Dual function laser for space laser communications

Claim 1

A dual function laser system providing a first laser beam radiation at a first wavelength and a second laser beam radiation radiating in the opposite direction from the said first beam and at a second wavelength that is approximately one-half the said first wavelength, comprising: a. an optical cavity resonant at the said first wavelength having a first leg, and an intersecting second leg positioned substantially at a right angle to the said first leg, the said optical cavity having a flat mirror highly reflective to the said first wavelength and highly transmissive to the said radiation of the said second wavelength positioned at approximately 45° to each of the said legs at their said intersection, the said flat mirror optically connecting the said first leg and the said second leg to form the said resonant cavity; b. a laser rod element positioned in the said first leg of the said optical cavity, stimulated to provide laser emission circulating in the said resonant cavity at the said first wavelength; c. a frequency doubling crystal positioned in the said second leg of the said optical cavity intercepting the said circulating laser emission at the said first wavelength, the said crystal generating from the said circulating emission the said second laser beam having the said second wavelength that is half the said first wavelength, whereby the said second laser beam is coincident with the said first laser emission in the said second leg of the said optical cavity and propogates through the said flat mirror; and d. means for extracting from the said second leg of the said optical cavity laser radiation at the said first wavelength propogating in the opposite direction from the said propogating second wavelength radiation.