Optical Spectral Linewidths in Solids

Donny R. Pearson, Ashwith Varadaraj Prabhu, Selvin Tobar +5 more

Rare-earth emitters in solids are well suited for implementing efficient, long-lived quantum memory coupled to integrated photonics for scalable quantum technologies. They are typically introduced as dopants in a solid-state host, but this introduces disorder and limits the available density of emitters. Stoichiometric materials can offer high densities with narrow optical linewidths. The regular spacing of emitters also opens possibilities for quantum information processing and collective effects. Here, we show narrow optical linewidths in a layered stoichiometric crystalline material, NaEu(IO_{3})_{4}. We observed an inhomogeneous linewidth of 2.2(1) GHz and a homogeneous linewidth of 120(4) kHz. Using spectral hole-burning techniques, we observe a hyperfine spin lifetime of 1.9(4) s. Furthermore, we demonstrate an atomic frequency comb delay of up to 800 ns.

A.L. Schawlow

Matthew J. Sellars, Richard S. Meltzer, Peter Fisk +1 more

Optical hole burning is used to study optical dephasing of the 7F0 ⇒ 5D0 transition in samples of Y2O3:Eu3+ grown by both flame fusion and laser-heated pedestal growth. The samples exhibited a wide variation in their low-temperature hole widths, and the measured hole linewidths were in reasonable agreement with homogeneous linewidths obtained from values of T2 that were determined with two-pulse photon echoes. The sample that had the longest value of T2 (510 μs) from the echo measurements gave a hole width of 3.5 kHz. This is believed to be the narrowest spectral feature observed directly in the frequency domain for a solid. Other samples produced wider holes that were not correlated with the Eu3+ impurity concentrations. Time-resolved hole burning in one of the samples showed a slow and continuous broadening of the spectral hole from 130 kHz at 3 ms to 900 kHz at 10 s after hole burning. It is suggested that the additional broadening is associated with some form of disorder modes in this ordered crystalline solid.

Donald W. Goodwin

Fariba Islam, Chang-Min Lee, Kyu-Young Kim +4 more

Silicon T centers are promising spin-photon interfaces in solid-state platforms for telecom-compatible, scalable quantum information technologies. A major challenge for T centers in nanophotonics is spectral diffusion, where fluctuations in the local electric-field environment from surface and bulk charge states broaden the optical transition and reduce photon indistinguishability. Strategies that directly suppress spectral diffusion are therefore critical for improving T-center-based quantum photonic devices. Here, we use atomic-layer-deposited Al2O3 to passivate the silicon surface and demonstrate a systematic narrowing of T center optical linewidths. Across our measurements, Al2O3 passivation reduces the T center emission linewidth by up to 57%. Complementary above-bandgap illumination and spectral hole burning measurements show that the remaining linewidth contains a significant spectral-diffusion component caused by adjacent charge traps, while placing an upper bound of approximately 75 MHz on the homogeneous linewidth. This work provides a CMOS-compatible path toward generating indistinguishable photons from silicon T centers for scalable quantum photonic applications.

Baldassare Di Bartolo