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The influence of amplified spontaneous emission (ASE) on the dynamic characteristics of transversely diode pumped erbium-ytterbium glass laser with Co:spinel Q-switch has been investigated. ASE cavity loss coefficient for passively Q-switched laser has been determined. The dependences of ASE cavity loss coefficient on the active element length, output mirror reflection coefficient, and initial transmission of the passive Q-switch have been defined. Laser dynamics has been modelled on the basis of the rate equation set for ion population densities and photon numbers, taking into account the amplified spontaneous emission. It has been shown that ASE accounting does not influence significantly the energy and duration of the output laser pulse. Variations of the laser turn-on time and pulse repetition rate of about 5-10% have been revealed in the case of ASE taken into consideration.

LASTEC Delhi in a joint collaborative activity with LEOS, Bangalore is developing a space qualified diode array pumped Nd:YAG laser transmitter delivering 30 mJ @ 10 pps of 10 ns duration. For space applications laser diodes are preferred because of their excellent reliability with lifetimes exceeding 100,000 hours. However, they are extremely sensitive to electro-static discharge, excessive current levels, and current spikes and transients. Small variations in bias voltage may produce large fluctuations in the current causing instability and damage to the device. Hence instead of the traditional power supplies a current controlled laser diode driver is required. This paper presents the design of a Q-CW laser diode driver based on closed loop current regulator, capable of driving 24 QCW laser diode bars each with 75W peak power at 70 A. The driver can generate up to 100 Amp peak current and 200µsec pulse width operating at 10 Hz. The current source design includes special circuits for low noise operation, slow turn-on and turn-off, circuits for over voltage and transient current protection; and good regulation. Space qualified and radiation hardened components are required to be used to sustain stringent space environment requirements during mission life of two years.