ISP SYSTEM designs and manufactures deformable mirrors dedicated to intense lasers for 15 years. The design patented by ISP uses electro-mechanical actuators and allows high order optical correction with a very high stability even unpowered. It can be adapted to any laser beam size and shape and membrane can be easily replaced. Laser peak-power increases continuously thanks to higher energy and shorter pulse duration, repetition rates are more and more important, leading to new technical challenges: high damage threshold for coatings, increased beam size, higher average power absorbed by the optics. ISP SYSTEM has improved continuously his deformable mirror in order to fulfill these requirements. Aperture has been increased using larger thin substrates and larger coating chambers for these substrates but keeping an acceptable actuator quantity. Optical test bench for calibration has also been upgraded for beams up to Ø500mm. Outgassing rates and cleanliness have been improved thanks to new materials, new lubricants and new cleaning processes coming from space and semiconductor industries. Outgassing of complete deformable mirror can be measured thanks to Rest Gas Analysis. Actuators have been improved in term of resolution, foot print and actuation speed. Actuators with very small diameter have been designed in order to increase the actuator density and improve the correction of high order Zernike. An active cooled deformable mirror is under development for applications with high average power of the laser beams up to 30 kW. This active cooled version is based on a technology similar to the standard deformable mirrors designed by ISP System and thus takes advantage of the electromechanical actuators benefits. It is adapted to CW and high repetition rate lasers and it is designed to able to dissipate continuously a thermal power of 300W. Optical correction quality is similar to the standard deformable mirror. Outgassing rates and cleanliness have been improved thanks to new materials, new lubricants and new cleaning processes coming from space and semiconductor industries. Outgassing of complete deformable mirror can be measured thanks to Rest Gas Analysis. Actuators have been improved in term of resolution, foot print and actuation speed. Actuators with very small diameter have been designed in order to increase the actuator density and improve the correction of high order Zernike. An active cooled deformable mirror is under development for applications with high average power of the laser beams up to 30 kW. This active cooled version is based on a technology similar to the standard deformable mirrors designed by ISP System and thus takes advantage of the electromechanical actuators benefits. It is adapted to CW and high repetition rate lasers and it is designed to able to dissipate continuously a thermal power of 300W. Optical correction quality is similar to the standard deformable mirror.
ACMAS program, in partnership with CNES and DGA, intends to develop an innovative concept of deformable mirror (DM) for next generation space telescopes, to manufacture an engineering model and to test it on optical and mechanical points of view.
The design of this space compatible DM is based on ISP System’s technology, and is adapted to space constraints (ECSS) particularly in terms of vibrations and reliability. These electro-mechanical DMs offer some innovative characteristics for space telescopes with low speed wavefront variations.
A specific version of the patented AME actuator is developed for space applications, and tested to TRL6. The deformable mirror’s actuators pattern is optimized in terms of quantity and position with respect to the wavefront corrections expected to apply during mission. The DM design is optimized thanks to finite element modeling in order to withstand the vibrations and shocks due to launching, and improve thermo-mechanical stability, and an innovative redundancy method is developed.
The performance of an engineering model is measured using an optical test bench with high resolution wavefront sensor. The correction thermal stability is also measured and the performance with one and two disabled actuators is evaluated. Vibrations are then injected into the DM. All these measures are compared to simulation values and show an impressive correlation..
ISP SYSTEM has developed a range of large aperture electro-mechanical deformable mirrors (DM) suitable for ultra short pulsed intense lasers. The design of the MD-AME deformable mirror is based on force application on numerous locations thanks to electromechanical actuators driven by stepper motors. DM design and assembly method have been adapted to large aperture beams and the performances were evaluated on a first application for a beam with a diameter of 250mm at 45° angle of incidence. A Strehl ratio above 0.9 was reached for this application. Simulations were correlated with measurements on optical bench and the design has been validated by calculation for very large aperture (up to Ø550mm). Optical aberrations up to Zernike order 5 can be corrected with a very low residual error as for actual MD-AME mirror. Amplitude can reach up to several hundreds of μm for low order corrections. Hysteresis is lower than 0.1% and linearity better than 99%. Contrary to piezo-electric actuators, the μ-AME actuators avoid print-through effects and they permit to keep the mirror shape stable even unpowered, providing a high resistance to electro-magnetic pulses. The MD-AME mirrors can be adapted to circular, square or elliptical beams and they are compatible with all dielectric or metallic coatings.
ISP SYSTEM has developed an electro-mechanical deformable mirror compatible with Ultra High Vacuum environment, suitable for ultra short pulsed lasers.
The design of the MD-AME deformable mirror is based on force application on numerous locations. μ-AME actuators are driven by stepper motors, and their patented special design allows controlling the force with a very high accuracy. Materials and assembly method have been adapted to UHV constraints and the performances were evaluated on a first application for a beam with a diameter of 250mm. A Strehl ratio above 0.9 was reached for this application. Optical aberrations up to Zernike order 5 can be corrected with a very low residual error as for standard MD-AME mirror. Amplitude can reach up to several hundreds of μm for low order corrections. Hysteresis is lower than 0.1% and linearity better than 99%. Contrary to piezo-electric actuators, the μ-AME actuators avoid print-through effects and they permit to keep the mirror shape stable even unpowered, providing a high resistance to electro-magnetic pulses.
The deformable mirror design allows changing easily an actuator or even the membrane if needed, in order to improve the facility availability. They are designed for circular, square or elliptical aperture from 30mm up to 500mm or more, with incidence angle from 0° to 45°. They can be equipped with passive or active cooling for high power lasers with high repetition rate.
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