Nanoengineered astronomical optics

Abstract

Abstract. We describe a technology for the fabrication of inexpensive and versatile mirrors through the use of a new type of nanoengineered optical material composed by the spreading of a self-assembling reflective colloidal film spread at the surface of a liquid. These new reflecting liquids offer interesting possibilities for astronomical instrumentation. For example, they can replace mercury in conventional rotating liquid mirrors. The main advantages offered include extremely low cost and, by coating a viscous liquid, the possibility of tilting the mirror by a few tens of degrees. We also have coated ferromagnetic liquids with these reflecting films. The resulting surfaces can be shaped by the application of a magnetic field, yielding reflecting surfaces that can have complicated shapes that can rapidly shift with time. These inexpensive and versatile optical elements could have numerous scientific and technological applications. Among possible astronomical applications, they could be used to make large inexpensive adaptive mirrors exhibiting strokes ranging from nanometers to several millimeters.

Tiltable rotating liquid mirrors: a progress report

“…Our early MELLFs were spread on water. Borra et al (2004) reported on a major improvement of the technology: the successful subsequent spreading of the MELLF at the surface of an organic oil. This feat greatly extends the range of physical and chemical characteristics of the available liquid substrates and also solves a major problem with water-based liquids: namely, evaporation.…”

“…We no longer depend on surfactants to bring the MELLF to the surface of the oil as in Borra et al (2004) but simply spray the MELLF on the surface of the hydrophilic liquid. Unfortunately this technique is limited to liquids with relatively high surface tensions (greater than 40 mN m −1 ), greatly restricting the number of liquids that can be used.…”

Characterization and closed-loop AO performance of a liquid deformable mirror

“…4 In all these applications the light was reflected from the air side of the liquid-air interface which means that the deformation of the liquid had to be induced from within the liquid. The method described here uses total internal reflection (TIR) in which the light is coupled into the mirror by a coupling prism to propagate through the liquid so that it is reflected by the liquid side of the liquid-air interface (Fig.…”

Liquid deformable mirror for high-order wavefront correction

“…The use of liquid as a deforming medium for wavefront correction is not well studied, probably because of the low reflectivity of most liquids. However, by employing an unconstrained floating reflective membrane on top of the deforming liquid surface or by using a colloidal mixture of reflective nanoparticles, 5 the issue of low liquid reflectivity can be solved. So far, in the past decade only two liquid-based deformable mirrors have been demonstrated.…”

“…To remedy the problem of the low reflectivity of a pure liquid surface, a freefloating reflective membrane or a dye-coated dielectric liquid can be utilized. A self-assembling reflective colloidal film spread at the surface of the dielectric liquid 5 can also be employed to achieve a higher reflectivity. With this configuration, an initially flat surface is easily achieved.…”