Photoinduced ultrasound is widely used in medical diagnosis, material characterization, nondestructive testing, structural health monitoring and other fields. These applications have specific requirements on ultrasonic intensity and bandwidth. This paper quantitatively analyzed the effects of photoacoustic materials and laser parameters on ultrasonic frequency and intensity. The following conclusions are drawn by relevant experiments. With the increase of the incident laser energy, the amplitude corresponding to all frequencies in the ultrasonic spectrum increases, and the incident laser energy is proportional to the amplitude of the ultrasound. Meanwhihle, the ultrasonic intensity increases by 15% with increase of 50 mJ laser energy. The change of incident laser frequency has no effect on ultrasonic signal. The increase of gold nanoparticle concentration can not only enhance the amplitude of ultrasound, but also increase the frequency of ultrasound. The thin layer of gold nanoparticles and polydimethylsiloxane leads to insufficient absorption of light energy, and the thick layer causes the attenuation of the high frequency component of ultrasound. The mixture of carbon black and polydimethylsiloxane produces higher intensity ultrasound than the mixture of gold nanoparticles and polydimethylsiloxane under the same circumstances, but the frequency distribution is concentrated in the low frequency domain.

Surface-enhanced Raman scattering (SERS) is widely employed for amino acids quantitative analysis due to its high-sensitivity molecular feature extraction and multiplex detection advantage. Stable and highly sensitive SERS substrates are crucial for achieving precise detection. Gold core silver shell nanoparticles (Au@Ag NPs) combine the chemical stability of gold nanoparticles with the high SERS enhancement effect of silver nanoparticles. They enable the screening and detection of seven amino acids, including phenylalanine and alanine. Except for isoleucine and glycine, which exhibited relatively lower sensitivity, the detection limits for the remaining amino acids reached 1×10-4$ \mathrm{m}\mathrm{o}\mathrm{l}/\mathrm{L} $. A linear correlation existed between concentration and SERS signal intensity, with correlation coefficients exceeding 0.94. This study provides a reference method for simultaneous quantitative detection of multiple amino acids on a single substrate.

The optical drive movement of anti-magnetic levitation pyrolytic graphite is of great significance to the optical manipulation of objects and the acquisition of optical energy. At present, the existing rotating system of optical drive based on pyrolytic graphite has the problems of low rotating speed and low energy conversion efficiency. Therefore, it is proposed to adjust the magnetic field around the magnetic levitation pyrolytic graphite to directionally enhance its rotation. Specifically, a magnetic levitation base structure with circular magnetic field defects was designed to improve the rotation speed of pyrolytic graphite under irradiation. Firstly, based on the magnetic field theory and heat conduction theory, a numerical analysis model was established, and the realization mechanism and motion law of the magnetic levitation pyrolytic graphite optical drive were explained. Then the optical driving effect of the designed magnetic levitation structure was verified by experiments. The results showed that the maximum rotation speed of pyrolytic graphite was 3.5 r/s driven by semiconductor laser with wavelength of 808 nm and power of 200 mW. Compared with the original structure, in the power range of 20 to 200 mW, driven by the laser with the same optical power, the rotating speed of the pyrolytic graphite was increased by 1 to 2 times. It had better stability and lower rotation threshold power. The research results provide reference for the design of optical drive rotating devices and new optical energy collection systems.

In this work, phase apodized silicon Bragg grating filters with varying sidewall ridge width and location were investigated, while the resonance wavelength, extinction ratio and rejection bandwidth could be tuned flexibly. The grating filters with a waveguide width of 500 nm and grating period of 400 nm were fabricated and characterized for a proof of concept. The resonance wavelength of the device could be shifted by 4.54 nm with varying the sidewall ridge width from 150 to 250 nm. The corresponding rejection bandwidth could be tuned from 1.19 to 2.03 nm by applying a sidewall ridge location offset from 50 to 200 nm. The experimental performances coincide well with the simulation results. The presented sidewall ridge modulated apodized grating filter can be expected to have great application prospects for optical communications and semiconductor lasers.

In order to improve the measurement accuracy of the elliptical Gaussian spot position in the four quadrant detector and the position detection accuracy of the elliptical spot and the center coordinate of the four quadrant detector with an offset rotation angle, a localization algorithm for the elliptical Gaussian spot is proposed. An elliptical light spot with Gaussian distribution was used as the incident light spot model, and infinite integral fitting algorithm and the least squares method were used to fit the optimal analytical expression. In order to establish all models of elliptical spot in the four quadrant detector, polynomial fitting was performed on the offset angle to simplify the calculation of the algorithm for locating the offset angle between the elliptical spot and the center coordinate of the four quadrant detector. Finally, based on simulation, the fitting relationship between the offset angle and the localization algorithm was determined. The positioning accuracy of the algorithm can reach sub-micron level, providing a theoretical basis for the localization algorithm of elliptical spots.

Terahertz (THz) radiation generated by femtosecond laser-pumped photoconductive antenna (PCA) is the most widely used THz wide-frequency source at present. A hemispherical or super-hemispherical silicon lens is usually integrated with a PCA to improve its radiation directivity, beam quality, and radiation efficiency. However, due to the misalignments of the laser focused spot, and between the PCA and the silicon lens, the THz radiation center is not on the rotation symmetrical axis of the silicon lens, resulting in the deviation of THz radiation direction, the deterioration of THz beam quality, and the reduction of radiation efficiency. In this work, a GaAs Schottky detector, mounted on a two-dimensional translation stage was used to obtain the spatial profile of a THz beam radiated from a PCA integrated with a silicon lens. The influence of misalignment between the PCA and the silicon lens on the radiation directivity was clarified. The problem of how to adjust the position of the lens when the radiation of the PCA is offset in the experiment is solved. The effects of misalignment between the PCA and the silicon lens are numerically simulated by using the CST electromagnetic simulation package. The simulation results are consistent with the experiment data.

Gain adjustable photodetectors based on avalanche photodiode (APD) are widely used in fields such as laser communication, laser radar and optical fiber sensing. Combining with low-noise broadband transimpedance amplifiers, they achieve high-sensitivity detection by utilizing the avalanche multiplication effect of the internal carriers in APD. To further enhance the gain dynamic range and response bandwidth of the APD detector, the study explored the relationship between the linear multiplication factor of the APD and the dark current to increase the gain factor of the APD. The amplification scheme of a transimpedance amplifier cascading an operational amplifier improved the gain adjustment range while guaranteeing the detector response bandwidth. In addition, a low-noise high-voltage direct current bias circuit module was designed with a ripple voltage of less than or equal to 2.5 mV. Adjusting the voltage enabled the rapid switching of the APD multiplication factor M between 1, 10, 50, 100 and 200. The maximum adjustable APD detector gain reached 74 dB. The bandwidth was 150 MHz, while the minimum noise equivalent power was only 0.02 pW·Hz-0.5. This low-noise and large-dynamic range technology solution expands the applications of APD photodetectors.

The study proposes a broadband absorber for visible band that is designed based on local surface plasmon resonance and incorporating monolayer molybdenum disulfide, gold nanopillars, and Bragg mirrors. Theoretical simulations using the finite-difference time-domain (FDTD) method demonstrated that the MoS2-based absorber achieved absorptivities exceeding 96.0% and 99.8% at resonance wavelengths of 422 nm and 571 nm, respectively. The spectral characteristics remained stable within an incidence angle range from 0° to 45° and exhibited polarization-independent behavior. Additionally, performance of the absorber could be tuned by modifying the geometric parameters of the periodic gold nanopillar array. This design strategy is applicable to other transition metal dichalcogenides (TMDCs), and its application effectively enhances light-matter interactions in such materials.

In this paper, by characterizing two samples, nanoporous gold (NPG) and graphene-coated nanoporous gold (G@NPG), using scattering near-field scanning optical microscopy (s-SNOM), it is found that graphene can weaken the localized surface plasmon resonance (LSPR) intensity of NPG. In order to investigate the reason why graphene weakens the hotspot of NPG, this paper analyzes the phenomenon by using finite-difference time-domain simulation, and the simulation results are consistent with the characterization results of s-SNOM. From the absorption spectra of the two samples, we find that graphene can eliminate the phenomenon of multiple LSPR modes caused by the irregular structure of NPG. The simulation results of graphene-coated gold nanoparticles (G@NP) show that the peak position of the LSPR peak of graphene-coated NPs shows an obvious red shift and the peak width increases, indicating that the lifetime of the plasmon is attenuated. This explains why the near-field signal intensity of G@NPG is weaker than that of NPG, and why graphene can eliminate the multiple LSPR modes of NPG. In the design of wavelength-selective NPG devices, graphene can be used as an alternative material to modulate the LSPR of nanoporous gold.

Three-dimensional culture of tumor cell spheres can truly simulate the growth environment of tumor cells in vivo, and thus be more suitable for drug screening and other related research. Combined with microfluidic technology, there are more ways to implement three-dimensional cell culture technology. In this study, a microfluidic chip for high-throughput three-dimensional tumor cell spheres culture was designed to enable rapid cultivation and drug screening of tumor cell spheres based on microcavity arrays. Compared to the current mainstream three-dimensional culture that takes 4 days, microfluidic chips only require 15 h to form tumor spheres. It significantly saves cultivation time. The reliability of three-dimensional culture in the chip was verified by tumor growth morphology monitoring and fluorescence imaging technology. Meanwhile, this research realized multi-drug rapid screening based on chip, presented good gradient dependence and verified the feasibility of drug screening in chip. This high-throughput microfluidic chip can be applied in multiple research fields such as oncology, providing a new technological means and experimental platform for achieving rapid drug screening in tumors.

The measurement system based on the white light interference principle (such as white light interference microscope) has the technical advantages of sub-nanometer longitudinal resolution, non-contact, high efficiency of field scanning, etc., and is often used to measure the surface morphology and structure of products on the micro/nano scale. The analysis, evaluation, and calibration of the measurement characteristics of white light interferometry instruments is a complex and practical work, which is the basis of the research and application of this kind of instruments. Based on the principle of white light interference and the definition and regulation of relevant national standards, the measurement characteristics of the white light interference measurement system and the quantities influencing the system are analyzed theoretically. On this basis, the measurement characteristics of WLIS for metrological application are presented, i.e., measuring range and indicating error. Then, the theoretical analysis of the above measurement characteristics and their measurement and calibration methods are discussed. The three-axis measurement deviation of the system is calibrated by the standard template of step height and line interval, and the 3D measurement traceability chain based on the white light interference system is constructed.

All-inorganic perovskite quantum dots CsPbI3 have excellent optical properties and are suitable for red light emitting diodes and solar cells. However, the large difference of their atomic radius, as well as the migration of halogen ion caused by the intrinsic soft-lattice nature, would lead to the phase transition and degradation of CsPbI3 quantum dots. In this paper, CsPbI3 quantum dots (CsPbI3@Pb-MOF-OLAMI) were synthesized using Pb metal organic framework (Pb-MOF) as lead sources in perovskite. The results showed that the thermal stability improves by 40%, and the light stability improves by 15 times after adding the lead iodide (PbI2) solution. This stability improvement is mainly due to the void-confinement effect. The porous structure of Pb-MOF hinders the migration of halogen ions, which avoids or reduces the formation of defects, and thus alleviates the degeneration of perovskite. This study provides a new strategy for improving the stability of CsPbI3 perovskite quantum dots.