Miletic, Danijela

2013-11-8, Gruet, Florian, Al-Samaneh, Ahmed, Kroemer, Eric, Bimboes, Laura, Miletic, Danijela, Affolderbach, Christoph, Wahl, Dietmar, Boudot, Rodolphe, Mileti, Gaetano, Michalzik, Rainer

2011, Boudot, Rodolphe, Miletic, Danijela, Dziuban, Piotr, Affolderbach, Christoph, Knapkiewicz, Pawel, Dziuban, Jan, Mileti, Gaetano, Giordano, Vincent, Gorecki, Christophe

Through the detection of Coherent Population Trapping (CPT) resonances, we demonstrate the temperature-dependence cancellation of the Cs clock frequency in microfabricated vapor cells filled with a mixture of Ne and Ar. The inversion temperature at which the Cs clock frequency temperature sensitivity is greatly reduced only depends on the partial pressure of buffer gases and is measured to be lower than 80±C as expected with simple theoretical calculations. These results are important for the development of state-of-the-art Cs vapor cell clocks with improved long-term frequency stability.

2009, Affolderbach, Christoph, Gruet, Florian, Miletic, Danijela, Mileti, Gaetano

We report on our development of a compact and high-performance laser-pumped Rubidium atomic frequency standard. The clock design is based on optical-microwave double-resonance using cw optical pumping, and a physical realization as simple as possible. Main development goals are a short-term instability of ≤ 6 × 10-13 τ-1/2 and a flicker floor of ≤ 1 × 10-14 up to one day. Here we discuss our approaches for controlling the clock's main physical parameters in view of optimized frequency stability.

, Miletic, Danijela, Bandi Nagabhushan, Thejesh, Affolderbach, Christoph, Mileti, Gaetano

We present a comparative study of the light-shifts (ac Stark shift) in a Rb vapour cell using two possible schemes for Rb atomic clocks: double resonance (DR) and coherent population trapping (CPT). For both schemes, the same wall-coated cell in a compact atomic resonator was used. The light-shift resulting from a monochromatic (DR) or a non-monochromatic (CPT) optical excitation was measured as a function of the laser intensity and the laser frequency and compared with existing theoretical results.

2012-9-21, Miletic, Danijela, Affolderbach, Christoph, Hasegawa, M, Boudot, R, Gorecki, C, Mileti, Gaetano

We report on studies on the light-shift in cae-sium miniature atomic clocks based on coherent populationtrapping (CPT) using a micro-fabricated buffer-gas cell(MEMS cell). The CPT signal is observed on the Cs D1-lineby coupling the two hyperfine ground-state Zeeman suble-vels involved in the clock transition to a common excitedstate, using two coherent electromagnetic fields. These lightfields are created with a distributed feedback laser and anelectro-optical modulator. We study the light-shift phe-nomena at different cell temperatures and laser wavelengthsaround 894.6 nm. By adjusting the cell temperature, con-ditions are identified where a miniature CPT atomic clockcan be operated with simultaneously low temperaturecoefficient and suppressed light-shift. The impact of thelight-shift on the clock frequency stability is evaluated.These results are relevant for improving the long-term fre-quency stability of CPT-based Cs vapour-cell clocks.

2010-9-20, Miletic, Danijela, Affolderbach, Christoph, Mileti, Gaetano

In this paper we present our spectroscopic studies on Coherent Population Trapping (CPT) in micro-fabricated Caesium cells and our evaluation of its application in miniature atomic frequency standards (atomic clocks). We observe the CPT signal on the Cs D1-line by coupling two hyperfine ground-state Zeeman sub-levels to a common excited state using two coherent electromagnetic fields created with a modulated DFB laser. Contrarily to double resonance, CPT does not require any microwave cavity, which should facilitate the miniaturization of a future atomic clock device. We study and report here on the light shift phenomena at different cell temperatures and laser wavelength. We also present resonance shifts due to cell temperature variations and clock frequency stability measurements. To the best of our knowledge, this article is the first report on light shift with Cs D1 line in a CPT vapour-cell atomic clock.

, Miletic, Danijela, Affolderbach, Christoph, Hasegawa, M., Boudot, R., Gorecki, C., Mileti, Gaetano

We report on studies on the light-shift in caesium miniature atomic clocks based on coherent population trapping (CPT) using a micro-fabricated buffer-gas cell (MEMS cell). The CPT signal is observed on the Cs D1-line by coupling the two hyperfine ground-state Zeeman sublevels involved in the clock transition to a common excited state, using two coherent electromagnetic fields. These light fields are created with a distributed feedback laser and an electro-optical modulator. We study the light-shift phenomena at different cell temperatures and laser wavelengths around 894.6 nm. By adjusting the cell temperature, conditions are identified where a miniature CPT atomic clock can be operated with simultaneously low temperature coefficient and suppressed light-shift. The impact of the light-shift on the clock frequency stability is evaluated. These results are relevant for improving the long-term frequency stability of CPT-based Cs vapour-cell clocks.

2012-4-27, Miletic, Danijela, Bandi, Thejesh, Affolderbach, Christoph, Mileti, Gaetano

We present a comparative study of the light-shifts (ac Stark shift) in a Rb vapour cell using two possible schemes for Rb atomic clocks: double resonance (DR) and coherent population trapping (CPT). For both schemes, the same wall-coated cell in a compact atomic resonator was used. The light-shift resulting from a monochromatic (DR) or a non-monochromatic (CPT) optical excitation was measured as a function of the laser intensity and the laser frequency and compared with existing theoretical results

2010, Miletic, Danijela, Dziuban, Piotr, Boudot, Rodolphe, Hasegawa, M., Chutani, R.K., Mileti, Gaetano, Giordano, Vincent, Gorecki, Christophe

Presented is the observation of a quadratic temperature dependence of the Cs 0-0 ground state hyperfine resonance frequency in a single Neon (Ne) buffer gas vapour microcell. The inversion temperature, expected to be theoretically independent of the buffer gas pressure, is measured to be about 80-C for two different samples. A proposal to develop chip scale atomic clocks with improved long-term frequency stability, simpler configuration (a single buffer gas instead of a buffer gas mixture) and then relaxed constraints on pressure accuracy during the cell filling procedure is presented.

, Gruet, Florian, Al-Samaneh, Ahmed, Kroemer, Eric, Bimboes, Laura, Miletic, Danijela, Affolderbach, Christoph, Wahl, Dietmar, Boudot, Rodolphe, Mileti, Gaetano, Michalzik, Rainer

We report on the characterization and validation of custom-designed 894.6 nm vertical-cavity surface-emitting lasers (VCSELs), for use in miniature Cs atomic clocks based on coherent population trapping (CPT). The laser relative intensity noise (RIN) is measured to be 1×10⁻¹¹ Hz⁻¹ at 10 Hz Fourier frequency, for a laser power of 700 μW. The VCSEL frequency noise is 10¹³ ƒ ⁻¹ Hz²/Hz in the 10 Hz < ƒ < 10⁵ Hz range, which is in good agreement with the VCSEL’s measured fractional frequency instability (Allan deviation) of ≈ 1 × 10⁻⁸ at 1 s, and also is consistent with the VCSEL’s typical optical linewidth of 20–25 MHz. The VCSEL bias current can be directly modulated at 4.596 GHz with a microwave power of −6 to +6 dBm to generate optical sidebands for CPT excitation. With such a VCSEL, a 1.04 kHz linewidth CPT clock resonance signal is detected in a microfabricated Cs cell filled with Ne buffer gas. These results are compatible with state-of-the-art CPT-based miniature atomic clocks exhibiting a short-term frequency instability of 2–3×10⁻¹¹ at τ = 1 s and few 10⁻¹² at τ = 10⁴ s integration time.