Mid-IR Spectroscopy & Molecular Sensing
Tunable mid-IR sources, MIR-grade optics, and detection for molecular fingerprinting — gas sensing, pharmaceutical QC, environmental monitoring.
Step 1 — Define your goal
What are you trying to achieve?
Pick the experiment / project closest to yours. We'll route you to the right system architecture and BOM.
Step 2 — Confirm the problem
Common project challenges
If any of these sound familiar, you're in the right place. WaveQuanta engineers have seen — and solved — every one of them.
MIR source path: OPA, DFG, QCL, supercontinuum?
Each has a different wavelength range, power, linewidth, and cost profile.
Wavelength tunability vs power
Tunable OPA gives access to fingerprint region but lower power; QCL is high-power at fixed wavelength.
Mid-IR optical materials
CaF₂, ZnSe, BaF₂, Ge — different transmission and damage thresholds.
Detector and spectrometer choice
MCT, InSb, pyroelectric — different sensitivity, speed, and cooling needs.
Sample / gas cell design
Path length, multipass, hermetic integration for trace species.
Beam alignment in invisible IR
Visible alignment laser strategy and sub-µrad pointing stability.
Lock-in / phase-sensitive detection
Required for detecting weak absorption against thermal background.
Calibration and validation
NIST-traceable reference cells and standardized validation protocols.
Step 3 — Understand the system
Typical system architecture
Most projects in this area follow a similar signal flow. Your specific architecture depends on resolution, throughput, and form-factor targets.
OPA / DFG / QCL — tunable or fixed-wavelength MIR generation matched to your target species.
Driven by 1030 nm or 800 nm fs source, generates signal/idler in MIR fingerprint region.
CaF₂, ZnSe, BaF₂, Ge windows / lenses / mirrors — wavelength-matched.
Visible alignment laser, beam diagnostics, and pointing stabilization in invisible MIR.
Path-length-optimized cell — multipass for trace gas, hermetic for safety analyses.
Step 4 — Pick the modules
Recommended system modules
These are the building blocks. Each module is a category of products — pick the right brand and grade for your project stage below.
Mid-IR Source Module
OPA / DFG / QCL — tunable or fixed-wavelength MIR generation matched to your target species.
- OPA-driven 2–16 µm tunable
- QCL 4–12 µm high-power
- DFG narrow-linewidth
- Supercontinuum broadband
OPA / DFG Stage
Driven by 1030 nm or 800 nm fs source, generates signal/idler in MIR fingerprint region.
- Signal 1.5–3 µm, idler 3–10 µm
- Collinear or non-collinear
- Narrow-linewidth or broadband
MIR Optics Package
CaF₂, ZnSe, BaF₂, Ge windows / lenses / mirrors — wavelength-matched.
- Off-axis parabolic mirrors (gold)
- ZnSe lenses (broadband)
- CaF₂ for visible–MIR
- Ge / BaF₂ for narrowband
Beam Routing & Alignment
Visible alignment laser, beam diagnostics, and pointing stabilization in invisible MIR.
- 532 nm visible alignment laser
- MIR card / phosphor visualizer
- Iris and aperture set
Sample / Gas Cell
Path-length-optimized cell — multipass for trace gas, hermetic for safety analyses.
- 1 cm – 100 m path length
- Herriott multipass cell
- Hermetic cell for hazardous samples
MIR Detector
MCT, InSb, pyroelectric — chosen for wavelength, speed, and cooling tolerance.
- MCT (cooled) for sensitivity
- InSb for short-MIR
- Pyroelectric (uncooled) for low cost
Spectrometer / FTIR
FTIR for broadband, grating spectrometer for high resolution.
- FTIR (Bruker / Thermo)
- Grating spectrometer + linear array
- Monochromator + lock-in
Lock-in Detection
Phase-sensitive detection lifts MIR signal from thermal background — essential for trace species.
- Lock-in amplifier
- Mechanical chopper
- Wavelength modulation electronics
Step 5 — Match your project stage
Choose your project stage
Same modules, three configurations sized for where your project is today. Move up the tiers as you progress from research to validation to OEM.
Research Starter
Lab feasibility / small experiment
Benchtop MIR sensing setup. Validates the source-cell-detector combination on a known sample.
- Mid-power OPA or QCL
- 10 cm sample cell
- MCT detector + lock-in
- Visible alignment laser
- MIR optics starter set
BOM tier: $60k – $150k
Engineering Validation
Method development / pre-production
Locked-spec MIR sensing system. Multi-channel detection, multipass cell, automation-ready.
- Tunable OPA / QCL chain
- Multipass Herriott cell
- MCT array detection
- Lock-in + automation
- NIST-traceable reference
- Full validation report
BOM tier: $200k – $500k
OEM Production
Field instrument · 24/7
Productized MIR sensor for in-field operation. Locked BOM, environmental sealing, calibration-on-startup.
- Sealed QCL / DFG source
- Field-hardened cell
- Uncooled or TE-cooled detector
- Built-in calibration
- IP-rated enclosure
- Long-term supply
BOM tier: $500k+ · NRE + per-unit
Step 6 — Run the numbers
Recommended calculators
Sanity-check your design before talking to an engineer.
Step 7 — Configure the system
Configure your setup with our engineering tools
Two ways to go from "this is what I want to do" to "this is the BOM I need".
Open Mid-IR Sensing Virtual Lab
Place OPA, sample cell, MIR optics, and detector on a 3D layout. Verify wavelength range and SNR target.
Launch Virtual LabAsk AI to design my MIR sensing chain
Describe target molecule, expected concentration, sample type, throughput. AI proposes source, cell, detector, and BOM.
Open AI ConciergeStep 8 — Anchor SKUs
Featured products for this application
Common picks for this application area. Your final BOM will pull from a wider catalog and be sized to your project tier.
Yi-Laser
AURORA OPA — High Energy
Yi-Laser
HELIOS Femtosecond Laser
Princeton Instruments
Princeton InGaAs Spectrometer
WaveQuanta
Off-Axis Parabolic Mirror
WaveQuanta
AURORA-IR Mid-Infrared OPA — High Power
WaveQuanta
Mozza Mid-IR Detection Module
LBTek
Acousto-optic Modulator (AOM) SPD3303C
LBTek
Acousto-Optic Modulator (Chopper)
Step 9 — Common questions
Frequently asked questions
Quick answers to the questions our application engineers hear most often.
OPA vs QCL — when to use each?
OPA: tunable across the entire fingerprint region (2–16 µm), broadband, fs/ps pulses. Best for spectroscopy that needs many wavelengths. QCL: fixed-wavelength but high-power CW or pulsed, narrow linewidth. Best for industrial sensors targeting one specific molecule.
Why is MIR alignment hard?
You can't see the beam by eye. Standard solution: co-align a visible laser through the same beam path; use IR cards or phosphor visualizers to spot-check; have the system pre-aligned at WaveQuanta and shipped as an integrated unit.
CaF₂ vs ZnSe — which to use?
CaF₂: transmits visible–8 µm, low cost, but moisture-sensitive. ZnSe: 0.6–22 µm broadband, robust, but more expensive and toxic to machine. Most sensors use ZnSe at the cell windows and CaF₂ in the source area.
How sensitive can a multipass cell get?
Herriott cells achieve 100+ m optical path in <30 cm physical length, giving ppb sensitivity for strong absorbers. White cells are simpler but limited to ~20 m. Match path length to your absorption coefficient.
Cooled vs uncooled MIR detector?
Cooled MCT (LN₂ or TE): NEP ~ 1 pW/√Hz, sensitive to single molecules. Uncooled pyroelectric: NEP ~ 1 nW/√Hz, simpler but 1000× less sensitive. Choose based on signal level vs maintenance complexity.
Do I need lock-in detection?
For sub-mOD absorption (trace gases at ppb–ppm): yes, mandatory. Background MIR thermal flux dominates without phase-sensitive detection. For strong absorbers (% level): you can get away without it.
How do you handle calibration drift?
NIST-traceable reference cells in the optical path, automated background subtraction, and periodic span-gas calibration. Engineering Validation tier ships with a documented calibration protocol.
Can the system go field-deployed?
OEM Production tier ships in IP-rated enclosures with hermetically sealed optics and TE-cooled detectors. Designed for stack monitoring, atmospheric science, or roadside breath-alcohol sensors.
Step 10 — Engineering Review
Application Engineering Review
Tell us your application, current setup, and project context. A WaveQuanta application engineer will return initial recommendations within 1 business day.
- 1 Application
- 2 Current setup
- 3 Project & purchase