US 7,352,931 B1 · Method and phase mask for manufacturing a multi-channel optical grating

Abstract

A method for manufacturing a complex multi-channel optical grating using a phase mask is presented. A plurality of sub-gratings is designed, each having an individual spectral response designed to produce one of the channels of the multi-channel grating. The target profile of the grating is determined based on the combination of the index profiles of the individual sub-gratings, the target index profile defining a target spectral response of the multi-channel grating. A modified index profile having a smooth apodization profile but providing the same spectral response as the target index profile, at least within a spectral region of interest, is determined and encoded into the phase mask. The phase mask is then used to photoinduce the grating in a photosensitive medium.

Claims50

Dependent claims

A method for manufacturing a multi-channel optical grating in a photosensitive medium, each channel of said multi-channel grating having an individual spectral response, said method comprising the steps of:

a) for each channel, individually designing an index profile of a sub-grating providing the corresponding individual spectral response, each of said index profiles comprising an individual apodization profile and an individual phase profile of the corresponding sub-grating;
b) determining a target index profile Δnstruct(z) of the multi-channel grating based on a combination of the index profiles of said sub-gratings such that:
Δ
⁢
⁢
n
struct
⁡
(
z
)
=
Δ
⁢
⁢
n
offset
+
∑
k
⁢
Δ
⁢
⁢
n
k
⁡
(
z
)
⁢
ⅇ
ⅈ
⁡
(
θ
k
⁡
(
z
)
+
ϕ
k
)
where z is an optical axis of said multi-channel grating, k is an indicia representing said sub-gratings, Δnk(z) and θk(z) are respectively the individual apodization and phase profiles of each sub-grating, φk is a relative phases between the sub-gratings and Δnoffset is an index offset selected to make the target index profile strictly positive, said target index profile defining a target spectral response of said optical grating;
c) determining a modified index profile having a smooth apodization profile and providing said target spectral response at least within a spectral region of interest;
d) encoding a phase mask according to said modified index profile;
and
e) photoinducing said multi-channel grating in the photosensitive medium using said phase mask.

47 more elements

a) for each channel, individually designing an index profile of a sub-grating providing the corresponding individual spectral response;
b) determining a target index profile of the multi-channel grating based on a combination of the index profiles of said sub-gratings such that it corresponds to a seed grating multiplied by a sampling function, said sampling function being represented by:
∑
k
⁢
C
k
⁡
(
z
)
⁢
exp
⁡
[
j
⁢
2
⁢
π
⁢
⁢
k
Λ
s
⁢
z
]
where z is an optical axis of said multi-channel grating, k is an indicia representing said sub-gratings, Λs, is a sampling period and Ck(z) are amplitude coefficients of said target index profile defining a target spectral response of said optical grating;
c) determining a modified index profile having a smooth apodization profile and providing said target spectral response at least within a spectral region of interest;
d) encoding a phase mask according to said modified index profile;
and
e) photoinducing said multi-channel grating in the photosensitive medium using said phase mask.

30 more elements

A method for manufacturing a phase mask for photoinducing a multi-channel optical grating in a photosensitive medium, each channel of said multi-channel grating having an individual spectral response, said method comprising the steps of:

a) for each channel, individually designing an index profile of a sub-grating providing the corresponding individual spectral response each of said index profiles comprising an individual apodization profile and an individual phase profile of the corresponding sub-grating;
b) determining a target index profile Δnstruct(z) of the multi-channel grating based on a combination of the index profiles of said sub-gratings such that:
Δ
⁢
⁢
n
struct
⁡
(
z
)
=
Δ
⁢
⁢
n
offset
+
∑
k
⁢
Δ
⁢
⁢
n
k
⁡
(
z
)
⁢
ⅇ
ⅈ
⁡
(
θ
k
⁡
(
z
)
+
ϕ
k
)
where z is an optical axis of said multi-channel grating, k is an indicia representing said sub-gratings Δnk(z) and θk(z) are respectively the individual apodization and phase profiles of each sub-grating, φk is a relative phases between the sub-gratings and Δnoffset is an index offset selected to make the target index profile strictly positive, said target index profile defining a target spectral response of said optical grating;
c) determining a modified index profile having a smooth apodization profile and providing said target spectral response at least within a spectral region of interest;
and
d) encoding the phase mask according to said modified index profile.

46 more elements

a) for each channel, individually designing an index profile of a sub-grating providing the corresponding individual spectral response;
b) determining a target index profile of the multi-channel grating based on a combination of the index profiles of said sub-gratings such that it corresponds to a seed grating multiplied by a sampling function, said sampling function being represented by:
∑
k
⁢
C
k
⁡
(
z
)
⁢
exp
⁡
[
j
⁢
2
⁢
π
⁢
⁢
k
Λ
s
⁢
z
]
where z is an optical axis of said multi-channel grating, k is an indicia representing said sub-gratings, Λs is a sampling period and Ck(z) are amplitude coefficients, said target index profile defining a target spectral response of said optical grating;
c) determining a modified index profile having a smooth apodization profile and providing said target spectral response at least within a spectral region of interest;
and
encoding the phase mask according to said modified index profile.

29 more elements

A phase mask for photoinducing a multi-channel optical grating, each channel of said multi-channel grating having an individual spectral response, said phase mask comprising:

a plurality of grating corrugations having a periodical spatial distribution, said spatial distribution being encoded according to an index profile having a smooth apodization profile and providing a spectral response within a spectral region of interest corresponding to a target spectral response of said multi-channel optical grating, said target spectral response being defined by a target index profile Δnstruct(z) based on a combination of index profiles of a plurality of sub-gratings, the index profile of each sub-grating comprising an individual apodization profile and an individual phase profile and being selected to provide the individual spectral response of a corresponding one of said channels, said target index profile of the multi-channel grating being such that:
Δ
⁢
⁢
n
struct
⁡
(
z
)
=
Δ
⁢
⁢
n
offset
+
∑
k
⁢
Δ
⁢
⁢
n
k
⁡
(
z
)
⁢
ⅇ
ⅈ
⁡
(
θ
k
⁡
(
z
)
+
ϕ
k
)
where z is an optical axis of said multi-channel grating, k is an indicia representing said sub-gratings, Δnk(z) and θk(z) are respectively the individual apodization and phase profiles of each sub-grating, φk is a relative phases between the sub-gratins Δnoffset is an index offset selected to make the target index profile strictly positive.

42 more elements

Dependencies are inferred from the claim text.

Method and phase mask for manufacturing a multi-channel optical grating

Life of this patent

Method and phase mask for manufacturing a multi-channel optical grating

Life of this patent

Abstract

Claims50