No abstract

Optical microscopy of biological tissues at the 1700[Formula: see text]nm window has enabled deeper penetration, due to the combined advantage of relatively small water absorption and tissue scattering at this wavelength. Compared with excitation at other wavelengths, such as the commonly used 800[Formula: see text]nm window for two-photon microscopy, water absorption at the 1700[Formula: see text]nm window is more than one order of magnitude higher. As a result, more temperature rise can be expected and can be potentially detrimental to biological tissues. Here, we present theoretical estimation of temperature rise at the focus of objective lens at the 1700[Formula: see text]nm window, purely due to water absorption. Our calculated result shows that under realistic experimental conditions, temperature rise due to water absorption is still below 1[Formula: see text]K and may not cause tissue damage during imaging.

As computing-intensive mobile applications become increasingly diversified, mobile devices’ computing power is hard to keep up with demand. Mobile devices migrate tasks to the Mobile Edge Computing (MEC) platform and improve the performance of task processing through reasonable allocation and caching of resources on the platform. Small cellular networks (SCN) have excellent short-distance communication capabilities, and the combination of MEC and SCN is a promising research direction. This paper focuses on minimizing energy consumption for task migration in small cellular networks and proposes a task migration energy optimization strategy with resource caching by combining optimal stopping theory with migration decision-making. Firstly, the process of device finding the MEC platform with the required task processing resources is formulated as the optimal stopping problem. Secondly, we prove an optimal stopping rule’s existence, obtain the optimal processing energy consumption threshold, and compare it with the device energy consumption. Finally, the platform with the best energy consumption is selected to process the task. In the simulation experiment, the optimization strategy has lower average migration energy consumption and higher average data execution energy efficiency and average distance execution energy efficiency, which improves task migration performance by 10% ∼ 60%.

Based on vibrational spectroscopy, coherent Raman Scattering (CRS) microscopy allows label-free imaging of biological and chemical samples with endogenous image contrast. Two-color, synchronized picosecond pulses are typically used for high spectral resolution imaging, which in turn constitutes a dramatic laser source challenge for CRS microscopy. Recently, synchronized time-lens source, inspired from ultrafast optical signal processing, has emerged as a promising laser source solution and has found application in various modalities of CRS microscopy. Time-lens is based on space-time analogy, which uses a "lens" in the time domain to compress long optical pulses or even continuous waves to ultrashort pulses, mimicking a lens in the space domain. Phase and intensity modulators driven with electrical signals are used in the time-lens source for picosecond pulse generation. As a result, the time-lens source is highly versatile and naturally compatible with modulation capabilities. More importantly, if the electrical signals used to drive the time-lens source are derived from other laser sources, such as mode-locked lasers, then synchronization between them can be realized, underlying the physics of a synchronized time-lens source. In this paper, we review recent progress on the basic principle, design of the synchronized time-lens source, and its applications to CRS microscopy of both biological and chemical samples.

Two-photon excited fluorescence (TPEF) microscopy is a nonlinear optical microscopy technique. The advantages of TPEF microscopy include high temporal and spatial resolutions, high signal-to-noise ratio and inherent three-dimensional sectioning. In traditional TPEF microscopy, a wavelength tunable ultrashort pulsed laser is used as an excitation source. In practical applications, sample usually contains various fluorophores or unknown components. Therefore the excitation wavelength of the ultrafast laser has to be tuned to achieve optimal excitation efficiencies of various fluorophores. In order to acquire the fluorescent signals of different fluorophores simultaneously, we develop a multicolor TPEF microscope system based on a supercontinuum laser source. In experiments, TPEF images of Lily rhizome sample slide stained by two fluorescent dyes with different excitation and emission wavelengths are obtained without tuning the wavelength. Experimental results show that the high-contrast TPEF images of the sample with various fluorophores can be obtained simultaneously by using the multicolor TPEF microscope compared with by using traditional TPEF microscopy. The system is simple in structure, easy in operation, and can provide rich information about the sample, which allows it to be widely used in life and material sciences.