Junichiro Minowa

Estimation of direct current bias and drift of Ti:LiNbO3 optical modulators

The dc drift data of Ti:LiNbO3 optical modulators are well fitted to an exponential equation, describing the relaxation phenomena of the dielectric materials. The relaxation time and the saturation voltage ratio, which are necessary to estimate the dc bias follow‐up control, can be obtained from simple dc drift measurements.

Materials reliability for high-speed lithium niobate modulators

As demand for lithium niobate optical modulators for use in high-speed optical communication systems has increased, their device performance and reliability have been vigorously improved, and some devices have found practical applications in systems. However, there are few reports, yet, about the quality and reliability of the lithium niobate material itself, although such information is necessary for improving further the device reliability and the fabrication yield. Here is presented data concerning material reliability for z-cut lithium niobate wafers commercially supplied in Japan. A variation is detected sometimes in the device performance such as dc-drift and optical insertion loss, and it seems to be caused mainly by an unpredictable fluctuation in the performance of individual wafers.

Lifetime Estimation for Hermetically Packaged 10 Gb/sec LiNbO 3 Optical Modulators

A life expectancy of hermetically sealed 10 Gb/sec LiNbO3 optical modulators was obtained after aging them for 5000 hours at 85° C. After the test, no failure was found in the device parameters and the dc drift behavior. The lifetime was estimated to be over 20 years at ~50° C.

Ti:LiNbO3 waveguide polarizer with a Zn-doped overlayer prepared by liquid-phase epitaxy

Ti:LiNbO3 waveguide polarizers were obtained by an epitaxial growth of a Zn-doped LiNbO3 layer on the Ti:LiNbO3 waveguide. The film growth was carried out by a liquid-phase-epitaxy technique using a Li2O–V2O5 flux. Such an X-cut waveguide polarizer achieved a TE-mode (extraordinary ray) propagation with an extinction ratio over 30 dB at a light wavelength of 1.55 μm. This technique can be easily applied to Z- and Y-cut waveguide polarizers with TM- and TE-mode propagation, respectively.

Stabilized 20 GHz LiNbO 3 Polarization Scrambler

We developed a polarization scrambler with an embedded polarizer, angled at approximately 45° on the input side of the waveguide. The degree of polarization (DOP) of this scrambler is highly stable with the DOP less than 5% at 1558 ± 2 nm and less than 6% at approximately 10-40 °C. These scramblers are useful for long-haul communication systems and WDM systems.