Phase-Matching Optical Element for Semiconductor Laser Beam Quality
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Solution Overview
Problem
Semiconductor lasers face challenges in achieving high output power while maintaining acceptable beam quality, as designs that enhance one characteristic often degrade the other, particularly due to phase front distortion and thermal gradient-induced index variations in tapered designs at high powers.
Innovation Solution
A semiconductor laser design incorporating a single mode semiconductor laser section coupled with a flared power amplifier, featuring a phase-matching optical element such as a curved grating, binary optical element, or cylindrically curved optical element to reinforce the curved wave front, along with anti-reflection coatings and tilted facets to suppress reflections and maintain beam quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a flared semiconductor laser design is used to achieve high output power, then output power increases, but beam quality degrades due to phase front distortion and thermal gradient-induced index variations
Solution Approach 1:
The patent applies curvature to the wavefront by introducing a phase-matching optical element with a curved surface that matches the curved wavefront generated by the flared section. This curvature matching reinforces the curved wavefront and reduces phase front distortion, thereby maintaining beam quality while enabling high output power operation
Solution Approach 2:
The patent changes the optical parameter of the wavefront by introducing a phase-matching element that modifies the phase distribution. This parameter change compensates for the thermal gradient-induced index variations and phase front distortion that occur at high powers, allowing the laser to maintain acceptable beam quality while operating at high output power
2Manufacturing precision
If a ridge-waveguide laser design is used to achieve good beam quality, then beam quality is maintained, but output power is limited to approximately 1 watt
Solution Approach 1:
The patent segments the laser into two functional sections: a single-mode ridge-waveguide section for generating high-quality beams and a flared power amplifier section for boosting power. This segmentation allows each section to optimize for its specific function while working together to achieve both high beam quality and high output power
Solution Approach 2:
The patent merges the ridge-waveguide laser and flared power amplifier into a single integrated device with coupled sections. This merging allows the single-mode section to provide good beam quality while the flared section amplifies the power, achieving both high beam quality and high output power in one device
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 beam quality degradation at high output powers by dominating wave-front curvature and suppressing thermal and gain-index coupled perturbations, maintaining improved beam quality even at output powers greater than 5 watts.
Implementation Method 1
an optical element configured to reinforce the curved wave front of the output beam of the flared section through phase-matching
Implementation Method 2
the optical element is comprised of a curved grating integrated into the flared section of the device, where the curvature corresponding to the curved grating matches the phase and curvature of the curved wave front
Implementation Method 3
the outer, flared edge 107 of section 103 is typically coated with an AR coating
Implementation Method 4
the front facet of the flared section may be tilted at an angle θ away from the normal, where angle θ is greater than or equal to the critical angle θcritical which corresponds to the angle required to suppress reflections
Implementation Method 5
a fast-axis collimating lens is preferably interposed between the output surface of the flared section and the external optical element
Data Source
AI summary
A semiconductor laser that includes a single mode semiconductor laser coupled to a flared power amplifier is provided, the device including an internal or an external optical element that reinforces the curved wave front of the flared section of the device through phase-matching. By reinforcing the curved wave front via phase-matching, the device is less susceptible to thermal and gain-index coupled perturbations, even at high output powers, resulting in higher beam quality. Exemplary phase-matching optical elements include a grating integrated into the flared amplifier section; an intra-cavity, externally positioned binary optical element; and an intra-cavity, externally positioned cylindrically curved optical element.