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Understanding Optical Windows – Anti-Reflection (AR) Coatings


Anti-Reflection (AR) Coatings
Anti-reflection (AR) coatings are often put on optical windows to maximize transmission in the desired wavelength range. Honour Optics offers all  windows with a variety of anti-reflection (AR) coating options that vastly improve the efficiency of the optic by increasing transmission, enhancing contrast, and eliminating ghost images. Most AR coatings are also very durable, with resistance to both physical and environmental damage. For these reasons, the vast majority of transmissive optics include some form of anti-reflection coating. When specifying an AR coating for your specific application, you must first be fully aware of the full spectral range of your system. While an AR coating can significantly improve the performance of an optical system, using the coating at wavelengths outside the design wavelength range could potentially decrease the performance of the system. The figure below shows the reflection plots of all the standard AR coatings.

understanding optical windows coating 1


understanding optical windows coating 2
Equivalent Glass Types
Many glass manufacturers offer the same material characteristics under different trade names and most have modified their products and processes to be ECO-friendly (free of lead and arsenic). The table below shows the glass equivalents for common optical glasses.

Glass Material Equivalents
Listed Glass Name Glass Number Schott Equivalent Ohara Equivalent CDGM Equivalent
N-BK7 517/642 N-BK7 S-BSL7 H-K9L
N-K5 522/595 N-K5 S-NSL5 H-K50
N-PK51 529/770 N-PK51
N-SK11 564/608 N-SK11 S-BAL41 H-BaK6
N-BAK4 569/561 N-BAK4 S-BAL14 H-BaK7
N-BAK1 573/576 N-BAK1 S-BAL11 H-BaK8
N-SSK8 618/498 N-SSK8 S-BSM 28
N-PSK53A 618/634 N-PSK53A S-PHM52
N-F2 620/364 N-F2 S-TIM 2 H-F4
S-BSM18 639/554 S-BSM18 H-ZK11
N-SF2 648/338 N-SF2 S-TIM 22 H-ZF1
N-LAK22 651/559 N-LAK22 S-LAL54 H-LaK10
S-BAH11 667/483 S-BAH 11 H-ZBaF16
N-BAF10 670/472 N-BAF10 S-BAH 10 H-ZBaF52
N-SF5 673/322 N-SF5 S-TIM 25 H-ZF2
N-SF8 689/312 N-SF8 S-TIM 28 H-ZF10
N-LAK14 697/554 N-LAK14 S-LAL14 H-LAK51
N-SF15 699/301 N-SF15 S-TIM35 H-ZF11
N-BASF64 704/394 N-BASF64
N-LAK8 713/538 N-LAK8 S-LAL8 H-LAK7
S-TIH18 722/293 S-TIH18
N-SF10 728/284 N-SF10 S-TIH10 H-ZF4
N-SF4 755/276 N-SF4 S-TIH4 H-ZF6
N-SF14 762/265 N-SF14 S-TIH14
N-SF11 785/258 N-SF11 S-TIH11 H-ZF13
SF65A 785/261 SF65A S-TIH23
N-LASF45 800/350 N-LASF45 S-LAM66 H-ZLaF66
N-LASF44 803/464 N-LASF44 S-LAH65 H-ZLaF50B
N-SF6 805/254 N-SF6 S-TIH 6 H-ZF7LA
N-SF57 847/238 N-SF57 S-TIH53 H-ZF52
N-LASF9 850/322 N-LASF9 S-LAH71
S-NPH2 923/189 S-NPH2
N-SF66 923/209 N-SF66