What
is Resonant Holography?
Resonant holography is a novel technique to maximize the optical
efficiency of photorefractive holograms, which has been invented
by our group and now being developed exclusively. Photorefractive
holograms have great potential for optical interconnects,
data storage and imaging applications due to the flexibility
of reconfiguring the optical input-output relationship. However,
the optical efficiency of photorefractive materials with reasonably
fast recording speed is typically only a few percent. Recently,
we demonstrated that the efficiency of photorefrative holograms
can be dramatically increased by sandwiching the hologram
inside a Fabry-Perot resonator as shown in Fig. 1. The resonator,
which consists of a partially reflecting mirror (PRM) and
a perfect mirror, is tuned to make every partial diffracted
wave interfere constructively with all other partial diffracted
waves. In this condition known as optical resonance, the efficiency
is limited only by the losses inside the cavity. We call this
technique resonant holography.
Figure
1 Principle of resonant holography
(a)
overall view (b) close-up of resonator
Figure 2 Experimental system
What
are we going to do with Resonant Holography?
So far, resonant holography has been proven in principle,
but for practical use in the prospective application areas
such as optical data communication, optical computing, precision
measurement, etc., many challenges have to be faced to meet
reliability and cost requirements. First, we need to develop
to appropriate design procedures for resonant holographic
devices, which are optimized in terms of optical efficiency,
bandwidth, switching time, etc. Second, we need to develop
a control system to make the resonant holographic system to
be stable enough against all disturbances from outside of
the system such as thermal shock, airflows, etc. An exemplar
control system is shown in Fig. 3.
Figure
3 Schematic of the closed-loop control system
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