Handheld Raman
Materials ID (RMID) is generally used in pharmaceutical incoming materials inspection, recycling industry to sort plastics, and in processing plants to assure that the proper materials are introduced into storage containers. IPS offers ideal solutions for this application space.
Our Handheld Raman lasers are high output power, small, lightweight, stable in both power and wavelength, but most importantly – they are low power consumption. This allows for long battery life in the hand-held instrument.
IPS customers split evenly between the single mode TO-56 and the 14-pin fiber coupled BF package:
- Single mode lasers are extremely low power consumption, but they focus to a very small spot and have extremely high-power density as a result. In addition, the beam is Gaussian in intensity profile, so the middle of the beam is MUCH higher intensity than the edge. These 2 characteristics frequently cause materials to burn. So, it is important to either move the beam or move the material around to prevent burning [see for example US Patents 8,988,678, 9,523,610, 9,791,313, and 10,072,984]. In addition, Hand-Held units are commonly used with SERS particles (which are sensitive to burning). Finally, the small spot size of the SM laser makes it likely that the beam will focus interstitially between grains of a coarsely ground sample – so unless the sample or the beam are moved, there is a chance that you will focus in-between grains and get poor Raman signal. Last point – hand-held Raman units are commonly used for testing explosives. The use of the SM laser with its high-power density is much more likely to set off explosives than the MM fiber coupled or STUB laser options below.
- Multi-mode fiber coupled sources are more traditional for Hand-Held units, but the fiber coil diameter (minimum coil diameter is 2”) makes this product a bit more challenging to package than the TO can. The MM laser also has a higher threshold drive current as compared to the SM laser and requires more current to reach equivalent power levels, resulting in a lower battery life. However, the MM laser has higher power (which directly translates 1:1 into “more Raman signal) with LOWER power density (because the beam doesn’t focus to as small a spot as the SM laser) – so this type of source is less likely to burn samples. Finally, the MM fiber homogenizes the laser power intensity, so the illumination spot has roughly equal intensity across its area. This makes this type of laser ideal for SERS and for use with non-homogeneous samples where the constituents are not mixed well. Additionally, since the beam is not as focused as the SM laser, it is less likely to focus “interstitially” between grains of a coarsely structured sample (like Urea or salt).
- The STUB laser is a good compromise between the SM TO-Can and the fiber coupled MM laser. It doesn’t have the fiber coil, so it packages well; and it homogenizes the beam so the power density is low with a uniform intensity profile. Additionally, the STUB can shape the beam – so you can offer rectangular shaped illumination spots that are designed to match the slit shape and maintain brightness in the system (so the product can have higher collection efficiency than a traditional set-up using a round illumination spot vs a slit). The negative of the STUB package design is only in power consumption (so battery lifetime is not as good as the SM laser), and the package size (which makes the overall Raman instrument slightly larger than is possible using the TO-56. Ultimately, the STUB laser is a great compromise for hand-held systems.
For more information, check out our Literature References.
