The influence of phonon harmonicity on spectrally pure resonant Stokes fields

TL;DR

This paper investigates how phonon harmonicity affects the spectral purity of resonant Stokes fields in diamond Raman lasers, introducing a measurement method for temperature-dependent refractive index and demonstrating stabilized nanosecond pulses.

Contribution

It presents a novel method to accurately measure the temperature-dependent refractive index of diamond considering phonon effects and demonstrates stabilized Fourier-limited Stokes pulses.

Findings

Measured the temperature-dependent index of refraction of diamond.

Calculated the thermo-optic coefficient and Gruneisen parameter of diamond.

Achieved stabilized Stokes pulses with less than 4 MHz frequency deviation.

Abstract

Thanks to their highly coherent emission and compact form factor, single axial mode diamond Raman lasers have been identified as a valuable asset for applications including integrated quantum technology, high resolution spectroscopy or coherent optical communications. While the fundamental emission linewidth of these lasers can be Fourier limited, their thermo-optic characteristics lead to drifts in their carrier frequency, posing important challenges for applications requiring ultra-stable emission. We propose here a method for measuring accurately the temperature-dependent index of refraction of diamond by employing standing Stokes waves produced in a monolithic Fabry-Perot (FP) diamond Raman resonator. Our approach takes into account the influence of the temperature on the first-order phonon line and the average lattice phonon frequency under intense stimulated Raman scattering (SRS) conditions. We further utilize this model to calculate the temperature-dependent thermo-optic coefficient and the Gruneisen parameter of diamond in the visible spectral range. The theory is accompanied by the demonstration of tunable Fourier-limited Stokes nanosecond pulses with a stabilized center frequency deviation of less than <4 MHz.