The visible spectral region remains difficult to access with conventional tunable laser devices. This is why recently commercialized sources based on cw optical parametric oscillator or OPO technology gain market awareness – and become increasingly recognized as cost effective and user friendly turn-key solutions.
The low-frequency Raman region probes the same low-energy vibrational and rotational modes of molecular structures as terahertz spectroscopy (300 GHz – 6 THz). The THz region of Raman spectra contain important structural information about the molecules or crystal lattices under investigation. In the pharmaceutical industry, for instance, this structural information can help to determine the crystallinity, and therefore solubility, of pharmaceuticals. Read more about how here.
Choosing the best illumination wavelength for a given application is not always obvious. Many system variables must be considered to optimize a Raman spectroscopy experiment, and several of them are connected to the wavelength selection.
A vast number of experimental studies in that context call for high-quality continuous-wave (cw) laser light that is tunable throughout the visible spectral range, a region which is not straight forward to cover seamlessly with most of the common tunable laser designs. Alternative sources based on cw optical parametric oscillator (OPO) technology have become commercially available relatively recently only - and are gaining popularity remarkably quickly.
Digital holographic microscopy (DHM) is an interferometry-based variant of quantitative phase imaging (QPI) that typically uses a laser as a coherent light source and provides QPI by detecting specimen-induced optical path length changes against the surrounding environment. DHM can be modularly integrated into common optical microscopes which allows its integration as a label-free imaging modality in research laboratories.
Tip-enhanced Raman spectroscopy (TERS) is an approach that has been well recognized and relies on strongly localized enhancement of Raman scattering of laser light at the point of a near atomically sharp tip. However, not least due to the lack of sources delivering laser light tunable throughout the visible spectral range, the vast majority of TERS experiments so far has been limited to single excitation wavelengths. Read about how a CW tuanble laser can help change this!
There are essentially 5 types of solid state laser technology which meet the need for long coherence length in order to write holograms or HOE´s. All offering unique wavelengths, either fixed or tunable and output powers from 10´s mW up to multiple watts.
In the field of biology it is a general consensus that cancerous cells often use other metabolic pathways, than corresponding healthy cells, and thereby consume less oxygen. Read our application note on TRAST microscopy for measuring oxygen concentration in cancerous cells.
Key performance parameters when selecting a laser for Raman spectroscopy are: spectral linewidth, frequency stability, spectral purity, beam quality, output power and power stability. In addition, the compactness, robustness, reliability, lifetime and cost structure should be considered.
In the experimental quantum research community, widely tunable continuous-wave optical parametric oscillators (CW OPOs) are gaining recognition as novel sources of tunable laser light with great potential – not least due to their unprecedented wavelength coverage. Yet, the overall experimental requirements remain often challenging for the performance of turnkey OPO devices.