Pre-distorted Grating for DFB Laser Strain Compensation
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Solution Overview
Problem
DFB lasers experience grating pitch distortion and phase shift due to bonding-induced strain from CTE mismatch between the laser and submount materials, leading to laser kink or multimode operation, which significantly impacts production yield.
Innovation Solution
A pre-distorted grating with varying pitch is designed according to the longitudinal strain profile to compensate for bonding-induced stress, ensuring a uniform grating pitch post-bonding and minimizing phase shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a uniform pitch grating is used in the laser, then the laser structure is simple and manufacturing is easy, but bonding-induced strain causes pitch distortion and phase shift leading to laser failure
Solution Approach 1:
The grating pitch is pre-distorted during manufacturing to anticipate and compensate for the strain that will occur during bonding. By applying the opposite distortion beforehand, the grating returns to a uniform pitch state after bonding, preventing phase shifts and maintaining single-mode operation.
Solution Approach 2:
The grating is deliberately distorted in the opposite direction of the expected bonding-induced strain. This preliminary anti-action ensures that when bonding strain is applied, it counteracts the pre-distortion and restores the grating to its intended uniform pitch configuration.
2Reliability
If the grating pitch is varied to compensate for strain, then laser reliability improves, but manufacturing precision requirements increase
Solution Approach 1:
The grating pitch parameter is intentionally varied as a function of position along the grating length. By changing the pitch parameter according to a predetermined profile that matches the expected strain distribution, the grating compensates for bonding-induced deformation while maintaining manufacturability through systematic parameter control.
3Strength
If bonding is performed to assemble laser to submount, then mechanical strength and thermal management improve, but CTE mismatch induces strain causing laser kink or multimode operation
Solution Approach 1:
The invention accounts for thermal expansion differences between the laser and submount materials during bonding. By pre-distorting the grating to compensate for the expected thermal expansion mismatch strain, the system maintains grating uniformity despite the inherent CTE differences between bonded components.
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 pre-distorted grating effectively prevents laser kink failures and enhances production yield by maintaining a stable optical output and single mode operation, even under thermal expansion mismatch conditions.
Implementation Method 1
The grating is pre-distorted to vary a pitch of the grating according to a longitudinal strain profile of the grating to compensate for bonding induced stress such that the grating has a uniform pitch following bonding of the laser to the carrier
Implementation Method 2
DFB (Distributed Feedback) lasers are key components for silicon photonics. The active region of the device is periodically structured as a diffraction grating. The structure builds a one-dimensional interference grating that provides optical feedback for the laser.
Implementation Method 3
The active region of the device is periodically structured as a diffraction grating. The structure builds a one-dimensional interference grating that provides optical feedback for the laser.
Implementation Method 4
The active region of the device is periodically structured as a diffraction grating
Data Source
AI summary
In one embodiment, an apparatus includes a carrier and a semiconductor laser bonded to the carrier, the semiconductor laser comprising a grating extending longitudinally along the semiconductor laser. The grating is pre-distorted to vary a pitch of the grating according to a longitudinal strain profile of the grating to compensate for bonding induced stress such that the grating has a uniform pitch following bonding of the laser to the carrier.