OSA's Digital Library

Optics Express

Optics Express

  • Editor: J. H. Eberly
  • Vol. 4, Iss. 12 — Jun. 7, 1999
  • pp: 490–495
« Show journal navigation

High-power “Watt-level” CW operation of diode-pumped 2.7 μm fiber lasers using efficient cross-relaxation and energy transfer mechanisms

B. Srinivasan, J. Tafoya, and R. K. Jain  »View Author Affiliations


Optics Express, Vol. 4, Issue 12, pp. 490-495 (1999)
http://dx.doi.org/10.1364/OE.4.000490


View Full Text Article

Acrobat PDF (96 KB)





Browse Journals / Lookup Meetings

Browse by Journal and Year


   


Lookup Conference Papers

Close Browse Journals / Lookup Meetings

Article Tools

Share
Citations

Abstract

We report the demonstration of high power (660 mW) CW operation of a diode-pumped mid-IR Er fiber laser. This was achieved by using efficient depopulation of the lower laser level via enhanced cross-relaxation between Er ions and energy transfer to Pr ions (at doping densities much higher than those used previously in Er:ZBLAN), along with optimal pumping of such lasers via custom-designed double-clad fluoride fibers.

© Optical Society of America

Because of the strong water absorption near 3 μm in tissue and the consequent ultrashort penetration depths (of a few microns), compact high power (100 mW to 1 W) 2.7 μm laser sources with TEM00 beam quality have several important applications in ultrafine intraocular and endoscopic laser surgery including transmyocardial revascularization and other intra-arterial procedures [1–7

1. L. Esterowitz and R. Allen, “Rare Earth Doped IR Fiber Lasers for Medical Applications,” Proc. SPIE 1048, 129–132 (1989).

]. Compact and efficient sources of mid-IR radiation are also needed for infrared countermeasures applications, and for ppb (parts per billion) level spectroscopic monitoring [8

8. R. S. Eng, J. F. Butler, and K. J. Linden, “Tunable Diode Laser Spectroscopy: An Invited Review,” Opt. Engg. 19, 945–960 (1980).

] of several important species such as carbon monoxide (CO), formaldehyde (H2CO), nitric oxide (NO), nitrogen dioxide (NO2), hydrogen sulphide (H2S), arsine (AsH3), and phosphine (PH3).

The 2.7 μm transition in Er:ZBLAN is well-suited for several of the above applications. For instance, the broad tunability [9

9. T. Yamamoto, T. Komukai, and Y. Miyajima, “Wide-Band Erbium-Doped Fluoride Fiber Optical Amplifier at 2.7 μm with Fluoride Fiber Wavelength-Division Multiplex Coupler,” Jpn. J. Appl. Phys. 32, L62–L64 (1993). [CrossRef]

] of this transition (2.65–2.83 μm) should enable ppb spectral monitoring of H2S (2.65 μm) and NO (2.7 μm). However, as has been frequently stated, the longer natural lifetime of the lower laser level (4I13/2, 9.4 ms) relative to that of the upper laser level (4I11/2, 7.5 ms) of the 2.7 μm transition often results in a population bottleneck that inhibits efficient steady-state (CW) lasing in Er:ZBLAN fiber lasers [6

6. M. Pollnau, “The Route Toward a Diode-Pumped 1-W Erbium 3-μm Fiber Laser,” IEEE J. Quantum Electron. 33, 1982–1990 (1997). [CrossRef]

,7

7. E. Poppe, B. Srinivasan, and R. K. Jain, “980nm-Diode-Pumped Continuous Wave Mid-IR (2.7 μm) Fiber Laser,” Electron. Lett. 34, 2331–2333 (1998). [CrossRef]

,10–12

10. J. Y. Allain, M. Monerie, and H. Poignant, “Energy Transfer in Er3+/Pr3+-Doped Fluoride Glass Fibres and Application to Lasing at 2.7 μm,” Electron. Lett. 27, 445–447 (1991). [CrossRef]

]; as such this transition has been frequently called “self-terminating” [10

10. J. Y. Allain, M. Monerie, and H. Poignant, “Energy Transfer in Er3+/Pr3+-Doped Fluoride Glass Fibres and Application to Lasing at 2.7 μm,” Electron. Lett. 27, 445–447 (1991). [CrossRef]

,13

13. R. S. Quimby and W. J. Miniscalco, “Continuous-Wave Lasing on a Self-Terminating Transition,” Electron. Lett. 28, 14–16 (1989).

]. We have previously demonstrated alleviation of this bottleneck and strongly enhanced efficiencies and output powers [7

7. E. Poppe, B. Srinivasan, and R. K. Jain, “980nm-Diode-Pumped Continuous Wave Mid-IR (2.7 μm) Fiber Laser,” Electron. Lett. 34, 2331–2333 (1998). [CrossRef]

,14

14. X. Zhao, B. Srinivasan, P. Pulaski, S. Gupta, and R. K. Jain, “Mirror-Free, High Power (~140mW) Diode-Pumped 2.7 μm CW Fiber Laser,” Postdeadline paper, CLEO Europe ’98 Technical Digest (1998).

] by a simple technique, namely the use of fibers with high concentrations (>10,000 ppm) of Er. It was hypothesized that such high concentrations not only reduce the problem of ground state bleaching, but also cause significantly enhanced cross-relaxation via the formation of Er ion clusters [15

15. B. Srinivasan, G. Monnom, and R. K. Jain, “Indirect Measurement of the Magnitude of Ion Clustering at High Doping Densities in Er:ZBLAN Fibers,” to be published.

], whose net effect is to relax the excitation from the lower laser level (4I13/2) to the ground state (4I15/2), while upconverting an adjacent ion to the 4I9/2 state. A fringe benefit of the use of high Er doping densities is the natural amenability of the consequent high core absorption to optimized designs of double-clad fibers [16

16. S. Bedö, W. Lüthy, and H. P. Weber, “The Effective Absorption Coefficient in Double-Clad Fibers,” Opt. Commn. 99, 331–335 (1993). [CrossRef]

,17

17. A. Liu and K. Ueda, “The Absorption Characteristics of Circular, Offset, and Rectangular Double-Clad Fibers,” Opt. Commn. 132, 511–518 (1996). [CrossRef]

] capable of being pumped by relatively inexpensive high power diode arrays.

In this Letter, we demonstrate further improvements in the power and efficiency of CW lasing at the 2.7 μm transition in Er3+:ZBLAN fiber lasers by utilizing a complementary technique [6

6. M. Pollnau, “The Route Toward a Diode-Pumped 1-W Erbium 3-μm Fiber Laser,” IEEE J. Quantum Electron. 33, 1982–1990 (1997). [CrossRef]

,10

10. J. Y. Allain, M. Monerie, and H. Poignant, “Energy Transfer in Er3+/Pr3+-Doped Fluoride Glass Fibres and Application to Lasing at 2.7 μm,” Electron. Lett. 27, 445–447 (1991). [CrossRef]

,18

18. D. S. Knowles and H. P. Jenssen, “Upconversion versus Pr-Deactivation for Efficient 3 μm Laser Operation in Er,” IEEE J. Quantum. Electron. 28, 1197–1208 (1992). [CrossRef]

,19

19. L. Wetenkamp, G. F. West, and H. Többen, “Co-Doping Effects in Erbium3+- and Holmium3+-Doped ZBLAN Glasses,” J. Non-Crystalline Solids 140, 25–30 (1992). [CrossRef]

] for enhancing the rate of depletion of the 4I13/2 level of Er by energy transfer to the 3F3 and the 3F4 levels of Pr (see Fig. 1). In particular, we demonstrate 660 mW of CW output from a 791 nm diode array-pumped Er/Pr:ZBLAN rectangular-clad fiber laser with a slope efficiency of 13% with respect to the absorbed pump power [20

20. These results were submitted for presentation at the Conference for Lasers and Electro-Optics (CLEO) ’99 as a postdeadline paper on 4/26/99 (paper #CPD23, CLEO ’99, Baltimore, May 23–28, 1999).

]. The output power demonstrated here is nearly an order of magnitude higher than the highest powers previously reported [14

14. X. Zhao, B. Srinivasan, P. Pulaski, S. Gupta, and R. K. Jain, “Mirror-Free, High Power (~140mW) Diode-Pumped 2.7 μm CW Fiber Laser,” Postdeadline paper, CLEO Europe ’98 Technical Digest (1998).

] for a diode-pumped mid-IR fiber laser, and shows evidence of easy scalability to Watt power levels (by very simple improvements such as optimization of the Er-Pr concentrations, increase of the pump power and coupling efficiencies, and the use of optimized output coupling).

Figure 1. Dominant energy transfer pathways between laser levels in Er and resonantly-matched energy levels in Pr (k1 = 0.15×103 s-1 and k2 = 0.93×103 s-1 for our 20,000/5,000 ppm Er/Pr:ZBLAN fiber)

The fiber used in this work was a custom-designed rectangular-clad Er/Pr:ZBLAN fiber [21

21. This fiber was obtained from Thorlabs, Inc., NJ, USA.

]. The rare-earth concentrations in the core (dia.=13 μm, NA=0.16) were chosen to be 20,000 ppm of Er and 5,000 ppm of Pr, based on the requirements of efficient absorption in Er and rapid depopulation of the lower laser level (via enhanced cross-relaxation in Er and efficient energy transfer to Pr). The lifetimes for the 4I11/2 and the 4I13/2 upper and lower laser levels were measured to be 2.5 ms and 0.7 ms respectively (corresponding to a lifetime ratio κ of 3.57) for this specific co-doped system versus lifetimes of 4 ms and 2 ms respectively (κ = 2.0) for a singly-doped 20,000 ppm Er:ZBLAN fiber, and 7.5 ms and 9.4 ms respectively (κ = 0.8) [22

22. Note that the lifetime values quoted here were based on our own measurements in Er-doped ZBLAN fibers and as such show small deviations from other values reported in the literature for similar ZBLAN bulk samples and fibers and related fluoride hosts (see references 6,10,13,18).

,23

23. V. K. Bogdanov, W. E. K. Gibbs, D. J. Booth, J. S. Javorniczky, P. J. Newman, and D. R. MacFarlane, “Fluorescence from Highly-Doped Erbium Fluorozirconate Glasses Pumped at 800 nm,” Opt. Commn. 132, 73–76 (1996). [CrossRef]

] for the traditional ≤1,000 ppm low concentration self-terminating 2.7 μm Er:ZBLAN laser. Further details on the criteria used for choosing such dopant concentrations are given below.

Figure 2. Schematic diagram of diode-pumped double-clad fiber laser

A schematic diagram of the diode-pumped fiber laser setup is illustrated in Fig. 2. In our work, we used an OptoPower 791 nm diode array capable of delivering 10 Watts as the pump source. The inner cladding dimensions and NA of the undoped cladding of the double-clad fiber were chosen to be (100μm×200μm) and 0.55 respectively to facilitate high coupling efficiencies for the diode beam (whose characteristics are 8 mm square size, 6.5 mrad divergence in the vertical plane and -13 mrad divergence in the horizontal plane) to be used, as well as to obtain significantly high effective absorption coefficients [16

16. S. Bedö, W. Lüthy, and H. P. Weber, “The Effective Absorption Coefficient in Double-Clad Fibers,” Opt. Commn. 99, 331–335 (1993). [CrossRef]

,17

17. A. Liu and K. Ueda, “The Absorption Characteristics of Circular, Offset, and Rectangular Double-Clad Fibers,” Opt. Commn. 132, 511–518 (1996). [CrossRef]

]. In order to match the diode array beam shape to the rectangular-clad fiber, we used a cylindrical lens of 20 cm focal length and rotated its axis with respect to the plane of the diode array, to compensate simultaneously for beam-shaping and astigmatism effects and thereby optimize the coupling. The net coupling efficiency and the effective pump (791 nm) absorption coefficient were measured to be 65% and 0.6 dB/m respectively. Given the measured value of the effective pump absorption coefficient and the estimated value of the background losses (0.1 dB/m) at the lasing transition, we chose a fiber length of 14 m for the present experiments; the value of the measured pump absorption for the fiber was ~85%.

Figure 3. Photograph of the experimental setup shown schematically in Fig. 2

Fig. 3 shows a photograph of the experimental setup. Strong green (544 nm) fluorescence is observed when the diode radiation is coupled optimally to the fiber (and was used as a visual indicator to optimize coupling). As illustrated in Fig. 4, this fluorescence is caused by excited state absorption (ESA) [24

24. M. Pollnau, Ch. Ghisler, W. Lüthy, and H. P. Weber, “Cross-Sections of Excited-State Absorption at 800 nm in Erbium-Doped ZBLAN Fiber,” Appl. Phys. B 67, 23–28 (1998). [CrossRef]

] from the 4I11/2 level to the 4F5/2 level, followed by rapid non-radiative decay to the 4S3/2 level and subsequent fluorescence from the 4S3/2 level to the 4I15/2 level. Despite its visual advantages (including facilitation of the optimization of coupling), this upconversion mechanism represents a detrimental pathway for depopulation of the upper laser level. As such, the choice of the 791 nm pump wavelength was made in part to reduce the detrimental effects of this ESA (the ESA cross-section at 791 nm is approximately 100 times weaker than that at the peak value at 808 nm). Even lower values of ESA from the 4I11/2 level can be obtained by detuning the pump laser to shorter wavelengths, but at the expense of reduced ground state absorption and a reduction in the “beneficial” lower laser level (4I13/2) depleting ESA. Wavelength detuning of the order of 2–3 nm may be optimum for this case, and is well within the tuning range of the pump diode array. For a given power level, precise optimization is best done by detuning the pump wavelength for highest output powers.

Figure 4. Role of the excited state absorption (of 791 nm) from the upper laser level (4I11/2) in generation of green (544 nm) upconversion fluorescence in the Er-doped fiber

Because of the availability of sufficiently high pump powers and gains, we were able to achieve lasing off the 4% Fresnel reflections from the two ends of the fiber. All the data reported here corresponds to this condition. Fig. 5 shows the 2.7 μm output power as a function of the absorbed 791 nm diode power. As seen from the above plot, the laser threshold is 330 mW and the slope efficiency is 13% with respect to the absorbed power. The linearity of the plot and the lack of any evidence of saturation at the high pump powers clearly indicates scalability to over 1 Watt power levels simply by using higher pump powers or more efficient pump coupling and pump absorption techniques.

Figure 5. CW 2.7 μm output power vs. absorbed 791 nm pump power for our Er/Pr:ZBLAN fiber

Given the round-trip losses in the cavity, the round-trip gain is estimated to be as high as 29.4 dB at the threshold pump power density of 1.65 kW/cm2. The significantly lower threshold pump densities used, compared to the ≥100 kW/cm2 reported by earlier workers [10–12

10. J. Y. Allain, M. Monerie, and H. Poignant, “Energy Transfer in Er3+/Pr3+-Doped Fluoride Glass Fibres and Application to Lasing at 2.7 μm,” Electron. Lett. 27, 445–447 (1991). [CrossRef]

], are attributed to the choice of a double-clad fiber. The relatively high slope efficiency achieved in our work compared to other non-cascade lasing schemes [10

10. J. Y. Allain, M. Monerie, and H. Poignant, “Energy Transfer in Er3+/Pr3+-Doped Fluoride Glass Fibres and Application to Lasing at 2.7 μm,” Electron. Lett. 27, 445–447 (1991). [CrossRef]

,12

12. G. J. Kintz, R. Allen, and L. Esterowitz, “CW and Pulsed 2.8 μm Laser Emission from Diode-Pumped Er3+:LiYF4 at Room Temperature,” Appl. Phys. Lett. 50, 1553–1555 (1987). [CrossRef]

] is attributed to relatively efficient depopulation of the lower laser level. Further improvements in the threshold pump densities and slope efficiencies can be made by further optimization of the dopant concentrations, optimization of the output coupling efficiency, and reduction of intra-cavity losses (background absorption in the fiber at the lasing wavelength and scattering losses at the fiber ends).

In future work, we will also investigate power scaling of such sources by coherent array and beam-combining techniques. Additional work is also in progress on the demonstration of wavelength-tunable and pulsed (Q-switched, mode-locked and master-oscillator-pulsed power amplifier) high peak power sources based on such 2.7 μm fiber lasers; the latter should also enable the generation of longer mid-IR wavelengths relatively easily via efficient nonlinear optical (Raman/Difference Frequency Generation) techniques.

In summary, we report the first demonstration of high power (660 mW) CW operation of a diode-pumped mid-IR Er fiber laser. This was achieved by using efficient depopulation of the lower laser level via enhanced cross-relaxation between Er ions and energy transfer to Pr ions (at doping densities much higher than those used previously in Er:ZBLAN), along with optimal pumping of such lasers via custom-designed double-clad fluoride fibers. With optimized coupling optics, higher pump powers, and improved fiber design, >1 Watt power levels at 2.7 μm are anticipated in the near future.

Acknowledgments

This work was supported by the Air Force Office of Scientific Research. The authors also thank S. Gupta of Optopower for discussion on beam coupling of the laser diode to double-clad fibers.

References and links

1.

L. Esterowitz and R. Allen, “Rare Earth Doped IR Fiber Lasers for Medical Applications,” Proc. SPIE 1048, 129–132 (1989).

2.

K. F. Gibson and W. G. Kernohan, “Lasers in Medicine: A Review,” J. Med. Engg. and Tech. 17, 51–57 (1993). [CrossRef]

3.

O. Kermani, H. Lubatschowski, W. Ertmer, and G. K. Krieglstein, “Internal Ablative Sinostomy Using a Fiber Delivered Q-Switched CTE:YAG Laser (2.69 μm),” Intl. Ophthalmology 17, 211–215 (1993). [CrossRef]

4.

R. Kaufmann, A. Hartmann, and R. Hibst, “Cutting and Skin-Ablative Properties of Pulsed Mid-Infrared Laser Surgery,” J. Derm. Surg. & Oncol. 20, 112–118 (1994).

5.

R. Moosdorf, F. C. Schoebel, and W. Hort, “Transmyocardial Laser Revascularization: Morphology, Pathophysiology and Historical Background of Indirect Myocardial Revascularization,” Z. Kardiologie 86, 149–164 (1997). [CrossRef]

6.

M. Pollnau, “The Route Toward a Diode-Pumped 1-W Erbium 3-μm Fiber Laser,” IEEE J. Quantum Electron. 33, 1982–1990 (1997). [CrossRef]

7.

E. Poppe, B. Srinivasan, and R. K. Jain, “980nm-Diode-Pumped Continuous Wave Mid-IR (2.7 μm) Fiber Laser,” Electron. Lett. 34, 2331–2333 (1998). [CrossRef]

8.

R. S. Eng, J. F. Butler, and K. J. Linden, “Tunable Diode Laser Spectroscopy: An Invited Review,” Opt. Engg. 19, 945–960 (1980).

9.

T. Yamamoto, T. Komukai, and Y. Miyajima, “Wide-Band Erbium-Doped Fluoride Fiber Optical Amplifier at 2.7 μm with Fluoride Fiber Wavelength-Division Multiplex Coupler,” Jpn. J. Appl. Phys. 32, L62–L64 (1993). [CrossRef]

10.

J. Y. Allain, M. Monerie, and H. Poignant, “Energy Transfer in Er3+/Pr3+-Doped Fluoride Glass Fibres and Application to Lasing at 2.7 μm,” Electron. Lett. 27, 445–447 (1991). [CrossRef]

11.

M. Pollnau, Ch. Ghisler, G. Bunea, M. Bunea, W. Lüthy, and H. P. Weber, “150 mW Unsaturated Output Power at 3 μm from a Single-Mode-Fiber Erbium Cascade Laser,” Appl. Phys. Lett. 66, 3564–3566 (1995). [CrossRef]

12.

G. J. Kintz, R. Allen, and L. Esterowitz, “CW and Pulsed 2.8 μm Laser Emission from Diode-Pumped Er3+:LiYF4 at Room Temperature,” Appl. Phys. Lett. 50, 1553–1555 (1987). [CrossRef]

13.

R. S. Quimby and W. J. Miniscalco, “Continuous-Wave Lasing on a Self-Terminating Transition,” Electron. Lett. 28, 14–16 (1989).

14.

X. Zhao, B. Srinivasan, P. Pulaski, S. Gupta, and R. K. Jain, “Mirror-Free, High Power (~140mW) Diode-Pumped 2.7 μm CW Fiber Laser,” Postdeadline paper, CLEO Europe ’98 Technical Digest (1998).

15.

B. Srinivasan, G. Monnom, and R. K. Jain, “Indirect Measurement of the Magnitude of Ion Clustering at High Doping Densities in Er:ZBLAN Fibers,” to be published.

16.

S. Bedö, W. Lüthy, and H. P. Weber, “The Effective Absorption Coefficient in Double-Clad Fibers,” Opt. Commn. 99, 331–335 (1993). [CrossRef]

17.

A. Liu and K. Ueda, “The Absorption Characteristics of Circular, Offset, and Rectangular Double-Clad Fibers,” Opt. Commn. 132, 511–518 (1996). [CrossRef]

18.

D. S. Knowles and H. P. Jenssen, “Upconversion versus Pr-Deactivation for Efficient 3 μm Laser Operation in Er,” IEEE J. Quantum. Electron. 28, 1197–1208 (1992). [CrossRef]

19.

L. Wetenkamp, G. F. West, and H. Többen, “Co-Doping Effects in Erbium3+- and Holmium3+-Doped ZBLAN Glasses,” J. Non-Crystalline Solids 140, 25–30 (1992). [CrossRef]

20.

These results were submitted for presentation at the Conference for Lasers and Electro-Optics (CLEO) ’99 as a postdeadline paper on 4/26/99 (paper #CPD23, CLEO ’99, Baltimore, May 23–28, 1999).

21.

This fiber was obtained from Thorlabs, Inc., NJ, USA.

22.

Note that the lifetime values quoted here were based on our own measurements in Er-doped ZBLAN fibers and as such show small deviations from other values reported in the literature for similar ZBLAN bulk samples and fibers and related fluoride hosts (see references 6,10,13,18).

23.

V. K. Bogdanov, W. E. K. Gibbs, D. J. Booth, J. S. Javorniczky, P. J. Newman, and D. R. MacFarlane, “Fluorescence from Highly-Doped Erbium Fluorozirconate Glasses Pumped at 800 nm,” Opt. Commn. 132, 73–76 (1996). [CrossRef]

24.

M. Pollnau, Ch. Ghisler, W. Lüthy, and H. P. Weber, “Cross-Sections of Excited-State Absorption at 800 nm in Erbium-Doped ZBLAN Fiber,” Appl. Phys. B 67, 23–28 (1998). [CrossRef]

OCIS Codes
(060.2390) Fiber optics and optical communications : Fiber optics, infrared
(140.3480) Lasers and laser optics : Lasers, diode-pumped
(140.3500) Lasers and laser optics : Lasers, erbium
(140.3510) Lasers and laser optics : Lasers, fiber

ToC Category:
Research Papers

History
Original Manuscript: May 21, 1999
Published: June 7, 1999

Citation
Balaji Srinivasan, J. Tafoya, and R. Jain, "High-power "Watt-level" CW operation of diode-pumped 2.7 �m fiber lasers using efficient cross-relaxation and energy transfer mechanisms," Opt. Express 4, 490-495 (1999)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-4-12-490


Sort:  Journal  |  Reset  

References

  1. L. Esterowitz and R. Allen, "Rare Earth Doped IR Fiber Lasers for Medical Applications," Proc. SPIE 1048, 129- 132 (1989).
  2. K. F. Gibson and W. G. Kernohan, "Lasers in Medicine: A Review," J. Med. Eng. and Tech. 17, 51-57 (1993). [CrossRef]
  3. O. Kermani, H. Lubatschowski, W. Ertmer and G. K. Krieglstein, "Internal Ablative Sinostomy Using a Fiber Delivered Q-Switched CTE:YAG Laser (2.69 mm)," Intl. Ophthalmology 17, 211-215 (1993). [CrossRef]
  4. R. Kaufmann, A. Hartmann and R. Hibst, "Cutting and Skin-Ablative Properties of Pulsed Mid-Infrared Laser Surgery," J. Derm. Surg. & Oncol. 20, 112-118 (1994).
  5. R. Moosdorf, F. C. Schoebel and W. Hort, "Transmyocardial Laser Revascularization: Morphology, Pathophysiology and Historical Background of Indirect Myocardial Revascularization," Z. Kardiologie 86, 149- 164 (1997). [CrossRef]
  6. M. Pollnau, "The Route Toward a Diode-Pumped 1-W Erbium 3-mm Fiber Laser," IEEE J. Quantum Electron. 33, 1982-1990 (1997). [CrossRef]
  7. E. Poppe, B. Srinivasan and R. K. Jain, "980nm-Diode-Pumped Continuous Wave Mid-IR (2.7 mm) Fiber Laser," Electron. Lett. 34, 2331-2333 (1998). [CrossRef]
  8. R. S. Eng, J. F. Butler and K. J. Linden, "Tunable Diode Laser Spectroscopy: An Invited Review," Opt. Eng. 19, 945-960 (1980).
  9. T. Yamamoto, T. Komukai and Y. Miyajima, "Wide-Band Erbium-Doped Fluoride Fiber Optical Amplifier at 2.7 mm with Fluoride Fiber Wavelength-Division Multiplex Coupler," Jpn. J. Appl. Phys. 32, L62-L64 (1993). [CrossRef]
  10. J. Y. Allain, M. Monerie and H. Poignant, "Energy Transfer in Er 3+ /Pr 3+ -Doped Fluoride Glass Fibres and Application to Lasing at 2.7 mm," Electron. Lett. 27, 445-447 (1991). [CrossRef]
  11. M. Pollnau, Ch. Ghisler, G. Bunea M. Bunea, W. L?thy and H. P. Weber, "150 mW Unsaturated Output Power at 3 mm from a Single-Mode-Fiber Erbium Cascade Laser," Appl. Phys. Lett. 66, 3564-3566 (1995). [CrossRef]
  12. G. J. Kintz, R. Allen and L. Esterowitz, "CW and Pulsed 2.8 mm Laser Emission from Diode-Pumped Er 3+ :LiYF4 at Room Temperature," Appl. Phys. Lett. 50, 1553-1555 (1987). [CrossRef]
  13. R. S. Quimby and W. J. Miniscalco, "Continuous-Wave Lasing on a Self-Terminating Transition," Electron. Lett. 28, 14-16 (1989).
  14. X. Zhao, B. Srinivasan, P. Pulaski, S. Gupta and R. K. Jain, "Mirror-Free, High Power (~140mW) Diode-Pumped 2.7 �m CW Fiber Laser," Postdeadline paper, CLEO Europe '98 Technical Digest (1998).
  15. B. Srinivasan, G. Monnom and R. K. Jain, "Indirect Measurement of the Magnitude of Ion Clustering at High Doping Densities in Er:ZBLAN Fibers," to be published.
  16. S. Bed�, W. L?thy and H. P. Weber, "The Effective Absorption Coefficient in Double-Clad Fibers," Opt. Commn. 99, 331-335 (1993). [CrossRef]
  17. A. Liu and K. Ueda, "The Absorption Characteristics of Circular, Offset, and Rectangular Double-Clad Fibers," Opt. Commn. 132, 511-518 (1996). [CrossRef]
  18. D. S. Knowles and H. P. Jenssen, "Upconversion versus Pr-Deactivation for Efficient 3 mm Laser Operation in Er," IEEE J. Quantum. Electron. 28, 1197-1208 (1992). [CrossRef]
  19. L. Wetenkamp, G. F. West and H. T�bben, "Co-Doping Effects in Erbium 3+ - and Holmium 3+ -Doped ZBLAN Glasses," J. Non-Crystalline Solids 140, 25-30 (1992). [CrossRef]
  20. These results were submitted for presentation at the Conference for Lasers and Electro-Optics (CLEO) '99 as a postdeadline paper on 4/26/99 (paper #CPD23, CLEO '99, Baltimore, May 23-28, 1999).
  21. This fiber was obtained from Thorlabs, Inc., NJ, USA.
  22. Note that the lifetime values quoted here were based on our own measurements in Er-doped ZBLAN fibers and as such show small deviations from other values reported in the literature for similar ZBLAN bulk samples and fibers and related fluoride hosts (see references 6,10,13,18).
  23. V. K. Bogdanov, W. E. K. Gibbs, D. J. Booth, J. S. Javorniczky, P. J. Newman and D. R. MacFarlane, "Fluorescence from Highly-Doped Erbium Fluorozirconate Glasses Pumped at 800 nm," Opt. Commn. 132, 73-76 (1996). [CrossRef]
  24. M. Pollnau, Ch. Ghisler, W. L?thy and H. P. Weber, "Cross-Sections of Excited-State Absorption at 800 nm in Erbium-Doped ZBLAN Fiber," Appl. Phys. B 67, 23-28 (1998). [CrossRef]

Cited By

Alert me when this paper is cited

OSA is able to provide readers links to articles that cite this paper by participating in CrossRef's Cited-By Linking service. CrossRef includes content from more than 3000 publishers and societies. In addition to listing OSA journal articles that cite this paper, citing articles from other participating publishers will also be listed.


« Previous Article

OSA is a member of CrossRef.

CrossCheck Deposited