1,720,986 research outputs found
PRACTICAL REALIZATION OF THE DEFINITION OF THE METRE AT INRIM
No full textIn this paper we present the traceability chain for the calibration of the frequency of laser standards that realize the definition of the metre at the National Institute of Metrological Research (INRIM) in Italy in accordance with the mise en pratique issued by the CIPM. We describe the way our femtosecond laser frequency combs are referenced to the SI second and the new research activity on the production and testing of iodine cells
Laser Frequency Stabilization for Aerospace Applications
No full textLong term frequency stability of lasers is a key parameter in many research areas
ranging from dimensional metrology to fundamental physics. Many solutions have
been proposed by the scientific community and lasers whose frequency is referenced
to molecular transitions are commonly used when long term stability and wavelength
accuracy are needed. Our goal is the development of a frequency stabilization system
with a relative frequency stability (Allan variance) of 1E-12 over 1 second integration
time which will be suitable for aerospace applications. The frequency reference is a
10 cm long Fabry-Perot optical resonator which has been designed in order to
withstand the huge launch loads (up to 30g at 1 kHz). As the stability of the resonant
frequency is determined by the long term stability of the cavity length, a low CTE
material (ULE) was adopted as the cavity spacer. During the laboratory tests the
cavity has been housed inside a mechanical insulating vacuum chamber, thermally
controlled by a digital system. The laser is referenced to one of the cavity resonances
by means of a digital implementation of the Pound-Drever-Hall technique. An FPGA
equipped with a small number of auxiliary components provides a flexible and
reconfigurable digital system. A laser was locked to an iodine transition using the
“digital PDH” and a classical analog system; the same frequency stability (parts in
1E13 over a 1 second integration time) was measured. Currently we are working on the
implementation of the thermostat in order to properly length-stabilize the Fabry-Perot
resonator and to characterize the coefficient of thermal expansion of the ULE spacer
we are using
Multilayer control of an optical reference cavity for space applications
No full textThe paper is concerned with multilayer and fine thermal control of an optical reference cavity for space applications, under development at National Metrology Institute, Turin, Italy. The cavity, made by ultra low expansion glass (Corning ULE), must be kept close to the zero-expansion temperature (close to 25 °C) of the glass. The target can only be met by active control, while leaving the cavity free of sensor and actuators. This is obtained by two concepts: thermal bath and reference thermal sink, the latter allowing zero-expansion temperature to be reached by heaters in a wide environment range. Preliminary experiments of the two concepts leading to cavity design are detailed
Comparison between the 127I2 stabilized He-Ne lasers at 633 nm and 612 nm of the BIPM and the IMGC
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