US4915476A
Expired / Lapsed
US
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Single-notch rugate filters and a controlled method of manufacture thereof
Assignee: Raytheon Co
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Filing: 1988-05-31
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Granted: 1990-04-10
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Expires: 2008-05-31
Abstract
Abstract A process for forming a single-notch optical filter having a continually and accurately varying periodic profile. An optical medium is coated on a uniform substrate where the homogeneous optical medium produces a rugate filter, so that the profile of the refractive index follows a sinusoidal pattern and Bragg's law. As the optical medium is coated on the substrate, the depositing film is monitored by optical techniques, and feedback information is provided to a computer driven by a pre-programmed process control algorithm so that real time control of the manufacturing process may be accomplished.
Inventors
- 👤 James T. Hall
- 👤 Ronald T. Smith
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 17:31
CPC Classifications
C; C23; C23C; C23C16/00; C23C16/44; C23C16/52; G; G02; G02B; G02B5/00; G02B5/20; G02B5/28; G02B5/289; Y; Y10; Y10S; Y10S359/00; Y10S359/90
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
285 words
A method for forming a single notch rugate filter comprising a substrate having formed thereon a layer of an optical material having a refractive index that varies according to a predetermined sinusoidal pattern as a function of the thickness of said layer, comprising the steps of: (a) providing said substrate; (b) providing reactants which interact physically or chemically to form said optical material as a layer on said substrate; (c) providing an ideal target profile of refractive index versus thickness of said layer, said profile having said sinusoidal pattern, and determining from said profile ideal values of optical thickness at successive points in time corresponding to points along said profile; (d) providing target process conditions as a function of time for said reactants operative to form said layer having said ideal target profile; (e) initiating said process conditions to form a layer having a depositing profile; (f) performing continuous optical monitoring of said layer as deposited to provide an optical signal; (g) determining from said optical signal the measured increments of optical thickness of said layer as deposited and continuously monitoring said increments of optical thickness; (h) determining whether said optical thickness value is measured at the predetermined time relative to said target process conditions that produce said ideal target profile; (i) based on the results of (h), determining the sinusoidal phase angle adjustment required to be made to the depositing profile of refractive index versus thickness of said layer in order to follow accurately said ideal target profile; (j) altering said process conditions over time to provide said sinusoidal phase angle adjustment to said actual profile; (k) repeating steps "f" through "j" the number of times required to form said single notch rugate filter.
Claim 2
Independent Claim
285 words
A method for forming a single notch rugate filter comprising a substrate having formed thereon a layer of an optical material having a refractive index that varies according to a predetermined sinusoidal pattern as a function of the thickness of said layer, comprising the steps of: (a) providing said substrate; (b) providing reactants which interact physically or chemically to form said optical material as a layer on said substrate; (c) providing an ideal target profile of refractive index versus thickness of said layer, said profile having said sinusoidal pattern, and determining from said profile ideal values of optical thickness at successive points in time corresponding to points along said profile; (d) providing target process conditions as a function of time for said reactants operative to form said layer having said ideal target profile; (e) initiating said process conditions to form a layer having a depositing profile; (f) performing continuous optical monitoring of said layer as deposited to provide an optical signal; (g) determining from said optical signal the measured increments of optical thickness of said layer as deposited and continuously monitoring said increments of optical thickness; (h) determining whether said optical thickness value is measured at the predetermined time relative to said target process conditions that produce said ideal target profile; (i) based on the results of (h), determining the sinusoidal phase angle adjustment required to be made to the depositing profile of refractive index versus thickness of said layer in order to follow accurately said ideal target profile; (j) altering said process conditions over time to provide said sinusoidal phase angle adjustment to said actual profile; (k) repeating steps "f" through "j" the number of times required to form said single notch rugate filter.
Claim 3
Dependent Claim
40 words
The method of claim 1 wherein: (a) said optical thickness value in step "h" is measured after said predetermined time; and (b) said sinusoidal phase angle adjustment in step "i" produces a continuous horizontal segment adjustment to said depositing profile.
Claim 4
Dependent Claim
39 words
The method of claim 1 wherein: (a) said optical thickness value in step "h" is measured before said predetermined time; and (b) said sinusoidal phase angle adjustment in step "i" produces a vertical segment adjustment to said depositing profile
Claim 5
Dependent Claim
29 words
The method of claim 1 wherein: (a) said optical thickness signal in step "h" is received at said predetermined time; and (b) said sinusoidal phase angle adjustment is zero.
Claim 6
Dependent Claim
14 words
The method of claim 1 wherein steps "h" through "j" are under computer control.
Claim 7
Dependent Claim
68 words
The method of claim 1 wherein said optical monitoring of step "f" comprises directing an optical monitoring light beam at said layer as deposited so that said light beam is reflected off or transmitted through said layer at normal or near normal incidence into an optical detector means, wherein said detector means generates said optical signal which is a function of said light beam directed into said detector.
Claim 8
Dependent Claim
11 words
The method of claim 1 wherein said reactants comprise metal-organic materials.
Claim 9
Dependent Claim
23 words
The method of claim 7 wherein said reactants comprise trimethyl aluminum, trimethyl gallium, and arsine and said layer comprises epitaxial aluminum gallium arsenide.
Claim 10
Dependent Claim
78 words
The method of claim 1 wherein said determining of said sinusoidal phase angle adjustment required comprises applying the following equation: ##EQU3## where n=refractive index of optical material z=layer thickness n(z)=refractive index as a function of layer thickness n=average index of refraction over one period in film thickness space (z) λ o =notch wavelength (desired) *=parameters that can have local errors, which are compensated for by φ φ=sinusoidal phase angle adjustment to insure Bragg reflection at λ o .
Claim 11
Dependent Claim
31 words
A single notch rugate filter formed by the method of claim 1 wherein said filter produces a reflection at a single, narrow band of wavelengths and said reflection follows Bragg's law.
References Cited (Backward Citations)
US4545646A
Cited
US4707611A
Cited
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