Angled Facet Waveguide for Surface Emitting Photonic Devices
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Solution Overview
Problem
Existing surface-emitting photonic devices, such as semiconductor lasers, face challenges with facet formation methods that hinder monolithic integration and result in undesirable far-field intensity profiles with ripples, limiting their efficiency in coupling laser beams into optical fibers.
Innovation Solution
A surface-emitting photonic device with a waveguide structure featuring angled facets etched at specific angles, such as 44.4°, to direct light perpendicular to the substrate, reducing beam pointing and ripples in the far-field intensity profile, and allowing for monolithic integration and efficient laser beam coupling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If cleaved facets are used to form laser ends, then device fabrication is simplified, but the devices cannot be tested in full-wafer and cannot be monolithically integrated
Solution Approach 1:
The invention changes the geometric parameter of the facet from a cleaved surface to an etched facet at a specific angle (greater than the critical angle for total internal reflection). This parameter change enables both monolithic integration and full-wafer testing while maintaining fabrication feasibility through standard semiconductor processing techniques.
Solution Approach 2:
The invention replaces the mechanical cleaving process with an etching process to form the laser facets. This substitution enables monolithic integration with other photonic devices on the same substrate and allows for full-wafer testing, overcoming the limitations of cleaved facet devices.
2Adaptability or versatility
If etched 45° facets are used, then monolithic integration is enabled, but scatter occurs at each end of the laser cavity
Solution Approach 1:
The invention optimizes the facet angle parameter to be greater than the critical angle for total internal reflection but less than 45°, specifically in the range of 35°-40°. This optimized angle reduces light scatter at the cavity ends while maintaining monolithic integration capability and achieving low beam pointing.
Solution Approach 2:
The invention uses a composite structure combining etched facets at optimized angles with appropriate reflector configurations (such as distributed Bragg reflectors or high reflectivity stacks) to minimize scatter and achieve desirable far-field patterns with low beam pointing.
3Ease of operation
If VCSEL structure is used, then surface emission is achieved, but in-plane monolithic integration is not allowed and light exits only at perpendicular incidence
Solution Approach 1:
The invention introduces asymmetry by etching facets at specific angles (greater than critical angle but less than 45°) rather than using symmetric perpendicular exits. This asymmetric facet configuration enables both in-plane monolithic integration and flexible emission directions while maintaining surface emission characteristics.
Solution Approach 2:
The invention transitions from the VCSEL's perpendicular-only emission by introducing angled facets that redirect light propagation. This dimensional change in light path orientation enables both in-plane integration and controlled emission angles while preserving surface emission benefits.
4Productivity
If ripples are present in far-field intensity profile, then coupling into optical fiber is inefficient, but conventional facet formation methods produce ripples
Solution Approach 1:
The invention changes the facet angle parameter to an optimized value (greater than critical angle but less than 45°, specifically 35°-40°) that produces a smooth far-field intensity profile without ripples. This parameter optimization directly improves fiber coupling efficiency while maintaining manufacturability through standard etching 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
The solution achieves a low beam pointing angle and minimizes ripples in the far-field, enhancing the coupling of laser beams into optical fibers and enabling more efficient and integrated photonic device configurations.
Implementation Method 1
The waveguide structure has a trench formed therein transverse to the active region and defining a first wall forming an angled facet at one end of the active region, the first wall having a normal that is at a non-parallel angle relative to the longitudinal axis of the waveguide structure
Data Source
AI summary
A surface emitting photonic device including a substrate; and a waveguide structure on the substrate. The waveguide structure includes an active region along its longitudinal axis and the active region is for generating light. The waveguide structure also has a trench formed therein transverse to the active region and defining a first wall forming an angled facet at one end of the active region, the first wall having a normal that is at a non-parallel angle relative to the longitudinal axis of the waveguide structure. The trench also defines a second wall located opposite the first wall.