We claim: 1. An optical device comprising a glass substrate doped with a laser species and having one or more waveguides defined by channels in the substrate having a distinct refractive index from the substrate wherein the substrate is an alkali phosphate glass doped with Yb and Er, wherein the weight ratio of Yb:Er dopant is from 3:1 to about 8:1. 2. An optical device of claim 1, wherein the device has two or more waveguides. 3. An optical device of claim 2, wherein the waveguides are comprised of an alkali phosphate glass doped with Er and Yb, which has been treated so that the refractive index is higher than that of the substrate. 4. An optical device of claim 3, wherein the optical device is prepared by applying a mask to the substrate glass having apertures of a width and length corresponding to the waveguides to be formed in the substrate and conducting ion-exchange by contact with an ion-exchange solvent to form the waveguides through the apertures. 5. An optical device of claim 3, wherein the optical device is prepared by applying a mask to the substrate glass having apertures of a width and length corresponding to the waveguides to be formed in the substrate and conducting photolithography to form the waveguides through the apertures. 6. An optical device of claim 1, which further comprises a reflecting element in association with the waveguide to provide a laser effect when pumped. 7. The optical device of claim 6, wherein the reflecting element is a diffraction grating provided on the substrate. 8. The optical device of claim 6, wherein the reflecting element is a DBR grating provided on the substrate. 9. The optical device of claim 1, wherein the Yb:Er dopant weight ratio is about 4:1. 10. The optical device of claim 1, wherein the Er concentration in the substrate is up to 6.times.10.sup.20 ions/cm.sup.3. 11. The optical device of claim 1, wherein the Er concentration in the substrate is about 1.times.10.sup.20 ions/cm.sup.3. 12. The optical device of claim 1, wherein the substrate is doped with 1.15 wt % of Er.sub.2 O.sub.3 and 4.73 wt % Yb.sub.2 O.sub.3. 13. The optical device of claim 1, wherein the weight ratio of Yb:Er dopant is from about 4:1 to about 8:1. 14. The optical device of claim 1, which is in the form of a laser providing a power of over 20 mW and a slope efficiency of 28% or higher. 15. The optical device of claim 14, which is in the form of a laser providing a power of 25-180 mW. 16. The optical device of claim 1, which contains two or more waveguides. 17. An optical device in the form of a laser which has a length of 15 mm or less, comprising a glass substrate doped with a laser species and having one or more waveguides defined by channels in the substrate having a distinct refractive index from the substrate wherein the substrate is an alkali phosphate glass doped with Yb and Er and wherein the weight ratio of Yb:Er dopant is from about 1:1 to about 8:1, and further comprising a reflecting element in association with the waveguide to provide a laser effect when pumped. 18. The optical device of claim 17, wherein the reflecting element is a diffraction grating provided on the substrate. 19. The optical device of claim 17, wherein the reflecting element is a DBR grating provided on the substrate.