The HIT100SMD-GA-GET operates as a high-temperature incandescent emitter. Electrical current through the two-dimensional filament element raises its temperature to 1720 K; at this temperature, thermal radiation follows the Planck distribution with peak emission near 1.7 µm. Emission below 1 µm is significant — reaching into the near-infrared and visible-red — while emission extends to the MWIR limit imposed by the glass window transmission cut-off near 4.7 µm.

The key physics that distinguish this device from the HIS series are the operating temperature and its spectral consequences. Planck’s law dictates that a blackbody at 1720 K emits approximately 87 times more power per unit area than one at 900 K (the approximate operating temperature of HIS series emitters). Within the 0.6–4.7 µm band specifically, the advantage is even larger because the 1720 K Planck curve has its peak within this range, while the 900 K curve has most of its energy at longer wavelengths. This makes the HIT100SMD-GA-GET uniquely suited to applications requiring strong SWIR output, where HIS-series emitters are inefficient because their Planck emission at those wavelengths is negligible.

The argon fill is not incidental: argon’s role is to suppress filament evaporation and oxidation at the extreme operating temperature. In conventional incandescent lamps, a halogen fill performs a similar function through the tungsten halogen cycle; in the HITstar series, the inert argon atmosphere provides chemical stability without any reactive gas chemistry. The two-dimensional filament geometry provides a spatially uniform, well-defined radiation source with stable optical imaging properties — the filament structure can be imaged onto a spectrometer slit or detector array with consistent, repeatable results.

High-Temperature Operation: 1720 K Planck Peak at 1.7 µm

Operating at 1720 K places the Planck emission peak squarely within the SWIR band at ~1.7 µm, delivering intense radiation across the 0.6–4.7 µm range that no HIS-series emitter at 550–630 °C can approach. By the Stefan–Boltzmann law, radiated power per unit area scales as T⁴; the HIT100SMD-GA-GET’s filament emits orders of magnitude more spectral radiance per unit area in the SWIR than a low-temperature thermal source at the same emissivity. For spectroscopy systems that must detect overtone and combination absorption bands of hydrocarbons, water vapour, and many organic compounds in the 1–2.5 µm NIR/SWIR region, this is the enabling capability.

0.6–4.7 µm Spectral Coverage: Visible-Red Through MWIR

The 0.6–4.7 µm emission range spans visible-red, near-infrared (NIR), short-wave infrared (SWIR), and the near end of the mid-wave infrared (MWIR). This covers the overtone absorption bands of C–H, O–H, and N–H groups in the 1.0–2.5 µm region widely exploited in NIR spectroscopy; the combination bands and first overtones of hydrocarbons in the 1.6–2.3 µm range used in natural gas and process gas sensing; and the fundamental absorption bands of CO₂ (2.7 µm), H₂O (2.7 µm), and CO (2.35 µm) at the lower end of the mid-infrared. It also enables applications in spectral reflectance measurement, silicon-substrate photovoltaic inspection, and any other analytical technique requiring a high-radiance source in the 1–2 µm SWIR window.

175 mW from 1 mm²: Exceptional Spectral Radiance

The 175 mW optical output from a 1 mm² emitting area represents a spectral radiance far exceeding that of the larger HIS-series elements at their lower operating temperatures. This high radiance per unit area is what enables the HIT100SMD-GA-GET to be used in miniaturised spectrometers and compact analytical instruments where the beam must be concentrated into a small optical throughput: high radiance allows the source to be imaged onto a narrow spectrometer entrance slit without unacceptable throughput loss.

Two-Dimensional Filament for Stable Optical Imaging

The filament is fabricated as a planar two-dimensional structure, providing a spatially uniform, geometrically well-defined radiation source. Unlike coiled filaments, a 2D planar element can be reliably imaged onto a spectrometer slit, monochromator entrance aperture, or detector array with consistent, repeatable magnification and intensity distribution. This is a critical requirement for spectroscopy instruments where source spatial non-uniformity introduces spectral artefacts or calibration errors.

Argon Fill for Chemical Stability at Extreme Temperatures

At 1720 K, conventional nitrogen fill would react with hot metal surfaces; even trace oxygen would rapidly oxidise the filament material. Argon is a noble gas with no chemical reactivity at any temperature, making it the correct fill gas for this operating regime. The hermetic glass package seals the argon atmosphere and protects the filament from external contaminants, while the glass window transmits the emitter’s useful output across 0.6–4.7 µm.

Compact SMD Glass Package for Miniaturised Systems

The hermetically sealed SMD glass package enables integration into compact spectrometers, handheld analysers, and miniaturised sensor modules through standard PCB assembly. The glass package provides a hermetic seal that maintains the internal argon atmosphere and protects the filament from shock, vibration, and environmental contaminants, while the compact form factor supports the miniaturisation goals of modern portable analytical instruments.

Pulsable Operation for Modulated Detection

The HIT100SMD-GA-GET supports pulsed operation, enabling lock-in detection schemes that reject ambient light and thermal background. In SWIR spectroscopy, ambient light rejection is particularly important since the 0.6–1.0 µm range overlaps with visible radiation from room lighting and sunlight; modulated operation with synchronous detection suppresses these interference sources.

• NIR and SWIR Spectroscopy: Portable and laboratory spectrometers targeting overtone and combination absorption bands of hydrocarbons, organic compounds, water, and agricultural products in the 0.9–2.5 µm NIR/SWIR range, where the high Planck emission of the 1720 K source provides the spectral radiance needed for compact, high-throughput instruments.
• Hydrocarbon and Natural Gas Sensing: Detection of methane, ethane, and higher hydrocarbons via their combination band absorptions in the 1.6–2.3 µm SWIR range, where the HIT100SMD-GA-GET provides far stronger emission than HIS-series sources at the same wavelengths.
• CO₂ and H₂O Sensing at 2.7 µm: Detection of the 2.7 µm combination absorption bands of CO₂ and H₂O, accessible with higher source radiance from the HIT100SMD-GA-GET than from lower-temperature emitters, enabling more sensitive miniaturised sensors.
• Chemical Composition and Material Analysis: Reflectance and transmittance spectroscopy for food quality, pharmaceutical identification, polymer analysis, and agricultural product grading across the NIR/SWIR bands, where high source radiance enables fast measurements with compact detector arrays.
• Silicon Photovoltaic and Semiconductor Inspection: Transmission imaging and defect detection in silicon wafers and solar cells, exploiting the high-radiance SWIR emission of the 1720 K source in the 1.0–1.5 µm silicon transmission window.
• Portable and Handheld Spectrometers: Miniaturised NIR/SWIR spectrometers for field use in environmental monitoring, industrial process control, and consumer analytical devices, where the compact SMD package, high radiance, and efficient drive requirements match the constraints of battery-powered portable instruments.
• Defence and Aerospace Sensing: Compact high-temperature infrared sources for IR-based detection systems, active illumination in SWIR imaging, and analytical instruments requiring strong, spectrally broadband output from 0.6 to 4.7 µm.

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 technologies, including the HITstar SWIR/MWIR series
• Expert application support for NIR/SWIR spectroscopy, gas sensing, and high-temperature IR system design
• OEM consultation covering component selection, drive circuit design, optical system integration, 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