Abstract: A method and apparatus for forming an array of microcavities in the surface of a metal film uses an excimer laser or an ultrashort laser which to produce a beam of laser light pulses. An optical mask divides the beam into multiple beams and a lens system focuses the multiple beams onto the metal film. The device operates by generating multiple beams of laser pulses of a first diameter and then magnifying the pulses by a magnification factor less than 1 to produce multiple beams of pulses having a second diameter, less than the first diameter, which are applied to the metal film. The magnification factor and the intensity of the laser is such that the fluence of the laser on the optical mask is not sufficient to cause ablation while the fluence on the metal film is sufficient to cause ablation. A diffractive optical element may be used in the device in place of the optical mask. The apparatus includes a quarter wave plate that converts the beam of laser light pulses into a beam of circularly polarized pulses. The apparatus also includes a device that homogenizes the intensity of the laser light pulses before they are applied to the optical mask.

Abstract: A reflection and refraction optical system includes a polarization beam splitter, a concave mirror, a lens group and a quarter waveplate, wherein an additional waveplate is provided to transform S-polarized light from the polarization beam splitter into circularly polarized light.

Abstract: It is known that the differential group delay (DGD) due to polarization mode dispersion (PMD) can be effectively reduced by spinning the fiber during drawing. In this paper, we propose an analytical approach that allows optimization of the spinning design. The fundamental idea is that, in the absence of polarization coupling, an optimized spinning profile can balance the effects of the intrinsic linear birefringence so that the differential group delay can be forced to be periodic and, consequently, have a limited amplitude as a function of distance. Our approach Is independent of the spin profile. In other words, with a fixed set of parameters that characterize a particular spin function, we are able to find analytically the values corresponding to a periodic DGD in a deterministic regime. Numerical results based on waveplate model confirm the analytical prediction and show that PMD can be reduced by about two orders of magnitude with respect to the same fiber without spinning, even after the introduction of random polarization coupling.

Abstract: By a combination of quarter-wave plates made of different birefringent materials it is possible to produce achromatic quarter-wave plates whose degree of achromatism is dependant on the dispersions of birefringence and on the thicknesses of the individual quarter-wave plates. These waveplates are widely used in optical instrumentation and the residual errors associated with these devices can be very important in high resolution spectro-polarimetry measurements. The misalignment of optic axis in a double crystal waveplate is one of the main source of error and leads to elliptical eigenpolarization modes in the retarder and the oscillation of its orientation according to the wavelength. This paper will discuss, first, how the characteristics of a quartz-MgF2 quarter-wave plate is affected by such a misalignment. A correlation with the experiment is then achieved in order to highlight the interest of taking a possible tilt error into consideration when doing polarimetric measurements.

Abstract: A polarization mask for producing light of locally different polarization from unpolarized or uniformly polarized light. On the light output side, discrete areas with different polarization directions are present, which are either static or switchable. The mask is useful for, among other things, the transfer of polarization pattern onto a PPN layer.

Abstract: A spectroscopic ellipsometer having a multiwavelength light source, spectrometer (or wavelength-scanning monochromator and photodetector), a polarizer and polarization analyzer, and one or more objectives in the illumination and collection light paths, further comprises a stationary polarization modulator that modulates the light polarization versus wavelength. Modulator can be an optically active crystal rotating the linear polarization plane by a different angle for each wavelength or a non-achromatic waveplate retarder that varies the relative phase delay of the polarization components periodically over wavelength. The measured spectrum can be used to characterize selected features or parameters of a sample, e.g. by comparison with one or more theoretical spectra.

Abstract: A wavelength discretely tunable semiconductor laser that addresses wide wavelength tuning range, is mode hopping free, has high output power, has fast wavelength switching time, is wavelength locking free and is relatively simple. Four exemplary embodiments disclosed herein utilize a wavelength discretely tunable semiconductor laser that comprises a discretely tunable filter and laser amplifier. In the first embodiment, the tuning element comprises a pair of cascade Fabry-Perot filters, each having a plurality of characteristic narrow transmission passbands that pass only the cavity mode under the passband. The spacing between the narrow transmission passbands are slightly different in one filter from the other filter so that only one passband from each filter can be overlapped in any given condition over the entire active element gain spectral range, thereby permitting lasing only at a single cavity mode passed by the cascade double filters. One of the two etalon filters can be made with a plurality of transmission passbands predetermined by industry, application and international standards, making this element an intra-cavity wavelength reference and eliminating further wavelength locking needs for the tunable laser. In a second embodiment, one of the two etalons is replaced by a wedge filter. The filter optical path change and thus the transmission passband shift are achieved by translating the wedge filter in a direction perpendicular to the optical axis. In a third embodiment, one of the two etalon filters is replaced by a polarization interference filter. The polarization interference filter consists of an electro-optically-tunable birefringent waveplate, a fixed birefringent waveplate, the laser cavity and T.E. polarization light emitted from the laser diode. In a fourth embodiment, the laser and wavelength tuning structure are integrated on a semiconductor substrate by epitaxy processes.

Abstract: The present invention provides a broad band retardation plate that can be fabricated by a simple process and uniformly retards light incident of the entire visible light region. The retardation plate contains materials including positive or negative intrinsic double refraction values. When retardation values in wavelengths of 450 nm, 550 nm, and 650 nm are defined as Re(450), Re(550) and Re(650), respectively, the retardation plate satisfies the relational expression of Re(450)