Erbium-doped glass lasers operated near by 1 5 mm wavelength are helpful for medicine and biology optical communication and eye-safe range finder systems. Advances in erbium-doped glass especially phosphate glass and lasers based on it have been extensive in recent years. Nowadays we can approve that erbium glass lasers are not worse compared with the neodymium ones by many spectroscopic and laser properties. Developments of the energy spectral and temporal characteristics and tuning near the 1500 nm wavelength of the erbium - doped phosphate glass lasers are reported. 2. SPECTROSCOPIC PECULIARITIES OF THE ERBIUM DOPED GLASS Phosphate erbium-doped glass possess a number of spectroscopic peculiarities as a laser active medium. Energy level diagrams of Er3 ions and two other its co-doped ions -Yb3 and Cr3 and the actual transitions (radiate and nonradiate) between them are shown in Fig. 1 (a). Absorption spectrum of that phosphate glass is also shown in Fig. 1 (b) . One can see that the whole pum energy is absorbed only by coactivators - Yb Cr - Yb E r and Cr3 - and then quickly and efficiently transferred from them to Er3 ions. Thus ''7 lasing and pumping of the erbium glass are ''4 realized by means of quite different ions. 4 Thanks to that one can get a low laser threshold t1/2 usin a small doping of Er3 ions (about 1019 I3/2 cm ) and the same time have a high efficient 4T pumoing by using the big concentration of ions 15/2 Yb3 and Cr3 in them (1021 cm3 and 1020 b cm3 accordingly). Obstacles for high efficiency of the lasers may be connected with either increase of the back pump energy transfer from Yb3 ions to Cr3 ones by too large concentration of Cr3 ions or thermal distortions of the active medium. Optimal pumping conditions for lamp pumped Er - doped glass laser differ from neodymium ones. It is explained by the important role of pump energy transfer processes in Er - doped glass. In order to have of high efficient pumping it is necessary that energy transfer rates from Yb3 to Er3 - 3+ 3+ WybEr and from Cr to Yb - WCrYb would be a lot of more then pumping rate W p (mainly object to WYbEr W1). It means the need to use pump pulse durations of about 1O - 102 s and more in that lasers. 3. EFFICIENCY AND THERMAL DISTORTIONS IN THE LASERS Efficiency of the lamp pumped Cr - Yb - Er doped phosphate glass oscillator can be up to 3 or some more (slope efficiency is up to 3. 5 ) /1 at free - running operation and storage efficiency of amplifiers based on the glass can be up to 1. 2 / 3 /. It was achieved

Date Published: 19 November 1992
PDF: 7 pages
Proc. SPIE 1839, Solid State Lasers and New Laser Materials, (19 November 1992); doi: 10.1117/12.131788

Published in SPIE Proceedings Vol. 1839:
Solid State Lasers and New Laser Materials