Hello dear researchers,
I want to measure the value of the third-order nonlinear susceptibility (Chi3). I have only the third harmonic generation (THG) spectra in photon counts and I know the input power at the sample to be probed. In literature, people used some materials whose Chi3 is already known and after comparison, they gave a rough estimation of chi 3. The other way in the literature was used is the utilization of an additional laser to calibrate the power.
I would like to ask is there any other way to measure the output power or chi 3 value? any simpler way if you know the input power and output intensity in photon counts???
Unless you can translate the photon counts to an actual THG power (which is quite difficult), the main option is to do a measurement relative to a material with a known chi(3), and it will involve a lot less uncertainty in the measurement
You can certainly get the third order nonlinear optical susceptibility (CHi3) using the THE technique. Please see my early work.
https://www.osapublishing.org/josab/abstract.cfm?uri=josab-15-7-1895
The method needs to get materials coated on a fused silica substrate. The details can be found from the above lined paper.
You can use a Lock-In detection mechanism if the signal power is very weak. Otherwise if the signal is sufficiently strong (i.e. visible with human eyes), you can simply use a sensitive photodiode sensor which can measure upto pW of powers.
Which technique are you using for chi(3) measurements? Raul Rangel-Rojo
Hi, yes, it depends on the signal level, and the detectors available. Lock-in detection is very good to use with pin ohotodiodes, and gives very low noise levels (we can measure transmittance changes of the order of 1%). A good power meter can also be used, and even a photodiode and oscilloscope combination, with signal integration in this case.
There are many techniques to measure chi(3), it depends what information you want to get, you may want to characterize nonlinear absorption (related to Im chi(3)), nonlinear refraction (Re chi(3)), or even non degenerate nonlinearities such as that responsible for third harmonic generation. You can use the z-scan to characterize nonlinear absorption and refraction
I have been using Degenerate Four-wave mixing technique to measure the third-order nonlinear susceptibility. In this technique, I isolate the signal and then measure the signal power with a sensitive photodiode sensor. I calculate back chi(3) using this measured signal power along with my input powers which has been divided into two pumps and a probe. Raul Rangel-Rojo Kaleem Ullah
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