UV-Vis-NIR Spectroscopy

Ultraviolet-Visible-Infrared (UV-Vis-NIR) spectroscopy measures the absorption, reflection, and transmission spectrum of a material. It is used to characterize material properties such as optical density in polycarbonate lenses, molar extinction coefficient in metal-ligand compounds, and bandgap energy in quantum dots.

Ebatco’s Agilent Cary 7000 Universal Measurement Spectrophotometer (UMS) combined with a Diffuse Reflectance Accessory (DRA) is state-of-the-art when it comes to complete optical sample characterization. The base instrument is a double-beam spectrophotometer which accounts for light source intensity fluctuations and has a wavelength range of 175-3300 nm. In addition, the base instrument is capable of measuring up to an optical density of 10 Abs, meaning it can measure one part in 10 billion of transmitted light through a sample.

The Universal Measurement Accessory (UMA) allows for independent control of the sample angle and detection angle. The sample can be rotated a full 360° and the detector can be rotated around the sample from 10-350°. In addition, the input polarization can be tuned to S- or P-polarization, and any polarization in between. The UMA can achieve absolute reflectance, absolute transmittance, and absolute absorptance values at nearly any angle without having to touch the sample or beam routing optics.

Finally, the DRA is equipped with a 150-mm integrating sphere that is used for measuring the diffuse reflectance, diffuse transmittance, and diffuse transflectance of a sample.

The Cary 7000 UMS with DRA can be used in a wide range of industries including:

• Colorimetry
• Glasses
• Optics Manufacturing QA/QC
• Nanomaterials
• Photonics
• Polymers & Plastics
• Pharmaceuticals
• Roofing Materials
• Semiconductors
• Solar Cell Materials
• Visual Displays

Typical Experimental Results

Below are demonstrations of different instrument modalities that are uniquely configured to measure specific material properties:

Concentration Determination Using Absorbance Calibration Curve

Absorbance spectra can be used to determine the chemical concentration of a molecule in solution. The absorbance at a particular wavelength of standards with various concentrations are used to build a calibration curve. The concentration of the chromophore in an unknown solution can then be determined.

Absorbance spectrum (left) and calibration curve (right).

Polarization- and Angle-Resolved Reflectance

The specular reflection of a material is useful to know in industries such as optics manufacturing QA/QC and visual displays. Using the UMA, the polarization- and angle-resolved reflectance of a material can be determined. After initial sample loading into the UMA, robotics and automation take care of the rest.

Reflectance data taken by the Cary 7000 UMA (blue) and by the optics manufacturer (red).

Angle-Resolved %R and %T of a Dielectric Filter

The UMA is capable of measuring %R and %T for a single Angle of Incidence (AOI) without having to touch the sample. Below the broadband reflectance and transmittance spectra of a dielectric filter are shown.

Reflectance (red) and transmittance (blue) spectra.

Diffuse Transmittance Using DRA

The inside of the integrating sphere of the DRA is completely covered with a high-reflectance PTFE coating that allows it to collect diffusely scattered light in reflection, transmission, and transflection geometries. The inclusion of a beam trap port allows for the specularly reflected or transmitted light to be included in the measurement, where material properties such as percent haze can be calculated.

Percent haze across the visible spectrum for five common plastics compared to glass.

Instrument: Agilent Cary 7000 Universal Measurement Spectrophotometer

Instrument Key Specifications

Cary 7000 Base Spectrophotometer

UMA

DRA

For more information, please read our application notes:
Optics Characterization Using a Universal Measurement Spectrophotometer, PDF
All application notes can be found here

Optics Characterization Using a Universal Measurement Spectrophotometer

Precise, well-defined characterization of optical components such as mirrors, lenses, and filters is fundamental to advancing product development and manufacturing in industries such as display technologies, solar energy, and advanced photonics. Confirming that each optical component performs its intended function helps to support product quality and to meet required measurement standards demanded across industries. For example, knowing the angle-dependent reflection spectrum of glass in LCDs and OLEDs helps engineers understand how ambient light interacts with the display surface to avoid glare, contrast loss, and color shifting. Additionally, anti-reflective coatings on the optics in VR headsets must perform well across a wide range of angles to reduce the amount of ghosting and glare, which has a direct effect on the user’s immersive experience and eye strain. Having complete control over optical characterization parameters enables accurate, reproducible measurements that verify products like these meet their intended performance specifications.

Ebatco’s Agilent Cary 7000 Ultraviolet-Visible-Near Infrared (UV-Vis-NIR) spectrophotometer comes with a Universal Measurement Accessory (UMA) that is capable of measuring diffuse scatter, reflectance, transmittance, and absorptance through independent 360° sample rotation and 10-350° detector positioning. It can measure absolute specular reflectance with an angle of incidence (AOI) ranging from 5-85°. The UMA also comes with an automatic polarizer capable of controlling the input polarization at any angle from 0-90°. It leverages these independent degrees of freedom without a need to manually reposition the sample or adjust the input beam optics, ensuring robust measurements. To highlight the UMA’s diverse optical characterization capabilities, two measurements were made on different optics samples using different UMA modalities.

First, the reflectance spectra of an aluminum mirror using both vertical (S) and horizontal (P) polarized light were measured, as shown in Figure 1. For this measurement, the sample angle relative to the input beam was 12° and the detector angle was 24°. The blue traces are data taken by the Cary 7000, and the red traces are data reported by the optics manufacturer (note that the optics manufacturer data was taken on a mirror from a representative lot, so the Cary 7000 and optics manufacturer datasets were taken on different aluminum mirrors). The Cary 7000 data for both polarizations shows a flat reflectance from 1200 – 2500 nm, with a minimum in reflectance around 840 nm, a recovery towards 500 nm, and another decrease in reflectance in the UV region. This response is consistent with the optics manufacturer dataset. Ultimately, the manufacturer guarantees an average reflectance, R_avg, of greater than 90% from 450 nm – 2 µm. The Cary 7000 measures R_avg in that wavelength range of 92.6% for P polarization and 93.2% for S polarization, passing performance specifications.

Second, the reflectance and transmittance spectra of a dielectric filter were co-measured at a 45° sample angle—the manufacturer-specified AOI—which is shown in Figure 2. The purpose of the filter is to separate the shorter, blue wavelengths from the longer, red wavelengths. The detector angle was set to 90° for the reflection measurement and set to 180° for the transmission measurement. The optics manufacturer guarantees the average transmission, T_avg, from 600 to 1200 nm should be greater than 85%, and R_avg from 325 to 475 nm should be greater than 90%. With a measured T_avg of 95% the transmission specification is met. However, the R_avg was measured at 77%, indicating the filter does not reflect wavelengths in the UV-Vis range as well as advertised.

As demonstrated above, the Cary 7000 equipped with a UMA offers comprehensive control for the optical characterization of various materials. With its independent control of wavelength, polarization, sample angle, and detector angle, the instrument enables precise, reproducible measurements that meet the rigorous demands of modern optical component development.

ASTM Standards

ISO Standards