The HIS550R-B operates on the same resistive thermal emission principle as all HIS550R models. Electrical current through the NiCr filament raises its temperature to approximately 600 °C; the nanostructured surface radiates energy across a broad Planck-governed spectrum. The gold-plated reflector captures rear-hemisphere radiation and redirects it forward through the BaF₂ window, recovering energy that would otherwise be absorbed by the package walls.

Barium fluoride is one of the few window materials with useful infrared transmission extending to ~14 µm. Its transmission is governed by multi-phonon lattice absorption: the BaF₂ crystal remains transparent from the deep UV through to the mid-infrared, with transmission declining gradually beyond 10 µm and reaching its practical cut-off near 14 µm. Within this range, anti-reflection coating of the window surfaces can reduce Fresnel reflection losses at each air–BaF₂ interface, maximising transmitted power. Unlike sapphire, BaF₂ is a relatively soft and hygroscopic material, which is why the nitrogen fill and hermetic seal are particularly important: they prevent moisture exposure that would etch the window surface and degrade transmission over time.

In NDIR gas sensing, the broadband output passes through a sample gas cell; a bandpass filter and matched detector then isolate the specific absorption wavelength of the target gas. Pulsed modulation at up to 6 Hz enables lock-in detection to reject thermal background and low-frequency noise, improving long-term measurement stability in field instruments.

BaF₂ Window: Widest Spectral Range Among Sealed Variants

Barium fluoride transmits infrared radiation from ~0.15 µm to ~14 µm, giving the HIS550R-B access to molecular absorption features in the 6–14 µm long-wave mid-infrared band that are inaccessible through sapphire. This band contains the fundamental vibrational absorption features of SO₂, NH₃, N₂O, many chlorinated and fluorinated hydrocarbons, refrigerants, and a wide range of volatile organic compounds. The HIS550R-B is therefore the correct sealed-package choice for multi-gas instruments or applications targeting species with absorption wavelengths beyond 6 µm.

Highest Optical Output in the Sealed Series: Up to 200 mW

The 200 mW optical output of the HIS550R-B is the highest among the sealed-window variants of the HIS550R series, exceeding the HIS550R-A (135 mW, sapphire, 2–6 µm) due to BaF₂’s superior transmission across the broader spectral range. More of the filament’s total radiated power is transmitted through the window and contributes to the measured optical output figure.

Hermetic Sealing with Nitrogen Gas Fill

The nitrogen fill displaces oxygen and moisture from the package interior at the time of manufacture. Oxygen accelerates high-temperature oxidation of the NiCr filament; moisture promotes corrosion of internal metal surfaces and — critically for BaF₂ — attacks the hygroscopic window surface, causing surface etching that scatters radiation and degrades transmission irreversibly. The nitrogen fill and hermetic seal together prevent both failure modes, extending operational lifetime and reducing output drift in long-term deployments.

Large 11 mm² Element with Gold-Plated Reflector

The 11 mm² NiCr filament generates substantially greater total radiant flux than the 1.8 mm² elements of the SMD series, improving signal budget in instruments with long optical paths or lossy collection optics. The gold-plated reflector (>98% reflectivity across the mid-IR) captures rear-hemisphere emission and directs it forward through the window, recovering energy that would otherwise be lost to package wall absorption.

Patented Nanostructured High-Emissivity Surface

Emissivity exceeding 0.9 ensures near-blackbody spectral behaviour across the emission band, maximising the conversion of electrical power into radiant flux and producing a spectrally smooth, predictable output. This simplifies bandpass filter selection, reduces inter-unit calibration variation, and ensures that output power is consistent across production batches.

Robust TO-39 / TO-5 Industrial Package

The TO-39 hermetic metal package provides mechanical robustness, good thermal dissipation, and resistance to vibration and thermal cycling. It is a well-established platform in industrial optoelectronics with standardised mounting and connector options, reducing integration effort in both laboratory instruments and field-deployed gas analysers.

Pulsed Operation for Lock-In Detection

Modulated emission at up to 6 Hz supports synchronous lock-in detection architectures that reject DC thermal background and low-frequency noise, significantly improving signal-to-noise ratio and long-term baseline stability — particularly important in instruments operating over extended periods between calibration events.

• Broadband NDIR Gas Sensing: Detection of SO₂, NH₃, N₂O, refrigerants, chlorinated hydrocarbons, and VOCs with absorption features in the 6–14 µm band, alongside the standard CO₂, CO, and CH₄ targets covered by shorter-range emitters.
• Mid-Infrared Spectroscopy: Laboratory and portable spectrometers requiring a hermetically stable, high-power source covering the full molecular fingerprint region from 2–14 µm.
• Environmental and Emissions Monitoring: CEMS, refrigerant leak detection, and atmospheric monitoring systems targeting gases that absorb beyond 6 µm, requiring sealed packaging for outdoor or semi-outdoor deployment.
• Industrial Gas Analysis and Process Monitoring: Process gas analysers in chemical, pharmaceutical, and petrochemical facilities where long-term stability and broad spectral access are both required.
• Automotive and Engine Exhaust Analysis: Exhaust gas analysers targeting CO, CO₂, HC, and NOx across multiple absorption bands, including longer-wavelength features not accessible through sapphire windows.
• Medical and Clinical Gas Analysis: Anaesthetic agent monitoring and multi-gas respiratory instruments that must detect halogenated agents (e.g., isoflurane, sevoflurane) with absorption features beyond 6 µm.
• Scientific Research Instrumentation: Custom spectrometers, gas reference cells, and optical bench systems requiring a stable, high-power, broadband sealed infrared source covering the 2–14 µm molecular fingerprint region.

United Spectrum Instruments (USI) is a specialist distributor and application partner for advanced photonics, infrared sensing, and scientific instrumentation in India. USI combines access to globally leading component technologies with deep domain expertise, supporting customers from initial product selection through OEM system integration and volume production supply.

Key reasons to work with United Spectrum Instruments:

• Access to internationally leading infrared emitter and photonics technologies
• Expert application support for NDIR gas sensing, mid-IR spectroscopy, and high-power IR system design
• OEM consultation covering component selection, optical system design, and production ramp
• Reliable supply for evaluation samples and production quantities
• Established partnerships with leading international photonics manufacturers
• Fast, responsive technical communication and application-focused engineering guidance