Note: Measuring grating periods by diffraction method with a fore-end light path comprising fused fiber couplers and fiber port collimators

Abstract

Based on the Littrow and Littman configurations for autocollimation, two methods are proposed herein with a fore-end light path comprising fused fiber couplers and fiber port collimators to measure the diffraction grating period. The experimental data from a uniform-line-spacing grating with a nominal value of 1200 lines/mm agreed well with theoretical values and with measurement errors of the Littrow and the Littman configurations of 1.05 × 10 and 4.99 × 10, respectively. Both methods were demonstrated to reduce the diameter of the laser spot and improve the alignment precision of the measurement system.

Multi-parameter identification of gratings measurement by Experimental Ray Tracing

“…Furthermore, it is necessary to place a grating sample exactly at the center of a rotating stage, or an off-center inducing error occurs for measurement. A few methods for correcting the error is given by data processing (Hiroyuki & Tomohiro 2014;Hu et al 2004) or by improved setups (Wang et al 2015;Sheng et al 2017Sheng et al , 2018. Capability of conventional methods on measuring non-planar gratings or VLS (Varied Line Space) gratings is restricted.…”