Electro-optic constants of single-mode proton-exchanged slab waveguiding layers fabricated on z-cut LiNbO3 crystals are estimated, taking into account the field distribution of the propagating TM0 mode.

Bistable operation in inhomogeneously excited semiconductor lasers is discussed theoretically considering gain dispersion effects. The results indicate a significant dependence of bistable properties on lasing wavelength when the wavelength is fixed by some selection mechanisms such as distributed feedback structures.

Switching characteristics of bistable distributed feedback lasers are analyzed theoretically. The results predict that switch-on speed as well as switch-off speed is improved by a factor of two or more by detuning the Bragg wavelength to shorter wavelength from the wavelength at which the gain is the maximum. This improvement is mainly due to enhancement of the differential gain through the detuning effect.

Optical pulse compression by using optical fiber and either conventional Gires-Tournois interferometer or modified one, instead of the grating pair is analysed. The separation of adjacent two pulses by such separation system is also proposed and analysed for the first time.

A new type of passive TE/TM mode splitter device using the ion-exchanged LiNbO3 waveguide is proposed and demonstrated. The characteristics of this device is estimated by the Beam Propagation Method based on a simple model. The extinction ratio is predicted to amount to 40 dB in the optimal case. This device is experimentally demonstrated in the X-junction configuration by using the Ag+-exchanged waveguide an Ti-indiffused one, and the extinction ratio is measured to be 10.5 dB, while the calculated value is 15 dB.

A new method of the information reduction of the three-dimensional image is proposed and experimentally verified. This method, the optically sectionned holography, is based on the principle of the coincidence of the time of arrival of the object and the reference beam in the holography. The resolution in depth is analyzed by taking into account the phantom imaging of the optical sectioned holography. The result gives the information content of the obtained hologram. The resulted information content is in the same order to that of the monocular three-dimensional image. So, this system can reduce the fairly amount of the information, comparing to the Burckhard's sampled holography. The system for the optically sectioned hologram by using the mode-locked, and the second harmonic generating c. w. Nd: Y AG laser is experimentally realized, and the optically sectioned holograms are obtained. From these holograms, the three-dimensional image of the original object is restored. A c. w. dye-laser is also used to obtain the optically sectioned hologram. The resulted resolution in depth is about 5 mm, which corresponds to the pulse width of the Nd: Y AG laser.

A new acousto-optic tunable filter utilizing collinear acousto-optic interaction along the direction near to the optic axis is proposed and demonstrated by using LiNbO3 crystal. This near axis interaction lowers the driving frequency and also expands the angular aperture in the ordinary plane. The acousto-optic figure of merit M2 (p2/ρv3) of this filter is 7.510-18 sec3/g and tuning from 700 nm to 420 nm can be obtained by changing the acoustic frequency from 56 MHz to 119 MHz. At 514.5 nm the filter bandwidth of 1.1 nm and the angular aperture of about 6 in the ordinary plane have been obtained.

The effect of annealing on the electrooptic constant r33 in the proton-exchanged optical waveguides on three types of lithium niobate crystals: undoped, titanium-indiffused and MgO-doped, are investigated. The exact estimation shows that the deterioration of electrooptic constant is recovered by annealing; the best in undoped, then titanium-indiffused and the worst, MgO-doped.

A brief overview is done to the development of the fiber-optic technology. These recent topics, not the commonly established techniques, are described connecting with the developments of the basic concepts and the expected applications. Some of these newly introduced ideas will become the seeds for the future development of the fiber-optic technology. These seeds include the very deep understanding of the fiber material, new concepts for the fiber characteristics, the brandnew fiber-optic devices and the fiber-optic systems and the applications.

The optical damage in proton-exchanged and Ti-indiffused LiNbO3 optical waveguide are first quantitatively measured by photorefractive (photoinduced) grating method. The measured optical damage in the proton-exchanged waveguide is found to be 10-4 times as small as that in Ti-indiffused waveguide.

The crosstalk and the distortion of the optical pulse due to the random polarization coupling is calculated for the birefringent optical fiber from the random mechanical bending and twist, by using the generalized expression of the coupling coefficients. A long-tailed" crosstalk pulse is found to appear as a result of the random polarization coupling. The improvement of the polarization instability from the random deformation by increasing the birefringence is discussed.

The proton-exchanged waveguide formed on MgO-doped lithium niobate crystals is resistant to the optical damage or the photorefractive effect. Therefore, this waveguide is believed to be a promising device for optical information and processing. However, the optical damage can also be an important problem for this waveguide in the communication wavelength since the high-power optical source is used. In this report, a brief general review on the optical properties and its practical application of the lithium niobate crystal as the optical waveguide are given. Then the experimental research work aimed to clarify the properties and its mechanism of the electrooptic effect and the optical damage or photorefractivity of the lithium niobate optical waveguide is described. In this work, the optical damage in this proton-exchanged waveguide is measured quantitatively at various optical wavelengths including blue and red light by using the holographic grating method and the infrared communication wavelength (1550 nm) by using the prism coupler method. The optical damage is significant not only in blue wavelength but also in the red, and even at 1550 nm with high power (100 mW) laser diode for communication. So the optical damage cannot be negligible also in the communication wavelengths. The effect of annealing temperature is also discussed. At the relatively high temperatures, the optical damages are founde to be annealed out. The effect of the applied electric field to the optical damage is experimentally discussed and its enhancement is observed to the applied d.c. and a.c. fields. In conclusion, the optical properties as the electrooptic constant and the optical damage are experimentally measured and the many fundamental data are obtained to realize the useful and practical optical devices.