3-axis fiber-based interferometry replacing glass scales attocube systems AG

3-axis fiber-based interferometry replacing glass scales attocube systems AG Königinstr.11a D-80539 Munich Klaus Thurner attocube interferometric sensor for displacement tracking with nanometer precision

attocube systems Major ideas for the nano world Founded in 2001 Offices: Munich, Berkeley, New York 80 employees, 30% PhDs Turnover 2013/14: ~ 15 Mio. attocube displacement sensors Awards Nominee AMA Innovation Award 2014 TOP100 Innovation Award 2013 IVAM-Marketing Award 2013 R&D 100 Award 2012 CLEO/Laser Focus World Innovation Award 2012 Deloitte Technology Fast 50 Award 2010 Top 5 Nominee Hermes-Award Hannover Messe 2010 Deloitte Technology Fast 50 Award 2009 Bavarian Award for Medium-Sized Businesses 2009 R&D100 Award 2009 Deloitte Technology Fast 50 Award 2008 German Award for Outstanding Entrepreneurs 2008 Munich Award for Outstanding Entrepreneurs 2008 Landmark in the nationwide contest Germany Land of Ideas Finalist at the Innovations Award of the German Industry 2006 Bavarian Innovation Award 2006 Nominee for the Philip-Morris Research Award 2004 Winner of Munich Business Plan Competition 2001

Overview 1. Why replacing linear scales? 2. Principle of operation 3. Practical implementation: Sensor head and target 4. Environmental compensation 5. Outlook

Why replacing linear scales? Differences between linear scale encoder and interferometers Laser interferometry From Laser Linear scale encoders Laser Diode Pitch To detector Moving target (glass) Glass scale D1 + Accuracy: 50 ppb (vacuum) + Accuracy: better 0.5 ppm (ambient) + Simultaneous measurement of 3 channels + Primary reference measurement procedure (without relation to a measurement standard) + Pitch 0.8 µm - Sensitive to air fluctuations - Costs - Loss of position in case of beam interruption + Low cost + Robustness + Proven technology + Absolute scales available - Accuracy: 5 ppm typ. - Need for calibration - Pitch 20 µm typ. - Sensitive to ambient conditions - Alignment

Why replacing linear scales? Differences between linear scale encoder and interferometers Laser interferometry From Laser Linear scale encoders Laser Diode Pitch To detector Moving target (glass) Glass scale D1 + Easy integration and compactness (down to Ø 1 mm) + Position sensing at the sample level + Measurement of erratic pitch and yaw movement + Target vibration and rotation measurements + No need for calibration + UHV compatibility, non magnetic, cryogenic compatibility - Does not allow vibrometry

The challenges we faced Differences between linear scale encoder and interferometers Reducing interferometer price Telecom wavelength range Semiconductor diode laser with accuracy of metrological gas laser Technical improvements Increase robustness Increase usability Miniaturization of sensor heads and controller Environmental compensation Uncertainty due to change of temperature, pressure, humidity Ø 4 mm Ø 2.3 mm Ø 1.2 mm

Key specifications IDS3010 Resolution 1 pm Range 10 m Repeatability 0.1nm 10 100 1 0.1 1 1000 0.01 10 100 10 1M 100 Bandwidth 10 MHz i.e. Velocity 1m/s Accuracy 1 nm 1000 100 10 100 1 10 NO 0.1 cm 3 Compactness & ease of mount & ease of use & contactless 1 2 3 4 Multi-channels & deportability YES Environment (UHV, Cryogenic, Electric and Magnetic fields, ionizing radiation & non-invasive)

Overview 1. Why replacing linear scales? 2. Principle of operation 3. Experimental techniques: Sensor head and target 4. Environmental compensation 5. Outlook

Comparison between Michelson and Fabry-Pérot interferometry Detector Signal Intensity signal Comparison to existing technologies From Laser To detector Semi-transparent reference From Laser To detector Embedded semi-transparent reference From Laser Reference mirror Users target Users target Users target A Displacement B Displacement C Michelson - Large sensor heads - Reference beam is subject to thermal drifts and refractive index changes Fabry-Pérot + Miniaturization of sensor heads + Robust against external influences To detector Displacement 0 2 4 6 0 2 4 6 Target Displacement x ( /2) (λ/2)

Principle of operation Detector Intensity Signal Intensity Fiber-optic Fabry-Pérot interferometer DFB Laser Sensor head SMF Target Detector 4% 4% 0 2 4 6 Target Displacement x ( /2) x (λ/2) Ultra compact sensor head UHV compatibility, non magnetic, cryogenic compatibility Ultra low power No electrical leads

Principle of operation Detector Signal Intensity Fiber-optic Fabry-Pérot interferometer From Laser Moving target (glass) To detector Displacement Blind 0 2 4 6 0 2 4 6 x ( /2) Sensitive Target Displacement x (λ/2)

Principle of operation Fiber-optic Fabry-Pérot interferometer Detector Signal Intensity 10.1 1.5 10 1.0 00.0 0.5-0.1-1 Output Derivative Displacement Detector Intensity Derivative (µw) Displacement Eliminates blind spots Deterministic trajectory Gives motion direction 0 0.0 00 22 44 66 x ( /2) Target Displacement x (λ/4) Position reconstruction using wavelength modulation Quadrature detection scheme based on the demodulation of a high frequency modulated interference signal 10 /16 IR (µwatts) IDC (V) Intensity (µw) Detector To detector Idc % (2) Mod. (λ) Moving target From Laser + sin t 0-1 0 IR (µwatts) 1

Measurement of one direction with large angular alignment tolerance Embedded semi-transparent reference From Laser To detector 4% 4% Returning beam is offset with respect to the incident beam in order to reduce the back coupled light power Measurement of one dimensional movement with enhanced alignment tolerance (±4 deg) using corner cube retro reflector

Measurement of one direction High tracking velocity Displacement Speed Target velocity up to 2 m/s with pm resolution

Measurement of multiple directions Measurement of multiple directions with highest metrological accuracy and long dynamic range Embedded semi-transparent reference From Laser To detector Glass targets (sandblasted) in order to suppress reflections from the back surface Glass target Displacement up to 3 m with pm resolution

Measurement of multiple directions Reflecting target R>96% Sensor head SMF Ferrule Measurement of multiple directions with enhanced alignment tolerance Sensor head Reflecting target R>96% SMF Ferrule Measurement of multiple directions using confocal double pass configuration requiring high reflective mirrors enabling enhanced alignment tolerance (up to ±1 deg) Reduced accuracy and nanometer repeatability Dynamic range limited to 0.1 m Displacement up to 3 m with pm resolution

Application example Calibration of a 5 axes milling machine

Application example Measurement of rotation and vibration on sample level Measurement of rotation and vibration directly on milling spindle Only rotation frequency Idle state Rotation and vibration measurements on sample level not accessible by linear scales Different frequencies excited Milling

Benefits Measurement on sample level Runout measurement Ultra precise contactless detection of bearing errors with the FPS3010

Environmental compensation Measurements at ambient conditions Environmental effects are compensated using a weather station (ECU)

Environmental compensation Real-time measurements at ambient conditions Accuracy typically better than 1 ppm for pressure change of 400 mbar

Environmental compensation Measurements at ambient conditions Influence of different air parameters on measurement accuracy Temperature (T) dn/dt (K -1 ) -0.93 ppm Pressure (p) dn/dp (mbar -1 ) 0.27 ppm Humidity (h) dn/dh (% -1 ) -0.0087 ppm CO 2 content (x c ) dn/dx c (ppm -1 ) 0.00014 ppm Position uncertainty is given by

Outlook IDS3010 What's next? Referencing measurements at PTB Increasing dynamic measurement range Absolute distance measurement (referencing of the interferometer without the need to pass by a reference mark) Usage in quality control and production (for example in micro manufacturing for closed-loop position control)

Thank you for your attention! Thank you for your attention!