Simple phase noise measurement scheme for cavity-stabilized laser systems

Schmid, Fabian; Weitenberg, Johannes; Hänsch, Theodor W.; Udem, Thomas; Ozawa, A.

doi:10.1364/ol.44.002709

“…These lasers require stabilization, if no atomic reference is available at room temperature [8], to sophisticated and expensive reference cavities, with ultra-high stability and finesse, to reduce the free-running linewidth from hundreds of kHz to Hz [9]. In this case, a narrow full-width at half maximum (FWHM) linewidth may still not be indicative of sufficient spectral purity, given the broad phase noise 'pedestal' typical of high gain, edge-emitting semiconductor lasers, which have significant fast frequency noise [10]. Further, depending on the required emission wavelength, these systems often do not provide sufficient optical power.…”

Section: Introductionmentioning

confidence: 99%

Sub-kHz-linewidth VECSELs for cold atom experiments

Moriya

¹

,

Singh

²

,

Bongs

³

et al. 2020

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We report and characterize sub-kHz linewidth operation of an AlGaInP-based VECSEL system suitable for addressing the narrow cooling transition of neutral strontium atoms at 689 nm. When frequency-stabilized to a standard air-spaced Fabry-Perot cavity (finesse 1000) via the Pound-Drever-Hall (PDH) technique, it delivers output power >150 mW in a circularly-symmetric single transverse mode with low frequency and intensity noise. The optical field was reconstructed from the frequency noise error signal via autocorrelation and the Wiener-Khintchine theorem, leading to an estimated linewidth of (125 ± 2) Hz. Optical beat note measurements were performed against a commercial locked laser system and a second, almost identical, VECSEL system resulting in linewidths of 200 Hz and 160 Hz FWHM, respectively. To the best of our knowledge, this is the first demonstration of a VECSEL compatible with the narrowest of lines (few hundred Hz) used for cooling and trapping atoms and ions.

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“…The excitation dynamics of the 1 S-2 S transition in He + depends on many parameters. These include the power of the XUV radiation that drives the transition and that can contribute to ionization from the 2 S state, the focal size, the reduction of the carrier power due to residual phase noise [50], and perturbations of the ions by the trapping RF field [18]. Some of these contributions are difficult to estimate accurately.…”

Section: Discussionmentioning

confidence: 99%

“…We achieve this by tightly locking one infrared comb mode to a continuous wave (CW) reference laser at 1033 nm, corresponding to 1/17 of the 1 S-2 S two-photon transition frequency. The reference CW laser is stabilized to an ultra-stable reference cavity [50]. In addition, the phase noise introduced by path length fluctuations along the setup is measured by heterodyne beat detection with the same reference laser, right before the enhancement resonator for HHG.…”

Section: Laser Setupmentioning

confidence: 99%

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Toward XUV frequency comb spectroscopy of the 1 S–2 S transition in $$\hbox {He}^+$$

Moreno

¹

,

Schmid

²

,

Weitenberg

³

et al. 2023

Self Cite

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The energy levels of hydrogen-like atoms and ions are accurately described by bound-state quantum electrodynamics (QED). $$\hbox {He}^{+}$$ He + ions have a doubly charged nucleus, which enhances the higher-order QED contributions and makes them interesting for precise tests of QED. Systematic effects that currently dominate the uncertainty in hydrogen spectroscopy, such as the second-order Doppler shift and time-of-flight broadening, are largely suppressed by performing spectroscopy on trapped and cooled $$\hbox {He}^{+}$$ He + ions. Measuring a transition in $$\hbox {He}^{+}$$ He + will extend the test of QED beyond the long-studied hydrogen. In this article, we describe our progress toward precision spectroscopy of the 1 S–2 S two-photon transition in $$\hbox {He}^{+}$$ He + . The transition can be excited by radiation at a wavelength of 60.8 nm generated by a high-power infrared frequency comb using high-order harmonic generation (HHG). The $$\hbox {He}^{+}$$ He + ions are trapped in a Paul trap and sympathetically cooled with laser-cooled $$\hbox {Be}^{+}$$ Be + ions. Our recently developed signal detection scheme based on secular-scan spectrometry is capable of detecting $$\hbox {He}^{+}$$ He + excitation with single-event sensitivity. Graphic abstract

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“…From this, the phase noise power spectral density L(ω) can be determined as described in Ref. [36], see Fig. 4.…”

Section: Stirap Setupmentioning

confidence: 99%

Efficient conversion of closed-channel dominated Feshbach molecules of $^{23}$Na$^{40}$K to their absolute ground state

Bause,

Kamijo,

Chen

et al. 2021

Preprint

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We demonstrate the transfer of 23 Na 40 K molecules from a closed-channel dominated Feshbachmolecule state to the absolute ground state. The Feshbach molecules are initially created from a gas of sodium and potassium atoms via adiabatic ramping over a Feshbach resonance at 78.3 G. The molecules are then transferred to the absolute ground state using stimulated Raman adiabatic passage with an intermediate state in the spin-orbit-coupled complexOur measurements show that the pump transition dipole moment linearly increases with the closed-channel fraction. Thus, the pump-beam intensity can be two orders of magnitude lower than is necessary with open-channel dominated Feshbach molecules. We also demonstrate that the phase noise of the Raman lasers can be reduced by filter cavities, significantly improving the transfer efficiency.

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Simple phase noise measurement scheme for cavity-stabilized laser systems

Cited by 18 publications

References 26 publications

Sub-kHz-linewidth VECSELs for cold atom experiments

Sub-kHz-linewidth VECSELs for cold atom experiments

Toward XUV frequency comb spectroscopy of the 1 S–2 S transition in $$\hbox {He}^+$$

Efficient conversion of closed-channel dominated Feshbach molecules of $^{23}$Na$^{40}$K to their absolute ground state

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