In‐Source High‐Resolution Spectroscopy Using an Integrated Tunable Raman Laser

Tunable single-frequency lasers are the most prominent tool for high-resolution spectroscopy, allowing for the study and exploitation of the electronic structure of atoms. A significant milestone relies on the demonstration of integrated laser technology for performing such a task. The device presented here is composed of a compact Fabry–Perot monolithic resonator capable of producing tunable and Fourier-limited nanosecond pulses with a MHz-class frequency stability without active cavity stabilization elements. It also has the remarkable capability of exploiting the Raman effect to funnel efficiently the broad spectrum of an input laser to a spectrally-bright Stokes pulse at hard-to-access wavelength ranges. The targeted atom for the demonstrations is 152Sm, released as an atomic vapor in a hot cavity environment. Here, the Stokes field is tuned to a wavelength of 433.9 nm, while a crossed-beams spectroscopy setup is used to minimize the Doppler broadened spectral features of the atoms. With this work, the suitability of integrated diamond Raman lasers as a high-resolution in-source spectroscopy tool is demonstrated, enabling many applications in atomic and nuclear physics. The integrated form-factor and inherent simplicity makes such a laser an interesting prospect for quantum-technology based sensing systems and related applications

Tunable spectral squeezers based on monolithically integrated diamond Raman resonators

We report on the generation and tuning of single-frequency laser light in a monolithic Fabry–Pérot diamond Raman resonator operating in the visible spectral range. The device was capable of squeezing the linewidth of a broad multi-mode nanosecond pump laser ([Formula: see text] 7.2 ± 0.9 GHz at [Formula: see text] 450 nm) to a nearly Fourier-limited single axial mode Stokes pulse ([Formula: see text] 114 ± 20 MHz at [Formula: see text] 479 nm). The tuning was achieved by precise adjustment of the resonator temperature, with a measured frequency-temperature tuning slope of [Formula: see text] −3 GHz/K, and a temperature dependence of the first-order Raman phonon line of [Formula: see text] +0.23 GHz/K. The Stokes center frequency was tuned continuously for over 20 GHz (more than twice the free spectral range of the resonator), which, in combination with the broad Ti:Sapphire laser spectral tunability, enables the production of Fourier-limited pulses in the 400–500 nm spectral range. The Stokes center-frequency fluctuations were 52 MHz (RMS) when the temperature of the resonator was actively stabilized. Moreover, the conversion efficiency was up to 30%, yielding an overall power spectral density enhancement of [Formula: see text] from pump to Stokes pulse