Photonic Integrated Circuit Interferometric Frequency-Swept Source
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Solution Overview
Problem
Current optical measurement systems for detecting neural activity in the brain face challenges such as limited spatial resolution and depth penetration due to light scattering in tissues, and are complex and costly due to the need for multiple detectors and stable reference beams.
Innovation Solution
A non-invasive optical measurement system using a two-dimensional array of photonic integrated circuits (PICs) that emit and detect light within the brain, allowing for the determination of three-dimensional spatial locations of physiological events by analyzing scattered signal light and varying optical frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional optical detectors are used to measure neural activity through skull and tissue, then the system can be scaled to wearable or portable form factors, but spatial resolution is limited to centimeters and penetration depth is limited to a few millimeters due to light scattering
Solution Approach 1:
The patent combines multiple optical sources and detectors into a single photonic integrated circuit (PIC) device. The PIC integrates laser sources, modulators, waveguides, and detectors on a single chip, enabling portable form factor while achieving high spatial resolution through interferometric detection of scattered light from multiple source-detector pairs
Solution Approach 2:
The patent introduces a reference beam as an intermediary in an interferometric detection scheme. The reference beam interferes with the scattered sample light, enabling precise measurement of optical path length changes and scattering variations that encode spatial and temporal information about neural activity deep in tissue
2Measurement precision
If multiple optical sources and detectors are located along the surface of the head to increase spatial resolution, then bundles of photon paths can be identified, but the system complexity and cost increase significantly
Solution Approach 1:
The patent merges multiple optical sources and detectors into a single photonic integrated circuit (PIC) device. The PIC integrates laser sources, modulators, waveguides, and detectors on a single chip, enabling portable form factor while achieving high spatial resolution through interferometric detection of scattered light from multiple source-detector pairs
Solution Approach 2:
The photonic integrated circuit performs multiple functions: it generates coherent light, modulates the light frequency, directs light through waveguides to multiple detection points, and detects scattered light from multiple source-detector pairs. This multi-functionality in a single device reduces system complexity while maintaining high spatial resolution capability
3Measurement precision
If traditional OCT systems use coherent light and interferometric techniques to achieve micrometer-resolution imaging, then high z-resolution can be obtained at shallow depth (1 mm-2 mm), but the system is complex and requires stable reference beams
Solution Approach 1:
The patent combines multiple optical sources and detectors into a single photonic integrated circuit (PIC) device. The PIC integrates laser sources, modulators, waveguides, and detectors on a single chip, enabling portable form factor while achieving high spatial resolution through interferometric detection of scattered light from multiple source-detector pairs
Solution Approach 2:
The patent uses frequency modulation of the laser source as a key parameter change. By sweeping the laser frequency and detecting the temporal interference pattern, the system achieves depth resolution without requiring mechanical scanning or complex reference beam stabilization, simplifying the overall system
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 reduces system complexity and cost while enhancing spatial resolution and depth penetration, enabling effective detection of neural activity with improved temporal resolution.
Implementation Method 1
Traditional OCT systems use coherent light (typically light in the near-infrared spectrum) to capture sub-surface images
Implementation Method 2
Each PIC is configured for varying an optical frequency of the emitted sample light
Implementation Method 3
an optical detector monolithically integrated with the substrate... configured for detecting the signal light
Implementation Method 4
because optical imaging techniques rely on light, which scatters many times inside brain, skull, dura, pia, and skin tissues, the light paths occurring in these techniques comprise random or 'diffusive' walks
Implementation Method 5
OCT utilizes a holographic (or interferometric) technique to select, via optical path selection, the photons that directly reflect off of the sub-surface features (i.e., the ballistic backscattered photons), and reject photons that scatter multiple times
Implementation Method 6
light from a light source is split into two paths along two different arms of an interferometer: a reference arm and a sample arm
Implementation Method 7
an optical delay line... configured for delaying the propagation of the reference light
Implementation Method 8
an optical beam combiner... configured for combining the signal light and the reference light into an interference light pattern
Implementation Method 9
an edge emitting optical source (e.g., a distributed feedback (DFB) laser) that emits source light within the optical waveguide in a direction along a plane of the respective PIC
Data Source
AI summary
A non-invasive optical measurement system comprises a two-dimensional array of photonic integrated circuits (PICs) mechanically coupled to each other. Each PIC is configured for emitting sample light into an anatomical structure, such that the sample light is scattered by the anatomical structure, resulting in physiological-encoded signal light that exits the anatomical structure. Each PIC is further configured for detecting the signal light. The non-invasive optical measurement system further comprises processing circuitry configured for analyzing the detected signal light from each of the PICs, and based on this analysis, determining an occurrence and a three-dimensional spatial location of the physiological event in the anatomical structure.