Laser pulsed radar

Fig. 9.17 Range of soft ferrite components (i) TV scanning yoke (components kindly supplied by Philips Components Ltd.) (ii) UR core and TV line output transformer (iii) E core for switched mode power supply (iv) wide band transformer core (v) core giving good magnetic shielding (vi) high Q (adjustable) filter core (cf. Fig. 9.48) (vii) precision ferrite antenna for transponder (viii) multilayer EMI suppressors (ix) toroids for laser and radar pulse applications (x) typical EMI shields for cables, ((ii)—(x) Courtesy of Ferroxcube UK .)...

Over-the past decade, not only have pulse durations decreased from 10 to 10" s but there has been a dramatic increase in the tunability of lasers, such that tunable coherent radiation can now span the VUV to the very long wavelength laser radar. Femtosecond spectroscopy, like most advances, has begun in the visible region and considerable research and development is necessary to expand this present spectral range around 600 nm (4). However, it is also the case that for many problems in photo dynamics, for which the state selectivity or the nature of the optically prepared initial state is of paramount importance, the spectral line-width (Av) of the pulse must remain narrow. Thus the transform-limited bandwidth relationships (AvA K) govern the temporal properties of the laser pulse and, for example, a 5 ns pulse of 0.01 cm" linewidth prepares a different ensemble than a 300 fs pulse of 26 cm linewidth at the same wavelength. 

Safety Considerations. High-power lasers raise a number of safety issues. There are the flammability and the toxicity of dye solutions. Most importantly, the eye hazards of laser radiation require careful shielding of the beam, and interlocks that restrict access to the laser room and to the dome. The laser could also dazzle aircraft pilots if they look directly down the beam. It is therefore necessary to close a shutter in the beam when a plane comes too close, either manually by human spotters, or automatically by use of radar, thermal IR or CCD cameras. Care must also be taken to avoid hitting overhead satellites in the case of pulsed or high power laser systems. 

Chirped pulse amplification (CPA) [1,2] is a new technique to achieve extremely high optical intensities in compact laser systems. The basic idea, which has its counterpart in radar technology, is illustrated in Fig. 1 [3]. An initial, short pulse... 

K. Maatta, J. Kostamovaara, A high precision time-to-digital converter for pulsed time-of-flight laser radar applications, IEEE Transactions on Instrumentation and Mesurement 47, 521-536 (1998)... 

Li t Distance And Ranging (Lidar) Type of scanning radar in which the timing of returns from the pulsed laser yields a target s shape. FuU-waveform lidar allows detection of objects between the forest canopy and floor. 

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