Athermal fiber Bragg grating

A method for athermalizing a fiber Bragg grating, comprising:

• providing a platform of a first material having a first coefficient of thermal expansion (α1) between first and second attachment locations defining an attachment-length (L1) there between;
• providing a stick of a second material having a second coefficient of thermal expansion (α2) between first and second ends defining a stick-length (L2) there between;
• defining the grating as being of a third material having an effective third coefficient of thermal expansion (α3) between first and second ends defining a grating-length (L3) there between, wherein said effective third coefficient (α3) is based on a combination of thermal expansion and refractive index variation in the grating with respect to temperature;
• affixing said second end of said stick to said first end of the grating, affixing said first end of said stick to said first attachment location, and affixing said second end of the grating to said second attachment location;
• providing that said stick has an essentially same cross-sectional stick-area exhibited along said stick-length, that the grating has a cross-sectional grating-area at its said first end, and that said stick-area is equal to or less than said grating-area;
• and
• providing that said coefficients (α1, α2, and α3) and said lengths (L1, L2, and L3) are such that a resulting assembly of the grating, said stick, and said platform exhibit an effective overall coefficient of thermal expansion (αALL) in accord with the equation:
• αALL=(α1*L1+α3*L3−α2*L2)/L3≈0.

An athermal fiber Bragg grating assembly, comprising:

• platform means for providing first and second attachment locations defining an attachment-length (L1) there between, wherein said platform means is of a first material having a first coefficient of thermal expansion (α1);
• stick means for providing first and second ends defining a stick-length (L2) there between, wherein said stick means is of a second material having a second coefficient of thermal expansion (α2);
• and
• a fiber Bragg type grating having first and second ends defining a grating-length (L3) there between, wherein said grating is of a third material having an effective third coefficient of thermal expansion (α3) that is based on a combination of thermal expansion and refractive index variation in said grating with respect to temperature;
• and wherein:
• said second end of said stick means is fixed to said first end of said grating, said first end of said stick means is fixed to said first attachment location, and said second end of said grating is fixed to said second attachment location;
• said stick means has an essentially same cross-sectional stick-area exhibited along said stick-length, said grating has a cross-sectional grating-area at its said first end, and said stick-area is equal to or less than said grating-area;
• and
• said coefficients (α1, α2, and α3) and said lengths (L1, L2, and L3) are such that the assembly exhibits an effective overall coefficient of thermal expansion (αALL) in accord with the equation:
• αALL=(α1*L1+α3* L3−α2*L2)/L3≈0.