Zhang J.,CAS Shanghai Institute of Optics and fine Mechanics
Optics Express | Year: 2015
Greek ladder is a technique for approximating n√C by rational numbers where n is a positive integer and C is a positive real number. For the classical Greek ladder, the value is √C. Based on the continued fraction theory and algebraic equation, the classical Greek ladder in a special case can be reduced to the generalized Fibonacci sequence. By means of proper switching and binary, ternary or quaternary phase modulation, here we have successfully designed the various kinds of nano-photonic devices to produce three-dimensional array foci whose focusing properties satisfy the above mathematical characteristics. With this technology, the diffractionlimited array foci are freely designed or distributed under the requirement at the desired multiple focal planes. © 2015 Optical Society of America.
Bi Q.,CAS Shanghai Institute of Optics and fine Mechanics
Optics express | Year: 2010
The application of rectangular-groove fused-silica gratings as polarizing beam splitters (PBSs) under Littrow incidence is investigated. Based on the simple modal method, two different cases of PBS gratings are designed. The achieved solutions, which are independent on the incident wavelength, are verified by the rigorous coupled-wave analysis and expressed in several polynomials instead of listing one or two numerical solutions. More importantly, on the basis of the designed PBS gratings, a porous fused silica antireflective film is introduced to improve their performances. Theoretical results indicate that such modified rectangular-groove PBS gratings exhibit higher diffraction efficiencies (over 0.99) and larger spectral bandwidths.
Sugioka K.,RIKEN |
Cheng Y.,CAS Shanghai Institute of Optics and fine Mechanics
Lab on a Chip - Miniaturisation for Chemistry and Biology | Year: 2012
Femtosecond laser direct writing is a promising technique for fabricating optofluidic devices since it can modify the interior of glass in a spatially selective manner through multiphoton absorption. The chemical properties of laser-irradiated regions in glass are modified allowing them to be selectively etched by subsequent wet etching using aqueous solutions of etchants such as hydrofluoric (HF) acid. This technique can be used to directly form three-dimensional microfluidic systems. The two-step process can also be used to fabricate free-space optical components such as micromirrors and microlenses inside glass. In addition, femtosecond laser direct writing can alter the optical properties of a substrate to create a wide range of micro-optical components inside glass, including optical waveguides, Mach-Zehnder interferometers, and optical attenuators. The unique ability of femtosecond laser direct writing to simultaneously alter the chemical and optical properties of glass opens up a new avenue for fabricating a variety of optofluidic microchips for biological analysis. Optofluidic microchips fabricated using femtosecond lasers have been used to determine the functions of living microorganisms, determine the concentrations of liquid samples, detect and manipulate single cells, and rapidly screen algae populations. This paper presents a comprehensive review of optofluidic devices for biological analysis fabricated by femtosecond laser processing. © 2012 The Royal Society of Chemistry.
Wei J.,CAS Shanghai Institute of Optics and fine Mechanics
Optics Communications | Year: 2013
Researchers have developed nonlinear super-resolution optical storage for the past twenty years. However, several concerns remain, including (1) the presence of readout threshold power; (2) the increase of threshold power with the reduction of the mark size, and (3) the increase of the carrier-to-noise ratio (CNR) at the initial stage and then decrease with the increase of readout laser power or laser irradiation time. The present work calculates and analyzes the super-resolution spot formed by the thin film masks and the readout threshold power characteristic according to the derived formula and based on the nonlinear saturable absorption characteristic and threshold of structural change. The obtained theoretical calculation and experimental data answer the concerns regarding the dynamic readout threshold characteristic and CNR dependence on laser power and irradiation time. The near-field optical spot scanning experiment further verifies the super-resolution spot formation produced through the nonlinear thin film masks. © 2012 Elsevier B.V.
Xu J.,CAS Shanghai Institute of Optics and fine Mechanics
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2011
We theoretically demonstrate the generation of a high-order harmonic and isolated attosecond pulse in an orthogonally polarized laser field, which is synthesized by an 800-nm chirped laser pulse and an 800-nm chirp-free laser pulse. Owing to the instantaneous frequency increasingly reducing close to the center of the driving pulse, the extreme ultraviolet supercontinuum for the chirped synthesized field is even broader than that for an orthogonal chirp-free two-color laser field. It is found that the broadband supercontinuum spectrum can be achieved for the driving pulse with ten and above optical cycles. After phase compensation an isolated attosecond pulse with a duration of ∼16 as is produced. Furthermore, the optimization of the chirping rate parameters is investigated to achieve cutoff extension and an isolated short attosecond pulse. © 2011 American Physical Society.