I am setting up a CW THz system and have put together both transmission as well as reflection mode setups. Although the maximum photocurrent I am getting for the transmission mode is around 30 nA at 0.1 THz, the maximum I can get for the reflection mode is around 15 nA at 0.1 THz.
Do I need to work more to align the system or this is as much as I can get in a reflection mode.
Hi Shaumik,
to the best of my knowledge, the maximum signal should be the same in transmission and reflection. However, the reflection setup is considerably more difficult to align. You have one additional optical element, which (in the best case) has a planar surface, but still does not direct or focus the light - unlike a parabolic mirror or lens. This means that the THz wavefront differs from the geometry of the reflector.
Except for the 50% signal loss: is the bandwidth still the same?
Best regards,
Anselm
Hi Anselm.
Thanks for your clarification. We have been actually using two more parabolic mirrors to direct the THz beam to the sample and guide the reflected beam to the parabolic mirror infront of the photodetector. So I guess, we are not being able to properly guide and collect the waves from the sample surface.
Yes, 50 % loss is there, we can get more or less the same bandwidth but the SNR is obviously low.
Guess, I need to put in more effort. Thanks once again.
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