Light Source Device Substrate Removal for Normal Light Extraction
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Solution Overview
Problem
In light source devices with semiconductor lasers and waveguides, the alignment of the light-emitting point and the waveguide core is critical for efficient light extraction, but existing optical-path changing elements with inclined surfaces can cause reflected light to enter the substrate, reducing efficiency.
Innovation Solution
A light source device design featuring a sub-mount with a semiconductor laser element and a planar lightwave circuit, where the light-emitting point and waveguide core are aligned, and a light-reflecting surface is used to direct light normal to the propagating direction, with a portion of the substrate removed to prevent light from entering the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the optical-path changing element with inclined surface is flip-chip mounted, then the alignment between light-emitting point and waveguide core is improved, but light reflected at the inclined surface enters the substrate, reducing light extraction efficiency
Solution Approach 1:
The patent extracts the harmful function of the substrate by removing a portion of it in the light extraction region. This creates a dedicated light extraction window that prevents reflected light from entering the substrate while maintaining the flip-chip mounted alignment structure. The substrate is selectively removed only where light extraction is needed, separating the mounting function from the light extraction function.
Solution Approach 2:
The substrate is segmented into different functional regions: a mounting region that retains the substrate structure for mechanical support and electrical connection, and a light extraction region where the substrate is removed to allow efficient light extraction. This segmentation allows the device to simultaneously achieve precise alignment through flip-chip mounting and high light extraction efficiency.
2Volume of moving object
If the waveguide and light-reflecting surface are arranged in close proximity, then the device size is reduced, but light reflected at the light-reflecting surface may enter the substrate
Solution Approach 1:
The patent removes the substrate in the light extraction region to create a dedicated extraction window. This allows the light-reflecting surface to be positioned close to the waveguide for compact device size while preventing reflected light from entering the substrate, as there is no substrate material in the extraction path.
Solution Approach 2:
The substrate structure is modified locally in the light extraction region rather than uniformly throughout the device. The selective removal of substrate material creates a localized quality change that enables efficient light extraction specifically where needed, while maintaining the compact proximity arrangement between waveguide and light-reflecting surface.
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 design ensures efficient light extraction in a direction normal to the base surface, enhancing the light-emitting efficiency and preventing light from entering the substrate, even when the waveguide and light-reflecting surface are in close proximity.
Implementation Method 1
A light-reflecting surface is provided such that light emitted from the semiconductor laser element and propagating along a propagating direction in the planar lightwave circuit is reflected at the light-reflecting surface in a direction substantially normal to the propagating direction
Data Source
AI summary
A light source device includes a sub-mount, a semiconductor laser element flip chip mounted on the sub-mount, and a planar lightwave circuit (PLC) which is an optical member having a waveguide disposed on a substrate. The semiconductor laser element and the waveguide are arranged such that a light-emitting point of the semiconductor laser element and a core of the waveguide are substantially aligned. A light-reflecting surface is provided such that light emitted from the semiconductor laser element and propagating along a propagating direction in the planar lightwave circuit is reflected at the light-reflecting surface in a direction substantially normal to the propagating direction. A portion of the substrate of the planar lightwave circuit is removed at least in a predetermined range from an end opposite to a light incident surface of the planar lightwave circuit.