AXEL Optical Circuit Window Structure for Cleavage-Tolerant Output
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Solution Overview
Problem
The integration of a semiconductor optical amplifier (SOA) in EADFB lasers (AXEL) leads to increased reflected return light, affecting operation characteristics, and manufacturing variations in the cleavage process result in decreased chip yield due to insufficient suppression of reflected return light and inaccurate cleavage positions.
Innovation Solution
An optical circuit with integrated semiconductor laser and SOA, featuring a waveguide and a window region with simulated mesas parallel to the optical axis, where the window region is thickened with a bulk semiconductor layer to reduce optical loss and accommodate manufacturing variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a window structure portion is formed at the light emission edge face to reduce reflected return light, then optical loss is reduced and transmission characteristics are improved, but manufacturing precision is degraded due to cleavage position errors
Solution Approach 1:
The patent applies local quality by creating simulated mesas only in the window structure portion at the light emission edge face, while maintaining the normal waveguide structure in the core region. This localized modification allows the window region to have different optical properties (reduced reflection) without affecting the precision-critical waveguide coupling region, thereby resolving the contradiction between improving transmission characteristics and maintaining manufacturing precision.
Solution Approach 2:
The patent segments the light emission edge face into two distinct regions: a waveguide region that maintains precise coupling characteristics and a window structure portion that handles reflection reduction. By separating these functions into different spatial zones, the design allows the window region to accommodate cleavage position errors while the waveguide region maintains its precision, thus resolving the technical contradiction.
2Productivity
If the window region length is increased to accommodate cleavage position errors, then manufacturing yield is improved, but optical loss increases due to beam diffraction
Solution Approach 1:
The simulated mesas are placed only in the window structure portion away from the optical axis, allowing the window region to be extended for yield improvement without increasing optical loss in the critical beam propagation path. This localized structure enables the window region to serve as a tolerance buffer for cleavage errors while maintaining efficient light coupling.
Solution Approach 2:
The patent addresses the trade-off by transitioning from a one-dimensional optimization (window length) to a two-dimensional solution (simulated mesas positioned at specific distances from the optical axis). This dimensional approach allows the window region to be sufficiently long for yield improvement while the simulated mesas prevent excessive diffraction loss by providing alternative light propagation paths.
3Reliability
If simulated mesas are added to the window region to reduce optical loss, then transmission characteristics are improved, but device complexity increases
Solution Approach 1:
The patent merges the formation of simulated mesas with the existing window structure portion creation process. The simulated mesas are integrated into the window region during the same manufacturing steps used to create the window structure, combining multiple functions (reflection reduction, cleavage error tolerance) into a single structural feature without adding separate complex components or processes.
Solution Approach 2:
The simulated mesas serve multiple functions simultaneously: they reduce optical loss by providing alternative light paths, accommodate cleavage position errors by being positioned in the window region, and maintain manufacturing simplicity by using the same formation process as the window structure. This multi-functionality reduces overall device complexity despite the added structural element.
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 achieves high output and quality transmission characteristics by minimizing optical loss and maintaining stable optical output levels despite manufacturing errors, thereby improving yield and reducing defects.
Implementation Method 1
a window structure portion 108 including a plurality of simulated mesas 102 configured parallel to an optical axis 109 from an end of the waveguide 101 to the edge face 110 and being buried by a bulk semiconductor 106 except for the simulated mesas
Data Source
AI summary
The optical circuit of the present disclosure provides a new optical transmitter configuration that achieves both high output and high quality transmission characteristics regardless of variations at cleavage positions. The optical circuit of the present disclosure may be an optical transmitter having an AXEL configuration in which an EADFB laser and a semiconductor optical amplifier (SOA) are integrated. In a window structure portion of a chip emission edge face of the AXEL, a partially thickened bulk semiconductor layer is formed by a structure including a simulated mesa configured to be separated from an optical axis parallel to an optical axis of an emission optical waveguide.