Chirped Sampled Grating Laser for Mode Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional wavelength changeable semiconductor lasers with Sampled Grating Distributed Reflector (SG-DR) waveguides face mode stability degradation when changing wavelengths over a broad range, leading to unwanted laser emissions and difficulty in maintaining stability due to small Q values and wavelength dependence of optical longitudinal mode peak reflectivity.
Innovation Solution
A semiconductor laser with a Chirped Sampled Grating Distributed Reflector (CSG-DR) structure, featuring segments with varying optical lengths and refractive indices, which allows for controlled peak reflection intensity and wavelength dependence, stabilizing laser emission by optimizing the optical lengths and refractive indices of segments to enhance mode stability and reduce unwanted emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the wavelength tuning range is broadened in conventional SG-DR lasers, then more wavelength coverage is achieved, but mode stability deteriorates due to unwanted laser emissions
Solution Approach 1:
The SG-DR waveguide is divided into multiple segments with different optical lengths. Each segment contributes to the overall reflection spectrum, and by controlling the optical lengths differently, the patent achieves wavelength-dependent peak reflectivity enhancement that stabilizes mode selection across the tuning range while maintaining broad wavelength coverage
Solution Approach 2:
Different segments of the SG-DR waveguide are assigned different optical lengths to create local variations in reflection characteristics. This local quality differentiation enables wavelength-dependent control where specific wavelengths experience enhanced peak reflectivity, thereby stabilizing mode emission at desired wavelengths across the broad tuning range
2Adaptability or versatility
If temperature or current is changed to match optical longitudinal modes, then wavelength tuning is achieved, but mode stability is degraded due to wavelength dependence of peak reflectivity
Solution Approach 1:
The SG-DR waveguide segments are pre-configured with specific optical lengths before operation to establish wavelength-dependent peak reflectivity characteristics. This preliminary structural arrangement ensures that when temperature or current is adjusted for wavelength tuning, the desired mode experiences enhanced reflectivity, thereby maintaining mode stability throughout the tuning process
3Length of moving object
If a simple FP resonator is used, then the element length is reduced, but the Q value of reflection spectrum becomes small leading to unstable laser emission
Solution Approach 1:
The patent combines the FP resonator structure with an SG-DR waveguide featuring segments of different optical lengths. This composite structure integrates the compactness of the FP resonator with the wavelength-selective enhancement of the segmented SG-DR waveguide, achieving both reduced element length and improved mode stability through wavelength-dependent peak reflectivity
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 CSG-DR structure achieves stabilized laser emission with high peak reflectivity in a specific wavelength range, allowing for easy wavelength control and reduced mode degradation, thereby improving the stability and efficiency of laser emission.
Implementation Method 1
Each segment has a first area including a diffractive grating
Implementation Method 2
peak reflection intensity of an optical longitudinal mode has wavelength dependence
Implementation Method 3
a first optical element having a waveguide core
Data Source
AI summary
A semiconductor laser has a first diffractive grating area. The first diffractive grating area has a plurality of segments. Each segment has a first area including a diffractive grating and a second area that is space area combined to the first area. Optical lengths of at least two of the second areas are different from each other. A refractive-index of each of the segments are changeable.