Fiber optic devices having volume Bragg grating elements
Fiber optic devices including volume Bragg grating (VBG) elements are disclosed. A fiber optic device may include one or more optical inputs, one or more VBG elements, and one or more optical receivers. Methods for manufacturing VBG elements and for controlling filter response are also disclosed. A VBG chip, and fiber optic devices using such a chip, are also provided. A VBG chip includes a monolithic glass structure onto which a plurality of VBGs have been recorded.
1. A method for controlling filter response, the method comprising:
providing a mask that corresponds to a desired spectral filter response of a three-dimensional glass element having a Bragg grating recorded therein;
transmitting a signal recording beam through the mask such that the signal recording beam is transmitted through a lens to a recording medium that is sensitive to a wavelength of the signal recording beam, wherein the lens is adapted to perform a spatial Fourier transform of a transfer function associated with the mask such that a Bragg grating that corresponds to a Fourier transform of the desired spectral filter response is recorded on the recording medium.
2. The method of claim 1 , further comprising:
transmitting to the recording medium a reference recording beam in combination with the signal recording beam, wherein the reference recording beam has generally the same wavelength as the signal recording beam, such that the signal and reference recording beams are coherent.
3. The method of claim 2 , wherein the signal recording beam is incident on a surface of the recording medium, and wherein the reference recording beam is incident on the same surface of the recording medium as the signal recording beam.
4. The method of claim 2 , wherein an amplitude and phase of the Fourier transform are transferred to an amplitude and phase of an envelope of the Bragg grating recorded on the recording medium via coherent interference between the signal recording beam and the reference recording beam.
5. The method of claim 1 , wherein the recording medium is a sensitized silica glass.
6. The method of claim 1 , wherein an amplitude and phase of the Fourier transform are transferred to an amplitude and phase of an envelope of the Bragg grating recorded on the recording medium.
7. A three-dimensional optical element having a desired spectral filter response, the optical element made according to a method comprising:
providing a mask that corresponds to the desired spectral filter response of the element;
transmitting a signal recording beam through the mask such that the signal recording beam is transmitted through a lens to a recording medium that is sensitive to a wavelength of the signal recording beam, wherein the lens is adapted to perform a spatial Fourier transform of a transfer function associated with the mask such that a Bragg grating that corresponds to a Fourier transform of the desired spectral filter response is recorded on the recording medium.