The demanding science goals of future astrophysics missions currently under study for the 2020 Decadal Survey impose significant technological requirements on their associated telescopes. These concepts currently call for apertures as large as 15 m (LUVOIR), and operational temperatures as low as 4 Kelvin (OST). Advanced mirror technologies, such as those implementing a high degree of actuation at the primary, can help to overcome the challenges associated with these missions by providing in-situ wavefront correction capabilities. Active mirrors can also greatly reduce the cost/complexity associated with mirror fabrication as well as system I and T as on-orbit performance specifications can be achieved under a variety of test conditions (i.e. room/cryogenic temperatures, 0g/1g). JPL has significant experience in this area for visible/near-infrared applications, however future mission requirements create a new set of challenges for this technology. This paper presents design, analysis, and test results for lightweight silicon-carbide mirrors with integrated actuation capabilities. In particular, studies have been performed to test the performance of these mirrors at cryogenic temperatures.
AOA-Xinetics has been developing techniques for shaping grazing incidence optics with surface-normal and surface-parallel electrostrictive Lead magnesium niobate (PMN) actuators bonded to mirror substrates for several years. These actuators are highly reliable; exhibit little to no hysteresis, aging or creep; and can be closely spaced to correct low and mid-spatial frequency errors in a compact package. In this paper we discuss the design and fabrication of a 45cm grazing incidence mirror fitted with 45 PMN actuators and integral strain gauges and temperature sensors that allow sub-nanometer control of the surface figure.
X-ray telescopes use grazing incidence mirrors to focus X-ray photons from celestial objects. To achieve the large
collecting areas required to image faint sources, thousands of thin, doubly curved mirrors are arranged in nested
cylindrical shells to approximate a filled aperture. These mirrors require extremely smooth surfaces with precise figures
to provide well-focused beams and small image spot sizes. The Generation-X telescope proposed by SAO would have a
12-meter aperture, a 50 m<sup>2</sup> collecting area and 0.1 arc-second spatial resolution. This resolution would be obtained by
actively controlling the mirror figure with piezoelectric actuators deposited on the back of each 0.4 mm thick mirror
segment. To support SAO’s Generation-X study, Northrop Grumman used internal funds to look at the feasibility of
using Xinetics deformable mirror technologies to meet the Generation-X requirements. We designed and fabricated two
10 x 30 cm Platinum-coated silicon mirrors with 108 surface-parallel electrostrictive Lead Magnesium Niobate (PMN)
actuators bonded to the mirror substrates. These mirrors were tested at optical wavelengths by Xinetics to assess the
actuator’s performance, but no funds were available for X-ray tests. In 2013, after receiving an invitation to evaluate the
mirror’s performance at Argonne National Laboratory, the mirrors were taken out of storage, refurbished, retested at
Xinetics and transported to ANL for metrology measurements with a Long Trace Profilometer, a Fizeau laser
interferometer, and X-ray tests. This paper describes the development and testing of the adaptive x-ray mirrors at AOAXinetics.
Marathe, et al, will present the results of the tests at Argonne.
One of the science missions for the next generation of extremely large ground based telescopes (30-42m apertures) is the imaging and spectroscopy of exoplanets. To achieve that goal an Adaptive Optics (AO) subsystem with a very large number of corrected modes is required. To provide contrast ratios in the range of 10<sup>-9</sup> or better for a 42m telescope an AO system with 25,000 to 60,000 channels will be needed. This is approximately an order of magnitude beyond the current state of the art. Adaptive Optics Associates Xinetics has developed the Photonex Module Deformable Mirror (DM) technology specifically to address the needs of extreme AO for high contrast applications. A Photonex Module is a monolithic block of electrostrictive ceramic in which a high density of individually addressable actuators are formed by screen printing of electrodes and partial wire saw cutting of the ceramic. The printed electrode structures also allow all electrical connections to be made at the back surface of the module via flex circuits. Actuator spacings of 1mm or less have been achieved using this approach. The individual modules can be edge butted and bonded to achieve high actuator count. The largest DMs fabricated to date have 4096 actuators in a 64X64mm array. In this paper the engineering challenges in extending this technology by a factor of ten or more in actuator count will be discussed. A conceptual design for a DM suitable for XAO will be presented. Approaches for a support structure that will maintain the low spatial frequency surface figure of this large (~0.6m) DM and for the electrical interface to the tens of thousands of actuators will be discussed. Finally, performance estimates will be presented.
For more than two decades, Northrop Grumman Xinetics has been the principal supplier of small deformable
mirrors that enable adaptive optical (AO) systems for the ground-based astronomical telescope community. With
today’s drive toward extremely large aperture systems, and the desire of telescope designers to include adaptive
optics in the main optical path of the telescope, Xinetics has recognized the need for large active mirrors with the
requisite bandwidth and actuator stoke. Presented in this paper is the proposed use of Northrop Grumman Xinetics’
large, ultra-lightweight Silicon Carbide substrates with surface parallel actuation of sufficient spatial density and
bandwidth to meet the requirements of tomorrow’s AO systems, while reducing complexity and cost.
The TMT first light Adaptive Optics (AO) facility consists of the Narrow Field Infra-Red AO System (NFIRAOS) and the associated Laser Guide Star Facility (LGSF). NFIRAOS is a 60 × 60 laser guide star (LGS) multi-conjugate AO (MCAO) system, which provides uniform, diffraction-limited performance in the J, H, and K bands over 17-30 arc sec diameter fields with 50 per cent sky coverage at the galactic pole, as required to support the TMT science cases. NFIRAOS includes two deformable mirrors, six laser guide star wavefront sensors, and three low-order, infrared, natural guide star wavefront sensors within each client instrument. The first light LGSF system includes six sodium lasers required to generate the NFIRAOS laser guide stars. In this paper, we will provide an update on the progress in designing, modeling and validating the TMT first light AO systems and their components over the last two years. This will include pre-final design and prototyping activities for NFIRAOS, preliminary design and prototyping activities for the LGSF, design and prototyping for the deformable mirrors, fabrication and tests for the visible detectors, benchmarking and comparison of different algorithms and processing architecture for the Real Time Controller (RTC) and development and tests of prototype candidate lasers. Comprehensive and detailed AO modeling is continuing to support the design and development of the first light AO facility. Main modeling topics studied during the last two years include further studies in the area of wavefront error budget, sky coverage, high precision astrometry for the galactic center and other observations, high contrast imaging with NFIRAOS and its first light instruments, Point Spread Function (PSF) reconstruction for LGS MCAO, LGS photon return and sophisticated low order mode temporal filtering.
AOA Xinetics (AOX) has been at the forefront of Deformable Mirror (DM) technology development for over two
decades. In this paper the current state of that technology is reviewed and the particular strengths and weaknesses of the
various DM architectures are presented. Emphasis is placed on the requirements for DMs applied to the correction of
high-energy and high average power lasers. Mirror designs optimized for the correction of typical thermal lensing effects
in diode pumped solid-state lasers will be detailed and their capabilities summarized. Passive thermal management
techniques that allow long laser run times to be supported will also be discussed.
Grazing-incidence optics for X-ray applications require extremely smooth surfaces with precise mirror figures to provide well focused beams and small image spot sizes for astronomical telescopes and laboratory test facilities. The required precision has traditionally been achieved by time-consuming grinding and polishing of thick substrates with frequent pauses for precise metrology to check the mirror figure. More recently, substrates with high quality surface finish and figures have become available at reasonable cost, and techniques have been developed to mechanically adjust the figure of these traditionally polished substrates for ground-based applications. The beam-bending techniques currently in use are mechanically complex, however, with little control over mid-spatial frequency errors. AOA-Xinetics has been developing been developing techniques for shaping grazing incidence optics with surface-normal and surface-parallel electrostrictive Lead magnesium niobate (PMN) actuators bonded to mirror substrates for several years. These actuators are highly reliable; exhibit little to no hysteresis, aging or creep; and can be closely spaced to correct low and mid-spatial frequency errors in a compact package. In this paper we discuss recent development of adaptive x-ray optics at AOA-Xinetics.
Deformable mirrors (DMs) have been successfully used in astronomical adaptive optics at visible and near-infrared wavelengths, greatly reducing atmospheric-induced aberrations. Building upon the extensive techniques and methods developed for these applications, we propose to extend this capability to the soft and hard x-ray regime in order to take full advantage of the beam quality characteristic of new facilities such as the National Synchrotron Light Source (NSLS-II), and the Linac Coherent Light Source (LCLS). Achieving this goal challenges both current mirror manufacturing techniques and wavefront propagation modeling. Lawrence Livermore National Laboratory (LLNL), in collaboration with Northrop Grumman AOA Xinetics Inc., is currently developing an x-ray deformable mirror to correct for wave-front aberrations introduced along the beam path of a typical x-ray beamline. To model the expected performance of such a mirror, we have developed a simulation based on the wavefront propagation code PROPER. We will present the current implementation of the software, which models actuation of a deformable mirror and evaluates its effect on wavefront correction.
Grazing-incidence optics for X-ray applications require extremely smooth surfaces with precise mirror figures to provide well focused beams and small image spot sizes for astronomical telescopes and laboratory test facilities. The required precision has traditionally been achieved by time-consuming grinding and polishing of thick substrates with frequent pauses for precise metrology to check the mirror figure. More recently, substrates with high quality surface finish and figures have become available at reasonable cost, and techniques have been developed to mechanically adjust the figure of these traditionally polished substrates for ground-based applications. The beam-bending techniques currently in use are mechanically complex, however, with little control over mid-spatial frequency errors. AOA-Xinetics has been developing been developing techniques for shaping grazing incidence optics with surface-normal and surface-parallel electrostrictive Lead magnesium niobate (PMN) actuators bonded to mirror substrates for several years. These actuators are highly reliable; exhibit little to no hysteresis, aging or creep; and can be closely spaced to correct low and mid-spatial frequency errors in a compact package. In this paper we discuss recent development of adaptive x-ray optics at AOAXinetics.
Typical adaptive optics systems require a deformable mirror to provide high spatial frequency wavefront correction and a separate tip-tilt mirror so that the deformable mirror’s dynamic range is not exhausted on low order aberrations. Having two correction devices requires additional optical relays to be incorporated in the system, which in turn translates into more cost, size and complexity. If the two devices were combined into an integrated wavefront corrector (IWC), the cost, size and complexity of an adaptive optics system could be drastically reduced. This paper outlines the design and operation of an electro-ceramic driven tip tilt stage that has been designed specifically for a 37 channel deformable mirror. The tip tilt system can deliver more than 500 μradians of tilt, 20 microns of piston, and has natural frequencies greater than 400 hertz. The tip-tilt stage has a fast response time and the axis of rotation is centered at the optical surface. This prevents translation and wavefront shear associated with typical tip-tilt mirrors for which the axis of rotation is centered behind the surface of the mirror. The 37 channel deformable mirror has a 7mm actuator spacing and is designed with high temperature and low outgassing materials which are compatible with high temperature coatings. The IWC may be retrofitted with Xinetics actuators to operate at cryogenic temperatures. We also describe the use of this device in a closed loop adaptive optics system and outline its benefits.
Xinetics is working with NASA to develop a cryogenic deformable mirror (DM) specific to the needs of future Origins Program missions such as TPF and JWST. Of utmost importance was the development of an electroceramic material that exhibited electrostrictive properties at cryogenic temperatures. In this paper, the actuator developmental tests and subsequent cryogenic deformable mirror design and cryogenic testing performance of the 349-channel discrete actuator deformable mirror demonstrator are discussed. The cofired actuator stroke response was nearly constant from 35 to 65 K such that at 150V the actuator free-stroke was ~3 microns. The 349-ch cryogenic DM was designed and built with as few parts and materials as possible to minimize the CTE mismatch. The polished mirror was cycled twice from 300 to 35 K. The rms surface figure was monitored using a Zygo interferometer on cooling and consistent data was measured
during both temperature cycles. The figure changed from 0.5 waves (P-V) at 300 K to 5 waves at 35 K and returned to 0.6 waves at 300K. The actuators were powered and the influence functions were measured between 35 and 65 K. Even though it is not a functional DM at 35 K, it is a substantial step forward in the development of a cryogenic
deformable mirror technology.