This paper discusses the construction principles and performance of a pulsed time-of-flight (TOF) laser radar based on high-speed (FWHM $100 ps) and high-energy ($1 nJ) optical transmitter pulses produced with a specific laser diode working in an "enhanced gain-switching" regime and based on single-photon detection in the receiver. It is shown by analysis and experiments that single-shot precision at the level of 2W3 cm is achievable. The effective measurement rate can exceed 10 kHz to a noncooperative target (20% reflectivity) at a distance of 9 50 m, with an effective receiver aperture size of 2:5 cm 2 . The effect of background illumination is analyzed. It is shown that the gating of the SPAD detector is an effective means to avoid the blocking of the receiver in a high-level background illumination case. A brief comparison with pulsed TOF laser radars employing linear detection techniques is also made.

A multiple quantum well laser diode utilizing an asymmetric waveguide structure with a large equivalent spot size of ∼3 μm is shown to give high energy (∼1 nJ) and short (∼100 ps) isolated optical pulses when injected with <10 A and ∼1-ns current pulses realized with a MOS driver. The active dimensions of the laser diode are 30 μm (stripe width) and 3 mm (cavity length), and it works in a single transversal mode at a wavelength of ∼0.8 μm. Detailed investigation of the laser behavior at elevated temperatures is conducted; it is shown that at high enough injection currents, lasers of the investigated type show low temperature sensitivity. Laser diodes of this type may find use in accurate and miniaturized laser radars utilizing single photon detection in the receiver.Index Terms-Semiconductor lasers, quantum well lasers, optical pulses, gain switching, laser radar.

A compact laser pulser emitting ~100 ps, ~10 W pulses at >100 kHz is presented. The high pulsing frequency is achieved using a MOSFET-based current driver, whereas the high pulse power is a merit of the used laser diode with an asymmetric waveguide structure leading to enhanced gain switching. The pulsing frequency is higher than with avalanche transistor based current pulsing circuits due to lower heating, and the current pulse width is shown to be even shorter than with avalanche transistor based circuits. The laser diode transmitter was developed especially for the pulsed time-of-flight laser radar application utilizing a single photon avalanche diode (SPAD) matrix as the detector element. A demonstration measurement is done enabling centimeter-precision distance measurement to 50 m in a measurement time of ~5 ms outdoors in sunny weather.

A pulsed TOF laser radar utilizing the single-photon detection mode has been implemented, and its performance is characterized. The transmitter employs a QW double-heterostructure laser diode producing 0.6 nJ∕100 ps laser pulses at a central wavelength of ∼810 nm. The detector is a single-chip IC manufactured in the standard 0.35-μm HV CMOS process, including a 9 × 9 single-photon avalanche diode (SPAD) array and a 10-channel time-to-digital converter (TDC) circuit. Both the SPAD array and the TDC circuit support a time gating feature allowing photon detection to occur only within a predefined time window. The SPAD array also supports a 3 × 3 SPADs subarray selection feature to respond to the laser spot wandering effect due to the paraxial optics and to reduce background radiation-induced detections. The characterization results demonstrate a distance measurement accuracy of þ∕ − 0.5 mm to a target at 34 m having 11% reflectivity. The signal detection rate is 28% at a laser pulsing rate of 100 kHz. The single-shot precision of the laser radar is ∼20 mm (FWHM). The deteriorating impact of high-level background radiation conditions on the SNR is demonstrated, as also is a scheme to improve this by means of detector time gating.

In this paper we investigated the opportunities to improve the energy collection of solar chargers with the help of sensors on smartphones. We focused on the information of the ambient light sensor and the accelerometer in order to find suitable positions for solar modules. In particular under indoor environmental conditions, the location and orientation of solar chargers is crucial. If users are able to allocate beneficial positions for their chargers, the amount of power from solar modules can be increased up to 100 times. This is why we investigated the performance of sensors on smartphones, in particular in terms of their accuracy. We present experimental results obtained with the help of nowadays mobile phones and compare the measurement results against values which were collected with conventional measurement equipment under different light sources.