Diamond Radio Receiver: Nitrogen-Vacancy Centers as Fluorescent Transducers of Microwave Signals

We demonstrate a robust frequency-modulated radio receiver using electron-spin-dependent photoluminescence of nitrogen-vacancy centers in diamond. The carrier frequency of the frequency-modulated signal is in the 2.8-GHz range, determined by the zero-field splitting in the nitrogen-vacancy electronic ground state. The radio can be tuned over 300 MHz by applying an external dc magnetic field. We show the transmission of high-fidelity audio signals over a bandwidth of 91 kHz using the diamond radio. We demonstrate operating temperature of the radio as high as $350°\mathrm{C}$.

Figure 1

(a) Experimental schematic of the nitrogen-vacancy (NV) radio receiver. The NV centers in diamond demodulate frequency-modulated (FM) microwave signals and map it onto the fluorescence. The NV centers are pumped by a green (532 nm) laser. The dc magnetic field $B_0$ is applied to tune the detecting carrier frequency of the microwave signal. (b) The principle of NV FM microwave demodulation. The black trace shows experimentally measured optically detected magnetic resonance (ODMR) near 2.87 GHz of NV centers. The fluorescence intensity depends on the detuning of the input microwave frequency from the ODMR resonance. The carrier frequency ($f_c$) is positioned on the slope, and changes in microwave frequency are mapped onto the changes in fluorescence intensity. (c) Illustration of the input FM microwave signal to be demodulated (blue) and resulting output amplitude-modulated fluorescence signal (red).

Figure 2

The demodulated fluorescence intensities (shown in blue) compared to the original modulating signal (black). The curves are offset for clarity. In the case of (a) 1-kHz sine wave, (b) 1-kHz square wave, and (c) an audio signal. The carrier microwave is at 2.85 GHz.

Figure 3

(a) Optical response of an NV radio receiver on the frequency of modulating signals. The solid line is measured by the lock-in amplifier, and the dashed line is measured by the network analyzer. Lines of different color correspond to different carrier microwave powers indicated in the inset. Inset: dependency of $-3\mathrm{dB}$ optical bandwidth on the powers of input microwave signals. (b) The harmonic distortion of the output fluorescence intensity in the case of a 1-kHz sine wave as a modulating signal with a maximum frequency deviation of $\mathrm{\Delta }=2.42\mathrm{MHz}$. The power of the microwave signal is $-5\mathrm{dBm}$.

Figure 4

(a) Optical response on the dc magnetic field $B_0$ under different environmental temperatures. The magnetic field $B_0$ is controlled by the voltage applied on the electromagnet. The sign of the optical response indicates the polarity between the NV fluorescence signal and the modulating signal. (b) The maximum responses on the environmental temperature, the response amplitudes of optimum negative and positive detuning correspond to the minimum and maximum points in (a). (c) The optimum electromagnetic voltages required to compensate the temperature shifts.