Length and dimensional quantities
Research and development activities covering length and dimensional quantities are divided up into maintaining updated references and development studies.
In 2006, the main studies were focusing on :
- The implementation of one measuring system for wavelengths in vacuum based on the utilisation of a comb laser for the calibration of lasers used in length metrology ;
- he design of a positioning device with nanometric resolution coupled to one Atomic Force Microscope (AFM) for dimensional metrology.
Metrology traceability using comb technology
The aim of this study is to implement a device enabling to directly measure any wavelength ranging from 500 nm to 1 100 nm with relative uncertainty in the magnitude or some 10-12.
The device that is being developed is based on one Ti :Sa comb laser pumped at around 532 nm (figure 1) followed by one photonic crystal fibre so that the frequency comb can cover one octave.
Dimensional nanometrology
The LNE's dimensional metrology activity is concentrating on the development of a measurement capability for artefacts originating from the nanotechnologies.
The cornerstone of this activity under development is the conjunction of :
- a high accuracy three-dimensional positioning system ;
- an Atomic Force Microscope (AFM).
High accuracy three-dimensional positioning system
The LNE is constructing one three-dimensional positioning system (figure 2) that has a measurement range :
- of 300 mm along the X and Y axes (with an aimed standard uncertainty of 30 nm overall the range) ;
- of 50 µm along the Z axis (with an aimed standard uncertainty of 2 nm).
Fig. 2. - Positioning system within its environment
This device implements the principle of the dissociated metrology structure that is applied to the angular plate, national reference for angle.
Atomic Force Microscope (AFM)
The sensor selected to scan the topography of the samples is an Atomic Force Microscope . In order to ensure enhanced control over the instrument (more particularly regarding the measurements traceability aspects), the LNE has decided to develop an in-house AFM microscope (figure 3).
Fig. 3. - View of the AFM probe on its based used for coupling the 3D positioning system.
