Waveguide loss measurement- endfire coupling

AI Thread Summary
The discussion focuses on measuring propagation loss in nanophotonic structures designed for telecommunications at a wavelength of 1550nm. The setup involves coupling laser light through a tapered lensed fiber into a DUT chip, with output measured via an objective and photodetector. The user encountered a Fabry-Perot effect in their spectrum scan, complicating the analysis of loss measurements. Questions raised include the specifics of the laser wavelength and whether the observed oscillations are due to internal reflections within the chip. Clarification is sought on the appropriateness of using a 1550nm source for direct power measurement instead of spectral analysis.
maxclark153
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Hi, I am doing an experiment to investigate the propagation loss in some nanophotonics structures.

The laser light is coupled to the input of the DUT chip via a tapered lensed fiber and the output of the chip is go through a objective then a photodetector.

The chip is design for telecommunication propose, so wavelenght of interest is around 1550nm.

I did a spectrum scan for 1500 - 1600 nm and obtained the spectrum as below..

http://img134.imageshack.us/img134/7893/clipboard01ww2.th.jpg

Unfortunately , the spectrum is with the fabry perot effect.. (the oscillation), i try to calculated the path from the spectrum , but the calculated dimension doesnot match the fiber-chip facet or both end facet of chip .

So if you gurus outthere can help _?
 
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I'm not quite sure what your question is exactly.

There are some things that you should clear up:
- What wavelength laser are you putting into your chip? Is it broadband?
- The fabry-perot effect is arising from the reflections within the chip?
- If the chip is designed for 1550nm, why are you trying to measure spectral losses? Why can't you use a 1550nm source and just measure the total average power at the output?
 
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