Broadband Excitation by Chirped Pulses: Application to Single Electron Spins in Diamond

TL;DR

This paper demonstrates that using chirped microwave pulses in Ramsey experiments on NV-centers in diamond significantly broadens spectral bandwidth, enhances resolution, and reveals forbidden transitions without high power requirements.

Contribution

The study introduces a chirped pulse method for NV-center spectroscopy that improves bandwidth and resolution while enabling detection of forbidden transitions, surpassing conventional techniques.

Findings

Bandwidth increased by at least an order of magnitude.

Resolution improved by at least an order of magnitude.

Forbidden zero- and double quantum transitions detected.

Abstract

Pulsed excitation of broad spectra requires very high field strengths if monochromatic pulses are used. If the corresponding high power is not available or not desirable, the pulses can be replaced by suitable low-power pulses that distribute the power over a wider bandwidth. As a simple case, we use microwave pulses with a linear frequency chirp. We use these pulses to excite spectra of single NV-centers in a Ramsey experiment. Compared to the conventional Ramsey experiment, our approach increases the bandwidth by at least an order of magnitude. Compared to the conventional ODMR experiment, the chirped Ramsey experiment does not suffer from power broadening and increases the resolution by at least an order of magnitude. As an additional benefit, the chirped Ramsey spectrum contains not only `allowed' single quantum transitions, but also `forbidden' zero- and double quantum transitions, which can be distinguished from the single quantum transitions by phase-shifting the readout pulse with respect to the excitation pulse or by variation of the external magnetic field strength.