selection segment 28 being approximately 1 cm however waveguide substrates having a length of approximately 36 mm are contemplated at a first polished end of the waveguide substrate 23 the dielectric mirror 22 is bonded such as by using an ultraviolet curing epoxy similarly epoxy can be used to attach the wavelength selection segment 28 to the waveguide substrate 23 a particularly useful frequency for use in optical telecommunications is 1550 nm fig5 illustrates the energy levels of an erbium doped laser source having a useful output energy 56 in the 1530 nm to 1560 nm waveband referring to fig2 and 5 the laser pump 16 is used to create an excited state in the doped laser gain medium within the waveguide substrate 23 fig5 schematically represents operations in which the erbium is excited by the incoming light to progress from a low level state 58 to a high level state 60 rapid decay then results in a drop to an intermediate excited state 62 and a population inversion is created as understood by persons skilled in the art the outgoing energy 56 is generated by stimulated emission from the drop from the intermediate excited state 62 to the low level state 58 fig6 illustrates the energy band gaps for absorption and emission in an erbium doped laser source optionally a neodymium doped laser source may be used fig7 illustrates the energy band gaps for absorption and emission in such a laser source neodymium has a characteristic energy band gap in the region of 1300 nm and can be a.