Patterned Non-Reciprocal Optical Resonator for Semiconductor Integration
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Solution Overview
Problem
The integration of optical isolators on a semiconductor platform is challenging due to the need for patterning and etching of magneto-optical materials and engineering of magnetic domain structures, which are fabrication unfriendly, and existing devices have not been demonstrated experimentally.
Innovation Solution
A patterned nonreciprocal optical resonator structure is developed that uses a top cladding layer to expose the core of the resonator, allowing for the deposition of a magneto-optically active layer without patterning or etching the magneto-optical materials, enabling optical non-reciprocity with a uniform magnetic field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional bulk optical isolators based on Faraday effect are used, then optical isolation functionality is achieved, but device footprint is large and integration on semiconductor platform is difficult
Solution Approach 1:
The patent transitions from bulk 3D optical isolators to 2D planar photonic crystal resonator structures integrated on semiconductor substrates. The magneto-optical layer is deposited as a thin film on the planar resonator, enabling dimensional reduction and semiconductor platform compatibility while maintaining isolation functionality.
Solution Approach 2:
The patent changes the operating principle from bulk Faraday rotation to resonant enhancement in photonic crystals. By utilizing optical resonance conditions, the magneto-optical effect is significantly enhanced, allowing compact device footprint at semiconductor scale while achieving sufficient non-reciprocal phase shift for optical isolation.
2Area of stationary object
If previously proposed device structures are used to reduce footprint, then device footprint is reduced, but fabrication becomes unfriendly due to patterning and etching of magneto-optical materials
Solution Approach 1:
The patent separates the resonator structure from the magneto-optical layer. The photonic crystal resonator is fabricated using standard semiconductor processes, and the magneto-optical material is deposited as a separate thin film layer afterward. This segmentation allows the magneto-optical layer to be applied uniformly without requiring complex patterning or etching, greatly simplifying fabrication.
Solution Approach 2:
The resonator structure is fully fabricated and characterized before depositing the magneto-optical layer. The resonator design is optimized in advance to provide sufficient light-matter interaction with a thin magneto-optical film, eliminating the need for subsequent patterning or etching of the magneto-optical material and enabling straightforward integration.
3Reliability
If magneto-optical materials are patterned and etched to achieve optical isolation, then optical non-reciprocity is achieved, but device complexity and fabrication difficulty increase
Solution Approach 1:
The photonic crystal resonator structure itself provides the optical confinement and enhancement needed for magneto-optical interaction. The resonant modes naturally concentrate the optical field within the resonator cavity, where the magneto-optical layer is deposited, eliminating the need for additional patterning or etching of the magneto-optical material to achieve the desired optical non-reciprocity.
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 approach achieves optical isolation by lifting the degeneracy of forward and backward resonant wavelengths, demonstrating a high figure of merit and compact footprint without the need for complex fabrication steps, with experimental results showing an isolation ratio of 19.5±2.5 dB and insertion loss of 18.8±1.1 dB.
Implementation Method 1
Optical isolators based on Mach-Zehnder structure have been proposed and demonstrated on a garnet substrate platform. However such devices usually require larger footprint compared with the Faraday isolator counterpart owing to the weaker magneto-optical nonreciprocal phase shift (NRPS) effect
Implementation Method 2
Using resonance structures such as ring resonators or photonic crystals, the footprint of optical isolators were expected to significantly reduce from millimeter to micron meter level
Data Source
AI summary
A patterned nonreciprocal optical resonator structure is provided that includes a resonator structure that receives an optical signal. A top cladding layer is deposited on a selective portion of the resonator structure. The top cladding layer is patterned so as to expose the core of the resonator structure defined by the selective portion. A magneto-optically active layer includes a magneto-optical medium being deposited on the exposed core of the resonator structure so as to generate optical non-reciprocity.