Efficient optical pumping using hyperfine levels in ¹⁴⁵Nd³⁺:Y₂SiO₅ and its application to optical storage

Abstract

Efficient optical pumping is an important tool for state initialization in quantum technologies, such as optical quantum memories. In crystals doped with Kramers rare-earth ions, such as erbium and neodymium, efficient optical pumping is challenging due to the relatively short population lifetimes of the electronic Zeeman levels, of the order of 100 ms at around 4 K. In this article we show that optical pumping of the hyperfine levels in isotopically enriched 145 Nd + 3 :Y 2 SiO 5 crystals is more efficient, owing to the longer population relaxation times of hyperfine levels. By optically cycling the population many times through the excited state a nuclear spin flip can be forced in the ground state hyperfine manifold, in which case the population is trapped for several seconds before relaxing back to the pumped hyperfine level. To demonstrate the effectiveness of this approach in applications we perform an atomic frequency comb memory experiment with 33% storage efficiency in 145 Nd + 3 :Y 2 SiO 5 , which is on a par with results obtained in non-Kramers ions, e.g. europium and praseodymium, where optical pumping is generally efficient due to the quenched electronic spin. Efficient optical pumping in neodymium-doped crystals is also of interest for spectral filtering in biomedical imaging, as neodymium has an absorption wavelength compatible with tissue imaging. In addition to these applications, our study is of interest for understanding spin dynamics in Kramers ions with nuclear spin.

Initialisation protocol for efficient quantum memories using resolved hyperfine structure

“…The long hyperfine lifetime compared to the optical lifetime means the 167 Er 3+ background can theoretically be reduced to < 0.01 dB, and the I = 0 isotope impurities will then dominate, leading to a predicted efficiency of 34.5%. This is similar to AFC delay line efficiencies demonstrated in Pr (35%) [15], Eu (32%) [16], and 145 Nd (33%) [17].…”

Demonstrating the Potential of Alkali Metal-Doped Cyclic C6O6Li6 Organometallics as Electrides and High-Performance NLO Materials

“…Interest in designing high-performance nonlinear optical (NLO) materials is growing rapidly due to their widespread applications in optical computing, − optical communication, , optical switching, , optical logic functions, , dynamic image processing, , and many other optoelectronic fields. − Recently, a unique class of compounds known as electrides having isolated excess electrons has garnered great interest from the chemical society. − Due to this nontrivial electronic structure, they are easily polarizable and can serve as superior nonlinear optical materials. ,, Electrides due to their certain interesting properties such as the ultralow work function, relatively high catalytic activity, high electronic mobility, and optical and anisotropic properties have great potential for various applications. − In 1983, Dye and co-workers fabricated the first organic crystalline electride consisting of organic complexant cages in which alkali metals and electrons were trapped . Since then, various organic and inorganic electrides have been reported in literature, and their novel electronic structures have been investigated both computationally and experimentally. − …”

Coherence Time Extension by Large-Scale Optical Spin Polarization in a Rare-Earth Doped Crystal

“…As an example, we estimated the magnetic fields, SLR, and flip-flop rates necessary to achieve DEOP as efficiently as in 171 Yb 3þ ∶Y 2 SiO 5 for Er 3þ and Nd 3þ ions in Y 2 SiO 5 (see Table S III in Supplemental Material [38]). These materials have been investigated for quantum memories, optical to microwave quantum transducers, and quantum processors [2,30,[52][53][54]. We first found that magnetic fields in the range 1-100 mT are sufficient to partially remove transition overlap, thanks to Γ inh ¼ 0.2 (6) GHz and g ¼ 15 4for Er 3þ (Nd 3þ ).…”