A semiconductor laser with a strongly asymmetric waveguide structure and a relatively thick (~0.1 mum) active layer, resulting in an extremely large equivalent spot size, is proposed and analyzed for the purpose of generating high-power single-optical pulses by gain switching. An improvement in obtainable single-pulse energies of about an order of magnitude over conventional laser structures is predicted.

Asymmetric-Waveguide Laser Diode for High-Power Optical Pulse Generation by Gain Switching

An integrated receiver channel for a pulsed time-of-flight laser range finder is presented. The receiver operates in a wide dynamic range without gain control. This is achieved by converting the received unipolar pulse to a bipolar waveform already after the optical detector before the signal is fed to amplifier blocks. Thus the nonlinearities of the amplifiers have the minimum effect on the timing point, which is located in the zero crossing of the bipolar pulse. A parallel resonant circuit is used to shape the pulse in the input of the channel, which consists of a cascade of limiting voltage amplifiers followed by a comparator. The measurements show that the receiver has a walk error of 74 ps in the dynamic range of 1:1280. This corresponds to 11 mm in distance. The minimum usable input signal is limited by the noise of the receiver and equals 1.9 muA

Receiver channel with resonance-based timing detection for a laser range finder

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.

High-Energy Picosecond Pulse Generation by Gain Switching in Asymmetric Waveguide Structure Multiple Quantum Well Lasers

This paper presents a current-mode gain-control scheme that significantly increases the input dynamic range of a wideband optoelectronic receiver without affecting its bandwidth or delay or deteriorating its noise properties. A current buffer with variable attenuation is placed between the photodetector and the transimpedance preamplifier. In this way, the input dynamic range of the receiver can be increased, or alternatively, the signal dynamics can be reduced, by over 20 dB. A BiCMOS test circuit designed for a pulsed time-of-flight laser rangefinder has a measured bandwidth of 170 MHz and an input dynamic range of /spl sim/80 dB. The delay varies only /spl plusmn/5 ps when the gain is varied by 24 dB (1:15).

A current-mode gain-control scheme with constant bandwidth and propagation delay for a transimpedance preamplifier

It is theoretically shown that gain switching quantum well AlGaAs/InGaAs laser with a very large ratio of active layer thickness to optical confinement factor (~8 µm) can result in single, high-energy (1 nJ) short (~100 ps) single optical pulses at wavelengths ~1 µm. Calculations predict that high electrical-to-optical conversion efficiency can be achieved in such structures, which require an injection current pulse of a modest amplitude of ~10 A and a duration of 1.5–2 ns. A narrow asymmetric waveguide design is proposed as a way of implementing such a structure while maintaining good far-field properties of the single emitted mode.

https://iopscience.iop.org/article/10.1088/0268-1242/26/4/045010/pdf

Quantum well laser with an extremely large active layer width to optical confinement factor ratio for high-energy single picosecond pulse generation by gain switching

An integrated receiver channel with a wide dynamic range for a pulsed time-of-flight (TOF) laser rangefinder has been designed and tested. The circuit uses leading edge timing discrimination. The bandwidth of the receiver channel is 250 MHz and the maximum transimpedance 40 kΩ. The single-shot distance measurement accuracy is 65 mm, taking into account walk error (input signal amplitude varies in the range from 1 to 4000) and jitter (+/-3σ).

http://ieeexplore.ieee.org/iel5/9919/31528/01471301.pdf

A receiver channel with a leading edge timing discriminator for a pulsed time-of-flight laser radar

The pulsed time-of-flight laser range finding techniques based on laser diode transmitter enables one to realize a mm-level accuracy to non-cooperative targets in a distance measurement range of several tens of meters in industrial applications such as the measurement of level heights in silos, positioning of tools and vehicles, velocity measurement, anti-collision radars, proximity sensors, etc In this work the basic pulsed time-of-flight laser radar functions, the receiver channel and the time interval measurement unit, have been realized in the form of high-performance full-custom integrated circuits, which should pave the way for realizing a laser radar eventually as a component-like micro system thus increasing the number of possible applications for the developed techniques The integrated BiCMOS receiver channel produces a logic level output pulse for the time interval measurement from the received laser echo Two versions were realized, one detecting the leading edge of the received pulse and achieving an accuracy of +/- 35 mm in a dynamic range of 1:4000 In the other version gain control and constant fraction type of timing detection techniques are used to enhance the accuracy With this circuit an input dynamic range of 1:650 (SNR > 10) can be achieved with a timing accuracy of about +/- 3 mm The developed fully integrated CMOS time-to-digital converter realization is based on a counter and a novel parallel two- step interpolation method The single-shot precision and measurement range of the unit are 50 ps and 2 microseconds, respectively In averaging mode the linearity is better than +/- 5 ps Even better single-shot precision can be realized with analog interpolation techniques, however, at the expense of reduced stability

Integrated chip set for a pulsed time-of-flight laser radar

A laser pulse timing detector has been designed. The circuit consists of a low-noise transimpedance amplifier channel with gain control and a timing detector. The measured bandwidth of the amplifier channel is 10 MHz, transimpedance 340 k? - 2.7 M? and input referred noise 0.9pA/?Hz. The walk error of the timing detector is +/- 50ps, when its input signal amplitude varies from 150 mV to 2.5 V.

http://ieeexplore.ieee.org/iel5/5468575/5468576/05468603.pdf

Laser Pulse Timing Detector

An integrated BiCMOS receiver channel for a pulsed time-of-flight laser rangefinder has been designed. The circuit has two identical channels, one for the start pulse and the other for the stop pulse, each consisting of a low-noise transimpedance amplifier channel and a timing discriminator. The measured bandwidth of the amplifier channels is 5 MHz, Z/sub max/=8.4 M/spl Omega/ and the input referred noise 0.6 pA//spl radic/Hz. The timing error of the receiver is within +/-4.5 cm, when the amplitude of the input signal varies from 21 nA to 2.2 /spl mu/A (/spl sim/1:100). The measurement results show that a decimeter-level distance measurement accuracy has been achieved.

A low-noise receiver channel for a pulsed laser rangefinder

A receiver channel consisting of a low-noise transimpedance preamplifier, variable R-2R ladder attenuator, voltage amplifier, peak detector, r.m.s. noise meter and highpass/lowpass timing detector has been designed for a laser rangefinding device. The measured bandwidth of the amplifier channel is 10 MHz, transimpedance 340 k/spl Omega/ to 2.7 M/spl Omega/ and input referred noise 0.9 pA//spl radic/Hz. The walk error of the timing detector is +/- 50 ps, when its input signal amplitude varies from 150 mV to 2.5 V. Measurement results show that a dm-level distance measurement accuracy has been realized using integrated ASICs.

T. Peltola

Papers

A receiver channel with a leading edge timing discriminator for a pulsed time-of-flight laser radar

Integrated chip set for a pulsed time-of-flight laser radar

Laser Pulse Timing Detector

A low-noise receiver channel for a pulsed laser rangefinder

An integrated low-noise BiCMOS amplifier channel and timing detector