QUANTUM REFLECTION - ATOMIC MATTER-WAVE OPTICS IN AN ATTRACTIVE EXPONENTIAL POTENTIAL

We show that an attractive potential created by an evanescent wave qua ntum mechanically reflects an atom with nonzero probability if the ato m's incident de Broglie wavelength is larger than the decay length of the evanescent wave. The amplitude reflection coefficient is calculate d by use of an analytical solution of the corresponding Schrodinger eq uation. We also discuss electromagnetic wave analog of the effect, the partial reflection of light at an exponentially increasing index. We interpret the quantum reflection in terms of a virtual turning point, by means of a complex stationary phase approximation. If the potential remains exponential until it becomes as deep as several hundred recoi l energies, the reflection coefficient for a low-energy de Broglie wav e is independent of the details of the potential far from the virtual turning point. This means that, if the evanescent wave is strong enoug h, interactions between the atom and the glass surface at which the ev anescent wave is created can be neglected. (C) 1996 Optical Society of America