A Chip-Scale Optical Frequency Reference for the Telecommunication Band Based on Acetylene

Probing molecules in gas cells of subwavelength thickness with high frequency resolution

Miniaturizing and integrating atomic vapor cells is widely investigated for the purposes of fundamental measurements and technological applications such as quantum sensing. Extending such platforms to the realm of molecular physics is a fascinating prospect that paves the way for compact frequency metrology as well as for exploring light-matter interactions with complex quantum objects. Here, we perform molecular rovibrational spectroscopy in a thin-cell of micrometric thickness, comparable to excitation wavelengths. We operate the cell in two distinct regions of the electromagnetic spectrum, probing ν1 + ν3 resonances of acetylene at 1.530 µm, within the telecommunications wavelength range, as well as the ν3 and ν2 resonances of SF6 and NH3 respectively, in the mid-infrared fingerprint region around 10.55 µm. Thin-cell confinement allows linear sub-Doppler transmission spectroscopy due to the coherent Dicke narrowing effect, here demonstrated for molecular rovibrations. Our experiment can find applications extending to the fields of compact molecular frequency references, atmospheric physics or fundamental precision measurements.

Micro-fabricated components for cold atom sensors

Laser cooled atoms have proven transformative for precision metrology, playing a pivotal role in state-of-the-art clocks and interferometers and having the potential to provide a step-change in our modern technological capabilities. To successfully explore their full potential, laser cooling platforms must be translated from the laboratory environment and into portable, compact quantum sensors for deployment in practical applications. This transition requires the amalgamation of a wide range of components and expertise if an unambiguously chip-scale cold atom sensor is to be realized. We present recent developments in cold-atom sensor miniaturization, focusing on key components that enable laser cooling on the chip-scale. The design, fabrication, and impact of the components on sensor scalability and performance will be discussed with an outlook to the next generation of chip-scale cold atom devices.

Chip-scale atomic wave-meter enabled by machine learning

The quest for miniaturized optical wave-meters and spectrometers has accelerated the design of novel approaches in the field. Particularly, random spectrometers (RS) using the one-to-one correlation between the wavelength and an output random interference pattern emerged as a promising tool combining high spectral resolution and cost-effectiveness. Recently, a chip-scale platform for RS has been demonstrated with a markedly reduced footprint. Yet, despite the evident advantages of such modalities, they are very susceptible to environmental fluctuations and require an external calibration process. To address these challenges, we demonstrate a paradigm shift in the field, enabled by the integration of atomic vapor with a photonic chip and the use of a machine learning classification algorithm. Our approach provides a random wave-meter on chip device with accurate calibration and enhanced robustness against environmental fluctuations. The demonstrated device is expected to pave the way toward fully integrated spectrometers advancing the field of silicon photonics.

Linear Probing of Molecules at Micrometric Distances from a Surface with Sub-Doppler Frequency Resolution

We report on precision spectroscopy of subwavelength confined molecular gases. This was obtained by rovibrational selective reflection of NH_{3} and SF_{6} gases using a quantum cascade laser at λ≈10.6  μm. Our technique probes molecules at micrometric distances (≈λ/2π) from the window of a macroscopic cell with submegahertz resolution, allowing molecule-surface interaction spectroscopy. We exploit the linearity and high resolution of our technique to gain novel spectroscopic information on the SF_{6} greenhouse gas, useful for enriching molecular databases. The natural extension of our work to thin cells will allow compact frequency references and improved measurements of the Casimir-Polder interaction with molecules.