# Octave-spanning tunable parametric oscillation in crystalline Kerr microresonators

## TL;DR

This paper demonstrates that crystalline magnesium fluoride microresonators can generate widely tunable, coherent optical sidebands across an octave, enabling compact, efficient, and low-cost sources for various applications.

## Contribution

It introduces ultrahigh-Q crystalline microresonators with engineered dispersion for broad, low-power tunable parametric oscillation across an octave.

## Key findings

- Hundreds of nanometers of sideband tunability achieved
- Discrete tunability over an optical octave from 1083 nm to 2670 nm
- Mid-infrared sidebands observed near 4000 nm

## Abstract

Parametric nonlinear optical processes allow for the generation of new wavelengths of coherent electromagnetic radiation. Their ability to create radiation that is widely tunable in wavelength is particularly appealing, with applications ranging from spectroscopy to quantum information processing. Unfortunately, existing tunable parametric sources are marred by deficiencies that obstruct their widespread adoption. Here we show that ultrahigh-Q crystalline microresonators made of magnesium fluoride can overcome these limitations, enabling compact and power-efficient devices capable of generating clean and widely-tunable sidebands. We consider several different resonators with carefully engineered dispersion profiles, achieving hundreds of nanometers of sideband tunability in each device when driven with a standard low-power laser at 1550 nm. In addition to direct observations of discrete tunability over an entire optical octave from 1083 nm to 2670 nm, we record signatures of mid-infrared sidebands at almost 4000 nm. The simplicity of the devices considered -- compounded by their remarkable tunability -- paves the way for low-cost, widely-tunable sources of electromagnetic radiation.