Monitoring Thermal Effect in Femtosecond Laser Interaction With Glass by Fiber Bragg Grating

Measurement of the local temperature in transparent materials irradiated by femtosecond laser pulses is important for deep insight into light-matter interaction physics and for proper laser micronanomachining, which is, however, technically challenging. We solve the problem in this paper by using a femtosecond laser-written fiber Bragg grating that can stably work up to 1000°C as a high-sensitivity temperature sensor to monitor the thermal effect. The peak temperature of the thermal impulse is estimated as around 4800°C, which decays to around 500°C in the pulse interval for irradiation of 1.1 mJ under repetition rate of 1 kHz under 40 mm lens focusing.