用157 nm激光制作的光子晶体光纤法布里-珀罗传感器

157nm准分子激光用于微加工具有单光子能量高,峰值功率高,材料吸收系数高,分辨率高等优点。利用157nm激光微加工的方法,在光子晶体光纤上融切出微小矩形孔,从而构成腔长为45.6μm的微光纤法布里-珀罗干涉腔,得到的干涉条纹平滑,衬比度约为26dB,并从激光与石英材料的相互作用上分析了形成较好干涉条纹的原因。把这种微腔应用于应变测量,在550μm范围内,腔长增量相对于应变的灵敏度为0.32nm/μm,线形度达0.9994。实验证明该微腔对温度不敏感,800℃范围内腔长变化仅20nm。157nm准分子激光加工光纤法布里-珀罗腔方法简单,一次成型,具有较高的加工效率和精度,有望实现光纤法布里-珀罗腔的规模化批量制造,具有较好的应用前景。

Photonic Crystal Fiber Based Fabry-Perot Sensor Fabricated by Using 157 nm Laser Micromachining

A micro rectangle hole is ablated in a photonic crystal fiber by using 157 nm excimer laser pulses to form a fiber Fabry-Pérot cavity (PCF F-P), because the 157 nm excimer laser used in micromachining has high single-photon energy, high peak power, high absorption coefficient and high resolution. The PCF F-P cavity with a length of ～45.6 μm has obtained a smooth interference fringe and an excellent fringe visibility of ～26 dB. An explanation for the formation of such a high quality cavity is presented based on the interaction mechanism between the laser and silica material. This PCF F-P is used for measurement of strain and a sensitivity of 0.32 nm/μm and a linearity of 0.9994 within a range of 550 μm are obtained. Furthermore, it is verified that the PCF F-P sensor is insensitive to temperature change as the cavity length only changes 20 nm for a temperature range of 800 ℃. Such a fiber Fabry-Pérot cavity is fabricated easily and formed straightforwardly with high efficiency and precision, leading to the possibility of mass production of high-quality PCF F-P cavities then extensive applications.