1. 1 ICSO 2010 Rhodes October 4th-8th Development of Liquid Crystal based Adaptive Optical Elements for Space Applications Juan Barbero juan.barbero@alter-spain.com

2. 2 ICSO 2010 Rhodes October 4th-8th TOPICS Introduction Beam Steering Design considerations Substrate Liquid Crystal Alignment Driving and Interconnection Modelling Future works

3. 3 ICSO 2010 Rhodes October 4th-8th Introduction Objectives of the project: To identify, review and evaluate the current status of programmable optoelectronic adaptive elements (POE). To design and manufacture a POE produced to an agreed specification (Laser steering POE). To test and characterize the produced POE. A particularly important aspect of this contract is to further understanding of how the materials and technologies involved in POE structures react to environmental conditions experienced in space activities. To produce a technology roadmap that identifies the main areas of application for POE technologies and the developments necessary to achieve maximal performance and durability.

4. 4 ICSO 2010 Rhodes October 4th-8th LC-based Steering 2x 1D Passive matrix steering –Vast experience at UPM –In house manufacturing facilities Difficulties in achieving the diffraction efficiency –Challenging Photo lithography –Challenging interconnection –Compared to Lenses and filters much more expensive to develop A deviation of ±2º at 1064nm can be achieved with pitch side of 7.5µm

5. 5 ICSO 2010 Rhodes October 4th-8th Substrate technology Borosilicate Quartz Passive matrix of simple ITO (Indium Tin Oxide) tracks with external addressing Two options: 1mm Silica Float glass (CEC020-S Praezisions Glas & Optics GmbH). Gamma radiation tests showed no significant degradation (neither transmission, nor electro-optical response) of homogenous and vertical aligned for both substrates.

6. 6 ICSO 2010 Rhodes October 4th-8th Fast switching Reduced susceptibility to fringing Less crosstalk The vertical state absorbs less UV. Designed to withstand high light intensity and elevated working temperature (50ºC) Liquid Crystal Selection Liquid crystal technology Rod shape molecules that are self align creating a macroscopic uniaxial structure generally birrefringent. –Standard Liquid Crystals: optical and electrical positive anisotropy parallel –VAN (Vertical Align Nematics) liquid crystals perpendicular Study of transition times in a 1.5 mm thick cell (1781 A3) with 250 nm retardation

7. 7 ICSO 2010 Rhodes October 4th-8th Alignment Alignment orientation –The effect of angle of alignment orientation with respect to the electrode and fringing in the device will be assessed. The preferred 45º alignment, which eliminates the need for a ½ waveplate between the two deflectors, will affect the fringing. Alignment direction in LC devices is normally defined by polarised polymerization of organic polymers –Disadvange: Soft materials rupture or reorientation by crystallization at low T Inorganic Alignment material –Obliquely oxides generating a regular 3D structure which aligns the LC –Thermally deposit SiO x does not align higher birrefringence LC –E-gun deposited SiO 2 can align LC with high birrefringence –Extremely sensible to absorption of organic materials leading to changes in the alignment.

8. 8 ICSO 2010 Rhodes October 4th-8th Conventional electrode Fabrication ITO on Glass Optimised and adapted procedures –Cleaning –Photo resist depositing –Developing –Etching

9. 9 ICSO 2010 Rhodes October 4th-8th Lithography Fanout is manufatured using conventional photolithography Electrode separation is done using E-beam nanolithography and dry- etching –Photoresin ZEP520A deposition, “insolation”, and developing on ITO has been optimised –Argon + H 2 Reactive Ion Etching (RIE) parameters have been optimised –Awaiting slot time. Parameters need rechecking using the new substrates Fundamentally identical to the original 7  m design

10. 10 ICSO 2010 Rhodes October 4th-8th Driver design trade-off I -Chip-On-Glass A conventional solution for high-res micro displays Technology not tested in UPM facilities Impossible to separate electronics and device Reduced number of external connections Limited choice of drivers –Not all display drivers are suitable for this application

11. 11 ICSO 2010 Rhodes October 4th-8th Driver design trade-off II - Flexible circuit board (FCB) or Chip-On-Flex (COF) A conventional solution for high-res displays Technology not tested in UPM facilities –Necessary to purchase externally manufactured FCB –Possibility of soldering chips onto flex is studied by Emxys One critical high density connector per 500 lines Reduced number of external connections Interconnection of the driver circuit and the ITO Tracks is done with anisotropic conductive adhesive Hitachi ANISOLM® AC-8955YW-23

12. 12 ICSO 2010 Rhodes October 4th-8th Driving and Interconnection The microcontroller manages the communication from the PC with the chip SSD1783 (Solomon Systech Limited) via a serial SPI bus interface and also, between the POE board and the computer (using a Bluetooth link). The team decided to implement Bluetooth communications in order to improve the usability of the system during the POE tests on the optical bench.

13. 13 ICSO 2010 Rhodes October 4th-8th Driving and Interconnection POE Electronics: 5V power supply. Firmware can be updated via USB

14. 14 ICSO 2010 Rhodes October 4th-8th Modelling of response Simulation design for the beam steerer to meet the specifications : LabView Approximation: –LC switching is constant over the electrode –Constant phase retardation –Phase transition of the interpixel space is the average of the two electrodes

15. 15 ICSO 2010 Rhodes October 4th-8th Modelling of response The four step function simulating the LC behaviour in a device with a 3:1 ration be with the resulting Fourier transform showing a 84% diffraction efficiency.

16. 16 ICSO 2010 Rhodes October 4th-8th Beamsteerer Performance, tested using binary patterns

17. 17 ICSO 2010 Rhodes October 4th-8th TestTest conditionsQty SerializationAll devices with individual identification7 External Visual InspectionESCC 2055000. Signs of damage or degradation7 Electro-optical CharacterizationInitial characterisation of devices7 External & dimensionalESCC 2055000. Dimensions, mass 1 Internal VisualESCC 2049000. Non-destructive. Thermal Cycling 100 cycles [–50  +75ºC], non-operational Thermal Vacuum 5 cycles [-50  +80ºC], operational 2 VibrationECSS-E-10-03A. sine and random Gamma RadiationESCC 22900. 10, 25 & 50 krad, 430 rad/h2 Protons RadiationESCC 22900. >1E11 particles/cm2, 60 MeV2 Test Plan

18. 18 ICSO 2010 Rhodes October 4th-8th Test Plan Proposed samples allocation per test to maximise information with respect to performance under space environmental conditions

19. 19 ICSO 2010 Rhodes October 4th-8th Other possibilities: Modal Lenses Exhaustive analysis of organic high resistance control electrode material Manufactured lenses show inhomogeneities which will affect the performance Very high voltages (60- 100V@ 25kHz-1MHz) were needed for the cells to focus

20. 20 ICSO 2010 Rhodes October 4th-8th Other possibililies: Dual Voltage Lenses First lenses have been made High voltage 100-200V were needed for focusing (quasi DC waveform)

21. 21 ICSO 2010 Rhodes October 4th-8th Conclusions Programmable Optical Elements using Liquid Crystals is a promising technology of space use. A beam steerer, foreseen to be able to withstand space environment, has been design. Testing has not begun yet. Driving Electronics complexity due to the high number of pixels. But the driving electronics flexibility will lead to multipurpose LC devices.

22. 22 ICSO 2010 Rhodes October 4th-8th END OF PRESENTATION THANKS www.altertechnology.com