Immersed Wideband Nonpolarizing Beamsplitter

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This coating is immersed in glass (index 1.52) and light is incident at 45 degrees. As shown below, it divides the incident light so that the reflectance (and transmittance) of the S and P polarizations are between 45% and 55% for wavelengths from 420 nm to 680 nm -- a very wide bandwidth for this type of coating.

Plot of beamsplitter design

Three materials are used: L (1.35), M (1.9), and H (2.35). Starting with a thin, one-layer design, TFCalc's needle/tunneling method produced a sequence of designs of increasing complexity. This extremely difficult design consists of 97 layers.

Here is the design, with the first layer closest to the second glass and thickness given in nm: 

    H      23.08
    L      45.76
    M      60.64
    H      17.81
    L      39.04
    H      25.02
    M      73.64
    H      12.65
    L      16.00
    H      37.34
    M      73.42
    H      54.11
    M      70.54
    H      52.27
    M      70.68
    H      36.88
    L      57.77
    M      66.46
    L      53.10
    H      40.07
    M      74.46
    H      55.48
    M      73.49
    H      39.43
    L      25.81
    H       6.69
    M      71.86
    H      41.79
    M      16.56
    L       6.29
    H      46.20
    M      64.65
    H      14.75
    L      19.54
    H      29.31
    M      73.13
    H      58.23
    M      81.05
    H      31.51
    L      33.30
    H      20.84
    M      87.30
    H      17.08
    L      10.55
    H      47.58
    M      89.22
    H      50.65
    L      43.72
    M      71.18
    L      57.69
    H      45.85
    M      81.51
    H      52.09
    L      21.26
    H       9.86
    M      98.50
    H      19.81
    L      33.57
    H      35.44
    M      87.13
    H      57.45
    L      33.96
    M     103.64
    L      28.17
    H      53.02
    L      38.64
    M      87.61
    L      33.93
    H      50.20
    L      33.48
    M      90.45
    L      33.73
    H      54.17
    L      31.39
    M      93.36
    L      38.94
    H      54.81
    L      18.84
    M      92.27
    H      14.65
    L      40.94
    H      53.03
    L      15.54
    M     115.66
    L      40.12
    H      38.40
    L      34.52
    M     123.00
    L      25.44
    H      55.94
    L      40.76
    M      85.88
    L      72.40
    H      38.66
    L      58.32
    H      12.48
    M      33.23
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