Coatings for laser detector etalons

Claim 2

An etalon for modulating a radiation signal, comprising: a substrate having a first major surface and a second, opposite major surface, the first major surface having at least one step therein; and a plurality of dispersive coatings formed upon at least one of said major surfaces of said substrate, said plurality of dispersive coatings each having a spatially varying index of refraction through a depth thereof, the profile being selected as a function of a height of said at least one step and for reducing a falloff in modulation of said etalon due to a phase shift for radiation at said at least one step; wherein said plurality of dispersive coatings are rugate coatings having a spatially varying index of refraction profile n(x) that varies in accordance with a sinusoidal function, wherein n(x) is give by the expression: n(x)=n.sub.o (1+∫H(n.sub.i K(x-x.sub.o)/n.sub.o u(K)) sin (Kx+φ(K))dK/K) where n o is equal to the average index of refraction, K=4πn o /λ, [φ' is the internal angle in the coating] and λ is the wavelength, where u(K)=4tanh -1 (R(K)) 1/2 is a number of cycles in the coating to achieve a desired reflectivity R(K), n 1 is the peak deviation of the index from n o for a single wavelength, where φ(K) is the phase of reflected light as a function of K, where x is a distance into the coating, and where H is an envelope or apodizing function located at x o whose extent defines the region of index variation at the wavelength λ.

Claim 3

An etalon as set forth in claim 1 wherein said plurality of dispersive coatings are formed as multi-layered coatings.

Claim 4

An etalon for modulating a radiation signal, comprising: a substrate having a first major surface and a second, opposite major surface; and a plurality of dispersive coatings formed upon at least one of said major surfaces of said substrate, said plurality of dispersive coatings each having a spatially varying index of refraction profile through a depth thereof, the profile being selected for inducing a predetermined phase shift between two adjacent coatings; wherein said plurality of dispersive coatings are rugate coatings having a spatially varying index of refraction profile n(x) that varies in accordance with a sinusoidal function, wherein n(x) is give by the expression: n(x)=n.sub.o (1+∫H(n.sub.i K(x-x.sub.o)/n.sub.o u(K)) sin (Kx+φ(K))dK/K) where n o is equal to the average index of refraction, K=40πn o /λ, [φ' is the internal angle in the coating] and λ is the wavelength, where u(K)=4tanh -1 (R(K)) 178 is a number of cycles in the coating to achieve a desired reflectivity R(K), n 1 is the peak deviation of the index from n o for a single wavelength, where φ(K) is the phase of reflected light as a function of K, where x is a distance into the coating, and where H is an envelope or apodizing function located at x o whose extent defines the region of index at the wavelength λ.

Claim 5

An etalon for modulating a radiation signal, comprising: a substrate having a first major surface and a second, opposite major surface; and a plurality of dispersive coatings formed upon at least one of said major surfaces of said substrate, said plurality of dispersive coatings each having a spatially varying index of refraction profile through a depth thereof, the profile being selected for inducing a predetermined phase shift between two adjacent coatings; wherein said plurality of dispersive coatings are rugate coatings having a spatially varying index of refraction profile n(x) that varies in accordance with a sinusoidal function, wherein n(x) is give by the expression: n(x)=n.sub.o (1+∫H(n.sub.i K(x-x.sub.o)/n.sub.o u(K)) sin (Kx+φ(K))dK/K) where n o is equal to the average index of refraction, K=40πn o /λ, [φ' is the internal angle in the coating] and λ is the wavelength, where u(K)=4tanh -1 (R(K)) 178 is a number of cycles in the coating to achieve a desired reflectivity R(K), n 1 is the peak deviation of the index from n o for a single wavelength, where φ(K) is the phase of reflected light as a function of K, where x is a distance into the coating, and where H is an envelope or apodizing function located at x o whose extent defines the region of index at the wavelength λ.

Claim 6

An etalon as set forth in claim 3 wherein said plurality of dispersive coatings are formed as multi-layered coatings.

Claim 7

Apparatus for detecting coherent radiation, comprising: an etalon disposed for receiving coherent radiation, said etalon including a substrate having a first major surface and a second, opposite major surface, the first major surface having at least one step therein; a plurality of dispersive coatings formed upon at least one of said major surfaces of said substrate, said plurality of dispersive coatings each having a spatially varying index of refraction profile through a depth thereof, the profile being selected as a function of a height of said at least one step and for reducing a falloff in a modulation characteristic of said etalon due to a phase shift for coherent radiation at said at least one step; and detector means disposed relative to said etalon for detecting a presence of the coherent radiation; wherein said plurality of dispersive coatings are rugate coatings having a spatially varying index of refraction profile n(x) that varies in accordance with a sinusoidal function, wherein n(x) is give by the expression: n(x)=n.sub.o (1+∫H(n.sub.i K(x-x.sub.o)/n.sub.o u(K)) sin (Kx+φ(K))dK/K) where n o is equal to the average index of refraction, K=4πn o /λ, [φ' is the internal angle in the coating ] and λ is the wavelength, where u(K)=4tanh -1 (R(K)) 178 is a number of cycles in the coating to achieve a desired reflectivity R(K), n 1 is the peak deviation of the index from n o for a single wavelength, where φ(K) is the phase of reflected light as a function of K, where x is a distance into the coating, and where H is an envelope or apodizing function located at x o whose extent defines the region of index variation at the wavelength λ.

Claim 8

Apparatus for detecting coherent radiation, comprising: an etalon disposed for receiving coherent radiation, said etalon including a substrate having a first major surface and a second, opposite major surface, the first major surface having at least one step therein; a plurality of dispersive coatings formed upon at least one of said major surfaces of said substrate, said plurality of dispersive coatings each having a spatially varying index of refraction profile through a depth thereof, the profile being selected as a function of a height of said at least one step and for reducing a falloff in a modulation characteristic of said etalon due to a phase shift for coherent radiation at said at least one step; and detector means disposed relative to said etalon for detecting a presence of the coherent radiation; wherein said plurality of dispersive coatings are rugate coatings having a spatially varying index of refraction profile n(x) that varies in accordance with a sinusoidal function, wherein n(x) is give by the expression: n(x)=n.sub.o (1+∫H(n.sub.i K(x-x.sub.o)/n.sub.o u(K)) sin (Kx+φ(K))dK/K) where n o is equal to the average index of refraction, K=4πn o /λ, [φ' is the internal angle in the coating ] and λ is the wavelength, where u(K)=4tanh -1 (R(K)) 178 is a number of cycles in the coating to achieve a desired reflectivity R(K), n 1 is the peak deviation of the index from n o for a single wavelength, where φ(K) is the phase of reflected light as a function of K, where x is a distance into the coating, and where H is an envelope or apodizing function located at x o whose extent defines the region of index variation at the wavelength λ.

Claim 9

Apparatus as set forth in claim 5 wherein said plurality of dispersive coatings are formed as multi-layered coatings.

Claim 10

Apparatus for detecting coherent radiation, comprising: an etalon disposed for receiving coherent radiation, said etalon including a substrate having a first major surface and a second, opposite major surface; a plurality of dispersive coatings formed upon at least one of said major surfaces of said substrate, said plurality of dispersive coatings each having a spatially varying index of refraction profile through a depth thereof, the profile being selected for inducing a predetermined phase shift in the coherent radiation between two adjacent coatings; and detector means disposed relative to said etalon for detecting a presence of the coherent radiation; wherein said plurality of dispersive coatings are rugate coatings having a spatially varying index of refraction profile n(x) that varies in accordance with a sinusoidal function, wherein n(x) is give by the expression: n(x)=n.sub.o (1+∫H(n.sub.i K(x-x.sub.o)/n.sub.o u(K)) sin (Kx+φ(K))dK/K) where n o is equal to the average index of refraction, K=4πn o /λ,[φ' is the internal angle in the coating] and λ is the wavelength, where u(K)=4tanh -1 (R(K)) 178 is a number of cycles in the coating to achieve a desired reflectivity R(K), n 1 is the peak deviation of the index from n o for a single wavelength, where φ(K) is the phase of reflected light as function of K, where x is a distance into the coating, and where H is an envelope or apodizing function located at x o whose extent defines the region of index variation at the wavelength λ.

Claim 11

Apparatus for detecting coherent radiation, comprising: an etalon disposed for receiving coherent radiation, said etalon including a substrate having a first major surface and a second, opposite major surface; a plurality of dispersive coatings formed upon at least one of said major surfaces of said substrate, said plurality of dispersive coatings each having a spatially varying index of refraction profile through a depth thereof, the profile being selected for inducing a predetermined phase shift in the coherent radiation between two adjacent coatings; and detector means disposed relative to said etalon for detecting a presence of the coherent radiation; wherein said plurality of dispersive coatings are rugate coatings having a spatially varying index of refraction profile n(x) that varies in accordance with a sinusoidal function, wherein n(x) is give by the expression: n(x)=n.sub.o (1+∫H(n.sub.i K(x-x.sub.o)/n.sub.o u(K)) sin (Kx+φ(K))dK/K) where n o is equal to the average index of refraction, K=4πn o /λ,[φ' is the internal angle in the coating] and λ is the wavelength, where u(K)=4tanh -1 (R(K)) 178 is a number of cycles in the coating to achieve a desired reflectivity R(K), n 1 is the peak deviation of the index from n o for a single wavelength, where φ(K) is the phase of reflected light as function of K, where x is a distance into the coating, and where H is an envelope or apodizing function located at x o whose extent defines the region of index variation at the wavelength λ.

Claim 12

Apparatus as set forth in claim 7 wherein said plurality of dispersive coatings are formed as multi-layered coatings.