Development of flashlamp-pumped Q-switched Ho:Tm:Cr:YAG lasers for mid-infrared LIDAR application

A flashlamp-pumped 2.1 micron Ho:Tm:Cr:YAG laser was studied for both normal mode and Q-switched operations under a wide variety of experimental conditions in order to optimize performance. Laser output energy, slope efficiency, threshold and pulselength were determined as a function of operating temperature, output mirror reflectivity, input electrical energy and Q-switch opening time. The measured normal-mode laser thresholds of a Ho(3+) (0.45 atomic percent):Tm(3+) (2.5 atomic percent):Cr(3+) (0.8 atomic percent):YAG crystal ranged form 26 to 50 J between 120 and 200 K with slope efficiencies up to 0.36 percent with a 60 percent reflective output mirror. Under Q-switched operation the slope efficiency was 90 percent of the normal-mode result. Development of solid state lasers with Ho(3+), Tm(3+) and/or Er(3+) doped crystals has been pursued by NASA for eye-dafe mid-infrared LIDAR (light detection and ranging) application. As a part of the project, the authors have been working on evaluating Ho(3+):Tm(3+):Cr(3+):YAG crystals for normal-mode and Q-switched 2.1 micron laser operations in order to determine an optimum Tm(3+) concentration under flashlamp pumping conditions. Lasing properties of the Ho(3+) in the mid-infrared region have been studied by many research groups since the early 1960's. However, the technology of those lasers is still premature for lidar application. In order to overcome the inefficiency related to narrow absorption bands of the Ho(3+), Tm(3+) and Er(3+), the erbium has been replaced by chromium. The improvement in flashlamp-pumped Ho(3+) laser efficiency has been demonstrated recently by several research groups by utilizing the broad absorption spectrum of Cr(3+) which covers the flashlamp's emission spectrum. Efficient energy transfer to the Tm(3+) and then the Ho(3+) occurs subsequently. It is known that high Tm(3+) concentration and low Ho(3+) concentration are preferred to achieve a quantum efficiency approaching two and to avoid large reabsorption losses. However, determination of the optimum Tm(3+) concentration required to ensure efficient energy transfer from Cr(3+) to Tm(3+) and from Tm(3+) to Ho(3+) has not been made in the Ho:Tm:CR:YAG crystal. The results obtained so far are given

Ursinus College Alumni Journal, Spring 1942

Current comment • President\u27s page • Accelerated program data • Commencement advanced to May 15-18 weekend • Woman\u27s Club corner • Accelerated program puts May pageant in April • Noted speakers address campus organizations • College defense council formed • Students raise $200 for foreign student relief • Distinguished British scholar serves as visiting professor • Freshman customs changed • Alumni Association nominees • With the Grizzlies: Intramural program; Football to continue; Girls basketball; Varsity basketball; Freshman basketball; Wrestling • Publications choose editors • Miss Moll joins Army Nurses Corps • About ourselveshttps://digitalcommons.ursinus.edu/alumnijournal/1014/thumbnail.jp

Ursinus College Alumni Journal, Autumn 1941

Current comment • President\u27s page • Messages to the alumni • A new humanism: An address delivered by Dr. F. Cyril James, Principal and Vice-Chancellor of McGill University, to the Founders Day convocation at Ursinus College • 1941-42 enrollment data • Fall sports • About ourselves • Alumni Association officershttps://digitalcommons.ursinus.edu/alumnijournal/1013/thumbnail.jp

Ursinus College Alumni Journal, Autumn 1941

Current comment • President\u27s page • Messages to the alumni • A new humanism: An address delivered by Dr. F. Cyril James, Principal and Vice-Chancellor of McGill University, to the Founders Day convocation at Ursinus College • 1941-42 enrollment data • Fall sports • About ourselves • Alumni Association officershttps://digitalcommons.ursinus.edu/alumnijournal/1013/thumbnail.jp