Spectroscopy can be summarised as the study of the interaction between light and matter. The result tells us something about the molecular and atomic nature of the material. In particular, Raman spectroscopy yields unique information by investigating the vibrational and rotational modes of the molecule.

Cw lasers are typically used to avoid any damage to the sample. Much interest has been centred around NIR excitation wavelengths, however, the intensity of the NIR Raman signal is fairly weak. By using shorter wavelength lasers, such as the Cobolt SambaTM, at 532nm or Cobolt BluesTM, at 473nm there is complementary Raman information which can be collected. Narrow spectral bandwidth, spectral purity and a high level of wavelength stability are important features for this application.

The production of high quality holographic images has always relied on lasers with long coherence length and single mode properties in order to achieve stable interference for the entire exposure time. Today holograms are not only appreciated as art works but they are also used for improved security measures, for instance on credit cards and bank notes, for real-time sub-micron measurements and for advanced presentation in 3D format.

DPSS lasers are a very appropriate laser sources due to their extremely narrow linewidth, which translates to a long coherence length, very stable power and single mode properties. Stable single mode operation is particularly important for large area holograms where long exposure times are often required.

Laser Doppler Velocimetry is a well established method for analysing particle movement at a single point, either in a gas or a liquid. This information is typically collected using two intersecting collimated laser beams. The beams intersect and interfere in the region for analysis. The particles passing through this region reflect light and from this data it is possible to measure the Doppler shift and therefore velocity of the particles.

The laser source suitable for such applications needs to have long coherence length, operate single longitudinal mode, and have good power and noise stability. Naturally cw DPSS lasers are thus perfectly suited to such an application. In addition, Cobolt’s range of DPSS lasers means that shorter wavelengths can also be utilised giving additional information about the size of the particles.

The increasing demands of consumers today means that maintaining quality of transported perishable goods, in particular of fresh fruit and vegetables, often requires monitoring. This is typically done using a combination of lasers and spectroscopy.

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