Reference : UMR7345-ERIROS-025
Workplace : MARSEILLE 13
Date of publication : Wednesday, September 21, 2022
Type of Contract : FTC Scientist
Contract Period : 18 months
Expected date of employment : 1 November 2022
Proportion of work : Part time
Remuneration : between 2476,73 € and 3499,63 € gross monthly for an 80% share depending on experience
Desired level of education : PhD
Experience required : 1 to 4 years
Fine characterization of the REFIMEVE metrological signal, and development of a method for optimal servo-control of an optical frequency comb at the near end user to transfer the ultimate stability and traceability to the REFIMEVE IS, while limiting the high frequency phase noise.
-Definition and implementation of protocols to transfer the ultimate stability and traceability to the REFIMEVE IS, while limiting the transfer of high frequency phase noise, in two different situations: when the signal has traveled several hundred km (PIIM) or for a nearby user (<100 km, LPL).
-Highlighting of the optimal conditions of use of the REFIMEVE signal for the distant user.
-Management of measurement campaigns for the fine characterization of the REFIMEVE signal in two different experimental conditions, in two very different points of the network.
-Implementation of protocols for the control and/or use of the information provided by the signal
-Management of the exchange of technical information within the collaboration with the LPL (Laser Physics Laboratory).
Mastery of ultra-stable laser sources and their controllers.
Mastery of laser sources based on laser diodes and their control systems.
Mastery of pulsed laser sources of the optical frequency comb type
Mastery of the challenges of precision measurements in the optical frequency domain.
This experimental work will be conducted within the CIML team of the PIIM laboratory. This group has a long expertise on the trapping and laser interrogation of atomic ions, for precision measurements. It implements coherent protocols taking advantage of the simultaneous control of several lasers. The future post-doc will work in collaboration with several members of the group and will be able to acquire new know-how and skills, under the supervision of Caroline Champenois.
Constraints and risks
work on screen
In the PIIM laboratory, the availability of an exploitable signal by the REFIMEVE consortium has allowed us to confirm the performances of our Ultra-Stable Laser, estimated until now locally, i.e. a relative stability of 10-14 on a time scale ranging from 1 to 10 s. It also allowed us to verify the stability transfer of the LUS to the frequency comb over an octave, whereas until now our comparison covered only a few hundred MHz.
During the first years of the experiment, the frequency of the THz transition studied in a cloud of trapped ions was deduced from the measurement of the frep comb repetition frequency, referenced on a GPS signal. The uncertainty induced on the measurement of the THz transition frequency was then lower than 100 Hz. When interrogating the THz transition, real-time monitoring of the frequency difference between the REFIMEVE signal and the nearest comb tooth also allows us to avoid the frequency drift of the LUS, induced by the thermal drift of the high finesse ULE cavity which serves as a local reference. Because of the noisy short-term spectrum (<10 s) of the REFIMEVE signal received at PIIM, the strategy used so far is a "post-processing" mode: the frep value deduced from the beat at the optical frequency of REFIMEVE is time-stamped, to be included in the calculations of the transition frequency, which reduces the uncertainty on the absolute value of the frequency of the THz transition observed at values lower than 100mHz
To go further, the best use of the REFIMEVE signal without degrading the short term coherence of the frequency comb is a challenge to limit the frequency shifts of the CPT (Coherent Population Trapping) lines induced by light.
At LPL, it is the high frequency phase noise of the REFIMEVE signal that limits the resolution of molecular spectroscopy.
We talk about it on Twitter!