Spectrometer detector selection guide

Wavelength range

The required wavelength range is often the first factor in detector selection. Silicon detectors (CCD, CMOS, and NMOS) provide excellent performance from the UV and visible regions into the near-infrared, typically up to approximately 1100 nm. For measurements beyond 900 nm, and particularly above 1100 nm, InGaAs detectors are preferred.

Spectral Resolution

Applications requiring the ability to distinguish closely spaced spectral features benefit from detectors with a large number of small pixels – for example we commonly use a CMOS detector with 4096 pixels and a pixel spacing of 7 μm for high resolution spectrometer options.

Sensitivity

For low-light applications, the ability to detect weak optical signals can be improved through longer integration times and the use of detectors with high quantum efficiency and low read noise. For extended integration times, detector cooling may be required to reduce thermally generated charge carriers, commonly referred to as dark current, and the associated noise. In general, longer integration times require deeper cooling to maintain a high signal-to-noise ratio. For example, our most sensitive Raman spectrometers use a high-performance CCD detector cooled to -60 °C.

Measurement speed

Applications involving moving samples or pulsed light sources require fast and precise spectral acquisition. In these cases, detector frame rate and readout speed become important selection factors. Modern CMOS detectors often provide significantly higher frame rates than traditional CCD detectors, making them well suited for real-time measurements and high-throughput applications.

Small variations in intensity

For applications where subtle differences in spectral features must be detected and quantified, achieving a high signal-to-noise ratio (SNR) is essential. A higher SNR makes it easier to distinguish small intensity variations from measurement noise, improving the accuracy and repeatability of the results.
High SNR is typically achieved by selecting a detector with a large full-well capacity.

Large variations in intensity within the spectrum

Some applications require the simultaneous measurement of very strong and very weak spectral features within the same spectrum. In these cases, detector dynamic range becomes a critical parameter. A high dynamic range allows weak signals to be resolved without saturating on the strongest peaks.
Detectors with a large full-well capacity can store more photoelectrons in each pixel before reaching saturation. This enables the measurement of large intensity differences across the spectrum while preserving signal quality and linearity.

The table below compares common spectrometer detector technologies in terms of their usable wavelength range and typical integration times. Many of the detectors listed as examples are available across the Ibsen Photonics spectrometer portfolio, enabling the selection of the most suitable detector for a wide range of spectroscopy applications.