An apparatus (10', 10") comprising: a polarization splitter configured to receive input light, to direct a first polarization component of the received input light to a first optical path segment, and to direct a second polarization component of the received input light to a separate second optical path segment; a polarization-sensitive optically active medium having an internal optical axis, said active medium being configured to amplify said input light when suitable pumping energy is applied to thereto, said active medium having first and second optical ports (28, 30), the first port being at an end of the first optical path segment, the second port being at an end of the second optical path segment, said active medium being configured to output amplified light from one of the ports in response to receiving the input at the other of the ports, and an optical source of said pump energy, said source comprising at least one laser longitudinally coupled to said active medium, wherein said polarization splitter is configured to receive pump light from said laser, to direct a first polarization component of the received pump light to said first optical path segment, and to direct a second polarization component of the received pump light to said second optical path segment, said first and second optical path segments being configured so that the intensities of said first and second pump light components are substantially equal upon entering said active medium, and wherein said first and second optical path segments are configured so that the polarizations of said first and second input light components are substantially parallel to one another upon entering said ports. a polarization splitter configured to receive input light, to direct a first polarization component of the received input light to a first optical path segment, and to direct a second polarization component of the received input light to a separate second optical path segment; a polarization-sensitive optically active medium having an internal optical axis, said active medium being configured to amplify said input light when suitable pumping energy is applied to thereto, said active medium having first and second optical ports (28, 30), the first port being at an end of the first optical path segment, the second port being at an end of the second optical path segment, said active medium being configured to output amplified light from one of the ports in response to receiving the input at the other of the ports, and an optical source of said pump energy, said source comprising at least one laser longitudinally coupled to said active medium, wherein said polarization splitter is configured to receive pump light from said laser, to direct a first polarization component of the received pump light to said first optical path segment, and to direct a second polarization component of the received pump light to said second optical path segment, said first and second optical path segments being configured so that the intensities of said first and second pump light components are substantially equal upon entering said active medium, and wherein said first and second optical path segments are configured so that the polarizations of said first and second input light components are substantially parallel to one another upon entering said ports.