3D simulation of a Gaussian laser entering a spherical plasma

[wuwhan186]

Hello Blogger, I am currently working on a 3D simulation of a circularly polarized Gaussian laser entering a uniform spherical plasma. However, after building the model and running the simulation, I found that the laser does not appear. I would like to consult with you about how to set various parameters for circularly polarized lasers in 3D. How does it differ from 2D simulations?

[wuwhan186]

@Status-Mirror

[Status-Mirror]

Hi @wuwhan186,

We provide a 2D linearly-polarised Gaussian beam demo in our documentation. To convert this to 3D, you can add a new radial co-ordinate radial_yz = sqrt(y^2 + z^2) to a constant block, and then you should be able to replace any reference to y with the radial_yz variable.

For circular polarisation, you can try injecting two linearly polarised lasers on top of each other, with perpendicular polarisations and a pi/2 phase-shift.

I'm not currently able to test this, but maybe something like this would work:

begin:control
    nx = 2400
    ny = 1200
    nz = 1200
    t_end = 100e-15
    x_min = 0
    x_max = 20e-6
    y_min = -5e-6
    y_max = 5e-6
    z_min = -5e-6
    z_max = 5e-6
    stdout_frequency = 100
end:control

begin:boundaries
    bc_x_min = simple_laser
    bc_x_max = open
    bc_y_min = open
    bc_y_max = open
    bc_z_min = open
    bc_z_max = open
end:boundaries

begin:constant
    I_fwhm = 2.0e-6          # FWHM of laser intensity
    I_peak_Wcm2 = 1.0e15     # 0.5 * eps0 * c * E_peak^2
    las_lambda = 1.0e-6      # Laser wavelength
    foc_dist = 5.0e-6        # Boundary to focal point distance

    radial_yz = sqrt(y^2 + z^2)
end:constant

begin:constant
    las_k = 2.0 * pi / las_lambda    
    w0 = I_fwhm / sqrt(2.0 * loge(2.0))                  # Beam Waist
    ray_rang = pi * w0^2 / las_lambda                    # Rayleigh range
    w_boundary = w0 * sqrt(1.0 + (foc_dist/ray_rang)^2)  # Waist on boundary
    I_boundary = I_peak_Wcm2 * (w0 / w_boundary)^2       # Intens. on boundary
    rad_curve = foc_dist * (1.0 + (ray_rang/foc_dist)^2) # Boundary curv. rad.
    gouy = atan(-foc_dist/rad_curve)                     # Boundary Gouy shift
end:constant

begin:laser
    boundary = x_min
    intensity_w_cm2 = I_boundary
    lambda = las_lambda
    phase = las_k * radial_yz^2 / (2.0 * rad_curve) - gouy
    profile = gauss(radial_yz, 0, w_boundary)
end:laser

begin:laser
    boundary = x_min
    intensity_w_cm2 = I_boundary
    lambda = las_lambda
    pol = 90
    phase = las_k * radial_yz^2 / (2.0 * rad_curve) - gouy + 0.5*pi
    profile = gauss(radial_yz, 0, w_boundary)
end:laser

begin:output
    name = o1
    dt_snapshot = 10 * femto
    poynt_flux = always
end:output

Hope this helps,
Stuart

[wuwhan186]

@Status-Mirror Thank you very much for your help, . I will try to simulate it based on the ideas you provided. I really appreciate it.