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Properties of doped and natural impurities in Lithium Niobate single crystals are studied using the Whispering Gallery Mode method at low temperatures as a function of magnetic field. The study reveals considerable coupling of microwave photon modes to the Fe$^{3+}$ spin ensemble in iron-doped and non-doped crystals. The $S=5/2$ structure of the Fe$^{3+}$ impurities demonstrate Zero Field Splittings of $11.21$ and $20.96$ GHz, significant asymmetry of the Zeeman lines and additional lines with anomalous $\text{g}$-factors of $1.37$ and $3.95$. Also, interactions between different transitions of the Fe$^{3+}$ ion is observed. An additional ion impurity ensemble with a splitting of about $1.7$ GHz is shown to couple to the dominating Fe$^{3+}$ spins and the effect on $Q$-factors of microwave photon modes due to the Fe$^{3+}$ ion ensemble is also demonstrated. Measurements down to less than one photon level are made with a loss tangent of order $10^{-5}$ determined.

NAS 1.60:1144 Digitized from IA1177307-11-0050 .

Several samples of iron, copper, and magnesium doped lithium niobate were tested to determine their storage properties which would be applicable to an optical data storage system and an integrated optics data preprocessor which makes use of holographic storage techniques. The parameters of interest were the diffraction efficiency, write power, write time, erase time, erase energy, and write sensitivity. Results of these parameters are presented. It was found that iron doped lithium niobate samples yielded the best results in all parameters except for a few percent higher diffraction efficiency in copper doped samples. The magnesium doped samples were extremely insensitive and are not recommended for use in holographic optical data storage and processing systems.

I investigated the accuracy and precision of effective index of refraction measurements using prism coupling. I found that the coupling gap's geometry is critical to predicting the accuracy and resolution of measurements. I provide experimental evidence that there are advantages to using high coupling pressures that yield long coupling lengths. I present and evaluate an experimental technique aimed at reducing the effects of perturbation and find that it may not be applicable to all situations. I extend a previous model of prism coupling to include a finite coupling length. Also, I introduce an alternative model of prism coupling based upon a local normal-mode expansion and present its preliminary numerical results. I have observed more extraordinary polarized guide modes near cut-off in Ti in-diffused lithium niobate planar waveguides than are predicted by Ti in-diffusion models. I also observe these nearly cut-off modes in lithium niobate specimens fabricated without Ti under a variety of diffusion atmospheres. Values of the effective index of these nearly cut-off modes found do not agree with those calculated. jg