In this paper, a concave holographic grating aberration optimization method is designed, which performs well in the aberration optimization of multi-channel narrow-band gratings. Taking the grating in the the project of CAFE (the Census of warm-hot intergalactic medium, Accretion, and Feedback Explorer) proposed by the Purple Mountain Observatory, Chinese Academy of Sciences, as the optimization target, this paper compares the method proposed with the traditional aberration function method and the spot diagram method commonly used currently in terms of the evaluation perspectives such as the line density deviation, the focusing curve offset, and the exit slit luminous flux, etc., and the optimization time is one thirtieth and one sixtieth of the two methods, respectively.
Gold-coated photoresist grating (GCPG) is commonly employed in high-power femtosecond laser systems for its broadband and simple structure. The pyrolysis and low heat conductivity of photoresist substrates are well known to result in a low GCPG laser damage threshold, which restricts the power increase of laser systems. Gold-coated fused silica grating (GCFSG) has a high threshold potential since the grating pattern is transferred from the photoresist to the fused silica substrate by etching. In this paper, a rectangular GCFSG with a period of 1740 l/mm was designed and fabricated. Using rigorous coupled-wave analysis (RCWA), the ideal slot form for GCFSG with high diffraction efficiency was designed. After a comprehensive analysis of the impact of gold plating coating flaws on efficiency, iterations of the coating process were carried out to optimize the slot shape. For these GCFSG samples, magnetron sputtering was used as the gold deposition process and the samples had a bandwidth of at least 150 nm with the -1st-order diffraction efficiency of 93% around the central wavelength of 800 nm. The measured efficiency results were compared with our simulation calculations and good agreement was achieved. After being damaged by lasers, GCFSG can be reused with good economics by being cleaned and then gold-coated.
With the widespread application of polarizers in infrared detection, military, medical and other fields, infrared polarizers have developed rapidly in the last decade, and it is becoming increasingly crucial to fabricate high-performance and low-cost polarizers. The paper presents a design for fabricating a linear polarizer operating in the 7-14 um by metal-assisted chemical etching. A subwavelength gold grating is fabricated on a silicon substrate by the lift-off process, then a subwavelength silicon grating structure is fabricated by the metal-assisted chemical etching process of silicon, an aluminum film is coated on the bottom of the groove and the ridge of the fabricated subwavelength silicon grating by electron beam evaporation coating. The structure is optimized by the rigorous coupled-wave analysis, we assess the effect of the grating parameters on the extinction ratio and transverse magnetic wave transmittance and optimize the parameters, and finally determined that the grating period is 400 nm, the duty cycle is 0.5, and the groove depth is 1200nm. The numerical simulation results demonstrate that the polarizer has the advantages of high extinction ratio and wide manufacturing tolerance in long wave infrared region (7-14um). Grating structures with high aspect ratio can be fabricated by metal-assisted chemical etching, which makes it possible to enhance the transmission of the silicon substrate. Therefore, anti-reflection structures can be designed to enhance the transmission of the silicon substrate in the long-wave infrared based on the effective medium theory.
In this article, we designed and fabricated a high linear density concave variable line space holographic grating for the Lyman spectrometer, with level 3 working and the center line density is 3300line/mm. The focus curve is a circle with the grating vertex O as the center and a radius of 900 mm. We analyze the influence of the exposure error on the line density distribution and reduce the harm of errors through the method of multi-error compensation. To improve the diffraction efficiency, we use Finite Element Method software to get the best grating groove parameters. Finally, we initially prepared a holographic grating with a symmetrical arch groove with a groove depth of 175nm and a bottom duty cycle of 0.3.
As an essential component of the slitless spectrometer, the UV transmission blazed grating has the capability of high dispersion and high resolution. In this paper, a method for fabricating UV transmission blazed gratings by holography-ion beam etching is proposed. Holographic interference lithography is used to generate photoresist grating masks. The ion beam vertical etching transfers the photoresist mask pattern to the substrate to form a SiO2 grating mask. When the ion beam incident direction is at a certain angle to the normal direction of the substrate, the SiO2 mask is used to block the inclined ion beam, so that different parts of the mask bottom are bombarded by the ion beam with different fluxes, forming a blazing facet. When the mask is etched completely, the blazed grating is formed. Based on the idea of the line motion algorithm, the article establishes the geometric model of blazed grating etching, which provides the parameter guidance for precise control of the groove structure. Combined with the theoretical model, a UV transmission blazed grating with a line density of 333 lines/mm and a blazing angle of 13.2° is successfully fabricated.
We report on high-efficiency visible and near-infrared transmission gratings in fused silica generated by holographic recording and reactive ion beam etching technology. At a wavelength of 740 nm, near 100% diffraction efficiency is achieved under Littrow conditions. The design is based on the phenomenon of the high aspect ratio gratings by using the rigorous coupled wave analysis. A binary grating with the optimum grating period of 740 nm and groove depth of 1.55 had been fabricated in the paper. The grating wavelength bandwidth and angular bandwidth are extremely enhanced compared with conventional volume phase holographic gratings, making these gratings the key elements in high-resolution astronomical ground-based telescope spectrographs.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.