Spherical VPH Gratings for Enhanced Spectrograph Design

衍射光栅是许多天文仪器的核心部件，用来测量不同波长的光的分布。这样的测量携带着关于天文物体的化学成分及其运动动力学的大量诊断信息。一种更有效的光栅，称为体积位相全息(VPH)光栅，最近正在开发中，具有很大的实际应用前景。如果可以在球面上制作VPH光栅，则可以实现特别紧凑和光效高的光学设计。获得该奖项的提议是一种探索，目的是完善在球面上制造VPH光栅的技术。目前的光谱仪通常在平面波前完成光谱色散，这推动了光学设计转向大型仪器，因此也就是昂贵的仪器。VPH技术承诺在凹面或凸面上提供高质量的衍射光栅，从而实现替代和更紧凑的光谱仪设计，例如利用著名的Offner继电器的光谱仪设计。通过VPH光栅实现的设计可以具有更少的组件以及更小的组件，在某些情况下可以减少外来材料，同时提供更高的效率。获得该奖项后，将建造一台使用商用现成光学元件的探路者概念光谱仪，分辨率为R~1000，波长范围为380-790 nm，馈送2k探测器。这一试验项目将为未来更先进的光谱仪设计铺平道路，利用VPH光栅的力量。该项目具有重大的更广泛的影响，因为它可以在保持高性能的同时大幅减小体积和成本，适用于各种天文仪器。学生们将参与到这项工作的大部分方面。这个项目的资金由NSF的天文科学部通过其先进技术和仪器计划提供。

Diffraction gratings are a fundamental component at the heart of many astronomical instruments that measure the distribution of light at different wavelengths. Such measurements carry tremendous diagnostic information about the chemical composition of astronomical objects, and the dynamics of their motion. A more efficient kind of grating, called the Volume Phase Holographic (VPH) grating, has recently been under development, and offers great promise for practical applications. Particularly compact and light-efficient optical designs are made possible if VPH gratings can be made on spherical surfaces. The proposal for which this award was made is a pathfinding attempt to perfect the techniques for fabricating VPH gratings on spherical surfaces.Current spectrographs typically accomplish spectral dispersion on planar wavefronts, and this drives the optical design to large and hence expensive instruments. The VPH technology promises high-quality diffraction gratings on concave or convex spherical surfaces, enabling alternative and more compact spectrograph designs such as those utilizing the well-known Offner relay. The designs enabled by VPH gratings can have fewer as well as smaller components, and in some cases less exotic material while delivering higher efficiency. With this award, a pathfinder concept spectrograph using commercial off-the-shelf optical components will be built with resolving power R~1000 over the wavelength range 380-790 nm, feeding a 2k detector. This pilot project will pave the way for more advanced spectrograph designs in the future, exploiting the power of VPH gratings.This project has substantial broader impacts in that it could enable dramatically reduced size and cost while maintaining high performance, for a wide variety of astronomical instrumentation. Students will be involved in most aspects of the work.Funding for this project is being provided by NSF's Division of Astronomical Sciences through its Advanced Technologies and Instrumentation program.