Nowadays Raman spectroscopy has become a cost-efficient and much-appreciated tool with applications in material science and in-line process control for pharmaceutical, food & beverage, chemical and agricultural industries.
For instance, Raman probes and based on them Raman systems are used across the whole value chain in the pharmaceutical industry. High-resolution Raman microscopes help researchers in the development of new drugs. Hand-held Raman systems are used at pharmaceutical companies to inspect the purity of incoming new material used in drug manufacturing. Probe-based Raman systems are used to monitor the mixing of constituents in this manufacturing. Raman microscopes monitor the quality of compound distribution in produced medical pills and, finally, portable Raman instruments are used to detect and identify counterfeit drugs in the field.
Raman system manufacturers overcame the challenge of weak signals thanks to improvements in laser technology, detectors, spectral filters, along with developments of new schemes for signal generation and detection.
The laser is the principal source for creating the weak photon-phonon interactions that result in the Raman signal. In all cases, laser reliability is paramount. The required wavelength, power and performance specifications are dependent on the material being investigated, the desired resolution and the ultimate purpose for the system.
Many variables must be considered in order to optimize a Raman spectroscopy experiment, many of which are connected to the wavelength selection. The most commonly used wavelength in Raman spectroscopy is 785 nm. It offers the best balance between scattering, efficiency, an influence of fluorescence, detector efficiency and the availability of cost-efficient and compact, high-quality laser sources. However, it’s often desirable to have access to a selection of various laser wavelengths in the same Raman system, preferably with similar optical performance and similar user interfaces.
In addition to wavelength, there is a member of important performance parameters that should be taken into account when choosing the best laser sources for a Raman spectrometer:
- Spectral linewidth
- Frequency stability
- Beam quality
- Output power and power stability
- Optical isolation.
In addition to this, the compactness, robustness, reliability, lifetime and cost structure should be considered in the selection for a Raman system. For these reasons, most Raman systems are nowadays equipped with solid-state based laser sources than the gas lasers.
Optromix Raman fiber optic probes are miniaturized without compromising its performance, which is enabled by the technology of direct deposition of the dielectric filters at the fiber end faces. In results in a small, cost-effective Raman probe for different Raman systems and, for example, for endoscopic and other applications.
The fiber optic Raman probe is produced for multi-wave excitation in the range 690-785 nm and 1000-1064 nm, e.g. @785 nm – “Fingerprint” spectral range with fluorescence reduction, and @690 nm – “High wavelength” spectral range for conventional Raman spectrometers.