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	–	–