Phase-Shift Semiconductor Laser Layout to Suppress Hole Burning
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Solution Overview
Problem
The hole burning effect in semiconductor lasers with phase shift portions leads to increased spectral line width and loss of single-mode oscillation, degrading laser characteristics.
Innovation Solution
Incorporating a highly resistive element beneath the phase shift portion of the semiconductor laser to reduce current density and suppress the hole burning effect by minimizing current flow through this region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a phase shift portion is added to the grating to improve laser characteristics, then the laser can achieve better single-mode oscillation, but axial hole burning occurs causing spectral line width to increase and characteristics to degrade
Solution Approach 1:
The patent applies local quality by creating a highly resistive element specifically at the phase shift portion location. This localized modification changes the electrical properties only where needed - beneath the phase shift portion - to reduce current density and suppress hole burning, while leaving the rest of the laser structure unchanged. This resolves the contradiction by locally addressing the harmful effect without compromising the overall single-mode oscillation capability provided by the phase shift grating.
Solution Approach 2:
The highly resistive element acts as an intermediary between the electrode and the active layer at the phase shift portion. It mediates the current flow by providing high resistance specifically at this location, thereby reducing the current density that causes axial hole burning. This intermediary structure allows the phase shift portion to maintain its optical function while eliminating the harmful electrical effect, resolving the contradiction between improved single-mode oscillation and suppression of hole burning.
2Power
If current flows through the phase shift portion region, then the region contributes to light emission, but concentrated light intensity causes stimulated emission that depletes carriers and reduces gain
Solution Approach 1:
The patent implements local quality by introducing a highly resistive element specifically at the phase shift portion, creating a localized high-resistance region. This local modification reduces current density precisely where concentrated light intensity causes carrier depletion, thereby maintaining carrier density in the critical phase shift region without significantly impacting the overall light emission power of the laser.
Solution Approach 2:
The patent applies parameter changes by modifying the electrical resistance parameter locally at the phase shift portion through the highly resistive element. This changes the current density distribution parameter, reducing it in the phase shift region where carrier depletion occurs due to stimulated emission. This parameter modification resolves the contradiction by maintaining adequate carrier density while preserving sufficient light emission capability.
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 suppresses the hole burning effect, maintaining stable single-mode oscillation and improving the semiconductor laser's overall performance by reducing photon-induced carrier density fluctuations.
Implementation Method 1
a highly resistive element higher in electric resistance than the contact layer; and an electrode in contact with the contact layer, the highly resistive element being placed below at least a part of a portion of the electrode that overlaps with the phase shift portion
Data Source
AI summary
Provided is a semiconductor laser that includes: an active layer; a grating layer including a phase shift portion with partially different grating periods; a contact layer placed above the grating layer; a highly resistive element higher in electric resistance than the contact layer; and an electrode in contact with the contact layer, and the highly resistive element is below at least a part of a portion of the electrode that overlaps with the phase shift portion.