length becomes too large causing interference effects
Solution Approach 1:
The coherent radiation from a single wavelength is segmented into multiple wavelengths by using at least two semiconductor lasers with different main emission wavelengths. This segmentation maintains the coherence property within each wavelength component while the overall superposition reduces the total coherence length, preventing interference effects.
Solution Approach 2:
The invention creates a composite radiation source by superposing emissions from multiple semiconductor lasers with different wavelengths. This composite approach combines coherent radiation from each individual laser while the wavelength diversity reduces the overall coherence length, eliminating interference effects.
3Quantity of substance
If multiple semiconductor lasers with different wavelengths are superposed, then spectral bandwidth is increased and coherence length is reduced, but device complexity increases
Solution Approach 1:
The invention achieves increased spectral bandwidth by changing the wavelength parameter across multiple semiconductor lasers. Each laser is tuned to emit at a slightly different main emission wavelength (differing by 0.5 nm to 3 nm), creating a superposition with expanded spectral bandwidth while keeping the overall device structure relatively simple.
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 effectively reduces interference effects, allowing for the use of diffractive optics and minimizing speckle formation, while maintaining good beam quality and facilitating compact optical systems.
Implementation Method 1
Each semiconductor laser is provided for emitting coherent or at least partially coherent electromagnetic radiation
Implementation Method 2
a superposition of the electromagnetic radiation of all semiconductor lasers is performed
Data Source
AI summary
In an embodiment a semiconductor laser component includes a plurality of semiconductor lasers, each of the semiconductor lasers configured to emit primary electromagnetic radiation of a primary spectral bandwidth in a visible wavelength range and a beam combiner configured to combine the primary electromagnetic radiations emitted from the semiconductor lasers, form secondary electromagnetic radiation from a superposition of the primary electromagnetic radiations of the semiconductor lasers and couple the secondary electromagnetic radiation out from the beam combiner, wherein the secondary electromagnetic radiation has a secondary spectral bandwidth that is at least twice as large as an average value of the primary spectral bandwidths.