A photonic integrated circuit comprises a silicon nitride waveguide, an electro-optic modulator formed of a III-nitride waveguide structure disposed on the silicon nitride waveguide, a dielectric cladding covering the silicon nitride waveguide and electro-optic modulator, and electrical contacts disposed on the dielectric cladding and arranged to apply an electric field to the electro-optic modulator.

An electro-optic device is described. The electro-optic device includes a thin film electro-optic layer including lithium and a lithium barrier structure. The thin film electro-optic layer has a plurality of surfaces. The lithium barrier structure covers at least a portion of the plurality of surfaces.

To provide a Tb-containing rare earth-aluminum garnet ceramic which has a Verdet constant similar to that of a TGG single crystal used in an isolator, has an insertion loss and extinction ratio equal to or greater than those of a TGG single crystal, generates less heat when a high-power laser is applied thereto, and is unlikely to cause a thermal lens effect or thermal birefringence. The present invention relates to: a Tb-containing rare earth-aluminum garnet ceramic including a garnet polycrystal represented by the compositional formula (Tb.sub.xRe.sub.1-x).sub.3(Al.sub.ySc.sub.1-y).sub.5O.sub.12 wherein Re is at least one element selected from a group consisting of Y and Lu, x=1.0-0.5, and y=1.0-0.6, and including Si and at least one element selected from a group consisting of Ca and Mg; a method for producing same; and an isolator device obtained using the ceramic.

Provided is a dielectric thin film deposited substrate which includes a single crystal substrate having a c-axis aligned in an in-plane direction and a dielectric thin film formed on and in contact with the single crystal substrate and in which the dielectric thin film is made of a lithium niobate film having a c-axis oriented in one in-plane direction. In the dielectric thin film deposited substrate, an angle formed between the c-axis direction of the single crystal substrate and the c-axis direction of the lithium niobate film is preferably 0.4 to 5.