In order to extract accurate information from a thermoluminescence glow curve it is necessary to correct it for thermal quenching. Assuming that the dominant quenching process is due to nonradiative deactivation, the correction can be made by the Mott–Seitz equation. However, the experimentally determined quenching curve from the temperature dependence of luminescence intensity or integrated band area often suffers from a pronounced “bump” which we associate with thermoluminescence. It is shown that good data fits can be achieved by employing the higher temperature region above thermoluminescence. For demonstration, the commercial persistent luminescence phosphor SrAl2O4:Eu2+, Dy3+ has been chosen. The thermal quenching parameter WTQ was found to be 5016 ± 121 cm−1 and the quenching mechanism was deduced to be ionization to the conduction band. The corrected glow curves have been analyzed by the Kitis and initial rise methods and indicate a continuous distribution of traps at ~4000–5000 cm−1 below the conduction band. These are normally taken to be oxygen vacancies together with the cooperation of dysprosium ions.
In order to extract accurate information from a thermoluminescence glow curve it is necessary to correct it for thermal quenching. Assuming that the dominant quenching process is due to nonradiative deactivation, the correction can be made by the Mott–Seitz equation. However, the experimentally determined quenching curve from the temperature dependence of luminescence intensity or integrated band area often suffers from a pronounced “bump” which we associate with thermoluminescence. It is shown that good data fits can be achieved by employing the higher temperature region above thermoluminescence. For demonstration, the commercial persistent luminescence phosphor SrAl 2 O 4 :Eu 2+ , Dy 3+ has been chosen. The thermal quenching parameter W TQ was found to be 5016 ± 121 cm −1 and the quenching mechanism was deduced to be ionization to the conduction band. The corrected glow curves have been analyzed by the Kitis and initial rise methods and indicate a continuous distribution of traps at ~4000–5000 cm −1 below the conduction band. These are normally taken to be oxygen vacancies together with the cooperation of dysprosium ions.
Fast and accurate eye tracking in a virtual reality or augmented reality headset could lead to better display performance and enable novel methods of user interaction with the system. However, it remains a challenge for a system to combine the required operational speed and accuracy of eye tracking with a technology that has a small enough form factor and weight to be easily integrated into a user‐friendly headset. By using small, lightweight hardware comprising a high frame rate microLED array and fast single pixel detector, we report a model eye tracking system based on single pixel tracking and a specially developed set of deep learned illumination patterns. This model system is used to demonstrate eye tracking with an angular accuracy of better than one degree and a measurement rate of 2.33 kHz.
Realizing electrical tunability in passive athermal photonic devices has long been a challenge for photonic platforms that inherently lack electro‐optic tuning capability. Here, we demonstrate a tunable athermal Mach–Zehnder interferometer (AMZI) fabricated in the tantalum pentoxide (Ta2O5) platform and actuated by a lead zirconate titanate (PZT) chip. Athermalization is achieved through the structural compensation method and postfabrication trimming by a PZT actuator, yielding an intrinsic temperature‐dependent wavelength shift (TDWS) of 6.2 pm/K and a record‐low TDWS of 0.49 pm/K near 1550 nm with piezoelectric trimming. The PZT‐bonded AMZI exhibits a piezoelectric tuning efficiency of −58.5 pm/V and a 3 dB bandwidth of 2.6 kHz. Leveraging this tunability, the residual TDWS of the AMZI could be suppressed to sub‐pm/K level. The electrical tunability also renders long‐term thermal stability possible, as demonstrated in a proportional–integral–differential (PID)‐controlled output stabilization system. Under significant thermal perturbations, the output voltage experienced only minor deviations (<±0.1 V) and rapidly recovered to the setpoint once the temperature stabilized, underscoring the device’s improved resilience to environmental temperature fluctuations. The demonstrated piezoelectrically tunable athermal photonic device holds great promise for integrated photonic systems that require both high thermorefractive stability and reconfigurability.
The photothermal response of a gold nanorods array to near‐infrared irradiation is used to dynamically tune the Bragg reflection band of adjacent cholesteric liquid crystal (CLC) layers. By cascading two CLC cells with opposite handedness (right‐ and left‐handed) and with the same peak Bragg wavelength, a compact device capable of reflecting nearly 100% of unpolarized incident light is achieved. The thermoplasmonic heating enables reversible spectral tuning of the reflection band over ~80 nm in the visible range via temperature‐induced changes in birefringence and pitch. This strategy demonstrates a remotely actuated and contact‐free platform for tunable optical filters, with potential applications in smart photonic devices, optical communications, sensing, and liquid crystal displays.
