Alakai develops and customizes leading-edge technologies to detect threats long-range, protecting the life and safety of personnel. Our products can be tailored to detect explosives, chemicals, weapons of mass destruction, narcotics, and other hazardous materials.
Alakai experts lead the industry, authoring articles and papers and holding patents and patents pending for multiple generations of standoff spectroscopic sensor systems
Understanding Ultraviolet: The Alakai difference
Alakai technologies use ultraviolet lasers for Raman spectroscopy, offering several significant benefits.
The use of ultraviolet excitation provides enhanced Raman signal intensity compared to visible or near-infrared excitation wavelengths. This heightened signal allows for the detection and analysis of even low-concentration samples, improving sensitivity and expanding the range of detectable compounds.
Ultraviolet lasers enable the investigation of specific molecular bonds that are more readily excited in the UV region, allowing for a more detailed understanding of chemical structures and interactions.
Ultraviolet Raman spectroscopy is particularly valuable for detection applications, as it can probe materials with high fluorescence background or strong light scattering, overcoming limitations imposed by these interfering factors. Overall, the utilization of ultraviolet lasers in Raman spectroscopy opens new possibilities for advanced research, characterization, and identification of diverse substances.
Alakai has leveraged these benefits to create some of the most innovative standoff detection systems in the world. For standoff detection applications, the detection system must have the greatest signal-to-noise ratio (SNR) possible to scan for trace quantities, at longer ranges or cover large areas in a reasonable time.
The Raman signal-to-noise ratio (SNR) can improve with shorter laser wavelengths in Raman spectroscopy. One reason for this improvement is that shorter wavelengths, such as those in the ultraviolet (UV) range, provide higher photon energy. The higher energy photons interact more strongly with the sample, resulting in a more efficient Raman scattering process. Consequently, the Raman signal becomes stronger, leading to an increased SNR. This effect scales at 1/ λ4. Compared to typical near-infrared Raman systems with similar operating characteristics, Alakai can obtain around 100x signal strength improvement (1/λ4 or (830/262)4 ≈ 100X).
Additionally, shorter laser wavelengths are less prone to interference from background fluorescence and Rayleigh scattering. These unwanted signals can obscure the Raman spectrum and decrease the SNR. By using shorter wavelengths, particularly in the UV region, Alakai can minimize these interfering signals, thereby improving the SNR and enhancing the clarity of the Raman spectrum. We refer to operation in this region as being solar-blind and fluorescence-free because noise sources such as sunlight and other lights will not degrade or interfere with detection performance. For laser wavelengths below 250 nm, fluorescence is approximately two orders of magnitude lower than for longer wavelengths (see Figure 1.)
Figure 1 - DUV Raman spectra in fluorescence-free and solar-blind region.
It is worth noting that there is an optimal wavelength range for each substance of interest, beyond which the SNR may decrease due to increased sample damage or absorption. Alakai’s standoff detection systems operate at either 248nm or 262nm.
Employing shorter laser wavelengths in the UV range can enhance the Raman SNR by increasing the Raman signal strength and minimizing interference from background signals, improving spectral quality and analytical capabilities.
Additional benefits of DUV Raman compared to competing Raman systems include:
● Increased eye safety: Per ANSI Z136.1, the maximum permissible exposure is ≈600x greater in the DUV than in the NIR. Alakai’s patented eye-safety technology employed in the CPEDS product line allows DUV Raman to take full advantage of the increased energy. [USPTO 2014]
● DUV Raman is unlikely to ignite explosives like most other visible and NIR Raman systems.
● DUV Raman is less susceptible to interference from substrate pigments than other visible and 355nm UV Raman systems.
The use of UV Raman gives Alakai an advantage in the market over competing systems for standoff detection of chemical threats.