Transverse-mode selective resonant grating-mirrors for high power and high brightness emission.

The finite angular spectral width of a 2D resonant grating mirror is adjusted to select the fundamental transverse mode of a laser and to filter out higher order modes. The selection principle is explained phenomenologically on a simplified 1D model. The 2D design is made so as to sustain the large field concentration in the grating slab-waveguide mirror, and the technology permitting to obtain the resonant reflection within the gain bandwidth of two types of laser is described. The blank experimental measurements by means of a white light supercontinuum are shown to match the targeted specifications on the resonance spectral position and angular width.

Strong three-dimensional field localization and enhancement on deep sinusoidal gratings with two-dimensional periodicity.

The study of total light absorption due to excitation of localized surface plasmons on deep metallic crossed gratings having a sinusoidal profile with a two-dimensional periodicity shows a very strong increase in the electric field intensity, reaching 800 times the incident intensity. The region with high intensity is strongly localized at the groove top and is characterized by a volume much smaller than the diffraction limit, both in transverse direction along the grating plane, and in longitudinal direction when going away from the grating surface. The field enhancement and its localization are much more pronounced than in shallow gratings.

High efficiency, high selectivity ultra-thin resonant diffractive elements.

Resonant diffractive elements as the association of a surface corrugation with a surface wave exhibit boosted diffraction efficiency and high selectivity properties under the effect of ultra-shallow subwavelength surface reliefs. This is demonstrated by four examples of resonant functional structures made of very different material systems over the optical spectrum. All four structures are fabricated by slow wet etching as the inherent lateral broadening in corrugations of very small aspect ratio can be neglected.

Azimuthally polarized laser mode generation by multilayer mirror with wideband grating-induced TM leakage in the TE stopband.

A new intracavity laser polarization-mode selection scheme relying upon a TE/TM diffractive dichroism principle in a grating multilayer mirror is proposed and demonstrated. The grating diffracts the first orders between the TE and TM band edges of the angular spectra of the laser mirror inducing a leakage of the TM polarization into the mirror substrate through the multilayer stack whereas TE diffraction into the substrate is forbidden. This mechanism is non-resonant, thus relatively wide-band. Applied with a circular-line grating in the 1.0 µm - 1.1 µm wavelength range, this mirror filters out the radially polarization mode and causes the emission of the azimuthally polarized mode. An original amorphous silicon grating technology was developed and the optical function demonstrated in a Nd:YAG laser.

100 nm period grating by high-index phase-mask immersion lithography.

The interferogram of a high index phase mask of 200 nm period under normal incidence of a collimated beam at 244 nm wavelength with substantially suppressed zeroth order produces a 100 nm period grating in a resist film under immersion. The paper describes the phase mask design, its fabrication, the effect of electron-beam lithographic stitching errors and optical assessment of the fabricated sub-cutoff grating.

Integrated microinterferometric sensor for in-plane displacement measurement.

We present an integrated sensor based on a grating interferometer (GI) for in-plane displacement measurement in microregions of large engineering structures. The system concept and design, based on a monolithic version of Czarnek's GI, is discussed in detail. The technology chain of the GI measurement head (MH), including the master fabrication and further replication by means of hot embossing, is described. The numerical analyses of the MH by means of geometric ray tracing and scalar wave propagation are provided. They allow us to determine geometrical tolerance values as well as refractive index homogeneity and nonflatness of MH working surfaces, which provide proper beam guiding. Finally the demonstrative measurement performed with a model of the sensor is presented.

Narrow band resonant grating of 100% reflection under normal incidence.

A resonant grating mirror comprising a multilayer submirror and a grating slab waveguide submirror exhibiting constructive mutual reflection is shown experimentally to provide zero transmission. Its reflection line width of less than 1 nm, its polarization selectivity and low overall loss make the device usable as a longitudinal mode filter in a disk laser in the 1000-1100 nm wavelength range.

Spectral phase induced by the reflection on a mirror-based waveguide grating in the neighborhood of modal resonance.

A linearly polarized plane wave impinging on a mirror-based waveguide grating is shown to experience a 2pi phase shift of controllable slope in the reflection spectrum. Such a zeroth-order resonant grating effect is adequately confirmed by means of an ellipsometer. The close agreement between the analytical representation of grating coupled waveguide resonances with the experimental results confirms the relevance of the underlying phenomenological understanding of resonant gratings.