IBD: Calibrating Optical Thickness - Revision history

John d at 00:32, 7 March 2026

2026-03-07T00:32:18Z

← Older revision		Revision as of 00:32, 7 March 2026
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			'''''Tool: [[Ion Beam Deposition (Veeco NEXUS)\|Ion Beam Deposition (Veeco Nexus IBD-O)]]'''''

	Basic method for calibrating optical thickness, for [https://en.wikipedia.org/wiki/Distributed_Bragg_reflector DBR]/multi-layer optical coatings (2 alternating films only). Commonly used for SiO2/TaO DBR mirrors/filters.		Basic method for calibrating optical thickness, for [https://en.wikipedia.org/wiki/Distributed_Bragg_reflector DBR]/multi-layer optical coatings (2 alternating films only). Commonly used for SiO2/TaO DBR mirrors/filters.

John d: Corrected 1050/1100 FP correction

2024-03-09T17:19:15Z

Corrected 1050/1100 FP correction

John d: added category Process

2023-09-22T04:39:56Z

added category Process

← Older revision		Revision as of 04:39, 22 September 2023
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	<br />		<br />
	Developed by Demis D. John, Bob Farrell, Dustin Kleckner, ~2008-2010. This is the same method used by UCSB VCSEL groups years earlier, for calibrating VCSEL MOCVD/MBE growths. Please consider our [[Frequently Asked Questions#Publications acknowledging the Nanofab\|<u>publication policy</u>]] if you publish papers using this information.		Developed by Demis D. John, Bob Farrell, Dustin Kleckner, ~2008-2010. This is the same method used by UCSB VCSEL groups years earlier, for calibrating VCSEL MOCVD/MBE growths. Please consider our [[Frequently Asked Questions#Publications acknowledging the Nanofab\|<u>publication policy</u>]] if you publish papers using this information.
			[[category:Process]]

John d: fixed formula newlines

2023-09-16T00:15:39Z

fixed formula newlines

@@ Line 1: / Line 1: @@
 Basic method for calibrating optical thickness, for [https://en.wikipedia.org/wiki/Distributed_Bragg_reflector DBR]/multi-layer optical coatings (2 alternating films only).  Commonly used for SiO2/TaO DBR mirrors/filters.
-#Get dep rate & refractive index (RIX) of individual SiO and TaO films, using single-deps and [[Ellipsometer (Woollam)|J.A. Woolam Ellipsometer]] or equivalent tool. Approx. rate from previous user is also acceptable.
+*Get dep rate & refractive index (RIX) of individual SiO and TaO films, using single-deps and [[Ellipsometer (Woollam)|J.A. Woolam Ellipsometer]] or equivalent tool. Approx. rate from previous user is also acceptable.
-##Get RIX at the target wavelength, using "Derived Params" on JAW or Cauchy equation A/B/C params.  For example, if targeting a DBR centered at 1550nm (target λ=1550nm), you will want to know the RIX at 1550nm specifically.
+:*Get RIX at the target wavelength, using "Derived Params" on JAW or Cauchy equation A/B/C params.  For example, if targeting a DBR centered at 1550nm (target λ=1550nm), you will want to know the RIX at 1550nm specifically.
-#Calculate approximate dep. time to achieve a 1/4-wave thickness at the target wavelength, for each film (SiO and TaO).
+*Calculate approximate dep. time to achieve a 1/4-wave thickness at the target wavelength, for each film (SiO and TaO).
-##For example, if the dep. rate of SiO2 measured at 5.2nm/min and RIX is n<sub>1550</sub> = 1.494, then ''SiO 1/4λ thickness: d<sub>1/4λ</sub> = 1550nm / 4 / 1.494 = 259.4nm''  '''''SiO 1/4λ time''': t<sub>1/4λ</sub> = 259.4nm ÷ 5.2nm/min = 49.88min = '''2993.077 sec'''''  (and then do the same for TaO)
+:*For example, if the dep. rate of SiO2 measured at 5.2nm/min and RIX is n<sub>1550</sub> = 1.494, then
 *Sources of error: thick, stressy films exhibit the stress-optic effect, in which compressed films (closer to the substrate) will often show a reduction in RIX. In going from a 9-period DBR to a 18-period DBR, you might see a ~10-20nm blue-shift.  Some users for whom such a shift is outside the device tolerance will do a full DBR dep, then apply a % reduction to all dep times to further dial in the DBR reflectivity band.

John d: formatting updates to equations

2023-09-16T00:08:35Z

formatting updates to equations

John d at 00:03, 16 September 2023

2023-09-16T00:03:43Z

← Older revision		Revision as of 00:03, 16 September 2023
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	Basic method for calibrating optical thickness, for [https://en.wikipedia.org/wiki/Distributed_Bragg_reflector DBR]/multi-layer optical coatings (2 films only). Commonly used for SiO2/TaO DBR mirrors.		Basic method for calibrating optical thickness, for [https://en.wikipedia.org/wiki/Distributed_Bragg_reflector DBR]/multi-layer optical coatings (2 alternating films only). Commonly used for SiO2/TaO DBR mirrors/filters.

	#Get dep rate & refractive index (RIX) of individual SiO and TaO films, using single-deps and [[Ellipsometer (Woollam)\|J.A. Woolam Ellipsometer]] or equivalent tool. Approx. rate from previous user is also acceptable.		#Get dep rate & refractive index (RIX) of individual SiO and TaO films, using single-deps and [[Ellipsometer (Woollam)\|J.A. Woolam Ellipsometer]] or equivalent tool. Approx. rate from previous user is also acceptable.

John d: added publication policy

2023-09-16T00:03:09Z

added publication policy

John d: minor corrections

2022-11-22T23:57:58Z

minor corrections

← Older revision		Revision as of 23:57, 22 November 2022
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	##For example, if SiO2 measured at 5.2nm/min and RIX is n<sub>1550</sub> = 1.494, then ''SiO 1/4λ thickness: d<sub>1/4λ</sub> = 1550nm / 4 / 1.494 = 259.4nm'' '''''SiO 1/4λ time''': t<sub>1/4λ</sub> = 259.4nm ÷ 5.2nm/min = 49.88min = '''2993.077 sec''''' (and do the same for TaO)		##For example, if SiO2 measured at 5.2nm/min and RIX is n<sub>1550</sub> = 1.494, then ''SiO 1/4λ thickness: d<sub>1/4λ</sub> = 1550nm / 4 / 1.494 = 259.4nm'' '''''SiO 1/4λ time''': t<sub>1/4λ</sub> = 259.4nm ÷ 5.2nm/min = 49.88min = '''2993.077 sec''''' (and do the same for TaO)
	#Deposit a fabry-perot 1/2-λ of one film (SiO or TaO) cavity onto a Silicon piece, using the above 1/4-λ times (aka. SiO/4 or TaO/4), to calibrate that film's optical-thickness.		#Deposit a fabry-perot 1/2-λ of one film (SiO or TaO) cavity onto a Silicon piece, using the above 1/4-λ times (aka. SiO/4 or TaO/4), to calibrate that film's optical-thickness.
	##eg. for SiO Fabry-Perot cavity (aka. SiO-FP) ''SiO/4 + TaO/4 + SiO/4 + TaO/4 + SiO/4 + TaO/4 + ('''SiO/4 + SiO/4''') + TaO/4 + SiO/4 + TaO/4 + SiO/4 + TaO/4'' ~~Here we used only 3 periods of DBR on either side of the 1/2-λ cavity, to speed up the deposition.~~		##eg. for SiO Fabry-Perot cavity (aka. SiO-FP) ''SiO/4 + TaO/4 + SiO/4 + TaO/4 + SiO/4 + TaO/4 + ('''SiO/4 + SiO/4''') + TaO/4 + SiO/4 + TaO/4 + SiO/4 + TaO/4''
			##Here we used only 3 periods of DBR on either side of the 1/2-λ cavity, to speed up the deposition.
	#Measure the reflectivity on [[Optical Film Spectra + Optical Properties (Filmetrics F10-RT-UVX)\|Filmetrics F10-RT]].		#Measure the reflectivity on [[Optical Film Spectra + Optical Properties (Filmetrics F10-RT-UVX)\|Filmetrics F10-RT]].
	#Locate the wavelength of the minimum (dip) in the optical spectrum. Spectrum will typically be very broad, due to omitting many of the DBR layers for speed.		#Locate the wavelength of the minimum (dip) in the optical spectrum. Spectrum will typically be very broad, due to omitting many of the DBR layers for speed.
			##For example, the trough might show a minimum at 1600nm instead of the targeted 1550nm.
	##~~For example, the trough might show a minimum at 1600nm.~~ Here is an example of a Fabry-Perot cavity that was targeting a 1050nm, and measured a 1100nm trough:[[File:IBD SiO-FP - long 1100nm - Reflectivity Spectrum (EMpy).png\|alt=Simulated plot of SiO-FP reflectivity, for a 1050nm target but measured trough at 1100nm\|none\|thumb\|Example: Targeting a 1050nm SiO-FP, the measured trough location is at 1100nm. ]]In this case, one would apply a correction to the SiO/4 time by multiplying by ''1050÷1000''.		###Here is an example of a Fabry-Perot cavity that was targeting a 1050nm, and measured a 1100nm trough:[[File:IBD SiO-FP - long 1100nm - Reflectivity Spectrum (EMpy).png\|alt=Simulated plot of SiO-FP reflectivity, for a 1050nm target but measured trough at 1100nm\|none\|thumb\|Example: Targeting a 1050nm SiO-FP, the measured trough location is at 1100nm. ]](In this case, one would apply a correction to the SiO/4 time by multiplying by ''1050÷1000''.)
⚫	#~~Correct the film's optical thickness as so:~~ t<sub>1/4λ</sub> * λ<sub>target</sub> / λ<sub>measured</sub> = ''corrected'' t<sub>1/4λ</sub> ~~2993.077 sec * 1550nm / 1600nm = '''2899.543 sec''' for SiO/4 layers~~
			#Correct the film's optical thickness as so:
⚫	##Use this corrected time for all SiO/4 layers.
		⚫	##t<sub>1/4λ</sub> * λ<sub>target</sub> / λ<sub>measured</sub> = ''corrected'' t<sub>1/4λ</sub>
			##2993.077 sec * (1550nm / 1600nm) = '''2899.543 sec''' for SiO/4 layers
		⚫	###Use this corrected time for all SiO/4 layers.
	#Do the same Fabry-Perot correction for the other film, in this case TaO-FP, and apply the new TaO/4 time to the recipe.		#Do the same Fabry-Perot correction for the other film, in this case TaO-FP, and apply the new TaO/4 time to the recipe.
	#Perform a test-DBR deposition onto Silicon, eg. 9 periods (less than full, which could be 15 periods or more), and measure on [[Optical Film Spectra + Optical Properties (Filmetrics F10-RT-UVX)\|Filmetrics F10-RT]], to confirm that center wavelength is in the right spot. An example DBR test-dep targeting 1050nm looks like this:[[File:IBD 9-period DBR - Reflectivity Spectrum (EMpy).png\|alt=Example reflectivity spectra of the 9-period DBR test-dep, showing 1050nm center-wavelength in the middle of the DBR high-reflectivity spectrum.\|none\|thumb\|Example reflectivity spectra of the 9-period DBR test-dep.]]		#Perform a test-DBR deposition onto Silicon, eg. 9 periods (less than full, which could be 15 periods or more), and measure on [[Optical Film Spectra + Optical Properties (Filmetrics F10-RT-UVX)\|Filmetrics F10-RT]], to confirm that center wavelength is in the right spot. An example DBR test-dep targeting 1050nm looks like this:[[File:IBD 9-period DBR - Reflectivity Spectrum (EMpy).png\|alt=Example reflectivity spectra of the 9-period DBR test-dep, showing 1050nm center-wavelength in the middle of the DBR high-reflectivity spectrum.\|none\|thumb\|Example reflectivity spectra of the 9-period DBR test-dep.]]
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	*Sources of error: thick, stressy films exhibit the stress-optic effect, in which compressed films (closer to the substrate) will often show a reduction in RIX. In going from a 9-period DBR to a 18-period DBR, you might see a ~10-20nm blue-shift. Some users for who such a shift is outside the device tolerance will do a full DBR dep, then apply a % reduction to all dep times to further dial in the DBR reflectivity band.		*Sources of error: thick, stressy films exhibit the stress-optic effect, in which compressed films (closer to the substrate) will often show a reduction in RIX. In going from a 9-period DBR to a 18-period DBR, you might see a ~10-20nm blue-shift. Some users for who such a shift is outside the device tolerance will do a full DBR dep, then apply a % reduction to all dep times to further dial in the DBR reflectivity band.
	*The same method can be used to calibrate optical-thickness for arbitrary ~~binary~~ multi-layer optical filters.		*The same method can be used to calibrate optical-thickness for arbitrary multi-layer optical filters.

John d: added approx year developed

2022-03-31T19:55:10Z

added approx year developed

← Older revision		Revision as of 19:55, 31 March 2022
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	#Perform full-DBR deposition onto production parts. Include a flat Silicon witness for measuring the final DBR reflectivity spectrum.<br />		#Perform full-DBR deposition onto production parts. Include a flat Silicon witness for measuring the final DBR reflectivity spectrum.<br />

	* Sources of error: thick, stressy films exhibit the stress-optic effect, in which compressed films (closer to the substrate) will often show a reduction in RIX. In going from a 9-period DBR to a 18-period DBR, you might see a ~10-20nm blue-shift. Some users for who such a shift is outside the device tolerance will do a full DBR dep, then apply a % reduction to all dep times to further dial in the DBR reflectivity band.		*Sources of error: thick, stressy films exhibit the stress-optic effect, in which compressed films (closer to the substrate) will often show a reduction in RIX. In going from a 9-period DBR to a 18-period DBR, you might see a ~10-20nm blue-shift. Some users for who such a shift is outside the device tolerance will do a full DBR dep, then apply a % reduction to all dep times to further dial in the DBR reflectivity band.
	* The same method can be used to calibrate optical-thickness for arbitrary binary multi-layer optical filters.		*The same method can be used to calibrate optical-thickness for arbitrary binary multi-layer optical filters.


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	<br />		<br />
	Developed by Demis D. John, Bob Farrell, Dustin Kleckner. This is the same method used by UCSB VCSEL groups years earlier, for calibrating VCSEL MOCVD/MBE growths.		Developed by Demis D. John, Bob Farrell, Dustin Kleckner, ~2008-2010. This is the same method used by UCSB VCSEL groups years earlier, for calibrating VCSEL MOCVD/MBE growths.

John d: minor updates

2022-03-31T19:54:29Z

minor updates

← Older revision		Revision as of 17:19, 9 March 2024
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	*Get dep rate & refractive index (RIX) of individual SiO and TaO films, using single-deps and [[Ellipsometer (Woollam)\|J.A. Woolam Ellipsometer]] or equivalent tool. Approx. rate from previous user is also acceptable.		*Get dep rate & refractive index (RIX) of individual SiO and TaO films, using single-deps and [[Ellipsometer (Woollam)\|J.A. Woolam Ellipsometer]] or equivalent tool. Approx. rate from previous user is also acceptable.

	:*Get RIX at the target wavelength, using "Derived Params" on JAW or Cauchy equation A/B/C params. For example, if targeting a DBR centered at 1550nm (target λ=1550nm), you will want to know the RIX at 1550nm specifically.		:*Get RIX at the target wavelength, using "Derived Params" on JAW or Cauchy equation A/B/C params. For example, if targeting a DBR centered at 1550nm (target λ=1550nm), you will want to know the RIX at 1550nm specifically.

	*Calculate approximate dep. time to achieve a 1/4-wave thickness at the target wavelength, for each film (SiO and TaO).		*Calculate approximate dep. time to achieve a 1/4-wave thickness at the target wavelength, for each film (SiO and TaO).
⚫	:*For example, if the dep. rate of SiO2 measured at 5.2nm/min and RIX is n<sub>1550</sub> = 1.494, then

		⚫	:*For example, if the dep. rate of SiO2 measured at 5.2nm/min and RIX is n<sub>1550</sub> = 1.494, then
	::::''SiO 1/4λ thickness: d<sub>1/4λ</sub> = 1550nm / 4 / 1.494 = 259.4nm''		::::''SiO 1/4λ thickness: d<sub>1/4λ</sub> = 1550nm / 4 / 1.494 = 259.4nm''
	::::'''''SiO 1/4λ time''': t<sub>1/4λ</sub> = 259.4nm ÷ 5.2nm/min = 49.88min = '''2993.077 sec'''''		::::'''''SiO 1/4λ time''': t<sub>1/4λ</sub> = 259.4nm ÷ 5.2nm/min = 49.88min = '''2993.077 sec'''''
	::::(and then do the same for TaO)		::::(and then do the same for TaO)

	*Deposit a fabry-perot 1/2-λ of one film (SiO or TaO) cavity onto a Silicon piece, using the above 1/4-λ deposition <u>times</u> (aka. "SiO/4" or "TaO/4" in the following), to calibrate that film's optical-thickness.		*Deposit a fabry-perot 1/2-λ of one film (SiO or TaO) cavity onto a Silicon piece, using the above 1/4-λ deposition <u>times</u> (aka. "SiO/4" or "TaO/4" in the following), to calibrate that film's optical-thickness.

	:*eg. for SiO Fabry-Perot cavity (aka. SiO-FP):		:*eg. for SiO Fabry-Perot cavity (aka. SiO-FP):
	::::''SiO/4 + TaO/4 + SiO/4 + TaO/4 + SiO/4 + TaO/4 + <u>('''SiO/4 + SiO/4''')</u> + TaO/4 + SiO/4 + TaO/4 + SiO/4 + TaO/4''		::::''SiO/4 + TaO/4 + SiO/4 + TaO/4 + SiO/4 + TaO/4 + <u>('''SiO/4 + SiO/4''')</u> + TaO/4 + SiO/4 + TaO/4 + SiO/4 + TaO/4''
	::*Here we used only 3 periods of DBR on either side of the 1/2-λ cavity, to speed up the deposition.		::*Here we used only 3 periods of DBR on either side of the 1/2-λ cavity, to speed up the deposition.

	*Measure the reflectivity on [[Optical Film Spectra + Optical Properties (Filmetrics F10-RT-UVX)\|Filmetrics F10-RT]].		*Measure the reflectivity on [[Optical Film Spectra + Optical Properties (Filmetrics F10-RT-UVX)\|Filmetrics F10-RT]].
	*Locate the wavelength of the minimum (dip) in the optical spectrum. Spectrum will typically be very broad, due to omitting many of the surrounding DBR layers for speed.		*Locate the wavelength of the minimum (dip) in the optical spectrum. Spectrum will typically be very broad, due to omitting many of the surrounding DBR layers for speed.

	:*For example, the trough might show a minimum at 1600nm instead of the targeted 1550nm.		:*For example, the trough might show a minimum at 1600nm instead of the targeted 1550nm.

	*Correct the film's optical thickness as so:		*Correct the film's optical thickness as so:

	:::t<sub>1/4λ</sub> * λ<sub>target</sub> / λ<sub>measured</sub> = ''corrected'' t<sub>1/4λ</sub>		:::t<sub>1/4λ</sub> * λ<sub>target</sub> / λ<sub>measured</sub> = ''corrected'' t<sub>1/4λ</sub>
	:::2993.077 sec * (1550nm / 1600nm) = '''2899.543 sec''' for SiO/4 layers		:::2993.077 sec * (1550nm / 1600nm) = '''2899.543 sec''' for SiO/4 layers
	::*Use this corrected time for all SiO/4 layers.		::*Use this corrected time for all SiO/4 layers.
	::*You only need to edit the One "SiO2_dep" step in the IBD recipe, which will also change all "SiO2_dep" steps in the recipe.		::*You only need to edit the One "SiO2_dep" step in the IBD recipe, which will also change all "SiO2_dep" steps in the recipe.
	:*Here is an example of a Fabry-Perot cavity that was targeting a 1050nm center-wavelength, but measured a 1100nm trough:[[File:IBD SiO-FP - long 1100nm - Reflectivity Spectrum (EMpy).png\|alt=Simulated plot of SiO-FP reflectivity, for a 1050nm target but measured trough at 1100nm\|none\|thumb\|Example: Targeting a 1050nm SiO-FP, the measured trough location is at 1100nm. ]]In this case, one would apply a correction to the ''SiO/4 time'' by multiplying by (''~~1050÷1000~~)''.		:*Here is an example of a Fabry-Perot cavity that was targeting a 1050nm center-wavelength, but measured a 1100nm trough:[[File:IBD SiO-FP - long 1100nm - Reflectivity Spectrum (EMpy).png\|alt=Simulated plot of SiO-FP reflectivity, for a 1050nm target but measured trough at 1100nm\|none\|thumb\|Example: Targeting a 1050nm SiO-FP, the measured trough location is at 1100nm. ]]In this case, one would apply a correction to the ''SiO/4 time'' by multiplying by (''1050÷1100)''.

	*Do the same Fabry-Perot correction for the other film, in this case do an "TaO-FP", and apply the new TaO/4 time to the recipe.		*Do the same Fabry-Perot correction for the other film, in this case do an "TaO-FP", and apply the new TaO/4 time to the recipe.
	*Perform a test-DBR deposition onto Silicon, eg. 9 periods (less than full, which could be 15 periods or more), and measure on [[Optical Film Spectra + Optical Properties (Filmetrics F10-RT-UVX)\|Filmetrics F10-RT]], to confirm that center wavelength is in the right spot. An example DBR test-dep targeting 1050nm looks like this:[[File:IBD 9-period DBR - Reflectivity Spectrum (EMpy).png\|alt=Example reflectivity spectra of the 9-period DBR test-dep, showing 1050nm center-wavelength in the middle of the DBR high-reflectivity spectrum.\|none\|thumb\|Example reflectivity spectra of the 9-period DBR test-dep.]]		*Perform a test-DBR deposition onto Silicon, eg. 9 periods (less than full, which could be 15 periods or more), and measure on [[Optical Film Spectra + Optical Properties (Filmetrics F10-RT-UVX)\|Filmetrics F10-RT]], to confirm that center wavelength is in the right spot. An example DBR test-dep targeting 1050nm looks like this:[[File:IBD 9-period DBR - Reflectivity Spectrum (EMpy).png\|alt=Example reflectivity spectra of the 9-period DBR test-dep, showing 1050nm center-wavelength in the middle of the DBR high-reflectivity spectrum.\|none\|thumb\|Example reflectivity spectra of the 9-period DBR test-dep.]]
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	<br />		<br />
	Developed by Demis D. John, Bob Farrell, Dustin Kleckner, ~2008-2010. This is the same method used by UCSB VCSEL groups years earlier, for calibrating VCSEL MOCVD/MBE growths. Please consider our [[Frequently Asked Questions#Publications acknowledging the Nanofab\|<u>publication policy</u>]] if you publish papers using this information.		Developed by Demis D. John, Bob Farrell, Dustin Kleckner, ~2008-2010. This is the same method used by UCSB VCSEL groups years earlier, for calibrating VCSEL MOCVD/MBE growths. Please consider our [[Frequently Asked Questions#Publications acknowledging the Nanofab\|<u>publication policy</u>]] if you publish papers using this information.
	[[category:Process]]		[[category:Process]]

← Older revision		Revision as of 00:08, 16 September 2023
Line 4:		Line 4:
	##Get RIX at the target wavelength, using "Derived Params" on JAW or Cauchy equation A/B/C params. For example, if targeting a DBR centered at 1550nm (target λ=1550nm), you will want to know the RIX at 1550nm specifically.		##Get RIX at the target wavelength, using "Derived Params" on JAW or Cauchy equation A/B/C params. For example, if targeting a DBR centered at 1550nm (target λ=1550nm), you will want to know the RIX at 1550nm specifically.
	#Calculate approximate dep. time to achieve a 1/4-wave thickness at the target wavelength, for each film (SiO and TaO).		#Calculate approximate dep. time to achieve a 1/4-wave thickness at the target wavelength, for each film (SiO and TaO).
	##For example, if SiO2 measured at 5.2nm/min and RIX is n<sub>1550</sub> = 1.494, then ''SiO 1/4λ thickness: d<sub>1/4λ</sub> = 1550nm / 4 / 1.494 = 259.4nm'' '''''SiO 1/4λ time''': t<sub>1/4λ</sub> = 259.4nm ÷ 5.2nm/min = 49.88min = '''2993.077 sec''''' (and do the same for TaO)		##For example, if the dep. rate of SiO2 measured at 5.2nm/min and RIX is n<sub>1550</sub> = 1.494, then ''SiO 1/4λ thickness: d<sub>1/4λ</sub> = 1550nm / 4 / 1.494 = 259.4nm'' '''''SiO 1/4λ time''': t<sub>1/4λ</sub> = 259.4nm ÷ 5.2nm/min = 49.88min = '''2993.077 sec''''' (and then do the same for TaO)
	#Deposit a fabry-perot 1/2-λ of one film (SiO or TaO) cavity onto a Silicon piece, using the above 1/4-λ times (aka. SiO/4 or TaO/4), to calibrate that film's optical-thickness.		#Deposit a fabry-perot 1/2-λ of one film (SiO or TaO) cavity onto a Silicon piece, using the above 1/4-λ deposition <u>times</u> (aka. "SiO/4" or "TaO/4" in the following), to calibrate that film's optical-thickness.
	##eg. for SiO Fabry-Perot cavity (aka. SiO-FP) ''SiO/4 + TaO/4 + SiO/4 + TaO/4 + SiO/4 + TaO/4 + ('''SiO/4 + SiO/4''') + TaO/4 + SiO/4 + TaO/4 + SiO/4 + TaO/4''		##eg. for SiO Fabry-Perot cavity (aka. SiO-FP): ''SiO/4 + TaO/4 + SiO/4 + TaO/4 + SiO/4 + TaO/4 + <u>('''SiO/4 + SiO/4''')</u> + TaO/4 + SiO/4 + TaO/4 + SiO/4 + TaO/4''
	##Here we used only 3 periods of DBR on either side of the 1/2-λ cavity, to speed up the deposition.		##Here we used only 3 periods of DBR on either side of the 1/2-λ cavity, to speed up the deposition.
	#Measure the reflectivity on [[Optical Film Spectra + Optical Properties (Filmetrics F10-RT-UVX)\|Filmetrics F10-RT]].		#Measure the reflectivity on [[Optical Film Spectra + Optical Properties (Filmetrics F10-RT-UVX)\|Filmetrics F10-RT]].
	#Locate the wavelength of the minimum (dip) in the optical spectrum. Spectrum will typically be very broad, due to omitting many of the DBR layers for speed.		#Locate the wavelength of the minimum (dip) in the optical spectrum. Spectrum will typically be very broad, due to omitting many of the surrounding DBR layers for speed.
	##For example, the trough might show a minimum at 1600nm instead of the targeted 1550nm.		##For example, the trough might show a minimum at 1600nm instead of the targeted 1550nm.
			###
⚫	###Here is an example of a Fabry-Perot cavity that was targeting a 1050nm, ~~and~~ measured a 1100nm trough:[[File:IBD SiO-FP - long 1100nm - Reflectivity Spectrum (EMpy).png\|alt=Simulated plot of SiO-FP reflectivity, for a 1050nm target but measured trough at 1100nm\|none\|thumb\|Example: Targeting a 1050nm SiO-FP, the measured trough location is at 1100nm. ]](In this case, one would apply a correction to the SiO/4 time by multiplying by ''1050÷1000''.)
	#Correct the film's optical thickness as so:		#Correct the film's optical thickness as so:
	##t<sub>1/4λ</sub> * λ<sub>target</sub> / λ<sub>measured</sub> = ''corrected'' t<sub>1/4λ</sub>		##t<sub>1/4λ</sub> * λ<sub>target</sub> / λ<sub>measured</sub> = ''corrected'' t<sub>1/4λ</sub>
	##2993.077 sec * (1550nm / 1600nm) = '''2899.543 sec''' for SiO/4 layers		##2993.077 sec * (1550nm / 1600nm) = '''2899.543 sec''' for SiO/4 layers
	###Use this corrected time for all SiO/4 layers.		###Use this corrected time for all SiO/4 layers.
		⚫	##Here is an example of a Fabry-Perot cavity that was targeting a 1050nm center-wavelength, but measured a 1100nm trough:[[File:IBD SiO-FP - long 1100nm - Reflectivity Spectrum (EMpy).png\|alt=Simulated plot of SiO-FP reflectivity, for a 1050nm target but measured trough at 1100nm\|none\|thumb\|Example: Targeting a 1050nm SiO-FP, the measured trough location is at 1100nm. ]]In this case, one would apply a correction to the ''SiO/4 time'' by multiplying by (''1050÷1000)''.
	#Do the same Fabry-Perot correction for the other film, in this case TaO-FP, and apply the new TaO/4 time to the recipe.		#Do the same Fabry-Perot correction for the other film, in this case TaO-FP, and apply the new TaO/4 time to the recipe.
	#Perform a test-DBR deposition onto Silicon, eg. 9 periods (less than full, which could be 15 periods or more), and measure on [[Optical Film Spectra + Optical Properties (Filmetrics F10-RT-UVX)\|Filmetrics F10-RT]], to confirm that center wavelength is in the right spot. An example DBR test-dep targeting 1050nm looks like this:[[File:IBD 9-period DBR - Reflectivity Spectrum (EMpy).png\|alt=Example reflectivity spectra of the 9-period DBR test-dep, showing 1050nm center-wavelength in the middle of the DBR high-reflectivity spectrum.\|none\|thumb\|Example reflectivity spectra of the 9-period DBR test-dep.]]		#Perform a test-DBR deposition onto Silicon, eg. 9 periods (less than full, which could be 15 periods or more), and measure on [[Optical Film Spectra + Optical Properties (Filmetrics F10-RT-UVX)\|Filmetrics F10-RT]], to confirm that center wavelength is in the right spot. An example DBR test-dep targeting 1050nm looks like this:[[File:IBD 9-period DBR - Reflectivity Spectrum (EMpy).png\|alt=Example reflectivity spectra of the 9-period DBR test-dep, showing 1050nm center-wavelength in the middle of the DBR high-reflectivity spectrum.\|none\|thumb\|Example reflectivity spectra of the 9-period DBR test-dep.]]
	#Perform full-DBR deposition onto production parts. Include a flat Silicon witness for measuring the final DBR reflectivity spectrum.<br />		#Perform full-DBR deposition onto production parts. Include a flat Silicon witness for measuring the final DBR reflectivity spectrum.<br />

	*Sources of error: thick, stressy films exhibit the stress-optic effect, in which compressed films (closer to the substrate) will often show a reduction in RIX. In going from a 9-period DBR to a 18-period DBR, you might see a ~10-20nm blue-shift. Some users for ~~who~~ such a shift is outside the device tolerance will do a full DBR dep, then apply a % reduction to all dep times to further dial in the DBR reflectivity band.		*Sources of error: thick, stressy films exhibit the stress-optic effect, in which compressed films (closer to the substrate) will often show a reduction in RIX. In going from a 9-period DBR to a 18-period DBR, you might see a ~10-20nm blue-shift. Some users for whom such a shift is outside the device tolerance will do a full DBR dep, then apply a % reduction to all dep times to further dial in the DBR reflectivity band.
	*The same method can be used to calibrate optical-thickness for arbitrary multi-layer optical filters.		*The same method can be used to calibrate optical-thickness for arbitrary multi-layer optical filters.

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	Basic method for calibrating optical thickness, for [https://en.wikipedia.org/wiki/Distributed_Bragg_reflector DBR]/multi-layer optical coatings (2 films only). Commonly used for SiO2/TaO DBR mirrors.		Basic method for calibrating optical thickness, for [https://en.wikipedia.org/wiki/Distributed_Bragg_reflector DBR]/multi-layer optical coatings (2 films only). Commonly used for SiO2/TaO DBR mirrors.

	# Get dep rate & refractive index (RIX) of individual SiO and TaO films, using single-deps and [[Ellipsometer (Woollam)\|J.A. Woolam Ellipsometer]] or equivalent tool. Approx. rate from previous user is also acceptable.		#Get dep rate & refractive index (RIX) of individual SiO and TaO films, using single-deps and [[Ellipsometer (Woollam)\|J.A. Woolam Ellipsometer]] or equivalent tool. Approx. rate from previous user is also acceptable.
	## Get RIX at the target wavelength, using "Derived Params" on JAW or Cauchy equation A/B/C params. For example, if targeting a DBR centered at 1550nm (target λ=1550nm), you will want to know the RIX at 1550nm specifically.		##Get RIX at the target wavelength, using "Derived Params" on JAW or Cauchy equation A/B/C params. For example, if targeting a DBR centered at 1550nm (target λ=1550nm), you will want to know the RIX at 1550nm specifically.
	# Calculate approximate dep. time to achieve a 1/4-wave thickness at the target wavelength, for each film (SiO and TaO).		#Calculate approximate dep. time to achieve a 1/4-wave thickness at the target wavelength, for each film (SiO and TaO).
	## For example, if SiO2 measured at 5.2nm/min and RIX is n<sub>1550</sub> = 1.494, then ''SiO 1/4λ thickness: d<sub>1/4λ</sub> = 1550nm / 4 / 1.494 = 259.4nm'' '''''SiO 1/4λ time''': t<sub>1/4λ</sub> = 259.4nm ÷ 5.2nm/min = 49.88min = '''2993.077 sec''''' (and do the same for TaO)		##For example, if SiO2 measured at 5.2nm/min and RIX is n<sub>1550</sub> = 1.494, then ''SiO 1/4λ thickness: d<sub>1/4λ</sub> = 1550nm / 4 / 1.494 = 259.4nm'' '''''SiO 1/4λ time''': t<sub>1/4λ</sub> = 259.4nm ÷ 5.2nm/min = 49.88min = '''2993.077 sec''''' (and do the same for TaO)
	# Deposit a fabry-perot 1/2-λ of one film (SiO or TaO) cavity onto a Silicon piece, using the above 1/4-λ times (aka. SiO/4 or TaO/4), to calibrate that film's optical-thickness.		#Deposit a fabry-perot 1/2-λ of one film (SiO or TaO) cavity onto a Silicon piece, using the above 1/4-λ times (aka. SiO/4 or TaO/4), to calibrate that film's optical-thickness.
	## eg. for SiO Fabry-Perot cavity (aka. SiO-FP) ''SiO/4 + TaO/4 + SiO/4 + TaO/4 + SiO/4 + TaO/4 + ('''SiO/4 + SiO/4''') + TaO/4 + SiO/4 + TaO/4 + SiO/4 + TaO/4'' Here we used only 3 periods of DBR on either side of the 1/2-λ cavity, to speed up the deposition.		##eg. for SiO Fabry-Perot cavity (aka. SiO-FP) ''SiO/4 + TaO/4 + SiO/4 + TaO/4 + SiO/4 + TaO/4 + ('''SiO/4 + SiO/4''') + TaO/4 + SiO/4 + TaO/4 + SiO/4 + TaO/4'' Here we used only 3 periods of DBR on either side of the 1/2-λ cavity, to speed up the deposition.
	# Measure the reflectivity on [[Optical Film Spectra + Optical Properties (Filmetrics F10-RT-UVX)\|Filmetrics F10-RT]].		#Measure the reflectivity on [[Optical Film Spectra + Optical Properties (Filmetrics F10-RT-UVX)\|Filmetrics F10-RT]].
	# Locate the wavelength of the minimum (dip) in the optical spectrum. Spectrum will typically be very broad, due to omitting many of the DBR layers for speed.		#Locate the wavelength of the minimum (dip) in the optical spectrum. Spectrum will typically be very broad, due to omitting many of the DBR layers for speed.
	## For example, the trough might show a minimum at 1600nm. Here is an example of a Fabry-Perot cavity that was targeting a 1050nm, and measured a 1100nm trough:[[File:IBD SiO-FP - long 1100nm - Reflectivity Spectrum (EMpy).png\|alt=Simulated plot of SiO-FP reflectivity, for a 1050nm target but measured trough at 1100nm\|none\|thumb\|Example: Targeting a 1050nm SiO-FP, the measured trough location is at 1100nm. ]]In this case, one would apply a correction to the SiO/4 time by multiplying by ''1050÷1000''.		##For example, the trough might show a minimum at 1600nm. Here is an example of a Fabry-Perot cavity that was targeting a 1050nm, and measured a 1100nm trough:[[File:IBD SiO-FP - long 1100nm - Reflectivity Spectrum (EMpy).png\|alt=Simulated plot of SiO-FP reflectivity, for a 1050nm target but measured trough at 1100nm\|none\|thumb\|Example: Targeting a 1050nm SiO-FP, the measured trough location is at 1100nm. ]]In this case, one would apply a correction to the SiO/4 time by multiplying by ''1050÷1000''.
	# Correct the film's optical thickness as so: t<sub>1/4λ</sub> * λ<sub>target</sub> / λ<sub>measured</sub> = ''corrected'' t<sub>1/4λ</sub> 2993.077 sec * 1550nm / 1600nm = '''2899.543 sec''' for SiO/4 layers		#Correct the film's optical thickness as so: t<sub>1/4λ</sub> * λ<sub>target</sub> / λ<sub>measured</sub> = ''corrected'' t<sub>1/4λ</sub> 2993.077 sec * 1550nm / 1600nm = '''2899.543 sec''' for SiO/4 layers
	## Use this corrected time for all SiO/4 layers.		##Use this corrected time for all SiO/4 layers.
	# Do the same Fabry-Perot correction for the other film, in this case TaO-FP, and apply the new TaO/4 time to the recipe.		#Do the same Fabry-Perot correction for the other film, in this case TaO-FP, and apply the new TaO/4 time to the recipe.
	# Perform a test-DBR deposition onto Silicon, eg. 9 periods (less than full, which ~~may~~ be 15 periods), to confirm that center wavelength is in the right spot. An example DBR test-dep targeting 1050nm looks like this:[[File:IBD 9-period DBR - Reflectivity Spectrum (EMpy).png\|alt=Example reflectivity spectra of the 9-period DBR test-dep, showing 1050nm center-wavelength in the middle of the DBR high-reflectivity spectrum.\|none\|thumb\|Example reflectivity spectra of the 9-period DBR test-dep.]]~~<br />~~		#Perform a test-DBR deposition onto Silicon, eg. 9 periods (less than full, which could be 15 periods or more), and measure on [[Optical Film Spectra + Optical Properties (Filmetrics F10-RT-UVX)\|Filmetrics F10-RT]], to confirm that center wavelength is in the right spot. An example DBR test-dep targeting 1050nm looks like this:[[File:IBD 9-period DBR - Reflectivity Spectrum (EMpy).png\|alt=Example reflectivity spectra of the 9-period DBR test-dep, showing 1050nm center-wavelength in the middle of the DBR high-reflectivity spectrum.\|none\|thumb\|Example reflectivity spectra of the 9-period DBR test-dep.]]
			#Perform full-DBR deposition onto production parts. Include a flat Silicon witness for measuring the final DBR reflectivity spectrum.<br />

	Sources of error: thick, stressy films exhibit the stress-optic effect, in which compressed films (closer to the substrate) will often show a reduction in RIX. In going from a 9-period DBR to a 18-period DBR, you might see a ~10-20nm blue-shift. Some users for who such a shift is outside the device tolerance will do a full DBR dep, then apply a % reduction to all dep ~~time~~ to further dial in the DBR reflectivity band.		* Sources of error: thick, stressy films exhibit the stress-optic effect, in which compressed films (closer to the substrate) will often show a reduction in RIX. In going from a 9-period DBR to a 18-period DBR, you might see a ~10-20nm blue-shift. Some users for who such a shift is outside the device tolerance will do a full DBR dep, then apply a % reduction to all dep times to further dial in the DBR reflectivity band.
		⚫	* The same method can be used to calibrate optical-thickness for arbitrary binary multi-layer optical filters.

⚫	The same method can be used to calibrate optical-thickness for arbitrary binary multi-layer optical filters.