Xiang-Zhao Wang, Akira Hirai, Kouhei Shioya, Masashi Ohkawa, Seishi Sekine, and Shigeru Ando, "Fast and highly parallel content addressing of a large amount of information recorded in a holographic memory," Appl. Opt. 33, 3003-3009 (1994)
It has recently become possible to fabricate spatial light modulators for holographic information retrieval. We analyze the signal-to-noise ratios in two typical holographic information retrieval systems, serial and inverted, and we discuss the possibilities of implementing holographic information retrieval with a newly proposed spatial light modulator that uses a Fabry–Perot étalon with a piezoelectrically driven mirror.
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Example of Coded Secondary Information Corresponding to Original Information
Table 2
Specifications of Holographic Information Retrieval Systemsa
Elements
Serial-File System
Inverted-File System
Holograms
Lh × Lh = 80 × 80 mm,
M = 40 × 40 = 1600,
Lh × Lh = 6 × 6 mm,
M = 20 × 20 = 400,
n = 12,
ϕh = 0.5 mm,
n = 33,
ϕh = 0.5 mm,
lh = 1.5 mm,
lh = 0.1 mm,
L0 × L0 = 20 × 20 mm,
ϕ0 = 1 mm
L0 × L0 = 80 × 80 mm,
ϕ0 = 1 mm
Spatial light modulators
Ls × Ls = 20 × 20 mm,
ϕs = 1 mm
Ls × Ls = 6 × 6 mm,
ϕs = 0.5 mm,
T0 = 40 μs,
ηave = 1:120
T0 = 40 μs,
ηave = 1:1338
Photodetectors
Lp × Lp = 80 × 80 mm, A = 0.04 cm2,
Lp × Lp = 80 × 80 mm, A = 0.16 cm2,
D* = 3.052 × 1010 (cm Hz0.5/W),
D* = 5.478 × 109 (cm Hz0.5/W),
NEP = 6.553 × 10−12 (W/Hz0.5),
NEP = 7.302 × 10−11 (W/Hz0.5),
SNR = 10
SNR = 10
Lenses
ϕ1 = 131 mm, τ1 = 90%, f = 125 mm
Same
Light source
Semiconductor laser (0.1 μs, 1 W)
Same
Lh × Lh, dimensions of the hologram array; M, amount of information that can be processed by the system; n, number of bits of each piece of information; ϕh, diameter of the hologram; lh, space between each two adjacent holograms; L0 × L0, dimensions of the object used when the hologram is recorded; ϕ0, diameter of the hole in the object plane corresponding to one bit of information; Ls × Ls, dimensions of the SLM; ϕs, diameter of the window of the SLM; ηave, average extinction ratio of the SLM over θmax range; η, extinction ratio of the SLM at an angle of incidence θ; T0, switching time of the SLM; Lp × Lp, dimensions of the photodetector array; A, receiving area of the photodetector; D*, detectivity of the photodetector; NEP, noise equivalent power; SNR, SNR in the HIR system; τ1, transmittance of the lens.
Table 3
Optical Data of Mirrors
Mirror
Reflectivity (%)
Transmittance (%)
1
95.6
2.1
2
94.1
1.5
Tables (3)
Table 1
Example of Coded Secondary Information Corresponding to Original Information
Table 2
Specifications of Holographic Information Retrieval Systemsa
Elements
Serial-File System
Inverted-File System
Holograms
Lh × Lh = 80 × 80 mm,
M = 40 × 40 = 1600,
Lh × Lh = 6 × 6 mm,
M = 20 × 20 = 400,
n = 12,
ϕh = 0.5 mm,
n = 33,
ϕh = 0.5 mm,
lh = 1.5 mm,
lh = 0.1 mm,
L0 × L0 = 20 × 20 mm,
ϕ0 = 1 mm
L0 × L0 = 80 × 80 mm,
ϕ0 = 1 mm
Spatial light modulators
Ls × Ls = 20 × 20 mm,
ϕs = 1 mm
Ls × Ls = 6 × 6 mm,
ϕs = 0.5 mm,
T0 = 40 μs,
ηave = 1:120
T0 = 40 μs,
ηave = 1:1338
Photodetectors
Lp × Lp = 80 × 80 mm, A = 0.04 cm2,
Lp × Lp = 80 × 80 mm, A = 0.16 cm2,
D* = 3.052 × 1010 (cm Hz0.5/W),
D* = 5.478 × 109 (cm Hz0.5/W),
NEP = 6.553 × 10−12 (W/Hz0.5),
NEP = 7.302 × 10−11 (W/Hz0.5),
SNR = 10
SNR = 10
Lenses
ϕ1 = 131 mm, τ1 = 90%, f = 125 mm
Same
Light source
Semiconductor laser (0.1 μs, 1 W)
Same
Lh × Lh, dimensions of the hologram array; M, amount of information that can be processed by the system; n, number of bits of each piece of information; ϕh, diameter of the hologram; lh, space between each two adjacent holograms; L0 × L0, dimensions of the object used when the hologram is recorded; ϕ0, diameter of the hole in the object plane corresponding to one bit of information; Ls × Ls, dimensions of the SLM; ϕs, diameter of the window of the SLM; ηave, average extinction ratio of the SLM over θmax range; η, extinction ratio of the SLM at an angle of incidence θ; T0, switching time of the SLM; Lp × Lp, dimensions of the photodetector array; A, receiving area of the photodetector; D*, detectivity of the photodetector; NEP, noise equivalent power; SNR, SNR in the HIR system; τ1, transmittance of the lens.