The   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 CaF₂ window, recovering energy that would otherwise be absorbed by the package walls.

Calcium fluoride is a cubic fluorite-structure crystal with infrared transmission extending from the deep UV (~0.13 µm) to approximately 11 µm, where multi-phonon lattice absorption begins to attenuate transmission. Within the 2–11 µm operating band of the HIS550R-C, CaF₂ provides high and spectrally smooth transmission. Unlike BaF₂, CaF₂ is significantly less hygroscopic: it does not dissolve readily in water and is resistant to atmospheric moisture under normal storage and operating conditions. This makes it suitable for instruments that cannot guarantee a fully sealed optical path at the system level, or where the emitter may be exposed to temporarily humid conditions during maintenance or field handling.

The nitrogen fill removes reactive species from the package interior at the point of manufacture, eliminating internal oxidation and corrosion as degradation pathways. In NDIR gas sensing, the broadband output is filtered by a bandpass filter matched to the target gas absorption wavelength; pulsed modulation at up to 6 Hz enables lock-in detection to improve signal-to-noise ratio and long-term measurement stability.

CaF₂ Window: Broad Mid-IR Coverage with Superior Durability

Calcium fluoride transmits from ~0.13 µm to ~11 µm, covering both the near-infrared and the full molecular fingerprint region up to the long-wave mid-infrared. Compared to BaF₂ (2–14 µm), the CaF₂ cut-off at 11 µm sacrifices access to the longest-wavelength absorption features while offering substantially better mechanical and chemical durability: CaF₂ has a Mohs hardness of ~4 versus ~3 for BaF₂, and is significantly less hygroscopic — resisting moisture attack under normal atmospheric conditions where BaF₂ would slowly degrade. Compared to sapphire (2–6 µm), CaF₂ extends coverage by nearly two octaves into the mid-infrared, opening access to SO₂, NH₃, N₂O, and many organic compound absorption features not detectable through sapphire.

Hermetic Sealing with Nitrogen Gas Fill

The nitrogen fill displaces oxygen and moisture from the package interior at manufacture, eliminating the two primary degradation pathways for the NiCr filament: oxidative attack at operating temperature, and moisture-driven corrosion of internal metal surfaces. The hermetic package combined with the nitrogen fill ensures stable output power and minimises drift over the emitter’s service life, reducing calibration frequency in field instruments.

High Optical Output: Up to 190 mW

The 190 mW optical output is the same as the HIS550R-0WC and only marginally below the open-window HIS550R-0 (195 mW), reflecting CaF₂’s high and efficient transmission across the 2–11 µm operating band. This strong signal level supports long-path gas cells, multi-analyte detection platforms, and instruments with moderate optical insertion losses.

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 demanding optical configurations. The gold-plated reflector (>98% reflectivity across the mid-IR) captures rear-hemisphere emission and directs it forward through the window, maximising the useful optical output.

Patented Nanostructured High-Emissivity Surface

Emissivity exceeding 0.9 ensures near-blackbody spectral behaviour, maximising radiant efficiency and producing a spectrally predictable output. This simplifies bandpass filter selection and system calibration, and ensures consistent output power across production batches.

Robust TO-39 / TO-5 Industrial Package

The hermetic TO-39 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 options, reducing integration effort in both laboratory instruments and field-deployed analysers.

Pulsed Operation up to 6 Hz

Modulated emission at up to 6 Hz supports synchronous lock-in detection, rejecting DC thermal background and low-frequency noise to improve signal-to-noise ratio and long-term baseline stability. The 6 Hz rating is the same as the other HIS550R models, reflecting the consistent thermal mass of the 11 mm² element across the series.

• Broadband NDIR Gas Sensing: Detection of CO₂, CO, CH₄, N₂O, SO₂, NH₃, hydrocarbons, and organic compounds with absorption features across the 2–11 µm band, in applications where sealed-package durability is required alongside spectral coverage beyond 6 µm.
• Mid-Infrared Spectroscopy: Portable and benchtop spectrometers targeting molecular absorption features across the near- and mid-infrared fingerprint region up to 11 µm, where CaF₂’s combination of broad transmission and mechanical robustness is preferred over BaF₂.
• Environmental and Emissions Monitoring: CEMS, atmospheric monitoring, and greenhouse gas analysers requiring sealed packaging for outdoor deployment and spectral access to gases absorbing between 6–11 µm.
• Industrial Gas Analysis and Safety: Fixed-point and extractive gas detectors in chemical, petrochemical, and pharmaceutical facilities detecting species such as SO₂, NH₃, and VOCs in the mid-infrared fingerprint region.
• Automotive and Exhaust Analysis: Exhaust gas analysers and emission test benches measuring CO, CO₂, HC, and NOx, where the broader spectral range versus sapphire supports simultaneous detection across multiple absorption bands.
• Medical and Clinical Gas Analysis: Respiratory gas monitors and anaesthetic agent analysers requiring coverage of mid-infrared absorption features beyond 6 µm, with the improved handling robustness of CaF₂ versus BaF₂.
• Scientific Research Instrumentation: Laboratory spectrometers, gas reference cells, and optical bench systems requiring a stable, high-power, hermetically sealed broadband source covering the 2–11 µm 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