1,720,984 research outputs found
A pulsed-Laser Rb atomic frequency standard for GNSS applications
Full text linkWe present the results of 10 years of research related to the development of a Rubidium vapor cell clock based on the principle of pulsed optical pumping (POP). Since in the pulsed approach, the clock operation phases take place at different times, this technique demonstrated to be very effective in curing several issues affecting traditional Rb clocks working in a continuous regime, like light shift, with a consequent improvement of the frequency stability performances. We describe two laboratory prototypes of POP clock, both developed at INRIM. The first one achieved the best results in terms of frequency stability: an Allan deviation of σy(τ) = 1.7 × 10−13 τ−1/2, being τ the averaging time, has been measured. In the prospect of a space application, we show preliminary results obtained with a second more recent prototype based on a loaded cavity-cell arrangement. This clock has a reduced size and exhibited an Allan deviation of σy(τ) = 6 × 10−13 τ−1/2, still a remarkable result for a vapor cell device. In parallel, an ongoing activity performed in collaboration with Leonardo S.p.A. and aimed at developing an engineered space prototype of the POP clock is finally mentioned. Possible issues related to space implementation are also briefly discussed. On the basis of the achieved results, the POP clock represents a promising technology for future GNSSs
Precision test of the ac Stark shift in a rubidium atomic vapor
Full text linkThe ac-Stark shift (also known as the “light shift”) is one of the most important physical processes that arises in precision spectroscopy, affecting the basic understanding of field/matter interactions, measurements of fundamental constants, and even the atomic clocks onboard GPS satellites. Though the theory of the ac-Stark shift was fully developed by the 1960s/70s, precision tests of theory have, for the most part, been few. Taking advantage of recent developments in atomic clock technology, specifically the pulsed approach to atomic signal generation, which allows frequency measurements with a resolution of 10-15, we demonstrate a new methodology for measuring the ac-Stark shift. Here, we report results from a precision examination of the ac-Stark shift in a vapor phase system, examining the resonant frequency of the 87Rb 0-0 hyperfine transition for a perturbing laser tuned over a broad optical frequency range (18 GHz) around the D1 absorption resonance. Over the full frequency range the agreement between semiclassical theory and experiment is very good (better than 5×10-2), and in our experiments we test both the frequency dependence of the scalar and, for the first time, tensor components of the light shift
Recent Results on a Rb Pulsed Optically Pumped Clock for Space Applications
Full text linkWe report on the recent characterization of a Rb microwave clock based on the pulsed optical pumping (POP) principle. The clock is developed in the frame of a INRIM-Leonardo collaboration intended to implement a highly stable and compact device for space applications. The physics package developed by Leonardo S.p.A. includes space-graded components, weights less than 4 kg and occupies only a 4-liters volume. It has been characterized with custom optics and electronics developed at INRIM laboratories. By taking advantage of advanced stabilization techniques for the laser and microwave pulses, this arrangement exhibits state-of-the-art short- and mid-term stability, reaching σ y (40000s) = 6×10 −16 (drift removed) for a 200000s run
A cryogenic sapphire resonator oscillator with 10 − 16 mid-term fractional frequency stability
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Tracking DDS for Coherent Optical Links
No full textWe report on the design and the realization of a
digital architecture based on a tracking direct digital synthesizer (DDS) driven by a Field Programmable Gate Array (FPGA) for the implementation of a coherent optical link for time and frequency dissemination. The realized digital system has been implemented and characterized on a real fiber link on a 47 km metropolitan optical telecommunication network using a Dense Wavelength Division Multiplexing, that is shared with the internet data traffic. We describe the technique, the hardware and the characterization of the link, and we compare the new digital system with the analogic one, that uses common fiber links
electronics
All-optical microwave feedback oscillator with atomic cell resonator
No full textWe report the demonstration of an all-optical self-sustained cell-based microwave feedback oscillator. In this scheme, a microwave reso
nance, optically induced in a buffer-gas filled vapor cell resonator through coherent population trapping (CPT), is detected by a fast photodi
ode, amplified, and used to drive back, through a frequency divider, a Mach–Zehnder electro-optic modulator in a sustaining loop
configuration. The total gain and phase of the system was measured in an open-loop configuration with a network analyzer. In good agree
ment with values predicted by the Leeson effect, the CPT feedback oscillator demonstrates an absolute phase noise of 24 dBrad2/Hz at
1Hz offset frequency, compatible with a fractional frequency stability of 8 10 12 at 1 s, and a phase noise floor of 112 dBrad2/Hz, limited
by the low microwave power available at the photodiode output. The amplitude noise of the oscillator shows a comparable noise floor and,
for offset frequencies lower than 200Hz, a 1/f dependence, due to the presence of the frequency divider in the loop
Frequency-stability performances of the pulsed optically pumped rubidium clock: Recent results and future perspectives
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