Lithium niobate on insulator (LNOI), regarded as an important candidate platform for optical integration due to its excellent nonlinear, electro-optic, and other physical properties, has become a research hotspot. A light source, as an essential component for an integrated optical system, is urgently needed. In this Letter, we reported the realization of 1550 nm band on-chip LNOI microlasers based on erbium-doped LNOI ring cavities with loaded quality factors higher than 1 million at
∼
970
n
m
, which were fabricated by using electron beam lithography and inductively coupled plasma reactive ion etching processes. These microlasers demonstrated a low pump threshold of
∼
20
µ
W
and stable performance under the pump of a 980 nm band continuous laser. Comb-like laser spectra spanning from 1510 to 1580 nm were observed in a high pump power regime, which lays the foundation of the realization of pulsed laser and frequency combs on a rare-earth ion-doped LNOI platform. This Letter effectively promotes the development of on-chip integrated active LNOI devices.
Several near-stoichiometric lithium niobate (LiNbO3) plates were prepared by the vapour transport equilibrium technique. Domain reversal was carried out on these samples by electric field poling. A nonlinear dependence of switching field on the concentration of anti-site niobium (
) ions was observed. This nonlinear relationship was explained by a two-dimensional model based on the dynamics of the domain wall. A parameter of θc, denoting the critical position of the domain wall round
ions, was introduced to describe domain reversal. The domain wall energy per unit area for near-stoichiometric lithium niobate was also roughly calculated to be larger than 0.27 J m−2.
Numerous studies have indicated that intrinsic defects in lithium niobate (LN) dominate its physical properties. In an Nb-rich environment, the structure that consists of a niobium anti-site with four lithium vacancies is considered the most stable structure. Based on the density functional theory (DFT), the specific configuration of the four lithium vacancies of LN were explored. The results indicated the most stable structure consisted of two lithium vacancies as the first neighbors and the other two as the second nearest neighbors of Nb anti-site in pure LN, and a similar stable structure was found in the doped LN. We found that the defects dipole moment has no direct contribution to the crystal polarization. Spontaneous polarization is more likely due to the lattice distortion of the crystal. This was verified in the defects structure of Mg2+, Sc3+, and Zr4+ doped LN. The conclusion provides a new understanding about the relationship between defect clusters and crystal polarization.
Particular attention has been given to updatable or dynamic holographic displays in recent years. The absence of ideal recording materials hampered the realization of their commercial applications. A lithium niobate crystal codoped with 1.0 mol. % bismuth and 6.0 mol. % magnesium has been grown with a diameter of 2-in. A moderately large saturation diffraction efficiency of 26% can be achieved, which corresponds to a refractive index change of 2.45 × 10−5. However, the photorefractive response time turns out to be only 13 ms, and the photorefractive sensitivity reaches 1.63 × 102 cm/J. This is by a factor of 104 larger than the one of congruent lithium niobate. The codoped crystal was used to demonstrate a real-time holographic display with a refresh rate of 30 Hz, which is a significant step forward for inorganic crystals in holographic display applications. Band structure calculations indicate that the dopants influence the charge distribution of the oxygen atoms which may be the clue to the origin of their excellent properties.
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