Reflection-Enhanced Photo-Detector Absorption Length
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Silicon photonic photo-detectors face a tradeoff between high responsivity and low capacitance, as longer absorption lengths are required for high responsivity but conflict with the need for low capacitance in chip-to-chip interconnects, which affects bandwidth and power consumption.
Innovation Solution
Incorporating a mirror in the optical waveguide near the end of the photo-detector to reflect the optical signal back, increasing absorption length without adding capacitance, and using a distributed Bragg reflection grating or metal coating for high reflection efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the absorption length is increased to achieve high responsivity, then the responsivity is improved, but the capacitance increases which reduces bandwidth and increases power consumption
Solution Approach 1:
A mirror is introduced as an intermediary component in the optical waveguide to reflect the optical signal back through the photo-detector. This mediator enables the optical signal to traverse the absorption path multiple times without physically extending the photo-detector length, thereby increasing absorption length while maintaining low capacitance.
Solution Approach 2:
The solution transitions from a one-dimensional linear absorption path to a multi-pass optical path by introducing reflection. The optical signal propagates in multiple directions (forward and backward) through the photo-detector, effectively increasing the absorption length in the optical domain without increasing the physical dimensions of the photo-detector structure.
2Measurement precision
If the absorption length is increased to achieve high responsivity, then the responsivity is improved, but the power consumption increases due to larger transimpedance amplifier
Solution Approach 1:
The mirror serves as a mediator that enables multiple passes of the optical signal through the same photo-detector structure. This allows the system to achieve higher effective absorption without scaling up the photo-detector size, thereby avoiding the need for a larger transimpedance amplifier and reducing overall power consumption.
Solution Approach 2:
The system changes the optical path parameters by introducing reflection, transforming a single-pass linear geometry into a multi-pass configuration. This parameter change in the optical path enables enhanced absorption while maintaining the same physical component dimensions, thus avoiding increased power consumption associated with larger components.
3Use of energy by moving object
If the photo-detector capacitance is reduced for low power consumption, then the power consumption is reduced, but the absorption length must be shortened which reduces responsivity
Solution Approach 1:
The mirror acts as an intermediary that compensates for the shortened absorption length by reflecting the optical signal back through the compact photo-detector. This enables the system to maintain low capacitance while achieving sufficient absorption through multiple passes of the optical signal.
Solution Approach 2:
The solution exploits the optical path dimension rather than the physical structure dimension. By introducing reflection, the optical signal traverses the compact photo-detector multiple times, effectively increasing the absorption length in the optical domain while maintaining the same physical dimensions and low capacitance.
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 enhances responsivity by up to 25% and increases the signal-to-noise ratio by up to 2 dB without increasing capacitance or power consumption, improving photo-detector performance while maintaining low capacitance and high bandwidth.
Implementation Method 1
a mirror after and proximate to the second end of the photo-detector, where the mirror is in a plane of the optical waveguide. This mirror at least partially reflects the optical signal
Implementation Method 2
a photo-detector having a first end and second end, where the photo-detector is disposed on top of and is optically coupled to a surface of a region of the optical waveguide. This photo-detector converts the optical signal to an electrical signal
Implementation Method 3
the optical signal may be evanescently coupled between the optical waveguide and the photo-detector
Data Source
AI summary
An integrated optical device includes a photo-detector (such as germanium) optically coupled to an optical waveguide. This photo-detector is deposited on the optical waveguide, and an optical signal propagating in the optical waveguide may be evanescently coupled to the photo-detector. In order to increase the absorption length of the photo-detector, a mirror (such as a distributed Bragg reflection grating) is included in the optical waveguide near the end of the photo-detector. This mirror reflects the optical signal back toward the photo-detector, thereby increasing the absorption of the optical signal by the photo-detector. In addition, absorption may be reduced by using electrical contacts that are electrically coupled to the photo-detector at locations where the optical mode of the optical signal is largely in the underlying optical waveguide, and by using a fingered metal layer to couple to the electrical contacts.