[et_pb_section fb_built=”1″ _builder_version=”4.9.4″ hover_enabled=”0″ custom_margin=”0px|0px||0px|false|true” custom_padding=”0px|0px||0px|false|true” sticky_enabled=”0″][et_pb_row _builder_version=”4.9.4″ background_size=”initial” background_position=”top_left” background_repeat=”repeat” hover_enabled=”0″ width=”100%” custom_margin=”0px|0px||0px|false|true” custom_padding=”0px|0px||0px|false|true” sticky_enabled=”0″][et_pb_column type=”4_4″ _builder_version=”3.25″ custom_padding=”|||” custom_padding__hover=”|||”][et_pb_text _builder_version=”4.9.4″ background_size=”initial” background_position=”top_left” background_repeat=”repeat” custom_padding=”||10px||false|false” hover_enabled=”0″ sticky_enabled=”0″]<\/p>\n
Graham Carlow,* Brian T. Sullivan, Claude Montcalm, AND Alexander Miles <\/p>\n The wavefront error (WE) of a surface with an optical coating (\u201cfilter\u201d) is ideally measured at the in-band wavelength of the filter. However, quite often this is not possible, requiring that the filter be measured at an out-of-band wavelength (typically 633 nm), assuming that the filter transmits (for transmitted WE, or TWE) or reflects (for reflected WE, or RWE) at this wavelength. This out-of-band TWE\/RWE is generally assumed to provide a good estimation of the desired in-band TWE\/RWE. It will be shown in this paper that this is not the case for a large class of filters (i.e., bandpass) where the group delay is significantly different at the in-band and out-of-band wavelengths and where the optical filter exhibits a thickness non-uniformity across the surface. A theoretical explanation will be given along with an approach to predict the in-band TWE\/RWE based on the coating non-uniformity, the measured out-of-band TWE\/RWE, and the theoretical properties of the optical filter at the in-band and out-of-band wavelengths. A reasonable agreement between theory and measurement was demonstrated by measuring the TWE of an 11 nm wide bandpass filter (centered at 1048 nm) at both in-band (lambda <\/span>= <\/span>1048<\/span><\/span><\/span><\/span>n<\/span>m<\/span><\/span><\/span><\/span><\/span><\/span><\/span>) and out-of-band (lambda <\/span>= <\/span>625<\/span><\/span><\/span><\/span>n<\/span>m<\/span><\/span><\/span><\/span><\/span><\/span><\/span>) wavelengths. A similar treatment is provided for RWE.<\/p>\n \u00a9 2020 Optical Society of America<\/p>\n <\/p>\n [\/et_pb_text][et_pb_button button_url=”https:\/\/www.osapublishing.org\/ao\/abstract.cfm?uri=ao-59-5-A135″ url_new_window=”on” button_text=”Full Article” _builder_version=”4.2.2″ custom_margin=”||50px||false|false”][\/et_pb_button][\/et_pb_column][\/et_pb_row][\/et_pb_section]<\/p>\n","protected":false},"excerpt":{"rendered":" The wavefront error (WE) of a surface with an optical coating (\u201cfilter\u201d) is ideally measured at the in-band wavelength of the filter. However, quite often this is not possible, requiring that the filter be measured at an out-of-band wavelength (typically 633\u00a0nm), assuming that the filter transmits (for transmitted WE, or TWE) or reflects (for reflected WE, or RWE) at this wavelength. This out-of-band TWE\/RWE is generally assumed to provide a good estimation of the desired in-band TWE\/RWE. It will be shown in this paper that this is not the case for a large class of filters (i.e., bandpass) where the group delay is significantly different at the in-band and out-of-band wavelengths and where the optical filter exhibits a thickness non-uniformity across the surface. <\/p>\n","protected":false},"author":159,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_et_pb_use_builder":"on","_et_pb_old_content":" The wavefront error (WE) of a surface with an optical coating (\u201cfilter\u201d) is ideally measured at the in-band wavelength of the filter. However, quite often this is not possible, requiring that the filter be measured at an out-of-band wavelength (typically 633\u00a0nm), assuming that the filter transmits (for transmitted WE, or TWE) or reflects (for reflected WE, or RWE) at this wavelength. This out-of-band TWE\/RWE is generally assumed to provide a good estimation of the desired in-band TWE\/RWE. It will be shown in this paper that this is not the case for a large class of filters (i.e., bandpass) where the group delay is significantly different at the in-band and out-of-band wavelengths and where the optical filter exhibits a thickness non-uniformity across the surface. A theoretical explanation will be given along with an approach to predict the in-band TWE\/RWE based on the coating non-uniformity, the measured out-of-band TWE\/RWE, and the theoretical properties of the optical filter at the in-band and out-of-band wavelengths. A reasonable agreement between theory and measurement was demonstrated by measuring the TWE of an 11\u00a0nm wide bandpass filter (centered at 1048\u00a0nm) at both in-band ( \u00a9 2020 Optical Society of America<\/p> \u00a0<\/p>","_et_gb_content_width":"","footnotes":""},"categories":[2205,2211],"tags":[],"class_list":["post-17626","post","type-post","status-publish","format-standard","hentry","category-learning_center","category-tech_notes"],"acf":[],"yoast_head":"\n
Iridian Spectral Technologies Ltd., 2700 Swansea Crescent, Ottawa, Ontario K1G 6R8, Canada<\/em>
*Corresponding author: gcarlow@idexcorp.com<\/em><\/p>\nAbstract<\/strong><\/h4>\n
Abstract<\/h2>