Previously, we proposed and experimentally demonstrated enhanced recording speeds by using a resonant optical cavity to semi-passively increase the reference beam power while recording image bearing holograms. In addition to enhancing the reference beam power the cavity supports the orthogonal reference beam families of its eigenmodes, which can be used as a degree of freedom to multiplex data pages and increase storage densities for volume Holographic Data Storage Systems (HDSS). While keeping the increased recording speed of a cavity enhanced reference arm, image bearing holograms are multiplexed by orthogonal phase code multiplexing via Hermite-Gaussian eigenmodes in a Fe:LiNbO3 medium with a 532 nm laser at two Bragg angles for expedited recording of four multiplexed holograms. We experimentally confirmed write rates are enhanced by an average factor of 1.1, and page crosstalk is about 2.5%. This hybrid multiplexing opens up a pathway to increase storage density while minimizing modifications to current angular multiplexing HDSS.
The cavity supports the orthogonal reference beam families as its eigenmodes while enhancing the reference beam power. Such orthogonal eigenmodes are used as additional degree of freedom to multiplex data pages, consequently increase storage densities for volume Holographic Data Storage Systems (HDSS) when the maximum number of multiplexed data page is limited by geometrical factor. Image bearing holograms are multiplexed by orthogonal phase code multiplexing via Hermite-Gaussian eigenmodes in a Fe:LiNbO3 medium with a 532 nm laser at multiple Bragg angles by using Liquid Crystal on Silicon (LCOS) spatial light modulators (SLMs) in reference arms. Total of nine holograms are recorded with three angular and three eigenmode.
We report the experimental verification of cavity enhanced recording of image bearing holograms in Fe:LiNbO3 with a 532 nm wavelength, CW, single mode, DPSS, Nd:YAG, laser with a cavity on the reference arm. Diffraction efficiency evolution was monitored via pseudo-phase-conjugate readout during recording. Additionally, optimization of grating strengths in standing wave cavity writing is explored, and a means of eliminating unwanted gratings via quarter wave plates with isotropic recording media is proposed.
To satisfy the growing need for faster archival data storage and retrieval, we proposed an improvement to the read and write data transfer rates of Holographic Data Storage Systems (HDSS). Conventionally, reading and writing of data utilize only a fraction of the available light. Our techniques apply a resonator cavity to the readout and recording of holograms so that more of the available light is used. Functionally, more power is used than what is provided without violating energy conservation. Thus, data rates and/or capacities can be increased due to enhanced power. These improvements are also inversely related to the diffraction efficiency of a hologram, which makes these cavity enhanced techniques well suited to HDSS where large numbers of multiplexed holograms require low diffraction efficiencies.
Previously, we presented the theory of cavity enhanced HDSS, the experimental effect of enhancement on readout, and the lack of effects on Bragg Selectivity. We have now formalized the enhancement in writing power and experimentally evaluated the improvement in writing speed over conventional means for writing a single plane wave hologram in Fe:LiNbO3 with a 532 nm wavelength, CW, single mode, DPSS, Nd:YAG, laser with a cavity on one of the writing arms. The diffraction efficiency was read during the recording by using a 632.8 nm wavelength HeNe Laser. We found that the enhancement of recording power for this configuration asymptotically approaches a factor of two, while the use of cavities in both writing arms provides a power enhancement which is limited only by the losses in the cavities.
We formalize the theoretical effects of optical resonator enhancement on diffraction efficiency, read rate, and write rate
of plane wave holograms, with a view toward page based holographic data storage. Trade-offs in cavity enhancement are
also examined. Theory predicts ~160% of enhancement in diffraction efficiency is feasible when power loss of the
hologram is ~8% and diffraction efficiency is ~8%. We report experimental verification of ~30% enhancement of
diffraction efficiency for a hologram written in 0.03% Fe:LiNbO3 (Deltronic Crystal Industries, Inc.) with a 532 nm
wavelength, pulsed, DPSS, Nd-YAG, laser and read by a red He-Ne laser. The Bragg selectivity width under the cavityenhanced
readout is experimentally confirmed to be unaffected by cavity enhancement, and it agrees with theoretical