Mach-Zehnder type thermo-optic switch fabricated by proton beam writing

Ozawa, Yusuke*; Kubota, Hitoshi*; Miura, Kenta*; Hanaizumi, Osamu*; Noguchi, Katsuya*; Sato, Takahiro; Ishii, Yasuyuki; Koka, Masashi; Takano, Katsuyoshi*; Okubo, Takeru; Yamazaki, Akiyoshi; Kada, Wataru; Yokoyama, Akihito; Kamiya, Tomihiro

A Mach-Zehnder (MZ) type thermo-optic switch for a wavelength of 1.55 m was fabricated using Proton Beam Writing (PBW) in this study. The fabrication was carried out by the following processes: (1) a SiO under-cladding was deposited on a Si substrate, (2) a 10-m-thick PMMA film was spin coated onto the SiO layer as a core, (3) a MZ type waveguide with the width of 8 m was drawn on the PMMA film by PBW with the beam size of 1.1 m and current of 50 pA at 1.7 MeV, (4) a PMMA film was deposited again on the sample as an upper-cladding layer, and (5) a titanium heater as a phase shifter and aluminum electrodes were formed on the sample by vacuum evaporation with UV lithography and wet etching. In the operation test of this switch, the intensity of 1.55 m laser light through the switch was measured by a vidicon camera at the exit side along with varying the electric power for a titanium heater (the switching power). The intensity ratio of the output lights for ON/OFF of the heater was obtained as a function of the switching power. The result showed the fabricated switch worked as an MZ type thermo-optic switch with an ON/OFF ratio of 9.0 dB on a switching power of 43.9 mW.