Method of producing gas sensor element

A method of producing a gas sensor element, the gas sensor element including a solid electrolyte layer capable of conducting specific ions in a measurement gas, a first electrode provided to a first main surface of the solid electrolyte layer that is a measurement gas introduction-side surface, a second electrode provided to a second main surface of the solid electrolyte layer that is a surface facing away from the first main surface, a heater provided to be closer to the second main surface than to the first main surface for raising temperature of the solid electrolyte layer, and a diffusion resistance layer permitting the measurement gas to permeate therethrough and disposed in an introduction path through which the measurement gas is introduced to the first main surface where the first electrode is provided, the gas sensor element being capable of detecting a concentration of the specific ions in the measurement gas based on a limiting current passing between the first electrode and the second electrode according to a concentration difference of the specific ions, the method comprising:

• a temperature raising step of energizing the heater to raise the temperature of the solid electrolyte layer;
• a current measuring step of applying a voltage across the first electrode and the second electrode to measure the limiting current;
• and
• a control step of removing a part of the diffusion resistance layer from the gas sensor element by using an ultrashort pulsed laser to control a diffusion length that is a length of the introduction path to maintain the limiting current to be within a predetermined range,
• wherein in the control step, the ultrashort pulsed laser reduces an output as the limiting current increases.