Optical-fiber polarizer is widely used in fields of optical-fiber laser, optical-fiber sensing and surveying. Traditional optical-fiber polarizers consist of the following types: polarimeter-type optical-fiber polarizer, Type D optical-fiber polarizer and pyrometric cone-type optical-fiber polarizer, etc. Thereinto, the polarimeter-type optical-fiber polarizer-involved optical components have more spatial structures and are not convenient for adjustment. The Type D optical-fiber polarizer, subject to very high requirements for optical fiber grinding precision and coating film, has very low yield. The pyrometric cone-type optical-fiber polarizer works to generate polarization effect by coning and molding optical fiber in high-temperature fusion state and generating anisotropic crystal, with the band width of 30nm or so generally.
Cheng Guanghua, Zhao Wei and Bai Jingzhen with XIOPM Laboratory for Transient Optics and Photon Technology, after deep research on technical problems in traditional optical-fiber polarizer, have invented a new-structure femtosecond laser photoetching optical-fiber polarizer: using femtosecond pulse laser to induce change of quartz optical fiber envelop refraction index, generating cyclic nm grid with polarizing light conduction characteristic around optical fiber core. In optical fiber core, the transmission light’s evanescent wave is modulated by surrounding nm stripes; scattering characteristics of the horizontal and vertical polarization components are different; the vibronic component vertical to the nm plane scatters very obviously, and the polarization state is highly scattered, while the polarization state parallel to the nm plane has very low loss, and finally reaches high extinction ratio (>20db) after transmission of certain length. As nm grid’s polarization scattering characteristics are insensitive to wave length, nm stripes have very high polarization extinction ratio for different wave lengths. The optical-fiber polarizer working without space optical structure and broadband can be realized by selecting laser’s polarization direction and setting reasonable nm grid length and interval.
The femtosecond pulse laser photoetching optical-fiber polarizer proposed by this invention uses laser to induce cyclic nm structure only in traditional quartz optical fiber envelop, without needing integration of other optical components and metal membrane, or saving complicated grinding and coating film process. Therefore, the polarizer features simple optical structure, no need of light path calibration and adjustment, low insertion loss, high working band width, single molding, high production efficiency and easy batch production, for which it was granted a national invention patent recently.
Download：