The proper field intensity for THG
Posted: Tue Nov 30, 2021 2:39 pm
Dear all,
I am calculating THG for Si, GaAs and ZnSe. I am confused with the E field intensity setup.
For Si, the THG spectrum converged with intensity 1E6 ~ 1E8 kW/cm2. When I increase the k mesh, the Im(X3) increases and finally converged. Everything went well.
For GaAs, the THG spectrum can only converge with a narrow intensity range. For a 8*8*8 k mesh, only results with intensity 0.5*E5~E5 kW/cm2 converged. I set the intensity to E5 kW/cm2 and increased the k mesh. Strange things happened. Im(X3) converged for k 8*8*8 and 20*20*20, but not for 16*16*16 and 24*24*24.
For ZnSe, I found no converged results with intensities E1~ E11 kW/cm2.
Here are my questions:
1. Why is the X3 coefficient intensity dependent? Physically, this coefficient should be intensity independent. To my understanding, we can not set the intensity too small because there is numerical noise. If we set it too high, the crystal is damaged. Do I understand correctly?
2. How wide an intensity interval for convergence is reasonable. The convergence interval for GaAs as I calculated is only 0.5*E5 kW/cm2. I do not know if it is a reasonable result.
3. Dose convergence vary at different k mesh? Do I need to do a convergence test at each k mesh?
4. Why is there no proper field intensity for ZnSe?
Result attachment: https://mailsucaseducn-my.sharepoint.co ... w?e=lAqwec
I am calculating THG for Si, GaAs and ZnSe. I am confused with the E field intensity setup.
For Si, the THG spectrum converged with intensity 1E6 ~ 1E8 kW/cm2. When I increase the k mesh, the Im(X3) increases and finally converged. Everything went well.
For GaAs, the THG spectrum can only converge with a narrow intensity range. For a 8*8*8 k mesh, only results with intensity 0.5*E5~E5 kW/cm2 converged. I set the intensity to E5 kW/cm2 and increased the k mesh. Strange things happened. Im(X3) converged for k 8*8*8 and 20*20*20, but not for 16*16*16 and 24*24*24.
For ZnSe, I found no converged results with intensities E1~ E11 kW/cm2.
Here are my questions:
1. Why is the X3 coefficient intensity dependent? Physically, this coefficient should be intensity independent. To my understanding, we can not set the intensity too small because there is numerical noise. If we set it too high, the crystal is damaged. Do I understand correctly?
2. How wide an intensity interval for convergence is reasonable. The convergence interval for GaAs as I calculated is only 0.5*E5 kW/cm2. I do not know if it is a reasonable result.
3. Dose convergence vary at different k mesh? Do I need to do a convergence test at each k mesh?
4. Why is there no proper field intensity for ZnSe?
Result attachment: https://mailsucaseducn-my.sharepoint.co ... w?e=lAqwec