Overview: The space gravitational wave detection telescope is one of the core payloads of the gravitational wave detection satellite, simultaneously expanding and contracting the transmitted beam. Optical path stability is one of the core indices for the telescope, closely related to its structural stability. To meet the ultra-high path stability and structural stability requirements posed by the gravitational wave detection mission, it is essential to study the structural deformation measurement of the telescope. Currently, there are still several shortcomings in the research of multi-degree-of-freedom deformation measurement methods for gravitational wave detection telescopes, such as inaccurate selection of measurement points, inability to decouple multi-degree-of-freedom coupling, and unclear identification of error sources in multi-degree-of-freedom measurement. This paper deeply investigates the high-precision measurement of structural deformation of space-borne telescopes designed for space gravitational wave detection. It preliminarily establishes a framework and method system for measuring the structural deformation of space-borne telescopes, theoretically describing the measurement principle of the method. The feasibility of this method applied to space gravitational wave detection is verified through simulation analysis and error decomposition. The paper focuses on resolving the issue of decoupling multiple degrees of freedom, establishing a mathematical model using analytical methods, and conducting preliminary validation using Zemax. Finally, noise analysis of the measurement system is carried out, with experimental testing of the main noise components in the measurement system, validating the correctness of the theoretical noise model proposed in this paper. The experimental results show that near 1 Hz, the displacement noise background of the single-link interferometer is 100 pm/Hz^1/2. At 1 mHz in the low-frequency range, the displacement noise background reaches 10 nm/Hz^1/2. The noise level of the measurement system below 1 mHz is mainly limited by environmental temperature noise, while above 10 mHz, it is primarily constrained by laser frequency noise, phase acquisition background noise, and vibration noise. During the development phase of the space gravitational wave detection telescope, the research on this measurement method is expected to fulfill the telescope's multi-degree-of-freedom deformation measurement needs. It also provides data feedback for telescope design and offers guidance for the study of the telescope's optical path stability.

Plasmonics has aroused tremendous interest in photophysics, nanophotonics, and metamaterials. The extreme field concentration of plasmonics offers the ultimate spatial and temporal light control, single-particle detection, and optical modulation. Plasmon decay of metal nanostructures into hot carriers extends the application into photocatalysis, photodetectors, photovoltaics, and ultrafast nanooptics. The generated hot electron–hole pairs are transferred into adjacent dielectrics, well known to be more efficient than the hot carrier generation in dielectrics by direct photoexcitations. However, plasmon-induced hot-carrier-based devices are far from practical applications due to the low quantum yield of hot carrier extraction. Emergent challenges include low hot carrier generation efficiency in metals, rapid energy loss of hot carriers, and severe charge recombination at the metal/dielectric interface. In this review, we provide a fundamental insight into the hot carrier generation, transport, injection, and diffusion into dielectrics based on the steady-state and time-resolved spectroscopic studies as well as theoretical calculations. Strategies to enhance hot carrier generation in metals and electron transfer into dielectrics are discussed in detail. Then, applications based on hot carrier transfer are introduced briefly. Finally, we provide our suggestions on future research endeavors. We believe this review will provide a valuable overall physical picture of plasmon-induced hot carrier applications for researchers.

In this paper, we propose a temperature-sensing scheme utilizing a passively mode-locked fiber laser combined with the beat frequency demodulation system. The erbium-doped fiber is used in the laser ring cavity to provide the gain and different lengths of single-mode fibers inserted into the fiber ring cavity operate as the sensing element. Different temperature sensitivities have been acquired in the experiment by monitoring the beat frequency signals at different frequencies. The experimental results indicate that the beat frequency shift has a good linear response to the temperature change. The sensitivity of the proposed sensor is about -44 kHz/°C when the monitored beat frequency signal is about 10 GHz and the ratio of the sensing fiber to the overall length of the laser cavity is 10 m/17.5 m, while the signal-to-noise ratio (SNR) of the monitored signal is approximately 30 dB. The proposed temperature-sensing scheme enjoys attractive features such as tailorable high sensitivity, good reliability, high SNR, and low cost, and is considered to have great potential in practical sensing applications.