Time-Resolved Fluorescence Sensor Using Entangled Photons
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Solution Overview
Problem
Current time-resolved fluorescence techniques using pulsed lasers are limited by the need for external power sources, short on-chip cavity lengths, and narrow wavelength tuning ranges, making them unsuitable for distributable and wearable devices, as well as challenging for measuring multiple fluorescent probes or dynamics in local environments.
Innovation Solution
The use of deterministic temporal correlations between entangled photons created through spontaneous parametric down-conversion, allowing for low-power, on-chip fluorescence lifetime measurements using a continuous wave laser diode, which enables efficient and versatile time-resolved fluorescence imaging without the need for high-power pulsed lasers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pulsed lasers are used for time-resolved fluorescence measurements, then measurement precision is improved, but device complexity and power requirements increase
Solution Approach 1:
The patent uses an acoustic modulator as an intermediary device to modulate the continuous wave laser output, creating pulsed-like excitation without requiring a complex pulsed laser system. The acoustic modulator converts electrical signals into acoustic waves that physically modulate the laser cavity, providing the necessary temporal structure for time-resolved measurements while keeping the light source relatively simple.
Solution Approach 2:
The patent replaces the mechanical/electrical complexity of pulsed laser generation with acoustic modulation of a continuous wave laser. Instead of using complex pulsed laser electronics and cavity designs, the system uses acoustic waves to create the temporal structure needed for fluorescence lifetime measurements, simplifying the overall device architecture.
2Measurement precision
If pulsed lasers with short pulse widths are used, then time resolution is improved, but the repetition rate becomes too high for fluorophore relaxation
Solution Approach 1:
The patent dynamically adjusts the modulation parameters of the continuous wave laser using acoustic modulation. By controlling the acoustic frequency and duty cycle, the system creates excitation pulses with optimized width and spacing that allow fluorophores to fully relax between pulses while maintaining sufficient time resolution for accurate lifetime measurements.
3Weight of moving object
If on-chip pulsed lasers are used, then device portability is improved, but wavelength tuning range is limited
Solution Approach 1:
The patent uses a single continuous wave laser diode that can be acoustically modulated to serve multiple functions. By adjusting the acoustic modulation parameters and laser wavelength, the same hardware platform can measure fluorescence lifetimes of multiple different fluorophores with varying excitation wavelengths, eliminating the need for multiple specialized pulsed laser sources.
4Use of energy by stationary object
If continuous wave laser with acoustic modulation is used, then power consumption is reduced, but achieving pulsed excitation becomes more complex
Solution Approach 1:
The acoustic modulator serves as an efficient intermediary that converts low-power electrical signals into high-power acoustic waves that directly modulate the laser cavity. This approach allows the system to use minimal electrical power while still achieving effective pulsed excitation of the fluorophores, as the acoustic modulation leverages the existing laser gain medium rather than requiring full electrical re-excitation.
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 provides equivalent or superior performance to traditional pulsed laser methods, enabling efficient, low-power, and versatile time-resolved fluorescence measurements suitable for wearable devices and multiple fluorophore analysis, with the potential for wide-ranging applications in spectroscopy and microscopy.
Implementation Method 1
two photons created from the down-conversion of one photon emitted from a constant wavelength or other non-pulsed source in nature but with deterministic temporal correlations
Implementation Method 2
a second detector D2 detects a fluorescence photon emitted by an excited state of matter excited by the second photon
Data Source
AI summary
A device including a continuous (CW) wave source of pairs of entangled photons, each pair comprising a first photon entangled with a second photon; a pair of channels comprising a first channel terminated by a first detector configured to detect the first photon and a second channel terminated by a second detector configured to detect a output photon emitted by an excited state of matter excited by the second photon in the second channel; a splitter for splitting the pairs of entangled photons into the channels, so that the first photon comprising a reference photon is transmitted to the first channel and the second photon is transmitted to the second channel; and a timing circuit coupled to the detectors operable to measure a time delay between arrival times measured at the detectors of the output photon and the first photon entangled with the second photon used to generate the output photon (e.g., fluorescence photon).