Femtosecond-Laser Micromachining of a Thermal Blocking Trench for an Enhanced PLC Variable Optical Attenuator

In this paper, a trench structure was fabricated by femtosecond-laser machining to eliminate thermal crosstalk in a multichannel variable optical attenuator (VOA), to prevent decreasing attenuation efficiency of the VOA. Trenches of a variety of widths and depths were fabricated on the VOA chips by femtosecond-laser processing. After the machining, attenuation according to current change was observed in each VOA chip module with trenches. As a result, we could observe high responsivity of attenuation and low power consumption, and that the heat of each channel barely influenced other channels.