Abstract The influence of the spectral linewidth of single-frequency lasers on the parameters of the electromagnetically induced absorption resonances in rubidium vapour is examined. We use two counter-propagating pump and probe beams to prepare high-contrast magneto-optical resonances in a Hanle-configuration on Rb atoms contained in a paraffin-coated optical cell. Due to the spectral linewidth of the excitation laser, various groups of atoms are involved in creating the coherent resonance, which changes its parameters. The experimental results show the potential of the system to improve the signal-to-noise ratio for more sensitive measurement of weak magnetic fields.Abstract The influence of the spectral linewidth of single-frequency lasers on the parameters of the electromagnetically induced absorption resonances in rubidium vapour is examined. We use two counter-propagating pump and probe beams to prepare high-contrast magneto-optical resonances in a Hanle-configuration on Rb atoms contained in a paraffin-coated optical cell. Due to the spectral linewidth of the excitation laser, various groups of atoms are involved in creating the coherent resonance, which changes its parameters. The experimental results show the potential of the system to improve the signal-to-noise ratio for more sensitive measurement of weak magnetic fields.

Journal of Physics Conference SeriesApr 1, 20250 citations

Collisional dephasing and the reduction of laser phase-noise to amplitude-noise conversion in a resonant atomic vapor

John G. Coffer, M. Anderson, James C. Camparo

When resonant laser light passes through a vapor, the laser's intrinsic phase fluctuations induce random variations in the atomic coherence, which in turn give rise to fluctuations in the medium's absorption cross section. Hence, laser phase modulation noise (PM) is converted to transmitted laser intensity (i.e., amplitude) modulation noise (AM). Here, we consider the influence of collisional dephasing on the PM-to-AM conversion process. Specifically, we measure the relative intensity noise of a diode laser beam, resonant with the Rb ${D}_{1}$ transition at 794.7 nm, after it has passed through a ${\mathrm{Rb}}^{87}/{\mathrm{N}}_{2}$ vapor as a function of nitrogen number density. Our results demonstrate that when collisional dephasing is very rapid, the spectral density of cross-section fluctuations is reduced, so that there is a significant decrease in the efficiency of PM-to-AM conversion at low Fourier frequencies. These results imply that, in general, when laser PM-to-AM conversion is the dominant noise process, pressure broadening can actually increase spectroscopic sensitivity.When resonant laser light passes through a vapor, the laser's intrinsic phase fluctuations induce random variations in the atomic coherence, which in turn give rise to fluctuations in the medium's absorption cross section. Hence, laser phase modulation noise (PM) is converted to transmitted laser intensity (i.e., amplitude) modulation noise (AM). Here, we consider the influence of collisional dephasing on the PM-to-AM conversion process. Specifically, we measure the relative intensity noise of a diode laser beam, resonant with the Rb ${D}_{1}$ transition at 794.7 nm, after it has passed through a ${\mathrm{Rb}}^{87}/{\mathrm{N}}_{2}$ vapor as a function of nitrogen number density. Our results demonstrate that when collisional dephasing is very rapid, the spectral density of cross-section fluctuations is reduced, so that there is a significant decrease in the efficiency of PM-to-AM conversion at low Fourier frequencies. These results imply that, in general, when laser PM-to-AM conversion is the dominant noise process, pressure broadening can actually increase spectroscopic sensitivity.

Physical Review AFeb 6, 200240 citations

Classical theory of laser noise

Jacques Arnaud

Optical and Quantum ElectronicsFeb 1, 199523 citations

Quantum-Noise Measurement in Difference Frequency Generation

Jianming Huang, Prem Kumar

Quantum Electronics and Laser Science ConferenceMay 12, 19910 citations

420 nm Rb optical frequency standard with short-term frequency stability below 2 × 10 −13

RenPing Sun, WeiHao Zhao, Yu Zhang +4 more

We experimentally study the character of saturated absorption spectroscopy (SAS) of the 87 Rb 5 S 1/2 → 6 P 3/2 transition at 420 nm in a miniature cubic glass cell (3 × 3 × 3 mm 3 ). The influences of the laser intensity and cell temperature on the saturated absorption resonance are comprehensively investigated to determine the optimal parameters for a compact stabilized frequency standard. By stabilizing the laser frequency to the optimized SAS signal, a beatnote stability of 2.4 × 10 −13 at 1 s is measured between two identical SAS systems, corresponding to a single-laser stability of 1.7 × 10 −13 at 1 s, assuming equal contribution from each laser. A further analysis of the noise budget reveals that the main contributions of short-term stability arise from the intermodulation effect and the laser frequency noise through the frequency modulation to amplitude modulation (FM-AM) conversion process. Our work provides a promising route toward high-performance miniaturized optical frequency standards based on high-lying excited-state transitions.We experimentally study the character of saturated absorption spectroscopy (SAS) of the 87 Rb 5 S 1/2 → 6 P 3/2 transition at 420 nm in a miniature cubic glass cell (3 × 3 × 3 mm 3 ). The influences of the laser intensity and cell temperature on the saturated absorption resonance are comprehensively investigated to determine the optimal parameters for a compact stabilized frequency standard. By stabilizing the laser frequency to the optimized SAS signal, a beatnote stability of 2.4 × 10 −13 at 1 s is measured between two identical SAS systems, corresponding to a single-laser stability of 1.7 × 10 −13 at 1 s, assuming equal contribution from each laser. A further analysis of the noise budget reveals that the main contributions of short-term stability arise from the intermodulation effect and the laser frequency noise through the frequency modulation to amplitude modulation (FM-AM) conversion process. Our work provides a promising route toward high-performance miniaturized optical frequency standards based on high-lying excited-state transitions.

Optics ExpressJul 7, 20261 citation

{D}_{1}

transition at 794.7 nm, after it has passed through a

{\mathrm{Rb}}^{87}/{\mathrm{N}}_{2}

vapor as a function of nitrogen number density. Our results demonstrate that when collisional dephasing is very rapid, the spectral density of cross-section fluctuations is reduced, so that there is a significant decrease in the efficiency of PM-to-AM conversion at low Fourier frequencies. These results imply that, in general, when laser PM-to-AM conversion is the dominant noise process, pressure broadening can actually increase spectroscopic sensitivity.