16 except for the tapered ends thereof is approximately four to six micrometers and illustratively the x direction length of each of the active regions 14 and 16 is about three to five centimeters the upper cladding layer 36 shown in fig2 is advantageously made of phosphosilicate glass exemplarily by standard low pressure chemical vapor deposition techniques the z direction thickness of the layer 36 is for example about ten to fifteen micrometers in accordance with the invention the pumping signal that is guided to repeatedly propagate around the loop configured waveguide 22 shown in fig1 and 2 is effective to simultaneously couple pumping energy into both of the active regions 14 and 16 in that way pumping radiation is absorbed by ions in each of these regions thereby promoting at least some of the ions therein to a state that is a lasing level of atomic excitation as is well known in the art in one particular illustrative example the y direction distance d fig2 between the facing sidewalls of the pumping waveguide 22 and each of the signal waveguides 10 and 12 is approximately one micrometer or less along substantially the entire lengths of the waveguides 10 and 12 that respectively underlie the active regions 14 and 16 such a spacing provides effective coupling of radiation from the pumping signal propagating in the waveguide 22 into the active regions 14 and 16 for illustrative purposes each of the embodiments described herein shows active regions formed on top of their respective waveguides but it is also feasible to form the active regions as part of or even as the entirety of the signal carrying waveguides also the pumping waveguide.