Deer Yi

Broadband polarizing beam splitter based on the form birefringence of a subwavelength grating in the quasi-static domain

We propose a novel broadband polarizing beam splitter with a compact sandwich structure that has a subwavelength grating in the quasi-static domain as the filling. The design is based on effective-medium theory an anisotropic thin-film theory, and the performance is investigated with rigorous coupled-wave theory. The design results show that the structure can provide a high polarization extinction ratio in a broad spectral range.

Design of three-dimensional superresolution filters and limits of axial optical superresolution

Theories to design a three-dimensional superresolution filter (TDSF) for confocal microscopy are proposed that can obtain a globally optimal solution through linear programming. The designed TDSF is proved to be a phase-only element introducing a phase delay of 0 or pi. Five design examples of the TDSF are presented to demonstrate the validity of these theories, Regardless of transverse superresolution, a curve of Seu(Ga+/-) defined as the maximum value of Strehl ratio S under the axial resolving power of Ga+/- is calculated to set the fundamental limits of axial optical superresolution. Finally, what is to our knowledge a novel analytic expression of Seu(Ga+/-) is deduced.

Theories for the design of a hybrid refractive–diffractive superresolution lens with high numerical aperture

By geometrical optics and the Rayleigh-Sommerfeld diffraction formula, theories for the design of a hybrid refractive-diffractive superresolution lens (HRDSL) with high numerical aperture are constructed. Differences between the profile of the diffractive superresolution element (DSE) with high numerical aperture and that with low numerical aperture are indicated. Optimization theory can obtain a globally optimal solution through a linear programming much more simplified than the corresponding one in Liu et al. [J. Opt. Soc. Am. A 19, 2185 (2002)]. The rules of the structure of the designed DSE are both theoretically proved and numerically verified. Comparison of this optimization theory with the other design theories and examples of designing the HRDSL with high numerical aperture are provided. Last, some limits of optical superresolution with high numerical aperture are set and compared with those for low numerical aperture.

Semiconductor laser diode to single-mode fiber coupling using diffractive optical elements

Abstract An integrated mode converter consisting of two diffractive optical elements (DOEs) and a Silicon slab is presented for low-loss coupling between a semiconductor laser diode (LD) and a single-mode fiber (SMF). The phase structures of the DOEs are designed using iterative phase retrieval algorithm. We introduce a new far-field amplitude constraint into the iteration to provide very high mode conversion quality. Compared with previously published mode converters, the scheme is more universal because it’s applicable for any semiconductor LD. In simulation, coupling losses lower than 0.02 dB are predicted for all the discussed LDs with aspect ratios of the elliptical fields from 1 to 9. The requirements on axial displacement and rotation angle have been removed. The tolerance for 1-dB loss increment for lateral misalignment is 0.9 μm. And the coupling loss is insensitive to tilt angle.

Design of flat-field arrayed waveguide grating with three stigmatic points

A new-type flat-field arrayed waveguide grating (AWG), with the focal signals of all wavelengths of operation focusing along a straight line, has been designed. The work bases on the aberration theory of AWG, in which the restraints imposed on the conventional Rowland-type AWG have been released. In the design of flat-field AWG, three stigmatic points restrain three dominant geometry parameters: geometry of star couplers, ports distribution of phased-array, and length increment between adjacent paths. An eight-channel 200-GHz spacing flat-field AWG has been designed and simulated. As stigmatic points introduced, the aberration of this device is much lower than that of the Rowland-type AWG.

Integrated diffractive optical mode converter for fiber-to-waveguide coupling

Integrated diffractive optical mode converter, consisting of a diffractive optical element (DOE) and a slab waveguide, is used for fiber-to-waveguide coupling. The phase of the DOE is generally designed by optimization algorithm. In this paper, the precise design, a new method with one more restrictive way, is adopted to design the diffractive optical mode converter for fiber-to-waveguide coupling. Through this method, the intensity of any point on the output plane is fully filled with the required demand. Compared with what previously published, the coupling loss of the precise designed converter is lower.

Achromatic quarterwave-plate for visible spectrum region using the dispersion of form birefringence

Sub-wavelength gratings could function as polarization components, such as wave-plates and polarized beam splitters. Furthermore, gratings in resonate regime could act as achromatic wave-plate. Here, an achromatic quarter-wave plate of a submicrometer grating with sinusoidal profile is designed based on diffractive optics. Rigorous coupled wave theory (RCWT) was used to analyze the subwavelength grating made on photo-resist in ambient air. Design of a broadband form-birefringent phase retarder for 400nm to 800nm visible region is discussed. A sinusoidal sub-wavelength grating with good properties was designed. Its phase retard maintains at about 90° and maximum deviation is about 15%, which approaches normal binary waveplate.

Beam-shaping application in laser heat processing

Beam-shaping plays a very important role in the field of laser processing. Laser quench needs a rectangular speckle, which has a flat top, steep sides, high efficiency and low sidelobes. Diffractive phase elements (DPEs) have many superexcellent characters, which conventional optical elements have difficulties to achieve. Designing of the phase plane comes down to phase retrieval problem. Geometrical transformation and multiform iterative algorithms, such as G-S algorithm, Input-Output algorithm, ST algorithm are adopted. Through comparison of the results from different methods, some evaluations about algorithms are made. ST algorithm is the most feasible method for the problem, the result of which can meet the requirements of practical process. Some simulation experiments and discussions about algorithms have been done. To be fabricated as a binary optical element (BOE), the result of design has been quantified to 16 steps.

Shrinkage of spacing in fabricating sol-gel optical elements

Real-time effect was investigated with the binary masks and contact copy method in the processing of sol-gel hybrid material. The height of the real time relief increases slowly with the increase of exposure dose, but is no relation with the variation of the spatial frequency of the mask. Moreover, the height of the real-time relief is dependent on the thickness of the film deposited on the substrate. Compared with the mask, the spacing of the exposed areas in sol-gel film shrinks, and the shrinkage rate is about 10-20%. The possible reason causing the real- time effect is discussed.

Planar integrated optical disk pickup

Though DVD becomes more and more popular, there are still millions of CD-R disk in using. The ability of reading both DVD and CD-R disk is necessary in compatible disk drive. Traditional optical pickup consists of different bulk components, which result in high cost, high difficulty in assembly and low reliability. Integration is a way to overcome these troubles. Based on planar optics, an integrated digital versatile disk (DVD)/compact disk recordable (CD-R) compatible optical pickup has been developed. In this device, the beams of two wavelengths follow different zigzag optical paths inside a few-mm thick glass substrate, which is used as a light guide. It is demonstrated that a beam combiner, a polarized beam splitter, a Fresnel prism, and a beam separator were integrated around a glass substrate, and such a planar optical pickup exhibited an excellent performance with high efficiency. It confirms that planar optics is an effective way to realize compatibility of DVD/CD-R.