Method and system utilizing inverted master for holographic recording
Disclosed herein is methods and apparatus for recording a holographic waveguide utilizing an inverted holographic master technique. In some embodiments, an apparatus for recording a holographic waveguide is provided. The apparatus may include a source of light configured to provide a recording beam; a master substrate with a non-grating modulated surface and a grating modulated surface, wherein the grating modulated surface is opposite to the non-grating modulated surface and is configured to diffract the recording beam; a bottom substrate with opposing light transmitting surfaces coated with anti-reflection coatings overlaying the grating modulated surface of the substrate and separated from the master substrate by a gap; and an exposure cell containing holographic recording material directly facing the non-grating modulated surface of the master substrate. Advantageously, the inverted holographic master technique mitigates the effects of unwanted reflected exposure light.
1 . An apparatus for recording a holographic waveguide, comprising:
a source of light configured to provide a recording beam;
a master substrate with a non-grating modulated surface and a grating modulated surface, wherein the grating modulated surface is opposite to the non-grating modulated surface and is configured to diffract the recording beam;
a bottom substrate with opposing light transmitting surfaces coated with anti-reflection coatings overlaying the grating modulated surface of the master substrate and separated from the master substrate by a gap; and
an exposure cell containing holographic recording material directly facing the non-grating modulated surface of the master substrate.
2 . The apparatus of claim 1 , wherein said grating modulated surface supports a master grating which is configured to diffract the recording beam into a diffracted first-order beam and a refracted zero-order beam.
3 . The apparatus of claim 2 , wherein the diffracted first order beam interferes with a neighboring refracted zero-order beam in the exposure cell.
4 . The apparatus of claim 2 , wherein the refracted zero-order beam interferes with a neighboring diffracted first-order beam in the exposure cell.
5 . The apparatus of claim 1 , wherein the master substrate is transparent.
6 . The apparatus of claim 1 , wherein the grating modulated surface is coated with a reflective film which forms a master grating.
7 . The apparatus of claim 6 , wherein the reflective film is chrome.
8 . The apparatus of claim 1 , wherein the exposure cell comprises a holographic recording material positioned between transparent substrates.
9 . The apparatus of claim 1 , wherein the exposure cell comprises a transparent substrate coated with a holographic recording material.
10 . The apparatus of claim 1 , wherein the gap is air filled.
11 . The apparatus of claim 1 , wherein the gap is filled with low refractive index material.
12 . The apparatus of claim 1 , wherein a reflected beam formed by the master substrate at least partially exits the bottom substrate without being reflected back into the master substrate.
13 . The apparatus of claim 12 , wherein the reflected beam comprises a reflected zero-order beam and/or a reflected first-order beam.
14 . The apparatus of claim 13 , wherein the reflected first-order beam is suppressed by the gap.
15 . The apparatus of claim 12 , further comprising a light trap which keeps the light exiting the bottom substrate from being reflected back into the master substrate.
16 . The apparatus of claim 15 , wherein the light trap comprises a polarization modification layer.
17 . The apparatus of claim 15 , wherein the light trap comprises an optical element for trapping light.
18 . The apparatus of claim 15 , wherein the light trap comprises a light absorber.
19 . The apparatus of claim 1 , wherein the master substrate is configured to diffract the recording beam into a first order beam and a zero-order beam.
20 . The apparatus of claim 1 , wherein the anti-reflection coatings have angular characteristics varying across the bottom substrate tuned to the angles of unwanted light rays incident on the bottom substrate at different points.
21 . The apparatus of claim 1 , wherein the exposure cell comprises a release layer.
22 . The apparatus of claim 1 wherein the non-grating modulated surface is curved.