A scanning three-dimensional coherent laser radar (ladar) based on the frequency modulated continuous wave (FMCW) is proposed and demonstrated, which can obtain many three-dimensional high-quality images. The system utilizes an electro-optic modulator and an optical filter to output a linear FMCW with a bandwidth of 2 GHz. The flexible and variable rotating double prism is used for beam scanning. The images of flight demonstration are formed by attitude compensation correction. The experiment result validates the performance of our system for airborne three-dimensional scanning imaging.

Using theoretical simulations for optical fiber surface plasmon resonance (SPR) sensors and prism-based SPR sensors coated with negative permittivity material (NPM), we investigated the effect of the permittivity of NPM on the transmitted spectrum of optical fiber SPR sensors and the reflected spectrum of prism-based SPR sensors and then obtained optimum permittivity of the NPM, which can excite the sharpest SPR spectrum in the white light region (400–900 nm).

A static-mode synthetic aperture imaging ladar (SAIL) in which the target and carrying platform are kept still during the collection process is proposed and demonstrated. A target point of 0.5 mm×0.5 mm and a two-dimensional (2D) object are reconstructed in the experiments, in which an optical collimator with a focal length of 10 m is used to simulate the far-field condition. The achieved imaging resolution is in agreement with the theoretical design. The static-mode down-looking SAIL has the capability to eliminate the influence from the atmospheric turbulence and can be conveniently operated outdoors.

We propose a method for simultaneous 3D temperature and velocity measurement of a micro-flow field. The 3D temperature field is characterized with two-color laser-induced fluorescence particles which are tracked with micro-digital holographic particle tracking velocimetry. A diffraction-based model is applied to analyze defocused particles to determine the intensity ratio of two fluorescent dyes on the particle. The model is validated with experimental images. As the result shows that the intensity ratio nearly remains unchanged with respect to depth positions, defocused particles can be used as 3D temperature sensors. Numerical work is carried out to check the method, and 3D temperature and velocity field in a 120 μm×120 μm×80 μm test volume are retrieved.

We propose a reflection-type infrared biosensor by exploiting localized surface plasmons in graphene ribbon arrays. By enhancing the coupling between the incident light and the resonant system, an asymmetric Fabry–Perot cavity formed by the ribbons and reflective layer is employed to reshape the reflection spectra. Simulation results demonstrate that the reflection spectra can be modified to improve the figure of merit (FOM) significantly by adjusting the electron relaxation time of graphene, the length of the Fabry–Perot cavity, and the Fermi energy level. The FOM of such a biosensor can achieve a high value of up to 36/refractive index unit (36/RIU), which is ～4 times larger than that of the traditional transmission-type one. Our study offers a feasible approach to develop biosensing devices based on graphene plasmonics with high precision.

This Letter introduces a trigger-controlled Geiger-mode avalanche photodiode (GM-APD). A hierarchical look-back-upon tree recurrence method is given to predict the performance of trigger-controlled GM-APDs under different trigger-count upper limits. In addition, the normalized detection probability is defined to evaluate the detection performance of trigger-controlled GM-APDs in typical weak optical signal detection (impulse noise and continuous noise situations). Theoretical analyses show that the trigger-controlled GM-APD improves the detection performance of GM-APDs in weak optical signal detection via the optimization of the trigger-count upper limit, compared with single-trigger and multi-trigger GM-APDs.

To achieve radar and infrared stealth, an infrared stealth layer is usually added to the radar absorbing material (RAM) of stealth aircraft. By analyzing the millimeter-wave (MMW) emissivities of three stealth materials, this Letter investigates the impact of the added infrared stealth layer on the originally “hot” MMW emission of RAM. The theoretical and measured results indicate that, compared with the monolayer RAM, the MMW emission of the bilayer material is still strong and its emissivity is reduced by 0.1–0.2 at almost every incident angle. The results partially demonstrate the feasibility of detecting stealth aircraft coated with this bilayer stealth material.

The output amplitude of the differential circuit is studied for differential discrimination in pulsed laser time-of-flight systems. Based on the studies of the probability of detection and the probability of false alarms, the minimum detectable input signal of differential discrimination can be calculated. The results indicate that the differential discrimination detectability of the small signal will be reduced. A combined discrimination is proposed in this Letter to improve the time resolution of the large signal and ensure the probability of detection of the small signal at the same time. A proper value of the circuit parameter is found to balance the time resolutions of the small and large signals.

Infrared signatures of aircraft are the basis for detection and monitoring. In past years, most of the studies focused on the aircraft’s infrared signature in the mid-wave spectral region and long-wave spectral region for missile guidance or aircraft survivability studies. For the security of civil aviation, methods and instruments that can detect and monitor aircrafts from space are expected to be developed in the coming years. A short-wave infrared hyperspectral imager aboard the Tiangong-1 spacecraft acquired some civil aircraft’s spectral data. The differences between the aircraft and the background in their spectral signatures are analyzed and discussed. Less absorption in the vapor absorption bands and a reflection spike is discovered at the 1.84 μm spectral band. The result shows that 1.84 μm and other vapor absorption bands can make contributions to aircraft detection in the daytime.

In this Letter, we propose an efficient compression algorithm for multi-spectral images having a few bands. First, we propose a low-complexity removing spectral redundancy approach to improve compression performance. Then, a bit plane encoding approach is applied to each band to complete the compression. Finally, the experiments are performed on multi-spectral images. The experiment results show that the proposed compression algorithm has good compressive property. Compared with traditional approaches, the proposed method can decrease the average peak signal noise ratio by 0.36 dB at 0.5 bpp. The processing speed reaches 23.81 MPixels/s at the working frequency of 88 MHz, which is higher than the traditional methods. The proposed method satisfies the project application.