Electron beam lithography inscribed varied-line-spacing and uniform integrated reflective plane grating fabricated through line-by-line method

A varied-line-spacing (VLS) and uniform integrated reflective plane grating was inscribed by electron beam lithography (EBL) and reactive ion etching method, and its displacement sensing characteristics was tested. For the VLS grating, the groove density was varied from 868 to 442 L/mm over the device, according to the designed linear density function, and the device was coated with an aluminized surface to reflect light. For the uniform grating, the groove density was 655 L/mm. A Y-type twin-core fiber with a collimator head was used to input light from a broadband source and collect reflected light from the integrated grating for analysis by an optical spectrum analyzer. The inscribed integrated grating length and width were 50 × 10 mm, and the input light angle was fixed at 23°.The integrated grating displacement characteristics was varied, when the light spot was irradiated at VLS and uniform grating simultaneously, with the result that as the light spot moved to different grating positions, two peaks of diffracted light were collected. For 0–35 mm displacement changes in 5 mm increments, for the VLS grating, the diffracted light wavelength changed from 945.3 to 1612.2 nm with sensitivity of 18.68 nm/mm, and linearity of 0.975; for the uniform grating, the wavelength shift was less than 3.2 nm.