Development of a near-infrared single-photon 3D imaging LiDAR based on 64×64 InGaAs/InP array detector and Risley-prism scanner.

A near-infrared single-photon lidar system, equipped with a 64×64 resolution array and a Risley prism scanner, has been engineered for daytime long-range and high-resolution 3D imaging. The system's detector, leveraging Geiger-mode InGaAs/InP avalanche photodiode technology, attains a single-photon detection efficiency of over 15% at the lidar's 1064 nm wavelength. This efficiency, in tandem with a narrow pulsed laser that boasts a single-pulse energy of 0.5 mJ, facilitates 3D imaging capabilities for distances reaching approximately 6 kilometers. The Risley scanner, composing two counter-rotating wedge prisms, is designed to perform scanning measurements across a 6-degree circular field-of-view. Precision calibration of the scanning angle and the beam's absolute direction was achieved using a precision dual-axis turntable and a collimator, culminating in 3D imaging with an exceptional scanning resolution of 28 arcseconds. Additionally, this work has developed a novel spatial domain local statistical filtering framework, specifically designed to separate daytime background noise photons from the signal photons, enhancing the system's imaging efficacy in varied lighting conditions. This paper showcases the advantages of array-based single-photon lidar image-side scanning technology in simultaneously achieving high resolution, a wide field-of-view, and extended detection range.

Fast surface signal extraction method for photon point clouds with strong background noise without prior altitude information.

It is extremely challenging to rapidly and accurately extract target echo photon signals from massive photon point clouds with strong background noise without any prior geographic information. Herein, we propose a fast surface detection method realized by combining the improved density-dimension algorithm (DDA) and Kalman filtering (KF), termed the DDA-KF algorithm, for photon signals with a high background noise rate (BNR) to improve the extraction of surface photon signals from spacecraft platforms. The results showed that the algorithm exhibited good adaptability to strong background noise and terrain slope variations, and had real-time processing capabilities for massive photon point clouds in large-scale detection range without prior altitude information of target. Our research provides a practical technical solution for single-photon lidar applications in deep space navigation and can help improve the performance in environments characterized by strong background noise.

Inter-/intra-pulse dual-wavelength-operated mid-infrared optical parametric oscillator.

We demonstrate a pulsed mid-infrared (MIR) optical parametric oscillator (OPO) with both inter-pulse and intra-pulse dual-wavelength operation capability. A fiber master oscillator power amplifier incorporating an acousto-optic tunable filter (AOTF) was employed as the pump for the OPO. By finely adjusting the drive wave packets for the AOTF, dual-wavelength pump can be realized within each pulse or between two adjacent pulses. These special temporal-spectral behaviors of the pump can be transferred to MIR via an OPO. In the proof-of-principle experiments, two pump wavelengths at ∼1065 and ∼1076 nm were generated and amplified to ∼31.2 W with equivalent spectral intensities for both pulsation modes. At the highest pump power, total idler power of ∼3.5 W was achieved at ∼3.45 and ∼3.55 µm under both pulsation modes. To the best of our knowledge, this is the first demonstration of both inter-pulse and intra-pulse dual-wavelength MIR generation via an OPO with an identical configuration. It is believed that our design may provide a promising solution to many practical applications including differential absorption lidar and tunable terahertz wave generation.

Gerontechnology for better elderly care and life quality: a systematic literature review.

Gerontechnology as multidisciplinary research has expanded in recent years due to its significant role in ensuring better care and improved quality of life for older adults and their caregivers. With a substantial increase in studies on reasons behind less inclination of older individuals to accept gerontechnology, barriers to its non-acceptance appear to be persistent. In addition, there is a dearth of research on the adoption of gerontechnology from the perspectives of social caregivers, given that caregivers bear a substantial burden in the form of chronic stress, which adversely affects their health and that of older people. Therefore, the aim of this study is to present a holistic perspective of older adults and their caregivers by systematically reviewing literature on gerontechnology acceptance. Adopting the preferred reported items for systematic and meta-analysis (PRISMA) framework, publications specifically on gerontechnology from 2002 to 2022 in Scopus, Web of Science and PubMed, that focused on older people (50 years and above) and caregivers (informal and formal) were reviewed. We critically evaluated 25 publications and synthesised them thematically. The results highlight that gerontechnology acceptance by older adults and their social caregivers is highly contingent on certain personal, physical, socio-cultural and technological indicators. However, this paper concludes that a generalised policy approach for gerontechnology and a better quality of life may be ineffective, considering that older adults and social caregivers constitute two heterogeneous groups.

Cross-Border Medical Services for Hong Kong's Older Adults in Mainland China: The Implications of COVID-19 for the Future of Telemedicine.

Cross-border services and support are becoming an increasingly important part of Hong Kong's social policy because an increasing number of its older citizens are choosing to live in mainland China. Unfortunately, with the recent outbreak of COVID-19, medical services for cross-border older adults have been blocked due to strict immigration controls. This article examines the effects of COVID-19 on these older adults, with a specific focus on the interruption of medical services and the remedial measures taken by the government and non-governmental organizations. It also discusses the prospect of delivering care for cross-border older people using telemedicine, which is considered one of the most important methods for overcoming space-distance and reducing the risk of cross-contamination caused by close contact.

Flexible wavelength generation from a Yb-doped fiber laser incorporating multifunctional acousto-optic tunable filter.

We have demonstrated a Yb-doped fiber laser (YDFL) based on a multifunctional acousto-optic tunable filter (AOTF) with flexible wavelength generation capability. The number of channels, as well as their diffracted wavelengths and corresponding peak transmittances of the AOTF, can be widely tuned by changing the composite drive signal from a homemade arbitrary wave generation (AWG) board enabling single-/multi-wavelength lasing with different central wavelengths and relative intensities. The maximal wavelength tuning range and minimal resolved wavelength spacing are ∼80nm and ∼1.5nm, respectively, with 3 dB bandwidth less than 0.15 nm for each laser line, showing great potential for further nonlinear frequency conversion. To the best of our knowledge, this is the first demonstration of flexible wavelength generation from a multifunctional AOTF-based YDFL directly driven by an AWG board.

Quantum lidar based on a random interleaved optical pulse sequence consisting of wavelength-time quantum states.

Based on a random interleaved optical pulse sequence consisting of wavelength-time quantum states, we have established a quantum lidar model. Multiple quantum states are used as a detection tool for the interception and interference of a target, and multiple wavelengths spanning the ultraviolet to near-infrared waveband are used to avoid interference and improve the detection efficiency. We elaborate upon the working principle of the entire quantum lidar detection system and demonstrate its feasibility through simulations, thereby establishing a foundation for the application of quantum lidar systems aboard satellite platforms at long distances from the high-precision detection of targets.