基于亚毫米尺度波导研究磁流体的窄带滤波特性

Research on narrow band filter of magnetic fluid based on optical waveguide with submillimeter scale

利用一种样品空间层达亚毫米尺度的双面金属波导,将磁流体注入波导样品空间层作为导波层来研究磁流体的窄带滤波特性。首先将波长为1 550nm的激光入射到波导表面,选择合适的入射光导模共振角,激发波导中的超高阶导模,使磁流体处于光波导的振荡场中;然后,应用超高阶导模的高灵敏度特点,将磁场施加在波导上改变磁流体的折射率,使波导耦合效率发生变化,通过接收波导反射光,得到波导的窄带滤波特性。实验中测试的入射光波长调谐在1 549.440～1 549.585nm,窄带滤波带宽为0.06nm。当波长为1 549.516nm,所加磁场为0～51.9kA/m时,获得反射光的变化达到11.9dB。实验结果表明,该方法获得的滤波特性具有带宽窄、灵敏度高的特点。

A type of ultrathick double metal cladding optical waveguide with a submillimeter scale was used to investigate the narrow bandwidth filter of magnetic fluid,in which the magnetic fluid were injected into the sample as a guided layer.While the 1 550 nm laser beam was incident on the waveguide with resonance angle,ultrahigh order modes would be excited;the magnetic fluid was in the oscillating field.Then based on ultrahigh order modes,the refractive index of magnetic fluid was changed owing to the strong concentration of the magnetic field.The characteristics of narrow bandwidth filter were obtained by detecting the reflected beam on waveguide.In the experiment,the wavelength of the incidence beam was to be form 1 549.440 nm to 1 549.585 nm,and the bandwidth filter to be 0.06 nm.Obtained results show that the change of reflected beam is 11.9 dB when the magnetic field changed from 0 to 51.9 kA/m in the wavelength of 1 549.516 nm.Experimental results indicate that the optical filter has narrow waveband and higher sensitivity.