Efficient excitation of dye molecules for single photon generation

Abstract

A reliable single photon source is required for many aspects of quantum technology. Organic molecules are attractive for this application because they can have high quantum yield and can be photostable, even at room temperature. To generate a photon with high probability, a laser must excite the molecule efficiently. We develop a simple model for that efficiency and discuss how to optimise it. We demonstrate the validity of our model through experiments on a single dibenzoterrylene (DBT) molecule in an anthracene crystal. We show that the excitation probability cannot exceed 75% at room temperature, but can increase to over 99% if the sample is cooled to liquid nitrogen temperature. The possibility of high photon generation efficiency with only modest cooling is a significant step towards a reliable photon source that is simple and practical.

Narrow and Stable Single Photon Emission from Dibenzoterrylene inpara‐Terphenyl Nanocrystals

“…Fitting this data with a single exponential decay we find an excited state lifetime of 4.60±0.02 ns. This is in line with the lifetime of DBT in Ac [1,27] . Switching back to the cw excitation, we sent the resulting fluorescence to a spectrometer to obtain a fluorescence spectrum for an ensemble of DBT in pT at room temperature, shown in Figure 2(b).…”

“…The sharp cut‐on at 750 nm is due to the filter used to reject excitation light. Fitting the spectrum with a single Lorentzian, combined with a step function to account for the filter, gave a central wavelength of 772.1±0.2 nm and a linewidth of ≈9 THz, similar to the 8 THz seen for DBT in Ac at room temperature [27] . This Lorentzian fit does not account for the inhomogeneous distribution of molecules or the vibrational transitions and is intended to be a guide to cryogenic measurements.…”

Polymer-encapsulated organic nanocrystals for single photon emission

“…Similarly, the S value matches the expected value from the laser power used and the previous saturation measurements of S = 0.16 ± 0.01. These measurements show no significant deviation from expected values for DBT in both nanocrystals [5] and larger co-sublimation grown crystals [26]. Additionally, this molecule was excited at high intensities for many hours without any blinking or change in spectral properties, highlighting the suitability of the nano-encapsulation for protecting the emitter.…”

“…We find R ∞ = 760 ± 50 kcnt s −1 and P sat = 2500 ± 400 µW on fitting this data. The increase in P sat compared to the case of resonant pumping is mainly due to the 40 GHz width of the vibrational transition, which is ∼1000 times broader than the S 0,0 → S 1,0 transition [26]. To maximise the signal-to-background we adjusted the detuning of the laser from the vibrational transition to avoid exciting other nearby molecules.…”

Reverse Intersystem Crossing of Single Deuterated Perylene Molecules in a Dibenzothiophene Matrix

“…Some of these proven concepts of single molecules as probes are high sensitivity to electric fields and charges by an electrically‐ or optically‐induced Stark effect, [10–12] or single molecules as nano‐microphones of mechanically induced strain [13] . Recently, single‐molecule emitters have also received significant attention as stable and tunable single‐photon sources and non‐linear elements in integrated photonic devices [14–18] …”