Demonstration of interference and phase-shifting using a single laser pointer

Abstract Optical interferometers play a vital role in metrology, enabling precise measurements of surface thickness, roughness, optical power, material homogeneity, and distances through interference phenomena. A key technique used is phase-shifting interferometry (PSI), which involves shifting the phase of one of the interfering beams to produce measurable patterns. Experimental demonstrations of interference and PSI are crucial for a comprehensive understanding of these optical concepts, but their implementation can be challenging due to the specialized materials and expertise required. To address this, we propose an accessible method using a commercial laser pointer, which generates interference via an internal diffraction grating. Mechanical compression at specific points of the pointer enables phase-shifts in the interference patterns, while rotating two internal gratings allows the visualization of Moiré fringes. This approach provides a straightforward and effective demonstration of PSI and optical interference, making these concepts more accessible. Designed for instructors as well as undergraduate and graduate students in physics and engineering, this method serves as a practical teaching tool that enhances the understanding of wave optics and phase-shifting techniques through both guided instruction and self-directed experimentation.