Tunable diamond raman lasers for resonance photo-ionization and ion beam production

Abstract

Lasers with wide tunability and tailored linewidth are key assets for spectroscopy research and applications. We show that diamond, when configured as a Raman laser, provides agile access to a broad range of wavelengths while being capable of efficient and selective photo-excitation of atomic species and suitable spectroscopic applications thanks to its narrow linewidth. We demonstrate the use of a compact diamond Raman laser capable of efficient ion beam production by resonance ionization of Sm isotopes in a hot metal cavity. The ionization efficiency was compared with a conventional Ti:sapphire laser operating at the same wavelength. Our results show that the overall ion current produced by the diamond Raman laser was comparable -or even superior in some cases-to that of the commonly used Ti:sapphire lasers. This demonstrates the photo-ionization capability of Raman lasers in the Doppler broadening-dominated regime, even with the considerable differences in their spectral properties. In order to theoretically corroborate the obtained data and with an eye on studying the most convenient spectral properties for photo-ionization experiments, we propose a simple excitation model that analyzes and compares the spectral overlap of the Raman and Ti:Sapphire lasers with the Doppler-broadened atomic spectral line. We demonstrate that Raman lasers are a suitable source for resonance photo-ionization applications in this regime.

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

“…The saturation effect (also referred to as power broadening) on the measured transition linewidth can be fitted with a saturated Lorentzian function as follows: $$\alpha (\Delta \nu _s) \propto L(\Delta \nu _s)\times (1/(1+S L(\Delta \nu _s)))$$, where $$S$$ is a saturation parameter that depends on the overall laser intensity, $$\Delta \nu _s$$ the laser detuning and $$L(\Delta \nu _s)$$ is a Lorentzian function with width as the unsaturated linewidth of the transition. [ 29 ] The result of this fitting retrieves an unsaturated width of 0.51 GHz at FWHM. Compare this to the convolution of the laser linewidth ($$\Delta \nu _s \simeq$$ 300 MHz, Gaussian lineshape) and the PI‐LIST resolution ($$\Delta f_r \simeq$$ 0.4 GHz, Gaussian lineshape) which is around $$\Delta \nu _{res} = \sqrt {\Delta f_r ^2 + \Delta \nu _s^2} \simeq$$ 0.5 GHz.…”

“…[26,27] In terms of linewidth, the Stokes spectrum can resemble that of the pump in the so-called high Raman gain regime. [28,29] The Raman process can be further cascaded using multiple Stokes orders, extending the available spectral coverage at virtually no cost. [30,31] Embedding the laser resonator within the Raman media proved to have additional advantages, such as the ability to produce a frequency stable output directly from a monolithic Fabry-Perot resonator, circumventing the need of external mechanical feedback loops to control the cavity length.…”