Superposition Of Light Waves Research Articles

A Novel Method for Measurement of the Refractive Indices of Transparent Solid Media Using Laser Interferometry

The refractive index is a number that governs how light changes its direction of propagation as it enters one material medium from another. This phenomenon is known as refraction and the angles of incidence and refraction of light, referred to the normal to the interface of the two media at the point of incidence, are related by Snell’s law. The refractive index (RI) depends on the color (or wavelength λ) of light. Tables of values of refractive indices for various media and wavelengths of light, with respect to vacuum, are readily available. The refractive index of a material can be measured by many methods, for example, by using a spectrometer in conjunction with a prism made of the experimental substance. An important class of methods of measuring RI involves the formation of interference patterns. Interferometric measurements are concerned with the study of separation between bright fringes (or dark fringes) resulting from the superposition of light waves, originating from a single source and propagating along paths of different optical lengths (refractive index multiplied by geometric path length). Researchers have exploited (nearly) monochromatic light from laser sources to enhance precision in measuring refractive index by applying interferometric techniques.

Vibration insensitive THz wave interferometry for characterizing optical phase shifter

Optic interferometry is a well-known measurement technique with high precision attained through the optical interference caused by the superposition of lightwaves. However, with fiber-optic interferometry, the phases of the lightwaves are susceptible to interference via the fiber fluctuation that is unavoidably induced by the environmental vibration, which makes the measurement result unstable and limits the usage scenarios of the interferometric installation. In this paper, a fiber-optic THz wave interferometer aiming for vibration isolation is presented. Due to the longer wavelength of the THz wave, the influence of optical fiber fluctuation on the phase noise is considerably suppressed. For verifying the feasibility of the fiber-optic THz wave interferometer, it is used here to measure the optical phase shift at a fiber-pigtailed thermo-optic phase shifter. The experimental results show that, compared with an all-fiber interferometer, the fiber-optic THz interferometer enables accurate measurement of an optical phase shift as well as an improved signal-to-noise ratio of interference with 6dB gain.

Energy balance in the superposition of light waves with lossless beam splitters

The energy balance in the superposition of light waves with a lossless beam splitter is analyzed along with its connection with some general relations between the parameters describing beam-splitter effects on the two incoming waves. These general relations are derived either from the electromagnetic theory or from energy conservation considerations. The apparent paradox of a symmetric beam splitter producing complementary outputs is explained.