Integrated Optoelectronic Module for THz Power Combination
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Solution Overview
Problem
High-frequency photodiodes with small junction areas face challenges in optical coupling and packaging due to increased RC time constant and reduced operating current, leading to inefficient power combination in THz frequency ranges.
Innovation Solution
An integrated optoelectronic module utilizing a multi-mode interferometer waveguide with a reflection section formed by grooving an inclined surface, filled with a low-index material, and optionally a metal or dielectric mirror, to efficiently couple optical signals to photodiodes with small junction areas, allowing for effective power combination in arrays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the junction area of photodiode is reduced to decrease device capacitance for high frequency operations, then the operating frequency response is improved, but the upper limit on operating current decreases
Solution Approach 1:
Multiple photodiodes are integrated on a single semiconductor substrate to form an array configuration. The substrate integrates both the photodiode array and optical waveguides, merging optical signal distribution and electrical signal collection functions into one compact structure, thereby achieving high frequency response while maintaining sufficient operating current through combined output of multiple elements
Solution Approach 2:
The patent transitions from planar optical coupling to three-dimensional stacked configuration. The photodiodes are positioned vertically above the optical waveguides, utilizing the vertical dimension to achieve compact integration while maintaining efficient optical coupling through evanescent field interaction between the waveguide and photodiode active regions
2Manufacturing precision
If conventional lens optics is used to focus optical beam on small junction photodiode, then optical coupling to single photodiode is possible, but adjustment complexity increases
Solution Approach 1:
The optical waveguide structure provides self-aligning optical coupling to the photodiodes through evanescent field interaction. The waveguide modes automatically couple to the photodiode active regions without requiring precise external lens alignment, eliminating complex adjustment procedures while maintaining high coupling efficiency
Solution Approach 2:
The patent replaces mechanical lens-based optical focusing with waveguide-based evanescent field coupling. This substitution eliminates the need for mechanical alignment of lenses and focuses optical energy through electromagnetic field confinement in the waveguide, thereby simplifying the packaging structure
3Power
If antenna integrated photodiode with THz spherical lens is used, then THz power combination is achieved, but optical signal input to back-illuminated photodiode becomes difficult
Solution Approach 1:
The device is segmented into distinct functional layers: optical waveguides for signal input, photodiodes for detection, and antennas for THz emission. This segmentation allows optical signals to be coupled into waveguides from the side, avoiding interference with the back-illuminated photodiode structure while maintaining efficient optical input capability
Solution Approach 2:
The optical waveguide acts as an intermediary structure that couples optical signals to the photodiodes without requiring direct optical access to the back surface. The waveguide confines and guides optical energy to the photodiode active regions through evanescent field coupling, enabling indirect optical input that preserves both optical coupling efficiency and photodiode performance
4Adaptability or versatility
If evanescent optical coupling structure is used to integrate optical waveguide with photodiodes, then optical signal distribution to multiple photodiodes is achieved, but coupling efficiency is insufficient for small junction area photodiodes
Solution Approach 1:
The patent optimizes key parameters of the evanescent coupling structure: the vertical spacing between waveguide and photodiode, the lateral offset distance, and the interaction length. By precisely controlling these parameters, the coupling efficiency is maximized for small junction area photodiodes while maintaining the ability to distribute optical signals to multiple elements
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 enables efficient optical coupling and power combination for photodiodes with small junction areas, overcoming packaging challenges and achieving higher THz power levels with reduced noise and extended measurement times.
Implementation Method 1
an optical signal having propagated through the multi-mode interferometer waveguide is reflected by the reflection section and focused on the optical absorption layer section
Data Source
Figure 1A~1C
Figure 2
Figure 3
AI summary
An integrated optoelectronic module (11) comprising: a semiconductor substrate (1); a single-mode optical waveguide (2) comprising a semiconductor with a signal input section at a first end; a multi-mode optical waveguide (3) comprising a semiconductor connected to a second end of the single-mode optical waveguide; and a photodiode (20) disposed on and adjacent to the multi-mode interferometer waveguide and having at least one optical absorption layer section (5), wherein the single-mode optical waveguide, the multi-mode optical waveguide, and the photodiode being stacked on the semiconductor substrate, wherein the multi-mode interferometer waveguide comprises a reflection section (9) formed by partly grooving the multi-mode interferometer waveguide, and an optical signal having propagated through the multi-mode interferometer waveguide is reflected by the reflection section and focused on the optical absorption layer section.