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 ${7.85} \times {{10}^{ - 5}}$7.85×10-5. Combining the two technologies, we achieve lower stray light and straighter groove lines for the concave gratings, which is more effective, easy to implement, and incurs a low cost.

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 (Y-axis) and perpendicular to (X-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 Y-axis, and 5.2% of the X-axis, the groove angle is reduced by 1.33°, and the blazed wavelength of the first-order diffraction shifts toward the short-wave direction by 42.3 nm. The sensitivity of a spectrometer can be enhanced by tuning the blazed wavelength of the PDMS grating to the wavelength of the spectrum peak under observation in the bands from 460.8 nm to 503.1 nm.

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. Its spectral resolution reaches 0.049 nm, and its diffraction efficiency improves by 27% compared to the conventional Offner spectrometer with convex grating working at ${-}{1}$-1st order diffraction. This is suitable for small, light, and low-cost atmospheric gas monitoring satellites.

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 ∼0.4 with a ±5° field of view for 3 and 5 mm pupils.

[General calculation method of diffraction efficiency of concave blazed gratings].

In order to make diffraction energy of concave gratings more concentrated in the desired order, the present paper puts forward that the concave blazed grating with variable groove angles could be fabricated on the concave substrates by mechanical ruling method, and the theoretical method of simultaneously calculating the diffraction efficiency in the main section and non-main section is deduced by using Fresnel-Kirchhoff's diffraction formula, which makes up the shortage of the diffraction efficiency calculated only in the main section. Finally, the diffraction efficiency curves varied with wavelength is simulated by Matlab software, and the variation laws of the diffraction efficiency are compared for different production methods and application parameters, which provides a valuable reference for the design and production of the concave gratings.