Hiroshi Baba

Bio: Hiroshi Baba is an academic researcher from University of Tokyo. The author has contributed to research in topics: Lidar & Laser. The author has an hindex of 3, co-authored 7 publications receiving 288 citations.

Random modulation cw lidar

Abstract: A new lidar scheme using a pseudorandom code modulated cw laser as a transmitting laser source (RM-CW lidar) is proposed and a demonstration of its use for aerosol measurement is shown. A formula for estimating the SNR values in RM-CW lidar was derived, and it was demonstrated that the observed SNR value was in good agreement with the calculation.

Diode-laser random-modulation cw lidar.

Abstract: Practical lidar applications require an easy to operate compact system. Random-modulation continuous-wave (RM-CW) lidar enables us to use a cw laser with a power level of several tens of milliwatts as the light source. For this purpose, the diode laser is the most suitable candidate for a compact lidar system. Here we report construction of the first practical portable diode-laser RM-CW lidar system and its measurement of the spatial aerosol profile at nighttime. The low-level cw power and the current operational wavelength (780 nm) make the RM-CW lidar completely eye-safe by ANSI standards.

High-speed multichannel photon counter for time-resolved laser spectroscopy

Abstract: A versatile, high‐speed multichannel counter, which has maximum temporal resolution Δt=30 ns and channel length up to 4095, has been developed for various kinds of time‐resolved laser spectroscopic measurements. High speed, large counting capacity, low cost for fabrication, and ease of circuit assembly have been accomplished by introducing both parallel and pipe‐line processing. The performance of this system has been verified in the applications to cw laser radar, time‐of‐flight measurement of molecular beam, and radiative lifetime measurement.

Pseudo-Random-Modulation CW Lider for Air Pollution Measurement

Abstract: Pseudo-random-modulation CW lider (RM-CW lider) is a new lider technique, which is essentially an optical version of the pseudo-noise (PN) radar. However, the crossover function is introduced to the RMCW lider in order to suppress the near-, distance strong-echo contribution. In his paper, RM-CW lidar is theoretically treated both in Mie-scattering lidar and differential absorption lidar (DIAL) cases. The fundamental performance of the former is experimentally demonstrated and the ability ofthe latter is discussed in a detailed case using an Ar laser as a transmitting laser.

Complex photonics: Dynamics and applications of delay-coupled semiconductors lasers

Abstract: Complex phenomena in photonics, in particular, dynamical properties of semiconductor lasers due to delayed coupling, are reviewed. Although considered a nuisance for a long time, these phenomena now open interesting perspectives. Semiconductor laser systems represent excellent test beds for the study of nonlinear delay-coupled systems, which are of fundamental relevance in various areas. At the same time delay-coupled lasers provide opportunities for photonic applications. In this review an introduction into the properties of single and two delay-coupled lasers is followed by an extension to network motifs and small networks. A particular emphasis is put on emerging complex behavior, deterministic chaos, synchronization phenomena, and application of these properties that range from encrypted communication and fast random bit sequence generators to bioinspired information processing.

Long-range time-of-flight scanning sensor based on high-speed time-correlated single-photon counting.

Abstract: We describe a scanning time-of-flight system which uses the time-correlated single-photon counting technique to produce three-dimensional depth images of distant, noncooperative surfaces when these targets are illuminated by a kHz to MHz repetition rate pulsed laser source. The data for the scene are acquired using a scanning optical system and an individual single-photon detector. Depth images have been successfully acquired with centimeter xyz resolution, in daylight conditions, for low-signature targets in field trials at distances of up to 325 m using an output illumination with an average optical power of less than 50 microW.

Chaotic lidar

Abstract: A novel chaotic lidar (CLIDAR) system that utilizes a chaotic laser as the light source is proposed and studied. In CLIDAR, the detection and ranging are realized by correlating the signal waveform reflected back from the target with a delayed reference waveform. Benefiting from the very broad bandwidth of the chaotic waveform that can be easily generated by a semiconductor laser, a centimeter-range resolution is readily achieved. The correlation performance of CLIDAR is studied both numerically and experimentally. The power spectra, phase portraits, time series, and correlation traces of the chaotic waveforms obtained at different operating conditions are compared. The relation between the complexity of the attractor and the correlation property is examined. The correlation dimension and the largest positive Lyapunov exponent of each waveform are calculated. To compare the correlation performance of the waveforms quantitatively, peak sidelobe levels of the correlation traces with different correlation lengths and relative noise levels are investigated. Preliminary experiments show a subcentimeter accuracy in ranging with a 3-cm-range resolution, which currently is limited by the bandwidth of the oscilloscope used.

Resolving range ambiguity in a photon counting depth imager operating at kilometer distances

Abstract: Time-correlated single-photon counting techniques have recently been used in ranging and depth imaging systems that are based on time-of-flight measurements. These systems transmit low average power pulsed laser signals and measure the scattered return photons. The use of periodic laser pulses means that absolute ranges can only be measured unambiguously at low repetition rates (typically 1 km) to ensure that only one pulse is in transit at any instant. We demonstrate the application of a pseudo-random pattern matching technique to a scanning rangefinder system using GHz base clock rates, permitting the acquisition of unambiguous, three-dimensional images at average pulse rates equivalent to >10 MHz. Depth images with centimeter distance uncertainty at ranges between 50 m and 4.4 km are presented.