We report room-temperature pulsed up-conversion laser oscillation in Er-doped LiYF4 and KYF4 at 551 and 562 nm, respectively. In both crystals laser oscillation is observed on the S-4(3/2)-I-4(15/2) ground state transition. Excitation was provided by a tunable flashlamp-pumped Ti:sapphire laser in the spectral region around 810 nm. Additional pumping with a continuous wave krypton ion laser at 647 nm was beneficial to both lasers. Laser action has also been observed in Er-doped Y3Al5O12 on the same transition

Brede, R.

Chai, B.

Danger, T.

Heumann, E.

Huber, G.

Koetke, J.

English

Crossref

University of Central Florida (UCF): STARS (Showcase of Text, Archives, Research & Scholarship)

University of Central Florida STARS Faculty Bibliography 1990s Faculty Bibliography 1-1-1993 Green Up-Conversion Laser-Emission In Er-Doped Crystals At Room-Temperature R. Brede E. Heumann J. Koetke T. Danger G. Huber See next page for additional authors Find similar works at: https://stars.library.ucf.edu/facultybib1990 University of Central Florida Libraries http://library.ucf.edu This Article is brought to you for free and open access by the Faculty Bibliography at STARS. It has been accepted for inclusion in Faculty Bibliography 1990s by an authorized administrator of STARS. For more information, please contact STARS@ucf.edu. Recommended Citation Brede, R.; Heumann, E.; Koetke, J.; Danger, T.; Huber, G.; and Chai, B., "Green Up-Conversion Laser-Emission In Er-Doped Crystals At Room-Temperature" (1993). Faculty Bibliography 1990s. 652. https://stars.library.ucf.edu/facultybib1990/652 Authors R. Brede, E. Heumann, J. Koetke, T. Danger, G. Huber, and B. Chai This article is available at STARS: https://stars.library.ucf.edu/facultybib1990/652 Appl. Phys. Lett. 63, 2030 (1993); https://doi.org/10.1063/1.110581 63, 2030© 1993 American Institute of Physics.Green up-conversion laser emission in Er-doped crystals at room temperatureCite as: Appl. Phys. Lett. 63, 2030 (1993); https://doi.org/10.1063/1.110581Submitted: 22 June 1993 . Accepted: 13 August 1993 . Published Online: 04 June 1998R. Brede, E. Heumann, J. Koetke, T. Danger, G. Huber, and B. ChaiARTICLES YOU MAY BE INTERESTED INRoom-temperature green laser emission of Er:LiYF4Applied Physics Letters 63, 729 (1993); https://doi.org/10.1063/1.109942Green upconversion continuous wave Er3+:LiYF4 laser at room temperatureApplied Physics Letters 65, 383 (1994); https://doi.org/10.1063/1.112335Blue and green cw upconversion lasing in Er:YLiF4Applied Physics Letters 57, 1727 (1990); https://doi.org/10.1063/1.104048Green up-conversion laser emission in &doped crystals at room temperature R. Brede, E. Heumann, J. Koqtke, T. Danger, and G. Huber Institut ftir Laser-Physik, Universitat Hamburg, Jungiusstrasse 9-11, 2000 Hamburg 36, Germany B. Chai Center for Research in Electra Optics and Lasers, University of Central Florida, Orlando, Florida 32826 (Received 22 June 1993; accepted for publication 13 August 1993) We report room-temperature pulsed up-conversion laser oscillation in Er-doped LiYF, and KYF., at 551 and 562 mn, respectively. In both crystals laser oscillation is observed on the 4s3,2-4r ,sj2 ground state transition. Excitation was provided by a tunable flashlamp-pumped Ti:sapphire laser in the spectral region around 810 nm. Additional pumping with a continuous wave krypton ion laser at 647 nm was beneficial to both lasers. Laser action has also been observed in &-doped Y3Al,0i2 on the same transition. The advent and rapid improvement of laser diodes in the infrared and red spectral regions has caused new inter- est in the development of up-conversion lasers, which may provide compact “all solid-state” laser sources in the blue and green spectral ranges. Visible up-conversion lasing at room temperature has already been demonstrated in Tm- doped crystals”2 and in various rare-earth-doped fluorozir- conate fibers (e.g., Ref. 3). However, up to now visible up-conversion lasers in Er-doped crystals required cryo- genic temperatures, which clearly limited their applica- tions.4’5 Only under direct excitation laser oscillation has been achieved.6 We now report efficient pulsed green up- conversion lasing in Er-doped crystals at room tempera- ture. In our opinion the Ersf ion is a very attractive can- didate for diode pumped up-conversion lasers, because it offers various ground and excited state transitions near 800 and 970 nm, where high power laser diodes are available (see also, Ref. 7). The relevant part of the energy level scheme of Er3+ with respect to the laser experiment is shown in Fig. 1. The ground state absorption (GSA) processes and the excited state absorption (ESA) characterizing the pumping scheme are also shown. As pump sources a continuous wave krypton ion laser operating at 647 nm and a flash- lamp pumped Ti:sapphire laser could be used simulta- neously. In principle both lasers could be replaced by diode lasers for an all solid-state device. In the first step the krypton laser and/or the Ti:sap- phire laser are exciting the short living 4Fg/2 and 4Is,2 states of the Er3+ ion, respectively. From these levels the excitation rapidly decays into the metastable ‘1il12 level and subsequently to the metastable 4113,2 level. ESA tran- sitions near 800 nm originate from both metastable levels. Additionally, high populations of the me&table levels bleach the GSA at the green laser transition. Note that for 1% Er concentration the GSA at the Ti:sapphire wave- length (around 800 nm) is very weak. In the second step, ESA at the Ti:sapphire wavelength populates the upper laser level 4S’3,q of the green laser tran- sition. From highly resolved ESA measurements we con- clude that at a wavelength of 810 nm, where the best re- sults were obtained, the ESA mainly originates from the 41, 1,2 level. The experimental setup is presented schematically in Fig. 2. A dielectrically coated mirror (Ml) combined the pump beams of the Ti:sapphire and the krypton ion laser. The pulse width of the flashlamp pumped Ti:sapphire laser was about 50 ps. With a birefringent filter the wavelength could be tuned to ground state and excited state transitions of the Er3+ ion near 800 nm. The emission bandwidth of about 5 nm of the Ti:sapphire laser was comparable to that of high power laser diodes. In order to obtain a low thresh- old, a near concentric resonator with r=5 cm mirrors was used. To increase the absorbed pump energy, the output coupler was highly reflecting at both pump laser wave- lengths. With this setup we achieved pulsed laser oscilla- tion on the 4S3,2-41,5,2 ground state transition in Er( 1%):LiYF4(YLF), Er(5%):YLF, Er( l%)KYF4 U-F), and in Er(0.5%):Y3Al,0i2(YAG). To our knowledge this is the first time that laser action on this transition has been reported in Er:KYF at all. The results are presented in Figs. 3 and 4. In both crystals lasing oc- curred in r polarization, at 551 nm for YLF and 562 nm for KYF. Using both pump beams, a maximum output energy of 0.95 m.T has been achieved with the 6.9-mm-long Er( 1 %):YLF sample, which absorbed only 15% of the Ti:sapphire radiation. Pumping with the Ti:sapphire laser alone yielded a maximum output energy of 0.57 mJ and a slope efficiency of almost 20% (see Fig. 3). With an output coupling of 8%, 34%, reabsorption losses per roundtrip, and an emission cross section of 2~ 10m2’ cm2 (Ref. 6), a FIG. 1. Energy level diagram of the Eg+ ion (schematically) and pump- ing scheme. 2030 Appl. Phys. Lett. 63 (15), 11 October 1993 0003-6951/93/63(15)/2030/2/$6.00 @  1993 American Institute of Physics 2030 ..” . --- Tkatwhire laser il f=5cm cry-’ tiiter detector . . ...* r=5cm rz5cm FIG. 2. Setup of the up-conversion laser experiment. population of about 10% can be estimated for the upper laser level 4S3,2 at threshold. On the other hand, this pop- ulation can be obtained by a simple rate equation model for the pump process, taking into account the GSA and ESA transitions at the Ti:sapphire wavelength. With a measured ESA cross section of 0.5 X 10m2’ cm2, a GSA cross section of 0.05 x 10eu’ cm2, a pump energy of 10 mJ incident on the crystal, a pump spot size of 10m4 cm2, and a pump pulse width of 50 ps, an upper laser level population of 11% is obtained at the end of the pump pulse in agreement with the above estimation. The main role of the krypton laser is to populate the metastable 4111,2 level, where the ESA transition used for pumping originates. Without the krypton laser, the Ti:sapphire laser has to popGate this level via the weak GSA transition before the ESA process can efficiently populate the upper laser level and laser os- cillation can start. In the Er( 1% ) :YLF crystal we observed simultaneous lasing at 850 nm on the 4S3n- 4113,2 transition in spite of an output coupling of more than 80% through each mirror. Both laser transitions originate from the same upper laser level. Therefore, suppression of the 850 nm laser emission may increase the efficiency of the green laser transition. In order to obtain maximum output energy we had to tune the Ti:sapphire laser close to the maximum of the ESA. This contirms that at low Er concentrations ESA is the main pump process. With increasing Er concen- tration the “true” up-conversion process (4111,2,4111,2 absorbed Ti:sapphire energy [mJl FIG. 3. Output energy of the Er( l%):YLF laser, 1(Ti:sapphire):810 mn, 8% output coupling, the inset shows the power emitted by the kryp- ton laser at 647 nm. biii d ,~y/ r :*;;3b 1 Tksapphire energy [mJ] FIG. 4. Output energy of the Er(l%):KYF laser, A(Ti:sapphire):812 nm, 16% output coupling, the inset shows the power emitted by the krypton laser at 647 mn. + 4%2, 4115,2) becomes more effective, but, due to cross relaxation, the upper laser level lifetime rapidly decreases. The 7.3-mm-long Er ( 1% ) :KYF crystal absorbed only a few percent of the Ti:sapphire laser radiation. As it was difficult to measure the absorbed pump energy, we decided to plot the energy of the Ti:sapphire laser incident on the crystal in Fig. 4. The weak absorption is probably the main reason for the low output energy of the Er:KYF laser. The output energy of the Er:YAG laser at 561 nm was much lower in comparison with the fluorides and de- creased even further after the first few shots. We believe that the inferior performance of YAG can only partly be attributed to the shorter upper laser level lifetime-15 ps in Er(l%):YAG compared to 400 ps in Er(l%):YLF. Note that the pump pulse lasted only 50 ps. There are indications that parasitic ESA at the laser wavelength due to the 4113n-‘H9,2 transition may reduce the efficiency of green Er-doped lasers8 In conclusion, we have demonstrated pulsed green up- conversion lasing in Er-doped YLF, KYF, and YAG at ambient temperature for the first time. With the Er(l%):YLF sample an output energy of 0.95 mJ has been achieved. Pumping only with the Ti:sapphire laser yielded a slope efficiency of almost 20%. From recent ESA measurements we expect that the performance of these la- sers can be further improved by pumping around 970 nm. ‘D. C. Nguyen, G. E. Faulkner, M. E Weber, and M. Dulick, SPIE Solid State Lasers, 1223, 54 ( 1990). 2R. J. Thrash and L. F. Johnson, Compact Blue-Green Lasers, February 20-21, 1992, Santa Fe, New Mexico, Technical Digest Series 6, ThB3- l/17 (1992). 3T. J. Whitley, C. A. Milk, R. Wyatt, M. C. Brierley, and D. Szebesta, Electron. Lett. 27, 1785 (1991). 4T. Hebert, R. Wannemacher, W. Lenth, and R. M. Macfarlane, Appl. Phys. Lett. 57, 1727 (1990). ‘P. Xie and S. C. Rand, Opt. Lett. 17, 1198 (1992). 6R. Brede, T. Danger, E. Heumann, G. Huber, and B. Chai, Appl. Phys. Lett. 63, 729 (1993). ‘R. R. Stephens and R. A. McFarlane, Opt. Lett. 18, 34 (1993). s M. Pollnau, E. Heumann, and G. Huber, Appl. Phys. A 54,404 ( 1992). 2031 Appl. Phys. Lett., Vol. 63, No. 15, 11 October 1993 Brede et al. 2031 

Green Up-Conversion Laser-Emission In Er-Doped Crystals At Room-Temperature

https://stars.library.ucf.edu/cgi/viewcontent.cgi?article=1651&amp;context=facultybib1990

Green Up-Conversion Laser-Emission In Er-Doped Crystals At Room-Temperature

Abstract

Similar works

Full text

Available Versions

Crossref

University of Central Florida (UCF): STARS (Showcase of Text, Archives, Research & Scholarship)