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Hello. We have an Aurora-2 NSOM with probe model 1640-00. The operational wavelength of the optical fiber attached to the model 1640-00 probe is specified as 633nm, single mode.I have the following questions regarding the NSOM tips:
1. Can a 488nm/514nm lasers that we are using be used for the NSOM measurement with the 633nm single mode fibers?2. What is the specification of the 633nm single mode fiber attach to the tip?3. Do you provide NSOM probes with 488/514nm fibers?
4. What are the requirements if one wants to connect the fiber connected to laser coupler (e.g., same diameters, same operational wavelength as the fiber on the tip)?5. We are trying to collect Raman scattering (i.e., get a Raman spectrum) via the NSOM tip. Is it necessary to match the wavelength of laser and the optical fiber?
Thanks,
Dave
Di David,
Let's go through your questions step by step:
1. Yes. If you use the fiber for illuminating the sample that is not a problem.
2. As you pointed out, the fiber is singlemode at 633nm. That sets the core of the fiber to around 3 um, NA around 0.1. The outside diameter is 125/250um cladding/buffer. Fibers like that can be found at Thorlabs or Newport as an example.
3. No. As the fiber is capable of being used with shorter wavelength there was no need.
4. Single mode tip fibers can be connected directly into a fiber coupler. This is not easy as the fibers are not that long. In any case, you need a single mode laser coupler (check Newport) for stability and accuracy. The more user friendly way would be to have that single mode fiber coupler couple into a (longer) delivery fiber and have a cam-splicer close to the actual NSOM instrument. This way you do not have to recouple all the time when changing fiber tips and you can move your (noisy) laser far away. You will loose of course some light at the connection point but if you have a laser with decent power that should not be a problem. The diameter of the delivery and tip fiber should be matched for the splicer to work and you need to make sure that the "chuck" in the coupler is capable of grabbing the fiber properly.
5. Please see answers in 1-4. Would you will notice that with the standard 50-80nm aperture fibers you will most probably not get enough light out of the aperture to get a useful Raman signal. 100nm apertures should help here a bit. I have done some Raman measurements using these fibers but used the SERS effect to enhance the signal. If that is what you are shooting for it might work.
6. If you are looking for a solution providing co-localized Raman and AFM capabilities you may want to check out our NEOS-SENTERRA combination. If you are interested in tip enhanced capabilities you may want to look into our IRIS offering which offers a TERS ready solution for transparent and opaque sample.
Best, Stefan
Thanks Stefan for the quick response.