Mid-IR Laser Spectrometer Chip Without Optical Alignment

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Current mid-infrared tunable laser absorption spectroscopy (TLAS) systems are bulky, complex, and susceptible to surface contamination, limiting their miniaturization and detection capabilities due to the need for optical alignment and long waveguides.

Innovation Solution

A monolithically integrated mid-infrared laser-based spectrometer on a chip, incorporating a single-mode distributed-feedback quantum cascade laser and detector, which eliminates the need for optical alignment and utilizes a plasmonic waveguide to guide most of the optical mode through the sample, enabling miniaturization and accurate detection of gases like CO, CO2, and H2O.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If long waveguides are used to increase effective pathlength, then detection sensitivity is improved, but device volume and susceptibility to surface contamination increase

Engineering Contradiction:

Improvedetection sensitivityVSAvoiddevice volume

Core Design Contradiction:

Measurement precisionVSVolume of stationary object

Solution Approach 1:

The patent merges the laser source, waveguide, and detector onto a single integrated photonic chip. This consolidation allows the effective optical pathlength to be extended through multiple passes within a compact footprint, achieving high detection sensitivity without proportionally increasing device volume. The integration enables the optical mode to interact with molecules in a confined space while maintaining long effective pathlength through repeated reflections.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent employs a folded optical path configuration where the light propagates through multiple dimensions within the chip structure. By using vertical cavities and lateral waveguides, the effective pathlength extends in three-dimensional space rather than requiring a long linear path, thus achieving meter-scale effective pathlength in a millimeter-scale physical device.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Adaptability or versatility

If complex optical alignment components are used, then wavelength tuning capability is improved, but device complexity and volume increase

Engineering Contradiction:

Improvewavelength tuning capabilityVSAvoidoptical alignment complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent replaces mechanical optical alignment components with integrated photonic waveguides that are fabricated using standard semiconductor manufacturing techniques. The wavelength tuning is achieved through electro-optic or thermo-optic effects within the integrated circuit, eliminating the need for mechanical adjustment of mirrors, lenses, and other optical components. This substitution dramatically reduces device complexity while maintaining full wavelength tuning capability across the mid-infrared spectrum.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If discrete optical components are used, then optical throughput is maintained, but device mass and volume increase

Engineering Contradiction:

Improveoptical throughputVSAvoiddevice mass

Core Design Contradiction:

ReliabilityVSWeight of stationary object

Solution Approach 1:

The patent combines multiple discrete optical components (laser, waveguide, detector, tuning elements) into a single monolithic integrated photonic device. This merging maintains optical throughput by ensuring efficient coupling between components through direct waveguide interfaces, while simultaneously reducing device mass by eliminating mounting structures, alignment mechanisms, and housing required for discrete component assemblies.

Inventive Principle:

Principle #5Merging (Combining)

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 system achieves sub-ppm detection levels with reduced volume and weight, eliminating the need for optical alignment and minimizing interference from other gases, while maintaining high sensitivity and robustness against contamination.

Implementation Method 1

when the single mode laser outputs a wavelength of radiation overlapping one of the substance's rotational-vibrational energy levels, the substance at least partially absorbs the radiation

Methodology Applied

Scientific EffectRotational-vibrational absorption: Absorption (EM radiation)

Implementation Method 2

the single mode detector is configured to measure the amount of narrow wavelength radiation that is not absorbed by the substance between the single mode detector and the single mode laser

Methodology Applied

Scientific EffectRadiation detection:

Data Source

PatentUS12492992B2Spectroscopy device incorporating a mid-infrared laser

Publication Date: 2025.12.09 CALIFORNIA INST OF TECH

AI summary

Disclosed herein is a spectroscopy device incorporating a mid-infrared laser. In one particular embodiment a spectroscopy device is provided including: a substrate; a single mode laser positioned on the substrate; a single mode detector positioned opposite to the single mode laser on the substrate. A gap is formed between the single mode laser and the single mode detector and a substance is positioned in the gap. The single mode laser is configured to output a tunable narrow wavelength of radiation towards the detector and when the single mode laser outputs a wavelength of radiation overlapping one of the substance's rotational-vibrational energy levels, the substance at least partially absorbs the radiation. The single mode detector is configured to measure the amount of narrow wavelength radiation that is not absorbed by the substance between the single mode detector and the single mode laser.