Multi-wavelength Diode Laser Array Using Uniform Gratings
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Solution Overview
Problem
The high cost of manufacturing wavelength chirped volume holographic gratings limits the adoption of multi-wavelength laser arrays for applications requiring high spectral brightness, as they are more expensive than uniform volume holographic gratings.
Innovation Solution
A multi-wavelength laser array is created using a uniform volume holographic grating, where each beam incident at a different angle is locked to a unique wavelength, eliminating the need for wavelength chirped gratings by employing a monolithic array of deflector elements and a folded external cavity configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If wavelength chirped volume holographic gratings are used to lock each emitter to a unique wavelength, then high spectral brightness is achieved, but manufacturing cost significantly increases
Solution Approach 1:
The system segments the wavelength locking function across multiple uniform volume holographic gratings, each responsible for a specific wavelength range, rather than using a single complex chirped grating. This segmentation allows each grating to be manufactured with standard uniform specifications, reducing individual grating costs while collectively achieving the full spectral coverage needed for high spectral brightness
Solution Approach 2:
Multiple uniform volume holographic gratings are combined in series within the optical cavity to achieve the cumulative wavelength selection effect that would otherwise require a single chirped grating. This merging approach maintains the high spectral brightness function while using cheaper uniform grating components throughout the system
2Ease of manufacture
If multiple uniform volume holographic gratings are used instead of wavelength chirped gratings, then manufacturing cost is reduced, but device complexity increases due to multiple grating components
Solution Approach 1:
Each uniform volume holographic grating is designed to perform multiple functions: wavelength selection, beam reflection, and cavity mirror function simultaneously. This multi-functionality reduces the need for separate components and simplifies the overall device architecture despite using multiple gratings, as each grating element does the work of several dedicated components
Solution Approach 2:
The system employs adjustable mounting mechanisms for the multiple uniform gratings, allowing dynamic optimization of their positions and orientations during system alignment and operation. This dynamic adjustability simplifies the assembly process and reduces the complexity of precise fixed positioning, making the multi-grating configuration more manageable
3Ease of manufacture
If a single volume holographic grating is used to lock all emitters to a single wavelength, then manufacturing cost is reduced and assembly is simplified, but spectral brightness is limited due to narrow spectrum output
Solution Approach 1:
The single wavelength selection function is segmented across multiple uniform gratings, each selecting a different wavelength band. This segmentation allows the system to maintain the manufacturing simplicity of uniform gratings while collectively providing multi-wavelength output that achieves high spectral brightness through the combination of multiple wavelength channels
Solution Approach 2:
The system transitions from selecting wavelength along a single spectral dimension to utilizing multiple wavelength dimensions simultaneously through the stacked grating configuration. This dimensional expansion in spectral space enables high spectral brightness by combining power across multiple wavelength channels while maintaining uniform grating manufacturing benefits
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 solution reduces manufacturing costs significantly while maintaining high spectral brightness, enabling efficient wavelength locking and beam combination without the need for expensive wavelength chirped gratings.
Implementation Method 1
each beam incident upon the volume holographic grating at a different angle is locked to a different wavelength by the grating
Implementation Method 2
volume holographic grating
Implementation Method 3
monolithic array of deflector elements
Data Source
Figure 1~3
Figure 2
Figure 4
AI summary
A multi-wavelength laser array (10) of a plurality of emitters in a diode bar (12) or stack where each beam passes through a first deflector (12) comprising an array of prisms and is deflected by a different angle to be incident upon a uniform volume holographic grating (18). A portion of the beam is diffracted by the grating (18) and reflected by a second deflector (20) as a feedback portion while a further portion provides a wavelength tuned output unique to each emitter. The arrangement of a uniform volume holographic grating with deflectors such as phaseplates eliminates the need to use expensive wavelength chirped gratings.