Integrated Bragg Mirror for Laser Wavelength Stabilization and Backreflection Protection
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Solution Overview
Problem
Semiconductor lasers face issues with wavelength uncertainty due to temperature and driving current fluctuations, and existing solutions for stabilizing wavelengths are costly and complex, as they require external components like Bragg mirrors to prevent backreflected light from entering the internal cavity, which increases system complexity and cost.
Innovation Solution
A gain element module with a holographically recorded volume feedback Bragg mirror and an isolating volume Bragg mirror, where the mirrors are configured at an angle to the optical axis, allowing stray backreflected light to bypass the internal cavity while maintaining stabilized output wavelengths, and an isolating mirror blocks backreflected signal light without impeding the chip light, thus providing cost-effective protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a Bragg mirror is used to stabilize wavelength, then wavelength stability is improved, but system complexity and cost increase
Solution Approach 1:
The patent combines the wavelength stabilization function and the backreflection protection function into a single integrated Bragg mirror component. This merged structure eliminates the need for separate optical isolators and simplifies the overall system architecture while maintaining wavelength stability through the Bragg mirror's selective reflection properties.
Solution Approach 2:
The Bragg mirror is designed to perform multiple functions simultaneously: it provides wavelength stabilization by reflecting specific wavelengths back into the laser cavity, and it protects the laser diode from harmful backreflections by rejecting unwanted wavelengths. This multi-functional design reduces system complexity by eliminating dedicated protection components.
2Object-affected harmful factors
If optical isolators are placed downstream to protect from backreflected light, then protection from backreflected light is improved, but system complexity and cost increase
Solution Approach 1:
The patent extracts the protection function from a separate optical isolator and integrates it into the Bragg mirror structure. The Bragg mirror's wavelength-selective reflection inherently blocks backreflected light at specific wavelengths while allowing the desired wavelength to pass, eliminating the need for additional isolation components.
Solution Approach 2:
The Bragg mirror serves as an intermediary component that mediates between the laser diode and the external cavity. It selectively reflects desired wavelengths to provide feedback for wavelength stabilization while simultaneously rejecting unwanted backreflected wavelengths, thereby protecting the laser diode without requiring separate protection mechanisms.
3Measurement precision
If photosensitive material is used to record Bragg mirror, then wavelength selectivity is improved, but backreflected light into internal cavity increases
Solution Approach 1:
The patent applies local quality by designing the Bragg mirror with spatially varying reflection properties. The photosensitive material is recorded to create a grating structure that reflects specific wavelengths while transmitting others. By controlling the local optical properties of the photosensitive material, the system achieves wavelength selectivity while minimizing harmful backreflections into the laser cavity.
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 stabilizes the output wavelength of semiconductor lasers, prevents damage from backreflected light, and reduces system complexity and cost by automatically aligning the mirrors, ensuring reliable and robust operation.
Implementation Method 1
a feedback Bragg mirror reflecting a portion of light emitted by the gain element back into an internal cavity of the gain element
Implementation Method 2
when a portion of chip's output light bounces back from the slanted face of the slab before it impinges upon the VBG, a stray backreflected chip light bypasses the internal cavity of the laser chip
Implementation Method 3
an isolating volume Bragg mirror recorded in a slab of transparent material, the isolating volume mirror being operative to block propagation of a backreflected signal light
Data Source
AI summary
A gain module, operative to output a laser light coupled into a laser system, is structured with at least one gain element radiating the laser light and a spectrally-selective element. The spectrally-selective element includes a slab of photosensitive material and two parallel feedback and isolating Bragg mirrors recorded in the slab. The feedback Bragg mirror is operative to provide a wavelength-dependent feedback so as to cause the laser chip to generate the laser light at the resonance wavelength of the feedback Bragg mirror. The isolating Bragg mirror is automatically adjusted to retroreflect a backreflected signal light, which is generated by the laser system at a signal wavelength different from the resonance wavelength, upon positioning the feedback mirror orthogonally to the laser light.