Spectral and Angular Dependences of the Efficiency of Three-Layer Relief-Phase Diffraction Elements of the IR Range

Within the framework of the scalar and rigorous diffraction theory based on solving a system of Maxwell equations, saw-tooth relief-phase three-layer microstructures designed for the work with polychromatic radiation of the mid-IR range (3 ≤ λ ≤ 5 μm) are studied. The series of effective microstructures composed of different optical materials is extended, and the depths of their reliefs are minimized. The series is extended, in particular, owing to microstructures in which Fresnel losses for reflection from both reliefs do not exceed 10%. This factor, in combination with the relatively low total relief depth, can turn out to be decisive when choosing one or another microstructure for solving a specific scientific or technological problem.     

Harmonic Kinoform Lens: Diffraction Efficiency and Chromatism

Sawtooth microstructures with a relief depth significantly exceeding the central wavelength of the working spectral range are studied within the scalar and strict diffraction theories. The possibility of maintaining high diffraction efficiency, irrespective of the working spectral bandwidth and at allowed angles of incidence, which can reach 45° or more, is shown. It is also shown that the chromatism of such lenses is controlled in a very wide range and can be less than that of the lightest crown glasses.     

Minimization of the Total Depth of Internal Saw-Tooth Reliefs of a Two-Layer Relief-Phase Diffraction Microstructure

Results of studying the possibility to decrease the total depth of reliefs of a two-layer microstructure having two internal saw-tooth microreliefs reducing the dependence of the diffraction efficiency of the microstructure on the radiation wavelength and angle of radiation incidence on the microstructure are presented. These results allow one to minimize the complexity of obtaining optimum microrelief depths depending on requirements applicable to the diffraction optical element in the framework of the electromagnetic-diffraction theory. Optimum depths provide in the specified spectral range and interval of angles of radiation incidence the maximum possible (for the chosen width of the narrowest zone of the saw-tooth microrelief) value of the diffraction efficiency at the point of its minimum.     

Anomalous reflection of light in novel distributed-feedback structures

The possibility that lasing can occur in a rippled waveguide structure containing a high-reflectivity layer is studied. Lasing is achieved experimentally in a waveguide structure with an active buffer layer. Different mechanisms of distributed feedback in the structure are examined. Pis’ma Zh. éksp. Teor. Fiz. 65, No. 4, 301–305 (25 February 1997)     

Novel waveguide design for high brightness optoelectronic applications

We describe a novel compound ridge waveguide in which the highest order propagating mode is guided in the low index region of the structure and exhibits a narrow single lobe. For a prototype AlGaAs/GaAs was waveguide designed for operation at = 980 nm we show that due to the narrow lobed emission this mode produces significant improvements in source brightness and hence fibre coupling efficiency. In the case of a 61 m aperture laser diode operating in this mode 20% coupling efficiency is predicted between a structure and standard single mode fibre designed for = 980 nm operation.