Abstract

Externally modulated solid-state lasers are increasingly used for analog fiber-optic applications such as cable television. The solid-state laser functions as an active filter for a laser diode array, converting its output to the required diffraction-limited, high power, low noise output. The main concerns in these systems are thermal management and diode lifetime. The two issues are closely related; 10°C of thermoelectric cooling can double both the diode lifetime and the system heat load. Diode lifetimes can also be enhanced by reducing the diode current. Increased Nd laser efficiency addresses all these issues. Recent work with Nd:YLF has shown a 40% optical-to-optical conversion efficiency at 1313 nm, 20% better than for Nd:YAG at 1319 nm. This suggests the possibility of ESA in Nd:YAG. Optimized focussing optics and laser rod length improved the performance of Nd:YLF at both 1313 and 1047 nm. The latter device has exhibited optical-to-optical conversion efficiencies of more than 55%. It has been used in telecommunication systems as a pump for high-power Yb,Er phosphosilicate fiber amplifiers. Outputs of more than 200 mW have been obtained at 1536 nm. This device is useful as a power amplifier, especially in analog fiber-optic systems.

© 1992 Optical Society of America