The HIT500LB-GK operates as a high-temperature incandescent thermal emitter. Electrical current through the two-dimensional filament raises its temperature to 1900 K; the nanostructured surface radiates energy across a broad Planck-governed spectrum with peak emission near 1.53 µm. This peak lies squarely within the SWIR band, providing strong emission from the visible-red through the SWIR and into the near-MWIR up to the glass window cut-off at 4.7 µm.

At 1900 K, the Stefan–Boltzmann T⁴ relationship gives this device approximately 1.18× the radiated power per unit area of the HIT100SMD-GA-GET at 1720 K, and approximately 16× that of the HIS-series emitters at ~900 K. Combined with the 5× larger element area, total optical output is substantially higher than the SMD model. The Planck peak at 1.53 µm (vs. 1.7 µm at 1720 K) means the emission distribution is shifted slightly further into the SWIR, providing proportionally more output in the 1.0–2.0 µm region relative to the 3–5 µm MWIR range.

Krypton is selected as the fill gas for thermal efficiency and filament longevity reasons. In gas-filled lamp technology, heavier noble gases (krypton, xenon) reduce thermal conduction from the filament to the bulb wall, allowing the filament to operate at higher temperatures for the same electrical input or to reach the same temperature with less power. Krypton also suppresses tungsten evaporation more effectively than argon, reducing filament thinning and extending operational lifetime. The glass package provides hermetic sealing, and the glass window transmits the useful 0.6–4.7 µm output band.

1900 K Operation: Maximum SWIR Spectral Radiance

At 1900 K, the Planck emission peak is at ~1.53 µm, and total radiated power per unit area is approximately 1.18× that of the HIT100SMD-GA-GET at 1720 K and ~16× that of the HIS-series emitters at ~900 K. This is the highest operating temperature in the HITstar series covered here, providing the strongest possible SWIR spectral radiance for applications where detector signal is the limiting factor. The higher temperature also shifts more of the total emission into the 1–2 µm SWIR window relative to longer wavelengths, which is advantageous for NIR/SWIR spectroscopy applications specifically targeting overtone absorption bands below 2.5 µm.

5 mm² Element: High Total Output and Source Étendue

The 5 mm² two-dimensional filament provides five times the emitting area of the HIT100SMD-GA-GET’s 1 mm² element. This increases both total radiant flux (enabling stronger detector signals at any given optical throughput) and source étendue (the product of emitting area and output solid angle), which governs the maximum optical throughput achievable in an instrument with given collection optics. Higher étendue is particularly valuable for instruments with large entrance apertures, wide-acceptance-angle fibres, or imaging spectrometers that can exploit a large source area to increase throughput without aperture-limited losses.

Krypton Fill for Superior Thermal Efficiency and Lifetime

Krypton is a heavier noble gas than argon, providing significantly lower thermal conductivity between the filament and the glass envelope. This thermal insulation effect allows the filament to reach 1900 K with less wasted heat conducted to the package walls, improving electrical-to-radiant efficiency. Krypton also suppresses filament material evaporation more effectively than argon at high temperatures, reducing the rate of filament thinning that leads to eventual failure. These effects translate directly into longer operational lifetime at a given drive level, compared to an otherwise identical argon-filled device.

0.6–4.7 µm Spectral Range: Visible-Red Through Near-MWIR

The 0.6–4.7 µm emission range covers the full NIR and SWIR bands plus the near end of the MWIR, enabling detection across the overtone and combination absorption bands of hydrocarbons (1.0–2.5 µm), the first overtone of C–H stretch in organic compounds (~1.7 µm), the combination bands of CO₂ and H₂O at 2.7 µm, and CO at 2.35 µm. The high emission intensity at 1900 K means that even applications requiring signal in the 0.6–1.0 µm visible-red region, where thermal emitters are typically weak, receive meaningful radiant flux.

Two-Dimensional Filament for Stable, Uniform Imaging

The planar 2D filament geometry provides a spatially uniform, well-defined radiation source with stable optical properties. Unlike coiled filaments, the planar structure can be reliably and repeatably imaged onto spectrometer slits, fibre input faces, and detector arrays, ensuring consistent spectral response and minimising wavelength calibration errors arising from source non-uniformity. This is a critical design requirement for quantitative spectroscopy instruments.

T1¾ Glass Bulb Package for Broad System Compatibility

The T1¾ format (approximately 5.6 mm diameter, 10 mm length) is a standard miniature lamp package used across a wide range of laboratory instruments, industrial sensors, and analytical systems. Its wire-lead termination is compatible with standard lamp sockets, PCB-mounted lamp holders, and custom instrument mounting arrangements, making the HIT500LB-GK a suitable replacement or upgrade source in existing instruments as well as a source for new designs. The glass envelope provides hermetic sealing and mechanical protection, while the glass window transmits the full 0.6–4.7 µm output band.

Pulsable Operation for Modulated Detection

Pulsed operation enables lock-in detection schemes that reject ambient light in the 0.6–1.0 µm visible-red and NIR region, where room lighting and sunlight can otherwise overwhelm detector signals. Synchronous detection referenced to the modulation frequency suppresses these broadband interference sources, improving measurement accuracy in non-darkened environments.

• High-Throughput NIR and SWIR Spectroscopy: Laboratory and process-line spectrometers requiring maximum SWIR spectral radiance for fast, high-signal-to-noise measurements of overtone and combination absorption bands in organic compounds, pharmaceuticals, food products, and agricultural materials across 0.9–2.5 µm.
• Natural Gas and Hydrocarbon Analysis: High-sensitivity SWIR sensors and analysers detecting methane, ethane, propane, and higher hydrocarbons via their combination band absorptions in the 1.6–2.3 µm range, with the 5 mm² element’s higher étendue improving coupling into multipass cells and fibre-optic probes.
• CO₂ and H₂O Sensing at 2.7 µm: High-accuracy detection of the 2.7 µm combination absorption bands of CO₂ and water vapour in environmental monitoring, combustion analysis, and process control instruments, with stronger source emission than either the HIT100SMD-GA-GET or any HIS-series device at this wavelength.
• Benchtop and Laboratory Analytical Instruments: Spectrophotometers, monochromators, and custom analytical instruments using the T1¾ package’s standardised lamp format, where the 1900 K high-radiance source improves signal levels compared to conventional low-temperature NIR sources.
• Industrial Process and Quality Control: On-line NIR/SWIR analysers for chemical, polymer, textile, and agricultural industries requiring high source radiance for rapid, non-destructive composition measurements of flowing materials or packaged products.
• Retrofit and Replacement Applications: Drop-in replacement or performance upgrade source for existing laboratory instruments and industrial sensors using T1¾ lamp formats, providing higher spectral radiance and improved SWIR performance compared to conventional incandescent bulbs.
• Environmental and Stack Gas Monitoring: Gas analysers measuring CO, CO₂, H₂O, and hydrocarbon species in the 2–4.7 µm range for combustion monitoring, emissions certification, and environmental compliance, where higher source power improves signal margin in high-attenuation optical paths.

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 HITstar SWIR/MWIR emitter technologies and the broader infrared sensing portfolio
• Expert application support for NIR/SWIR spectroscopy, high-temperature IR sources, and industrial gas sensing system design
• OEM consultation covering drive circuit design, optical system integration, thermal management, 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