THINFILM

Animation of Light Interacting with a Thin Film

This animation represents the transmission and reflection of light through a thin film. When the animation begins, the incident wave is in a medium with index of refraction n1=1 (like air) and the transmitted wave is in a medium with index of refraction n3=1.5 (like glass). The thin film has an index of refraction n2=1.38 (like magnesium flouride). The wavelength of the light (in air) is 633 nm (like a He-Ne laser). The direction of the incident wave is normal to the film (incident angle is zero). The thickness of the film is d=115 nm. At this value of d, the intensity of the reflected wave is at a minimum. The animation is simulating a nonreflective coating on a glass surface.

On the right side of the screen are shown the values of the indices of refraction. On the left side of the screen are shown the relative intensities of the incident, reflected, and transmitted waves. The intensity of the waves are indicated by the intensity of the colors of the waves in the animation. Near the bottom edge of the screen are shown values for the angle of the incident light (in degrees, measured from the normal to the surface), the wavelength of the light in air (in nm), the thickness d of the film (in nm), and the polarization of the incident wave (s or p). The color of the light is indicated by the color of the waves in the animation. Infrared and ultraviolet light is indicated by black.

Some parameters (n1, n2, n3, angle, d, wavelength, from, to) may be changed by the user. Click on the name of the parameter. The background of that name should turn red. Then enter a number (including a decimal point if desired) at the keyboard followed by pressing the enter key. When the number is completely entered, the new value of the parameter will appear on the screen unless it is invalid. The values of n1, n2, n3 must be between 1 and 2.5. The value of angle must be between 0 and 89 degrees. The value of d must be between 1 and 1000 nm. The value of wavelength must be between 100 and 1000 nm.

The program recognizes the following commands.

stop Stop animation. Press stop again to resume animation.
s_polarization This label indicates that the light is s polarized (E field pointing in a direction perpendicular to the plane of the screen). Pressing this button toggles the polarization to p.
p_polarization This label indicates that the light is p polarized (E field pointing in a direction parallel to the plane of the screen). Pressing this button toggles the polarization to s.
n1 Change the value of n1.
n1 Change the value of n1.
n1 Change the value of n1.
angle Change the value of the angle of incidence.
wavelength Change the value of the wavelength of the light in air.
d Change the value of d.
sweep Sweep the value of angle, wavelength, d, n1, n2, or n2. When you press sweep, new buttons appear on the screen. Press one of these to choose which parameter you want to sweep. After pressing one of them, the from and to buttons appear on the screen, allowing you to enter in the initial and final value of the parameter for the sweep. A begin button also appears. Pressing it begins the sweep. The sweep can be halted at any time by pressing sweep again.