Optical Device Using Phase-Shifting Cavity for Infrared Sensor Efficiency
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Solution Overview
Problem
Existing infrared sensor pixels suffer from low quantum efficiency, limited miniaturization, and resolution due to limited infrared light absorption in the active region, along with optical crosstalk issues.
Innovation Solution
An optoelectronic device is configured with a reflective polarizing filter, a phase-shifting element that adds a π/4 phase shift, an active region for light absorption, and a reflector, forming a polarizing optical cavity that increases the optical path in the active region, enhancing quantum efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a simple pixel structure with polarizing filter and active region is used, then the device complexity is low, but the quantum efficiency is low due to limited light absorption
Solution Approach 1:
The pixel structure is segmented into distinct functional layers: polarizing filter layer, phase-shifting element layer, active region layer, and reflector layer. This segmentation allows each layer to perform its specific function optimally, with the phase-shifting element creating multiple optical passes through the active region to enhance absorption without requiring a completely redesigned complex structure
Solution Approach 2:
The invention introduces a temporal dimension to light absorption by creating multiple passes of light through the active region. The phase-shifting element converts linearly polarized light into circularly polarized light, enabling the light to interact with the active region multiple times (first pass, reflection, second pass) before exiting, effectively increasing the absorption path length without increasing the physical thickness of the pixel
2Measurement precision
If the pixel size is reduced to improve resolution, then the imager resolution improves, but the quantum efficiency decreases due to less light absorption area
Solution Approach 1:
The phase-shifting element ensures continuous interaction between light and the active region by creating a circular polarization state that allows light to pass through the active region, reflect off the mirror, and pass through again. This continuous useful action maximizes the absorption probability within the limited pixel area, maintaining high quantum efficiency even as pixel size decreases for improved resolution
3Reliability
If a diffractive structure is added upstream of the active region to increase light path length, then the quantum efficiency improves, but the device complexity increases and a compromise between resolution and efficiency remains necessary
Solution Approach 1:
Instead of adding a diffractive structure that changes the spatial distribution of light, the invention changes the polarization parameter of the light using a phase-shifting element. This parameter change (from linear to circular polarization) enables multiple passes through the active region without requiring additional complex optical structures, achieving enhanced quantum efficiency with minimal increase in device complexity
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 configuration significantly improves quantum efficiency by allowing light rays to make multiple round trips within the optical cavity, thereby increasing absorption and reducing optical crosstalk, leading to enhanced imaging resolution.
Implementation Method 1
one reflective polarizing filter, configured to solely transmit light radiation rays exhibiting a first polarization
Implementation Method 2
one phase-shifting element configured to add a phase shift of π/4 in polarization to the light radiation rays passing through said phase-shifting element
Implementation Method 3
one active region configured to absorb at least partially the light radiation rays
Implementation Method 4
one reflector configured to reflect at least partially the light radiation rays
Data Source
AI summary
The disclosure relates to an optoelectronic device comprising in a stack: one reflection polarizing filter, one phase-shifting element configured to add a π/4 phase shift in polarization, one active region, one reflector, so that the light radiation rays reflected by the reflector and passing through the phase-shifting element exhibit a new polarization phase-shifted by π/2 with respect to their initial polarization, the rays then being reflected anew by the polarizing filter in the direction of the active region.