ABSTRACT
We report on a light-dispersing device consisting of two transmission gratings and a waveplate. The gratings separate two orthogonal polarization components of light incident at the Bragg angle. The waveplate, which is sandwiched between the gratings, functions as a polarization converter for oblique light incidence. With these optical parts suitably integrated, the resulting device efficiently diffracts unpolarized light with high spectral resolution. Using coupled-wave theories and Mueller matrix analysis, we constructed a device for a wavelength range of 680±50 nm with a 400 nm grating period. From the characterization of this optical device, we validated the proposed polarization-independent, light-dispersing concept.
ABSTRACT
We describe a laser soldering technology with diffractive optics. This technology provides efficient one-step laser illumination for components to be soldered. A phase-only computer-generated hologram set in a variable-focal-length optical configuration generates a diffraction pattern with the dimensions required for processing solder. We verified the effectiveness of the proposed scheme by sealing a ceramic package such that it could house a quartz device. The factors for successful soldering include alignment of the diffraction pattern to the work piece, the thermal properties of the materials involved, and the wavelength of the laser used to process the solder. The beam intensity across the diffraction pattern influences the process, and the 0th-order intensity should be minimized to prevent damage to the work piece.
ABSTRACT
Random-phase distributions that are statistically independent individually are used for computing kinoforms. These uncorrelated kinoforms are recorded and read out sequentially by a phase-only liquid-crystal spatial light modulator, and reconstructed images with well-developed speckles are added. The fidelity of the resultant image to an original is improved as the number of additions increases. The dependence of the speckle contrast on the initial random phase and the influence of the liquid-crystal spatial light modulator's display performance on the image quality are discussed.
ABSTRACT
We report on complete wave-front control with amplitude- and phase-modulation liquid-crystal devices (LCD's). A twisted nematic device is used for amplitude modulation, and an electrically controlled birefringent device is used for phase modulation. Because the LCD's are optically coupled with afocal optics and are driven by individual LCD driver circuits, the amplitude and the phase can be controlled two dimensionally and independently. Complex amplitude data are calculated, and on-axis computergenerated holograms are directly recorded. Furthermore, we discuss LCD performance requirements for high-quality reconstruction.
ABSTRACT
A programmable kinoform using an electrically controlled birefringent liquid-crystal spatial modulator (ECB-LCSLM) is discussed. The LCSLM is capable of continuous phase modulation from 0 to 2piFor the kinoform generation, the phase distribution is calculated by iterative methods and recorded on the LCSLM with 16 quantizing levels. We discuss the characteristics and the structure of the LCSLM for the implementation of the programmable kinoform while comparing the computed results and optical reconstructions.
