Spectroscopic System

WITec UHTS Raman Spectrometer

All WITec's Raman microscopes are operated with ultra-high throughput spectrometers (UHTS) that were distinctively developed for high speed and high resolution Raman imaging. The UHTS series comprises of six models in several focal lengths to accommodate multiple laser excitation wavelengths (UV to IR) and spectral resolution requirements.

All UHTS spectrometers are lens-based and feature an optical fiber port, resulting in an overall transmission efficiency of up to 70%.

The automated triple-grating turret can host up to three gratings. Customers can choose from among a variety of gratings matching individual requirements in terms of spectral range and resolution.

On the detector side several types of CCD cameras with quantum efficiencies exceeding 90% can be attached.


Key Features

ULTRA HIGHULTRA-high throughput

The ultra-high throughput of the UHTS series enables up to 70 % transmission. They are specifically designed for challenging Raman imaging and spectroscopy applications with intrinsically low light intensities.


ULTRA FASTULTRA-fast acquisition times

Utilizing our UHTS for data collection, the acquisition time for a single Raman spectrum can be reduced to below one millisecond per spectrum, providing essential benefits in Raman microscopy where commonly thousands of Raman spectra must be acquired.


ULTRA SHARPULTRA-sharp spectral information

WITec UHTS spectrometers deliver exceptional spectral and imaging quality. Symmetric peak shapes are ensured by design for coma/astigmatism-free spectra acquisition.


ULTRA CUSTOMIZABLEULTRA-customizable triple-grating turret

An automated three grating turret incorporates the flexible integration and combination of individual gratings. Switching from one grating to another to accommodate varying experimental requirements has never been easier.


ULTRA CONFIGURABLEULTRA-configurable: several focal lengths

The Raman spectrometers of the WITec UHTS series are available in several focal lengths to accommodate multiple laser excitation wavelengths and spectral resolution requirements for the most demanding Raman imaging experiments.













Focal length and grating dispersion influence signal intensity, detectable spectral range and resolution.

UHTS Series

SPECTRAL RANGESpecifications of all UHTS

  • Lens-based imaging spectrometers
  • Specifically designed for low light intensities
  • Throughput >70%
  • Symmetric peak shape (coma/astigmatism free)
  • Automatic triple-grating turret
  • FC/APC optical fiber port
  • Can be fitted with FI- and BI-CCD cameras
  • Controlled via WITec software



For excitation in the visible range the UHTS 300 VIS provides outstanding dispersive peak separation capabilities. The focal length of 300 mm is in accordance with the required sensitivity for demanding Raman imaging applications.



The UHTS 600 features an extended focal length of 600 mm for greater dispersion, which allows closely adjacent peaks to be resolved more readily. This new addition to the UHTS line enhances the chemical sensitivity and provides a high throughput at the same time. Therefore acquisition times for Raman spectra and images can be unparalleled fast. 



With an optical system adapted and tailored for UV starting at 355 nm, the UHTS 400 UV-VIS expands Raman imaging capabilities even further when exciting with lasers at or below 488 nm.



Applications requiring broadband excitation from the visible to the near-infrared can greatly benefit from the UHTS 300 VIS-NIR. This more affordable spectrometer is well suited for multiple laser configurations between 532 nm and 830 nm while maintaining the advantages of the UHTS family.



In the near-infrared regime the use of specific NIR-optimized optical components is essential for high throughput spectral acquisition. A focal length of 400 mm, a specialized set of gratings, and state of the art deep depletion CCD technology combine to form an ideal solution for NIR Raman spectroscopy.



The UHTS 300 IR covers excitation ranges from 800 to 1700 nm featuring infrared optimized optical components, gratings and detectors for highly precise and accurate Raman and photoluminescence experiments.

CCD Detectors

CCD CAMERAWITec spectroscopic systems can be individually configured to meet sophisticated requirements in a great variety of applications. Several different types of CCD cameras with quantum efficiencies exceeding 90% can be attached to the UHTS series.


Front-Illuminated (FI) CCD camera

A front-illuminated CCD is characterized by a broad range of possible applications and wavelengths, generally oriented toward budget-conscious or basic experimental setups.


Back-Illuminated (BI) CCD camera

With a quantum efficiency of 95% or more, a back-illuminated CCD sets the industry standard for efficient Raman signal detection in the visible range. Compared to a front-illuminated CCD, they offer twice the quantum efficiency and are therefore suitable for precise and sensitive FAST RAMAN IMAGINGR at the highest lateral resolution. (UV-optimized versions are also available.)


Electron-Multiplying (EM) CCD camera

For sophisticated and leading-edge Raman applications, an EM CCD provides the most advanced readout capabilities for low light-level detection or ULTRA-FAST RAMAN IMAGING. Readout-speed can be as low as 760 µs per spectrum (1300 spectra/s) and dark currents as low as 0.0001 electrons/pixel per second.


Open Electrode (OE) CCD camera

The open electrode (OE) CCD is a front-illuminated camera that enables the acquisition of almost the entire spectral bandwidth and is specifically well-suited to measurements in the UV. In order to achieve state-of-the-art signal-to-noise ratios it features a low dark current and a multi-purpose camera functionality for various applications. 


Low Dark-Current Deep Depletion CCD camera

Near-infrared (NIR) spectroscopic measurements of Raman and photoluminescence (PL) require specialized CCD detectors to prevent the spectral data from being influenced by “etaloning”, an effect that occurs when the Si-CCD chip materials become increasingly transparent to light at longer wavelengths. With the low dark-current deep depletion technology provided by this detector, critical NIR and PL experiments can be performed without signal loss.


InGaAs linear array detector

For scattering experiments above the Si-bandgap of approximately 1100 nm WITec supplies state-of-the-art Indium-Gallium-Arsenide (InGaAs) linear array detectors allowing for spectral imaging in the IR (up to 1700 nm) with peak quantum efficiencies near 90%.

Fiber-based Beam Delivery: Facts and Benefits

WITec uses the newest photonic fiber technology for highly efficient light transmission.

Your benefits are:

  • Virtually lossless energy transmission
  • Extremely efficient optical throughput
  • Highest spatial resolution and confocality provided by the fiber-generated diffraction-limited point light source
  • User-friendly operation and long-term stability through pre-configured and pre-aligned fiber-coupling units
  • Most intricate polarization-dependent measurements feasible through maintenance of the polarization plane of light
  • Reduced thermal or vibrational disturbances by lasers mounted distal of the microscope

Proven Measurement Power for High-Performance Raman Imaging

WITec spectroscopic systems enable the acquisition of Raman spectra, depth profiles and 3D images with exceptional spectral and spatial precision. This proven performance in speed, sensitivity and resolution is available without compromise or caveat, in your facility.


WITec CCl4 high performance

High-performance Raman image: (A) 3D confocal Raman image of an emulsion with corresponding Raman spectra shown in (B) Green: Alkane; Blue: Water; Yellow: CCl4 + Oil. Image parameters: 200 x 200 x 20 pixels, 100 x 100 x 10 μm3 scan range, 0.06 s integration time per spectrum, 532 nm excitation wavelength. (C) Zoom-in image with high spectral resolution. Image parameters: 100 x 100 pixels, 10 x 10 μm2, 0.08 s integration time per spectrum, UHTS 600 spectrometer, 1800 g/mm grating. (D) Due to the high spectral resolution of the spectroscopic system the CCl4 bands at around 460 cm-1 can be clearly resolved even at room temperature.

UHTS300 cyclohexane two spectra

Symmetric Peak Shape. Left: Raman spectrum of cyclohexane acquired with the UHTS 300 VIS. Right: Zoom-in at the 1020 cm-1 peak region. In addition to the measured spectra (blue) a Lorentzian-fitted curve is displayed (red). The almost perfect match of the measured spectra with the theoretically predicted curve shows the high accuracy of the measurement.

WITec 4th order Si

Sensitivity: The ability to resolve the peak of the 4th order band of Si is widely considered to be a measure of the sensitivity of a Raman spectroscopy system. The spectrum above shows the 4th order Si peak acquired with the UHTS 300 VIS equipped with an EMCCD. No data post-processing other than cosmic ray removal was applied. The very high signal-to-noise ratio along with the low intensity of the N2 peak indicate the true confocality of the system as the detected signals from the environment (e.g. air) are extremely low, showing that the contribution from out-of-focus light is effectively blocked by the pinhole.

Capability, versatility and expandability for Raman spectroscopy – Optimized today, ready for tomorrow

WITec spectroscopic systems can be individually configured to meet exacting requirements in a great variety of applications. Our Raman imaging specialists are happy to consult you in order to define an optimized system for your individual applications and budget requirements. Even future ambitions can be taken into consideration as WITec systems are typically fully upgradeable, extendable and able to incorporate additional excitation wavelengths, scan stages and microscopic techniques: If your scientific approach changes, the WITec system can easily follow.


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