UV-NIR Calibrated Irradiance Sources for Scientific Research

Oriel Calibrated Lamps are dependable sources of known spectral irradiance in the UV and VIS-NIR. Oriel Instruments can supply both individual lamps and complete sources, including a lamp (with calibration data), lamp mount, and a Radiometric Power Supply.

These NIST traceable calibrated lamps can be used to convert Oriel Instruments’ NIST traceable calibration to a spectrometer or spectroscopic detection system. Users can calibrate their own irradiance source with these systems. Near monochromatic light of known irradiance can be produced when these lamps are used with interference filters.

NIST Traceable

Oriel Calibrated Lamps are carefully tested to specification. Lamps are preconditioned and chosen as required. The irradiance measurements are made in Oriel Instruments’ specially outfitted calibration laboratory, where the highest levels of assurance is carefully maintained in the calibration transfer itself. The NIST offers original uncertainties for its standard lamps in the United States. This range varies in relation to wavelength and lamp structure.

Calibration Services

Oriel Instruments provides filter calibration services. Customers can select any neutral density or bandpass filter and the 63374 Filter Calibration Option. The company will supply a NIST Traceable filter with calibration data from 200 to 2400nm as an ASCII file and a hard copy transmittance curve. Deuterium lamps mostly emit UV radiation. Care must be taken to prevent fluorescence induced spectroradiometric errors when using filters with these lamps.

Calibrated Irradiance Sources

Oriel Instruments provides three types of calibrated irradiance sources:

  • Calibrated QTH Sources – are offered in 45W, 200W and 1kW powers with a calibration range of 250-2500nm
  • Calibrated Deuterium Sources – are available in 30W model only with a calibration range of 200-400nm (Figure 1)
  • Custom Sources/Calibrations – are used for calibration of lamps used by customers and have custom standards

Figure 1. 63979 Calibrated Deuterium Source

Lamps that produce irradiance close to the desired level to be measured in the wavelength range of interest need to be selected. The use of a lamp that generates, too little, or too much, irradiance puts more demands on the linearity of a detection system. The deuterium lamp is recommended for producing an irradiance standard below ~330nm. This lamp is calibrated down to 200nm, emits UV radiation more than the QTH lamps (Figure 2), and generates very low level of visible light. The very little visible and near IR radiation minimizes the out of band problems that are detrimental to UV calibration devices based on silicon photodiodes and other broadband detectors.

Typical irradiance of calibrated lamps, calibrated ranges are: 200 - 400nm for the D2 lamp and 250 - 2500nm for QTH lamps.

Figure 2. Typical irradiance of calibrated lamps, calibrated ranges are: 200 - 400nm for the D2 lamp and 250 - 2500nm for QTH lamps.

Quartz Tungsten Halogen Lamps

Quartz tungsten halogen lamps are coiled coil filament lamps selected for constant irradiance over a longer duration and for low directionality in output. The polarization of the output is merely 3%. Each lamp emits radiation in the range of 250-2500nm. Problems arise at the extremes of the range due to stray light and can be addressed using suitable filters.

Spectral irradiance data in mW m-2 nm-1 units is presented at 10nm intervals for the 250 to 2500nm spectral range. NIST spectral irradiance standards are certified at fewer points compared to Oriel calibrated lamps. Each lamp is also available with a Report of Calibration, which includes irradiance values, laboratory temperature, lamp orientation, lamp distance, guidelines for proper use and prescribed safety measures.

The irradiance data presented with calibrated QTH lamps is computed at a specific lamp current. The 45W and 200W calibrated lamps are powered by the 68931 Radiometric Power Supply. If the wattage required is not more than the 45W lamp, the 68938 is a cost-effective alternative to the 68931 with slight difference in performance and stability. The stability of the 45W calibrated lamp is slightly less than the 200W lamp due to its smaller bulb size. The 68935 was intended specially for the 1kW lamp.

Deuterium Lamps

Deuterium lamps produce useful radiation in the range of 200-400nm, but are particularly known for their high output range of 200-300nm. The 656.1nm spectral peak may be used as a wavelength calibration point when a measurement system reaches into the visible region. The peak irradiance is roughly the same as the deuterium irradiance level at 250nm and is normally used for calibrating closed-system spectrophotometers.

The radiation of deuterium lamps is caused by an electric arc discharge within the deuterium gas. Oriel lamps are particularly preferred for the directional uniformity of their output and for their long term stability. Each calibrated deuterium lamp is provided with a calibration report, which includes a complete list of test conditions to facilitate calibration transfer, spectral irradiance values covering the range from 200 to 400nm in 10nm steps, and guidelines for proper use.

Quartz Tungsten Halogen Lamps

If customers send their tungsten halogen or deuterium lamps, Oriel Instruments will calibrate the lamps for them within the wavelength range of 200-2400nm. Oriel Instruments can provide a custom standard based on the calibration requirements of customers. Oriel Instruments devised the 68940 Deuterium Power Supply to ascertain consistent current and low light ripple from the deuterium arc. This highly regulated, constant current source yields the high voltage required for starting the lamp and settles quickly to the prescribed current value. The preset constant current is significant for an accurate calibration of the deuterium lamp. This power supply also has a current and voltage monitoring feature.

Open Air Lamp Mounts

Open air lamp mounts are simple rod mounts holding the lamp in open air. A 1/4-20 tapped hole is made in the base of the mounts for an optical rod. Each source comes with a lamp mount suitable for lamps used by customers. A typical application of a Calibrated Irradiance Source is delineated in Figure 3, showing the calibration of the spectral response of a spectroscopic system. This enables accurate measurement of the radiation from an ‘unknown’ source, which could be another lamp, a fluorescing sample, plasma and much more.

A typical application of a Calibrated Irradiance Source is to calibrate the spectral response of a spectroscopic system.

Figure 3. A typical application of a Calibrated Irradiance Source is to calibrate the spectral response of a spectroscopic system.

About Oriel Instruments

Oriel Instruments, a Newport Corporation brand, was founded in 1969 and quickly gained a reputation as an innovative supplier of products for the making and measuring of light. Today, the Oriel brand represents leading instruments, such as light sources covering a broad range from UV to IR, pulsed or continuous, and low to high power.

Oriel also offers monochromators and spectrographs as well as flexible FT-IR spectrometers, which make it easy for users across many industries to build instruments for specific applications. Oriel is also a leader in the area of Photovoltaics with its offering of solar simulators that allow you to simulate hours of solar radiation in minutes. Oriel continues to bring innovative products and solutions to Newport customers around the world.

This information has been sourced, reviewed and adapted from materials provided by Oriel Instruments.

For more information on this source, please visit Oriel Instruments.

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