Two-dimensional stretchable blazed wavelength-tunable grating based on PDMS.

This paper reports a two-dimensional stretchable blazed wavelength-tunable grating based on polydimethylsiloxane (PDMS). In the elastic range, stretch the grating along (-axis) and perpendicular to (-axis) the grating line, fix the position of the +1st-order spot to maintain the grating period, and only change the groove angle to tune the blazed wavelength. By stretching the grating up to 20% of the -axis, and 5.

Low-stray-light concave holographic gratings processed by combining the methods of photoresist hot-melting and oxygen-ion ashing.

The principal motivation for this paper is to reduce stray light and line roughness in concave holographic gratings (CHG). Compared with other previously reported line-smoothing grating techniques such as dynamic-exposure near-field holography, we successfully improve the line smoothing of CHG to approximately 10 nm from 2 nm. Our method uses optimization technologies and a combination of photoresist hot-melting (PHM) and oxygen-ion ashing (OIA), thereby improving the degree of stray light before and after optimization by one order of magnitude; the level processed by OIA, PHM, and OIA successively is ${7.

Analytical design of a high-performing +1st order diffraction convex grating imaging spectrometer.

A novel concentric spectrometer having one convex grating and one concave mirror, working at ${+}{1}$+1st order diffraction, and with a small size, high resolution, and high diffraction efficiency, is proposed. It can simultaneously achieve high resolution and compactness by increasing the grating groove density. A compact spectrometer operating at a wavelength of 740-790 nm with an excellent imaging quality is designed.

Highly Sensitive Graphene/Polydimethylsiloxane Composite Films near the Threshold Concentration with Biaxial Stretching.

Uniformly dispersed graphene effectively improves the strain-sensing capability of the composite film under a low graphene load in nanocomposites prepared with polydimethylsiloxane (PDMS) and graphene (GNP) monolayer powder. The threshold concentration of graphene was determined by loading nanocomposites at different temperatures. For different concentrations, when using traditional uniaxial stretching, the rate of resistance change of films near the threshold concentration is five times higher than the rate of films with a high concentration.

Optimized multielement accommodative intraocular lens with a four-freeform-surface Alvarez lens and a separate aspheric lens.

This paper proposes an accommodative intraocular lens (IOL), which consists of a two-element Alvarez lens and an aspheric lens for changing focal power and refractive power, respectively. The four-freeform-surface Alvarez lens is optimized for a multiple field of view; further, the aspheric lens also corrects the aberrations induced by the corneal asphericity of the human eye over the whole range of accommodation. A simulation using optical design software demonstrates its excellent performance in that the values of the modulation transfer function at 100 cycles/mm all reach ∼0.

Multifacet echelle grating for intensity broadening on spectral plane fabricated by rotating ion-beam etching.

This paper describes a new type of multifacet echelle grating (MFEG) for use in an echelle spectrometer. This new type of echelle grating broadens the spectral distribution on the spectral plane. We built a geometric model of MFEG to analyze the influence of the blaze angle and number of facet shapes on the spectral evolution.

Flexible and Optical Fiber Sensors Composited by Graphene and PDMS for Motion Detection.

A stretchable optical sensor can quantify the strain generated by human movement, which has been widely studied in the development of health monitoring systems, human-machine interfaces and wearable devices. This paper reports a graphene-added polydimethylsiloxane (PDMS) fiber, which has high tensile properties and good light transmittance suitable for detecting human movement. When the graphene-added PDMS fiber is stretched, the concentration of graphene per unit volume is constant, and the sensor uses the optical loss of the beam through the graphene PDMS fiber to detect the tensile strain.

[The research of UV-responsive sensitivity enhancement of fluorescent coating films by MgF2 layer].

A low cost and less complicated expansion approach of wavelength responses with a Lumogen phosphor coating was adopted, as they increased the quantum efficiency of CCD and CMOS detectors in ultra-violet by absorbing UV light and then re emitting visible light. In this paper, the sensitivity enhancement of fluorescence coatings was studied by adding an anti-reflection film or barrier film to reduce the loss of the scattering and reflection on the incident interface. The Lumogen and MgF2/Lumogen film were deposited on quartz glasses by physical vacuum deposition.

[Preparation by spin-coating technology and characterization of UV-enhanced Lumogen film].

As an effective way to increase the UV response for CCD/CMOS, the advantage of the Lumogen film is the simple process and low cost. In the present paper the Lumogen film was deposited onto fused silica slides by the spin-coating way, which has less damage than PVD physical vacuum deposition) way. The main test and analysis of the thin-film include transmission spectrum, absorption spectrum, and excitation and emission spectrum.

Calculation of the diffraction efficiency on concave gratings based on Fresnel-Kirchhoff's diffraction formula.

Fraunhofer diffraction formula cannot be applied to calculate the diffraction wave energy distribution of concave gratings like plane gratings because their grooves are distributed on a concave spherical surface. In this paper, a method based on the Kirchhoff diffraction theory is proposed to calculate the diffraction efficiency on concave gratings by considering the curvature of the whole concave spherical surface. According to this approach, each groove surface is divided into several limited small planes, on which the Kirchhoff diffraction field distribution is calculated, and then the diffraction field of whole concave grating can be obtained by superimposition.

Colored image produced with guided-mode resonance filter array.

A method to reproduce colored images with a guided-mode resonance filter (GMRF) array is presented in this Letter. Because of their excellent characteristics, monochromatic light of the three primary colors with high purity can be achieved by using GMRF structures. Moreover, the primary colors are obtained without changing other GMRF parameters except the period, which could be realized easily with laser direct writing technology.

[Preparation and spectral characterization of Lumogen coatings for UV-responsive CCD image sensors].

Traditional charge-coupled devices (usually front-illuminated CCDs) and complementary metal oxide semiconductor (CMOS) have lower response in ultraviolet region particularly. The reason is that polysilicon gate material absorbs the ultraviolet radiation highly, which leads to a barricade of the radiation penetrating the gate to the channel of CCD. To enhance the detective responsibility of CCD in the ultraviolet region, a feasible method is to coat the surface of CCD polysilicon gate with a thin film.

Type of tunable guided-mode resonance filter based on electro-optic characteristic of polymer-dispersed liquid crystal.

A narrowband guided-mode resonance filter (GMRF) incorporating polymer-dispersed liquid crystal (PDLC) is designed. Simulating the characteristics of the filter with rigorous coupled-wave analysis, we find that the resonance wavelength of the new kind of GMRF can be tuned from 672.4 to 698.

[Investigation of multi-wavelength effect during the measurement of UV-enhanced film's emission spectrum].

The UV-responsive detector is a dual-use device for civilian and military after the laser and IR-responsive sensors. Typical image sensor coated with a layer of down-convert frequency thin film on it's photosurface to enhance UV response is the key technology of enhancing UV-response. The UV-enhanced thin film was made in the experimental laboratory using the Zn2SiO4:Mn phosphor by spin coating method.

Preparation of high laser induced damage threshold antireflection film using interrupted ion assisted deposition.

Single layers and antireflection films were deposited by electron beam evaporation, ion assisted deposition and interrupted ion assisted deposition, respectively. Antireflection film of quite high laser damage threshold (18J/cm2) deposited by interrupted ion assisted deposition were got. The electric field distribution, weak absorption, and residual stress of films and their relations to damage threshold were investigated.