Nulling interferometry without achromatic phase shifters

In the infrared wavelength region, a typical star is approximately a million times brighter than the planet that surrounds it, which is a major problem when we attempt to detect exoplanets in a direct manner. Nulling interferometry is a technique that one can use to solve this problem by attenuating the stellar light and enhancing that of the planet. Generally, deep nulling is achieved by use of achromatic phase shifters (APSs). Unfortunately, the technology needed to build these APSs is not yet fully developed. We show that deep nulling can also be achieved by using delay lines only. We investigate the nulling depth as a function of the width of the wavelength interval and the number of telescopes. We also show that we can obtain nulling depths of less than [10.sup.-6], which are required for exoplanet detection. Furthermore, we investigate the properties of the transmission map and make a comparison between our system and an APS system.