Multi-level (ML) recording technology increases the capacity of standard compact disc (CD) and digital versatile disc (DVD) rewritable systems with no change to the optical/mechanical unit. The feasibility of applying ternary run-length-limited (3L-RLL) modulation to recording/playback on standard CD/DVD phase change discs is discussed. The use of 3L-RLL modulation increases the recording density 50% relative to conventional binary RLL (2L-RLL) modulation currently used in CD and DVD systems.
We investigate transmission of a normally incident, linearly polarized plane wave through a circular sub-wavelength hole in a metal film filled by a high index dielectric medium. We demonstrate for the first time that the trans-mission efficiency of such holes exhibits a Fabry-Pérot like behaviour versus thickness of the metal film, similar to that exhibited by sub-wavelength slits in metal films illuminated by TM-polarized plane waves. We show that by reducing the imaginary part of the propagation constant of the hybrid HE11 mode and by fortifying the Fabry-Pérot resonance, the high index dielectric filling can greatly enhance light transmission through a circular sub-wavelength hole.
An extremely short external cavity that is realized when a Fabry-Perot laser diode is butt coupled to a waveguide or a fiber produces feedback that is effective for controlled wavelength tuning. We used butt coupling to tune a high-output-power laser diode over a wide range (as great as 15 nm) while maintaining constant driving current and temperature. Single-mode or multimode operation repeatedly occurred at specific points throughout the tuning range. An analytical model that includes the effect of multiple reflections from the external cavity, each attenuated by a modal overlap integral, and which is based on phenomenological principles, shows good agreement with the experimental results.
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