Photoluminescence and optical temperature sensing properties of Dy3+-doped Na0.5Bi0.5TiO3 multifunctional ferroelectric ceramics.

A series of Dy3+ doped Na0.5Bi0.5TiO3 (NBT: xDy3+, x = 0.003-0.018) lead-free ferroelectric ceramics were successfully prepared by a solid-state reaction method. The Dy3+ ions composition dependent photoluminescence properties were systematically studied. All the samples display intense characteristic emission of Dy3+ under an excitation wavelength of 454 nm, which are attributed to the transitions of 4F9/2 → 6HJ/2 (J = 13, 11 and 9). All the samples show strong orange-yellow emission, which could be applied to warm white light hopefully. When the content of Dy3+ is equal to 0.012, the ceramic has the optimal luminous performance. Remarkable thermal quenching of the luminous intensity ceramic occurs as the temperature is higher than initial temperature 293 K. Furthermore, Dy3+ activated photoluminescence performance combined with the presence of ferroelectricity in the NBT host can be applied to developing non-contact optical temperature sensitive materials and other future novel optoelectronic devices.

Variation on the Microstructure and Mechanical Properties of Ti-Al-N Films Induced by RF-ICP Ion Source Enhanced Reactive Nitrogen Plasma Atmosphere.

Acquiring the optimum growth conditions of Ti-Al-N films, the effects of gas atmosphere, especially the reactive plasma on the material microstructures, and mechanical properties are still a fundamental and important issue. In this study, Ti-Al-N films are reactively deposited by radio frequency inductively coupled plasma ion source (RF-ICPIS) enhanced sputtering system. Different nitrogen gas flow rates in letting into the ion source are adopted to obtain nitrogen plasma densities and alter deposition atmosphere. It is found the nitrogen element contents in the films are quite influenced by the nitrogen plasma density, and the maximum value can reach as high as 67.8% at high gas flow circumstance. XRD spectra and FESEM images indicate that low plasma density is benefit for the film crystallization and dense microstructure. Moreover, the mechanical properties like hardness and tribological performance are mutually enhanced by adjusting the nitrogen atmosphere.

Enhanced photoluminescence and ferro/piezoelectric performance in piezo-luminescent materials with outstanding water resistance and thermal stability.

Sm3+-Modified (1 -x)Na0.5Bi0.5TiO3-xCaTiO3 (NBT-xCT:Sm3+) piezo-luminescent ceramic materials were synthesized to investigate the influence of CaTiO3 (CT) concentration on their photoluminescence and electrical performance. Under 480 nm irradiation, the NBT-xCT:Sm3+ samples exhibit prominent orange-red emission, with a prime emission peak centered at 597 nm. A moderate amount of CT doping in the Sm3+-modified NBT ceramics boosts both their photoluminescence and piezoelectric properties significantly, with NBT-0.04CT:Sm3+ showing the optimal performance. Furthermore, outstanding luminescence thermal stability over a temperature range of 293-473 K and superior water resistance behavior are achieved in the NBT-0.04CT:Sm3+ ceramic. These results indicate that NBT-xCT:Sm3+ piezo-luminescent ceramics show great potential applications in white LEDs, as well as novel optical-electronic multifunctional devices.

Enhanced four-wave mixing in P T-symmetric optomechanical systems.

We investigate the enhanced four-wave mixing (FWM) process in a parity-time (P T)-symmetric optomechanical system, where an active cavity is coupled to a passive cavity supporting a mechanical mode. The passive cavity is optically driven by a strong control field and a weak probe field, and the mechanical mode is excited by a weak coherent driving field. By tuning the coupling strength between the two cavities with balanced gain and loss, we find that the FWM intensity can be significantly enhanced near the exceptional points (EPs) at low control power, which is about 12 orders of magnitude higher than that of the single-cavity case. Due to the interference effect induced by the optical and mechanical driving field, it is shown that the FWM intensity can be further enhanced or suppressed by tuning the amplitude and phase of the mechanical driving field. Moreover, the dependence of the FWM intensity on the frequency and power of the control field is also discussed. Our work provides a route to enhance the four-wave mixing process in a flexible way.

Photoluminescence properties, Judd-Ofelt analysis, and optical temperature sensing of Eu3+-doped Ca3La7(SiO4)5(PO4)O2 luminescent materials.

A series of Eu3+-doped Ca3La7(SiO4)5(PO4)O2 (CLSPO) multifunctional phosphors were synthesized by a high-temperature solid-state reaction method. The crystal structure of the CLSPO host was explored using Rietveld refinement. The photoluminescence properties of CLSPO: Eu3+ phosphors were investigated systematically. Upon 392 nm near-ultraviolet light excitation, the phosphor exhibited strong characteristic emissions of Eu3+ ions with a dominant red emission peak around 613 nm, indicating its potential use in solid-state lighting. Calculations of Ω2 and Ω4 Judde-Ofelt intensity parameters provided insight into the structure-luminescence correlation in the CLSPO: Eu3+ system. By exploring the temperature sensitivity of photoluminescence intensity, the application potential of the sample to optical thermometry was studied.

Phase-controlled amplification and slow light in a hybrid optomechanical system.

We theoretically investigate the transmission and group delay of a probe field incident on a hybrid optomechanical system, which consists of a mechanical resonator simultaneously coupled to an optical cavity and a two-level system (qubit). The cavity field is driven by a strong red-detuned control field, and a weak coherent mechanical driving field is applied to the mechanical resonator. With the assistance of additional mechanical driving field, it is shown that double optomechanically induced transparency can be switched into absorption due to destructive interference or amplification because of constructive interference, which depends on the phase difference of the applied fields. We study in detail how to control the probe transmission by tuning the parameters of the optical and mechanical driving fields. Furthermore, we find that the group delay of the transmitted probe field can be prolonged by the tuning the amplitude and phase of the mechanical driving field.

Tunable slow and fast light in parity-time-symmetric optomechanical systems with phonon pump.

We study the response of parity-time (PT)-symmetric optomechanical systems with tunable gain and loss to the weak probe field in the presence of a strong control field and a coherent phonon pump. We show that the probe transmission can exceed unity at low control power due to the optical gain of the cavity and it can be further enhanced or suppressed by tuning the amplitude and phase of the phonon pump. Furthermore, the phase dispersion of the transmitted probe field is modified by controlling the applied fields, which allows one to tune the group delay of the probe field. Based on this optomechianical system, we can realize a tunable switch between slow and fast light effect by adjusting the gain-to-loss ratio, power of the control field as well as the amplitude and phase of the phonon pump. Our work provides a platform to control the light propagation in a more flexible way.