Effect of Annealing
For a doubly doped lithium niobate (LiNbO3) crystal there exists an optimum oxidation/reduction state for desired performance. This optimum depends on the doping levels of shallow and deep traps as well as the annealing conditions for the crystal samples. This optimum state generally occurs when 95 – 98% of the deep traps are filled. In a strongly oxidized sample holograms cannot be easily recorded and the diffraction efficiency is very low. This is because the shallow trap is completely empty and the deep trap is also almost devoid of electrons. In a highly reduced sample on the other hand, the deep traps are completely filled and the shallow traps are also partially filled. This results in very good sensitivity (fast recording) and high diffraction efficiency due to the availability of electrons in the shallow traps. However during readout, all the deep traps get filled quickly and the resulting holograms reside in the shallow traps where they are totally erased by further readout. Hence after extensive readout the diffraction efficiency drops to zero and the hologram stored cannot be fixed.
Read more about this topic: Holographic Data Storage
Famous quotes containing the words effect of and/or effect:
“The cities of the world are concentric, isomorphic, synchronic. Only one exists and you are always in the same one. It’s the effect of their permanent revolution, their intense circulation, their instantaneous magnetism.”
—Jean Baudrillard (b. 1929)
“Airplanes are invariably scheduled to depart at such times as 7:54, 9:21 or 11:37. This extreme specificity has the effect on the novice of instilling in him the twin beliefs that he will be arriving at 10:08, 1:43 or 4:22, and that he should get to the airport on time. These beliefs are not only erroneous but actually unhealthy.”
—Fran Lebowitz (b. 1950)