KYOCERA develops temperature characteristics-free Etalon filter

JAPAN: Kyocera Corp. announced that its wholly owned subsidiary Kyocera Crystal Device Corp., in charge of development and manufacturing of crystal devices, has succeeded in developing a temperature characteristics-free etalon filter, a crystal device, which has applied the atomic diffusion bonding technique for the first time in the industry.

An etalon filter is a component which detects deviations in multiple light wavelengths in high-capacity optical communication transmissions systems. For this new product, Kyocera Crystal Device has realized a temperature characteristics-free etalon filter with high-accuracy, high-reliability and smaller size due to its success in developing a crystal device applying the atomic diffusion bonding technique. The product will be available on a sample basis starting January 2013.

The new product has achieved an industry-leading level of temperature characteristics of ±0.15pm/°C. This was achieved by applying a design technique combining positive temperature characteristic crystals with negative temperature characteristic crystals and an advanced crystal processing technique, along with industry's first application of the atomic diffusion bonding technique.

Furthermore, since the temperature characteristics-free etalon filter does not require a Peltier device for temperature adjustment, it can contribute to downsizing and energy conservation in tunable laser modules.

The atomic diffusion bonding technique is a direct bonding technique developed by Tohoku University's Prof. Takehito Shimatsu. It entails bonding the wafer and substrate together without applying heat, pressure or voltage, nor using organic adhesives. Through the joint-development with Prof. Shimatsu's research group, Kyocera Crystal Device has succeeded in bonding a crystal wafer in an extremely thin metal film thickness of several atomic layers to several dozen nanometers with high strength by applying the atomic diffusion bonding technique for crystal devices.

This method has solved the problems of optical contact, a conventional bonding method with lower bonding strength, and that of bonding using organic adhesive, for which the management of bonding thickness is difficult. It has also improved accuracy and reliability while reducing the size of the etalon filter.