Abstract: An asymmetric feedback structure in a ring laser produces essentially unidirectional lasing. The structure can be dynamic to permit directional control, or can be passive to provide unidirectional lasing in a predetermined direction. Dynamic control is obtained by a dielectric stack in the laser cavity, the stack including multiple layers having complex impedances for reflecting incident light. The amount and direction of reflection is controlled by varying the refractive indices or the absorption coefficients of the materials in the layers to produce cross-coupling for one direction which is different from the other direction. Passive control is obtained by introducing an asymmetry into the propagation path of the laser. This may be in the form of an optical diode structure or a tapered waveguide structure to produce asymmetric cross-coupling of counter-propagating modes of the laser light.

Abstract: Disclosed are multi-layer thin-film devices having adjacent insulator-semiconductor layers employing n-or-p-type semiconductors wherein a charge maintained at the insulator-semiconductor interface creates a depletion region that substantially suppresses tunneling of majority carriers while enhancing tunneling of minority carriers. When employed in a metal-insulator semiconductor (MIS) device wherein the semiconductor is a compound such as gallium arsenide (GaAs) or Cadmium Sulfide (CdS) such minority carrier injection substantially increases the luminescence efficiency.

Abstract: Disclosed are multi-layer thin-film devices having adjacent insulator-semiconductor layers employing n-or-p-type semiconductors wherein a charge maintained at the insulator-semiconductor interface creates a depletion region that substantially suppresses tunneling of majority carriers while enhancing tunneling of minority carriers. When employed in a metal-insulator semiconductor (MIS) device wherein the semiconductor is a compound such as gallium arsenide (GaAs) or Cadmium Sulfide (CdS), such minority carrier injection substantially increases the luminescence efficiency.

Abstract: A method of making optical gratings by the use of a Scanning Electron Microscope wherein (1) a substrate having a thin film of electron resist thereon is exposed in adjacent areas by an electron dosage and the amount of such dosage and the depth of the thin film are selected such that energy deposition in regions between adjacent exposed areas in said electron resist is below the threshold sensitivity of said resist for development, (2) the development time of the resist is made an inverse function of the electron dosage, and/or (3) the period of the grating is controlled by use of a standard scanning format.