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We demonstrate reconfigurable microfluidic photonic crystal double-heterostructure cavities by local fluid infiltration of select air holes. Properties of the microfluidic cavities are experimentally studied by evanescent coupling and analyzed by numerical simulations.

It is demonstrated that the reciprocity theorem holds true for gratings at whose surface energy losses by absorption occur. Among the applications of this theorem, it is shown how the Littrow mounting is singled out from other grating mountings.

Theoretical counterparts are presented for the experimental efficiency curves obtained by Hutley and Bird in the visible region for a holographic grating covered consecutively with films of silver, aluminium and gold. It is thus shown that the recently developed formulation of Maystre, which takes into account the finite conductivity of the grating surface, gives results in quantitative agreement with experiment. This not only validates the theory, but also demonstrates that the difficulties associated with profile determination and oxide films, which have in the past led some experimenters to renounce the visible region and perform measurements on millimetre-wave gratings, are not in fact insuperable. It is also shown that only a theoretical model which takes into account groove depth effects can hope to predict accurately the locations of regions of enhanced energy absorption by gratings.

Values provided by three different theories of the diffraction by gratings are compared with measurements made at millimetre wavelengths. The results based on the integral equation method of Pavage...

The non-linearity of photoresists results in holographic diffraction gratings having groove profiles which are distorted relative to the exposure distribution. It is shown that by appropriate exploitation of this distortion, greatly enhanced spectral performances can be obtained.

The problem of determining the form of the triangular profile for a diffraction grating which gives high efficiency over the widest possible spectral region is investigated theoretically, for a large range of grating periods. It is shown that rectangular profiles are generally to be preferred to those having higher apex angles (as suggested by Stroke [2]). A theoretical demonstration is given of an experimental result concerning the wavelength shift due to polarization, and a new phenomenon linking efficiency maxima and Wood anomalies is described.

A general theory of the diffraction by gratings is applied to gratings with a sinusoidal profile (of interest since the advent of holographic techniques in grating production), and also to gratings...

Diffraction gratings having optimized sinusoidal groove profiles are shown to have blaze properties comparable with those of triangular profile gratings of the same line density.

A theoretical method is outlined for the calculation of the profiles of holographic diffraction gratings produced in photo-resist. This method is shown to give results in agreement with all experimental observations of such profiles. Consideration is then given to the flexibility of arrangements for the formation of holographic gratings and an experimental system is discussed which fully utilizes this flexibility. The wide range of profiles which may be generated with such a system is demonstrated. Finally a theoretical programme of investigation is suggested which may well make possible the formation of holographic gratings of greatly improved spectral performance.

In many practical situations, it is important to know the optical constants (n and k) of thin absorbing films over a wide wavelength range. Knowledge of these optical constants enables the calculation of the interaction of electromagnetic radiation with the films when incorporated into devices such as heat mirrors, selective photothermal absorbers and photovoltaic cells. Less well known is the use of these constants in sum rules, in order to deduce bonding and structural information about the films [1,2].

Quantitative three-dimensional studies of morphology together with analysis of validity of quasistatic effective medium theories show the need for a diffraction treatment of the optical properties of solar selective black chrome. The spectral absorptance A(λ) is calculated for a doubly periodic modulation of chrome overcoated with Cr2O3 or a cermet of Cr2O3 and Cr metal. Various profiles, depths and coating thicknesses are used. Diffraction caused by the surface morphology explains the major features of A(λ) for black chrome. Internal structure is of secondary importance.