Optical Semiconductor Resonator Grating Pitch Compensation
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Solution Overview
Problem
Optical semiconductor devices manufactured using butt-joint growth exhibit non-uniform emission wavelengths due to the selective area growth effect, leading to reduced side-mode suppression ratio (SMSR) in distributed feedback lasers, as the effective refraction index varies along the optical axis, affecting the frequency symmetry and threshold gain difference between oscillation modes.
Innovation Solution
The optical semiconductor resonator incorporates a waveguide with varying effective refraction index and diffraction grating pitches along the optical axis, with narrower pitches where the refraction index is higher, ensuring a consistent emission wavelength and maintaining a high SMSR by adjusting the diffraction grating pitches based on the effective refraction index and thickness variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If butt-joint growth method is used to manufacture optical semiconductor device, then integration of resonator portion and modulator portion is achieved, but non-uniform emission wavelength occurs due to selective area growth effect
Solution Approach 1:
The patent applies local quality by making the diffraction grating pitch non-uniform along the optical axis, with narrower pitches in areas of higher effective refraction index and wider pitches in areas of lower effective refraction index. This local variation compensates for the non-uniform film thickness caused by selective area growth, maintaining uniform DFB wavelength across different locations while preserving the integrated structure benefits
2Ease of manufacture
If diffraction grating with uniform pitch is used, then manufacturing simplicity is maintained, but side-mode suppression ratio decreases due to non-uniform effective refraction index
Solution Approach 1:
The patent changes the pitch parameter of the diffraction grating along the optical axis to compensate for variations in effective refraction index. By adjusting the pitch to be narrower where the refraction index is higher and wider where it is lower, the DFB wavelength remains uniform, maintaining high side-mode suppression ratio while the overall structure remains relatively simple to manufacture
3Productivity
If film thickness increases toward mask end due to selective area growth effect, then crystal growth process is completed, but non-uniform DFB wavelength results affecting oscillation mode stability
Solution Approach 1:
The patent addresses the non-uniform film thickness by implementing local quality variations in the diffraction grating pitch. Areas with greater film thickness (higher effective refraction index) receive narrower grating pitches, while areas with lesser thickness receive wider pitches, compensating for the thickness non-uniformity and maintaining stable, uniform DFB wavelength across the entire resonator structure
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 approach prevents non-uniformity in emission wavelength, maintaining a high SMSR yield by ensuring a consistent DFB wavelength, thereby enhancing the stability and performance of optical communication devices.
Implementation Method 1
diffraction gratings formed along the optical axis direction of the waveguide
Implementation Method 2
distributed feedback (DFB) lasers
Data Source
AI summary
In order to prevent non-uniformity in emission wavelength among different sites along an optical axis direction, provided is a resonator portion including: a waveguide which includes at least two areas where an effective refraction index varies in the optical axis direction; and diffraction gratings formed along the optical axis direction of the waveguide. The diffraction grating that is formed in one of the at least two areas of the waveguide where the effective refraction index is large has a pitch narrower than a pitch of the diffraction grating that is formed in another of the at least two areas of the waveguide where the effective refraction index is small.