Optical Subassembly Layout for Stable SMSR in Multi-Mesa Lasers
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Solution Overview
Problem
The integration of multiple light emitting devices in optical semiconductor devices leads to increased manufacturing costs and reduced yield due to side mode suppression ratio (SMSR) failures, which are inherent when diffraction gratings extend to the back end surface and are coated with reflective films, causing phase control issues.
Innovation Solution
The optical semiconductor device features a semiconductor substrate with mesa stripes having diffraction gratings extending to the back end surface, a reflective film with 30% or more reflectivity, and a center-to-center distance of 150 μm or less between mesa stripes, allowing at least two mesa stripes to be driven simultaneously, thereby reducing phase differences and enhancing yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple light emitting devices are integrated in an optical semiconductor device, then manufacturing cost increases and yield decreases due to SMSR failures, but device functionality and optical signal transmission capability are improved
Solution Approach 1:
The patent applies parameter changes by precisely controlling the center-to-center distance between mesa stripes to be 150 μm or less. This parameter optimization reduces phase differences in reflected light, stabilizing SMSR and improving yield while maintaining multi-device functionality
Solution Approach 2:
The patent implements preliminary anti-action by pre-configuring the mesa stripe spacing to counteract the inherent phase control issues that would otherwise cause SMSR failures. The reflective film and diffraction grating are designed in advance to compensate for potential yield-reducing effects
2Illumination intensity
If diffraction gratings extend to the back end surface with reflective film coating, then optical performance is improved, but phase control issues cause SMSR failures and reduce yield
Solution Approach 1:
The patent changes the critical parameter of mesa stripe spacing to 150 μm or less, which fundamentally alters the phase relationship of reflected light. This parameter modification maintains the optical performance benefits of extended diffraction gratings while resolving the phase control issues that caused SMSR failures
Solution Approach 2:
The patent applies local quality by creating different functional zones within the optical semiconductor device. The mesa stripes are positioned with specific spacing to achieve optimal phase control in critical areas, while maintaining the diffraction grating structure for optical performance in other regions
3Ease of manufacture
If mesa stripes are positioned with larger spacing, then manufacturing and wire bonding are easier, but phase differences increase causing SMSR failures
Solution Approach 1:
The patent optimizes the mesa stripe spacing parameter to 150 μm or less, finding the optimal balance between manufacturing ease and SMSR stability. This parameter setting ensures sufficient space for wire bonding while maintaining phase control to prevent SMSR failures
Solution Approach 2:
The patent uses a standardized mesa stripe configuration that can be replicated across multiple devices on the semiconductor substrate. This copying approach maintains consistent phase relationships while enabling scalable manufacturing and simplified wire bonding processes
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 configuration stabilizes the side mode suppression ratio, increases the yield of the optical semiconductor device, and reduces the likelihood of SMSR failures, leading to a higher production yield and lower costs.
Implementation Method 1
a reflective film provided at back end surfaces of the plurality of mesa stripes and having a reflectivity of 30% or more
Implementation Method 2
each of which includes an active layer and a diffraction grating, the diffraction grating extending up to a back end surface of each of the plurality of mesa stripes
Data Source
AI summary
An optical semiconductor device includes a semiconductor substrate; a plurality of mesa stripes, which are arranged side by side on the semiconductor substrate, and each of which includes an active layer and a diffraction grating, the diffraction grating extending up to a back end surface of each of the plurality of mesa stripes; a plurality of electrodes, each of which is electrically connected to an upper surface of a corresponding one of the plurality of mesa stripes, having a pad portion for wire bonding; a plurality of waveguides, each of which is optically connected to the active layer of a corresponding one of the plurality of mesa stripes; and a reflective film provided at back end surfaces of the plurality of mesa stripes, and wherein at least two mesa stripes, of the plurality of mesa stripes, are configured to be driven at the same time.