Given today’s widespread use of Raman spectroscopy, it can be hard to believe Raman was a highly specialized analytical technique for most of its history. The technique’s potential was recognized from the beginning: When Raman scattering was first observed in 1928, it was widely believed to be one of the most important scientific discoveries of the 20th century to date. The effect’s discoverer, C. V. Raman, was awarded a knighthood, the presidency of the Indian Science Conference, a Nobel Prize and several honorary doctorates for his work.
But despite the scientific community’s enthusiasm, early Raman spectrometers found relatively few applied uses. While the value of the information Raman spectrometry provided was immediately recognized, the instrumentation of the time was too primitive for most applications. Unlike modern instruments, 1930s-era Raman spectrometers were difficult to operate, unreliable and imprecise. Because of these limitations, Raman spent several decades limited to material investigations and academic research that absolutely required the technique. Infrared (IR) spectrophotometers, which entered the market in the 1940s, handled the majority of applications in applied and industrial sectors.
Raman’s first major evolution occurred with the introduction of the laser. Raman spectrometers equipped with lasers were much more sensitive than their previous generation counterparts, which allowed them to produce results that were competitive with other techniques. The adoption of the laser as the primary excitation source for Raman spectrometers also meant that any improvements in laser technology would automatically translate into improved Raman performance. Because lasers were evolving so rapidly, Raman did as well.
The integration of the laser—as well as other technologies, such as improved monochromators and detectors—represented major evolutionary steps for the Raman technique. Raman continued its technological evolution in the late 80s and early 90s, with the development of compact, lower-cost lasers; integrated (and, eventually, automated) microscopes and multi-channel detectors.
While the incorporation of these technologies improved the science that drives Raman spectroscopy, it didn’t address the technique’s other major issue: accessibility. Raman spectrometers still required highly specialized skills to operate and specific knowledge to interpret their spectra. Additionally, they were often difficult to maintain and were location dependent, which meant most researchers needed to send samples to dedicated Raman spectroscopy laboratories for analysis. Even though the science and engineering had improved, accessibility issues continued to prevent the widespread adoption of Raman in the applied and industrial sciences.
Raman’s next evolution, which is already well underway, seeks to address these limitations by reducing the cost and expertise required to operate a Raman spectrometer. While previous generations of Raman instruments were defined by major improvements to the technology behind the analysis, the main driver of this new evolution in Raman is accessibility. Improving performance and accuracy will always be critical, but in this generation of Raman instruments those attributes have taken a backseat. Today’s analyzers use the same technology to do the same work as their predecessors—they just do it smarter, faster and, in some cases, smaller.
For most of their history, Raman instruments have required highly trained operators to function correctly. In addition to the knowledge required to make sense of the analytical data, spectroscopists also needed extensive training to calibrate and maintain the instrument. These skill requirements put a hard limit on the technology’s distribution and adoption.
The latest evolution of Raman reduces these skill requirements drastically. Modern benchtop instruments use intelligent software to take care of everything from calibration and alignment to background compensation and data analysis, making the technology accessible to even non-technical users. For laboratories without dedicated spectroscopists, these new capabilities allow them to use Raman analysis to its maximum effect. It’s even possible to automate entire analysis processes. The fact that Raman instruments no longer require an advanced spectroscopy degree to operate also means undergraduates can now make full use of them. This improves the breadth and depth of education and experience that today’s science students can receive.
Like most technologies, Raman instruments benefit from Moore’s Law. Over the past decade, the speed of Raman analysis has accelerated dramatically thanks to increased processing power and optical performance. But while increased processing power is important—especially insofar as it allows analyzers to run software that makes them more user-friendly—what’s really revolutionary is the dramatic decrease in overall time from sample collection to meaningful result.
Smaller, smarter and more capable Raman instruments require less infrastructure to perform analysis. In the past, Raman analysis typically required sending samples off to a specialized laboratory and often waiting several weeks for results. Modern Raman instruments, by contrast, allow users to get immediate results almost anywhere, from the laboratory to the field. Reducing the total time between sample collection and meaningful results has been enormously important for the viability and utility of the technology.
Raman analyzers have never been particularly small. For most of their history they were benchtop instruments. However, the next evolution of Raman instruments aims small. Over the past decade, analyzers have shrunk from their traditional benchtop dimensions down to portable handheld form factors that weigh less than 2 kg.
Combining smarter and faster with smaller revolutionizes the utility and potential applications of Raman. Portable handheld Raman analyzers can now give straightforward, unambiguous identification of materials of interest in the field—at the point of analysis and time of information need.
The development of ultra-small instruments has made it possible for the benefits of Raman analysis to be accessed anywhere and by anyone, including by non-technical users in low-infrastructure areas of the world. In Ghana, for example, handheld Raman analyzers are used to detect fake anti-malaria medication at the point of distribution. Previous generations of instruments would have required complex logistics to transport drug samples from Ghanaian distribution points to a central laboratory. Today’s handheld analyzers, by contrast, are small enough to travel directly to the point of need. In addition to detecting counterfeit drugs, handheld Raman analyzers are also used by police departments to identify drugs of abuse in the field.
The first 80 years of Raman spectroscopy’s evolution were driven by technological improvements: lasers, improved detectors, better cameras and miniaturization. Now that the technology is in place, this current phase of development is driven by accessibility first and technology second. Expect this trend to continue: Over the next decade, Raman instruments will become smarter, faster and potentially even smaller than they already are now, making this valuable analytical technique viable for even more applications.