I need to prepare a closed gas cell (with input and output for gas) which will sit on a waveguide (without damaging it) for gas sensing measurement. IR light will focus from an optical fibre on one end of waveguide and has to be collected at the other end by an optical fibre and the waveguide has to be closed from top for gas flow.
If any one has some insights or any relevant reference please share........
What is your application and what are you trying to achieve? What are the physical requirements for this apparatus in terms of performance for the intended function?
Dear Dr. Wilson, Our application is toxic gas detection and we are making use of a waveguide fabricated on a chip for this. IR light will be coupled on one end of the waveguide and the received intensity is recorder at the other end using an optical fiber. Most of the toxic gases such as CO, NO2 etc. (which are IR active) have a specific IR absorption. Hence our target is to utilize this feature for selective gas detection. Now to study the absorption of IR by gases we need to prepare a leak tight gas cell having an inlet and outlet for gases to control their flow and concentration. Hope i have made the requirement and intended function clear..............
Dear Vishal, usually when you do gas sensing using spectroscopy (analysis of the absorption wavelength in the spectrum) you want to have the longest optical path as it will ensure a good interaction of light with gas. Then, I'm not sure what is the reason you want to use a waveguide, or at least how it is : Silicon waveguide ? You work instead on the interaction of evanescent field of the waveguide with the gas ? Anyway, keep in mind that the more you will induce interaction of your light with the gas, the easier you will be able to detect it. If you need to have it fiber coupled, then, you can arrange setups with some air-gap between fibers that will fill with the gas, but interaction length will be short and you will introduce interferometric noise (you can always set the gap to a length that will produce interferences that won't disturb too much of the absorption line. You can also work with hollow fibres (capillaries where ligth propagate through air... Available from Ceramoptec) or also with hollow-core fibers. Another solution also could be to have an interaction cell which will facilitate the gas introduction and light will travel inside.. Many possibilities.. But depending on what you really want to do you should follow one specific way.. Hope this helps a bit.
Dear Miguel, Thanks for your reply. Ya it will be Si waveguide and we will be studying the interaction of evanescent field of the waveguide with the gas
Dear Vishal, I understand now. I would try to work with flow through cuvette/cell. They are cheap and can find them with many different shapes and sizes. Maybe you can find one that is like a box with a lid. You could just use the "box" with the lid and cover the waveguide with it. If you don't find, there is always the way to open a normal cell, but you will need some specific facilities to do it (people who know glass milling or work with femto lasers).
To keep hermetic you can glue it to the wafer or the part that holds the waveguide. Torr Seal is a very effective glue for gas and vacuum applications and can be found through Thorlabs. Maybe a little pump will help to flow the gas inside the cell and then allow a good interaction with the waveguide. But input and output from the flow through cuvettes will be very helpful.
I hope this will help and good luck !
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