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Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 18, Iss. 25 — Dec. 6, 2010
  • pp: 26720–26727
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Chalcogenide glass microsphere laser

Gregor R. Elliott, G. Senthil Murugan, James S. Wilkinson, Michalis N. Zervas, and Daniel W. Hewak  »View Author Affiliations


Optics Express, Vol. 18, Issue 25, pp. 26720-26727 (2010)
http://dx.doi.org/10.1364/OE.18.026720


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Abstract

Laser action has been demonstrated in chalcogenide glass microsphere. A sub millimeter neodymium-doped gallium lanthanum sulphide glass sphere was pumped at 808 nm with a laser diode and single and multimode laser action demonstrated at wavelengths between 1075 and 1086 nm. The gallium lanthanum sulphide family of glass offer higher thermal stability compared to other chalcogenide glasses, and this, along with an optimized Q-factor for the microcavity allowed laser action to be achieved. When varying the pump power, changes in the output spectrum suggest nonlinear and/or thermal effects have a strong effect on laser action.

© 2010 OSA

1. Introduction

In this paper we report on the laser performance of a rare earth doped chalcogenide glass microsphere. Chalcogenide glasses are interesting materials for laser production because of their low phonon energy and infrared transparency. These properties allow fluorescence with higher efficiencies and at longer wavelengths than in other rare earth doped glass [12

12. T. Schweizer, Rare-earth-doped Gallium lanthanum sulphide glasses for mid-infrared fibre lasers (University of Southampton, 2000) http://www.orc.soton.ac.uk/viewpublication.html?pid=1510T

] and could result in a new generation of solid state mid infrared lasers. There has been considerable work on chalcogenide glasses based on gallium lanthanum sulphide (GLS) as a laser and amplifying medium [12

12. T. Schweizer, Rare-earth-doped Gallium lanthanum sulphide glasses for mid-infrared fibre lasers (University of Southampton, 2000) http://www.orc.soton.ac.uk/viewpublication.html?pid=1510T

15

15. A. K. Mairaj, A. M. Chardon, D. P. Shepherd, and D. W. Hewak, “Laser performance and spectroscopic analysis of optically written channel waveguides in neodymium-doped gallium lanthanum sulphide glass,” IEEE J. Sel. Top. Quantum Electron. 8(6), 1381–1388 (2002). [CrossRef]

]. Compared to other chalcogenides GLS lends itself to active applications because of its excellent rare earth solubility [16

16. P. N. Kumta and S. H. Risbud, “Novel glasses in rare-earth sulphide systems,” Ceramic Bull. 69, 1977–1984 (1990).

]. Gallium and rare earth sulphide together are excellent glass formers and form an environmentally stable, yellow/orange glass with transmission from 0.5 to 10 microns [17

17. D. W. Hewak, “Chalcogenide glasses for photonics device applications”, in Photonic Glasses and Glass Ceramics, editor G.S. Murugan, ed. (Research Signpost, Kerala, India, 2010) Chap. 2 ISBN: 978–81–308–0375–3.

]. The refractive index of these glasses is approximately 2.5 at 500 nm wavelength; however the exact index will depend on the dopant and ratio of gallium to rare earth. Fluorescent properties of rare earth doped GLS glasses have been extensively studied by Schweizer [12

12. T. Schweizer, Rare-earth-doped Gallium lanthanum sulphide glasses for mid-infrared fibre lasers (University of Southampton, 2000) http://www.orc.soton.ac.uk/viewpublication.html?pid=1510T

] who identified 27 transitions between 2 and 5 microns, 7 of which had never previously been seen in a glass host. Table 1

Table 1. Spectroscopic properties of selected Nd3+- doped glasses.

table-icon
View This Table
compares the spectroscopic properties of a series of Nd3+-doped glasses. As can be seen, the emission cross sections are larger and the radiative lifetimes shorter than those reported for other glass hosts making this material a good candidate for laser applications [16

16. P. N. Kumta and S. H. Risbud, “Novel glasses in rare-earth sulphide systems,” Ceramic Bull. 69, 1977–1984 (1990).

].

Thermal analysis of GLS glasses reveals a glass transition temperature of approximately 520°C while crystallization behavior reveals a single exothermic peak indicating the crystallation of a single phase at approximately 740°C. Again these thermal properties will vary slightly with composition. Noteworthy is the relatively high characteristic temperatures, approximately 200°C higher than more well known arsenic or germanium based chalcogenides. Further details on the properties of these and other chalcogenide glasses are summarized in reference [17

17. D. W. Hewak, “Chalcogenide glasses for photonics device applications”, in Photonic Glasses and Glass Ceramics, editor G.S. Murugan, ed. (Research Signpost, Kerala, India, 2010) Chap. 2 ISBN: 978–81–308–0375–3.

].

The first reported chalcogenide lasers by Scheiwzer [14

14. T. Schweizer, B. N. Samson, R. C. Moore, D. W. Hewak, and D. N. Payne, “Rare-earth doped chalcogenide glass fibre laser,” Electron. Lett. 33(5), 414–416 (1997). [CrossRef]

] and later Mairaj [15

15. A. K. Mairaj, A. M. Chardon, D. P. Shepherd, and D. W. Hewak, “Laser performance and spectroscopic analysis of optically written channel waveguides in neodymium-doped gallium lanthanum sulphide glass,” IEEE J. Sel. Top. Quantum Electron. 8(6), 1381–1388 (2002). [CrossRef]

] exploited optical fibre and optical waveguide cavities formed in GLS glass. With the achievement of GLS microspheres by Elliott in 2007 [18

18. G. R. Elliott, D. W. Hewak, G. S. Murugan, and J. S. Wilkinson, “Chalcogenide glass microspheres; their production, characterization and potential,” Opt. Express 15(26), 17542–17553 (2007). [CrossRef] [PubMed]

] we set out to demonstrate laser action from an Nd3+ doped GLS sphere.

2. Experimental

Microspheres can be made by a number of methods, these include polishing, chemical etching and rapid quenching of liquid droplets [19

19. G. R. Elliott, Optical microresonators in chalcogenide glass (University of Southampton, 2009) http://www.orc.soton.ac.uk/viewpublication.html?pid=4445

]. Here the drop method was used for microsphere production. In this process crushed glass was dropped through a vertical furnace purged with argon. The crushed glass melts as it drops through the furnace and surface tension pulls it into a sphere which quenches into an amorphous state as it drops to the cooler region below the hot zone. Our microsphere fabrication is described in detail in reference [19

19. G. R. Elliott, Optical microresonators in chalcogenide glass (University of Southampton, 2009) http://www.orc.soton.ac.uk/viewpublication.html?pid=4445

].

Glass with a composition of 70 mol% gallium sulphide and 30 mol% lanthanum sulphide, doped with 1.5 mol% neodymium sulphide was used. Bulk glass synthesized as above was crushed to a suitable size and uniformity before microsphere production. The glass was crushed with a pestle and mortar, and in order to assert control over the diameter of microspheres produced, crushed particles are separated according to size before they are put into the furnace. The material that has passed through the furnace will typically contain a mixture of particles that have melted into spheres and particles that have not. This mixture can be separated according to the quality of the spheres by repeatedly rolling the material down progressively shallower slopes. This was achieved by placing the spheres in a glass container such as a Petri dish, tilting the container and allowing the spheres to roll. Each time the material is rolled down a slope, the non-spherical material will be left behind, the steepness of the slope will determine how precisely spherical the particle has to be in order to roll down the slope. Microspheres were collected, sorted while suspended in methanol and stored in vials of methanol until ready to be characterized (Fig. 1
Fig. 1 A selection of Nd3+-doped GLS microspheres as observed under an optical microscope.
.).

Typical microsphere diameters range from 30 to 300 micron, though spheres as small as 1-5 microns have been selected and individually manipulated. A typical fabrication run would yield several hundred spheres of good quality and close to the target diameter. From this collection, the best spheres were selected by inspection through an optical microscope. Among these, several representative spheres had their quality quantified through Q-factor measurements, as described in [18

18. G. R. Elliott, D. W. Hewak, G. S. Murugan, and J. S. Wilkinson, “Chalcogenide glass microspheres; their production, characterization and potential,” Opt. Express 15(26), 17542–17553 (2007). [CrossRef] [PubMed]

].

3. Results and discussion

The microspheres used in these experiments were fabricated in a typical run, which produced a large number of spheres which were sorted to a collection of spheres predominately 90 to 105 microns in diameter. Q-factors of representative spheres were measured as described in [18

18. G. R. Elliott, D. W. Hewak, G. S. Murugan, and J. S. Wilkinson, “Chalcogenide glass microspheres; their production, characterization and potential,” Opt. Express 15(26), 17542–17553 (2007). [CrossRef] [PubMed]

] and values were typically in the range 104 – 105 although spheres outside this range were also obtained. Poorer quality spheres were easily identified under an optical microscope and could suffer damage during fabrication and sorting. The highest quality spheres were difficult to identify it is conceivable that higher Q-factors than those measured were obtained and that the handling of spheres during characterization effected their quality.

Between threshold and the onset of multimode action, the power output increased linearly with a slope efficiency of 1.6 x 10-5%, but when the laser became multimode there was no consistent pattern to the power output for the laser peaks. However the position of the laser peaks did move linearly with the increasing pump power and this shift was the same for all modes. When the incident pump power was increased from 82 mW to 220 mW, the maximum pump power we used, the total wavelength shift was 2.5nm. It was also noted that the chop frequency at which the laser was pumped had an effect on the spectral content, but this has not yet been studied.

Tellurite glass has a high refractive index similar to GLS and it has been used to make Nd3+-doped microsphere lasers that were also pumped by free space coupling. Sasagawa et al. [21

21. K. Sasagawa, K. Kusawake, J. Ohta, and M. Nunoshita, “Nd-doped tellurite glass microsphere laser,” Electron. Lett. 38(22), 1355–1357 (2002). [CrossRef]

] reported an incident pump power threshold of 81mW with a coupling system that also utilized a microscope objective to couple. This is very similar to our threshold of 82mW which also coupled the pump with a microscope objective.

4. Concluding remarks

We have fabricated chalcogenide glass microspheres from Nd3+-doped gallium lanthanum sulphide glass and demonstrated laser action at wavelengths between 1075 and 1086 nm. The spheres had Q-factors on the order of 104; a value which we believe is close to optimum for a chalcogenide microsphere laser. Experimental evidence suggests higher Q’s could lead to thermal instability. The relatively high thermal stability of GLS glass compared to other chalcogenides allowed incident pump powers at 808 nm in excess of 200 mW. This is considerably higher than that reported for other chalcogenide microsphere [22

22. D. H. Broaddus, M. A. Foster, I. H. Agha, J. T. Robinson, M. Lipson, and A. L. Gaeta, “Silicon-waveguide-coupled high-Q chalcogenide microspheres,” Opt. Express 17(8), 5998–6003 (2009). [CrossRef] [PubMed]

] and this inherent thermal stability along with the excellent rare earth solubility make GLS an excellent candidate for solid state lasers, particularly in the mid-infrared. Further studies are now underway to fully characterize the laser performance and explore methods for efficient coupling and packaging of the laser device.

Acknowledgement

The authors would like to thank Yuwapat Panitchob, Elizabeth Tull and Phil Bartlett for helpful discussions; and Kenton Knight for technical support. Gregor Elliott would like to thank EPSRC for a PhD studentship. All authors acknowledge funding from the Engineering and Physical Science Research Council (United Kingdom) under grant numbers GR/S96500/01 Integrated Microsphere Planar Lightwave Circuits and in part by EP/C515668/1 Portfolio Partnership in Photonics.

References and links

1.

J. Tong, A. Liu, H. Lv, Y. Wu, X. Yi, and Q. Li, “Fabrication of glass microspheres using the powders floating method”, in Proceedings of the 2010 Symposium on Photonics and Optoelectronics, Chengdu, China June 19–21, 2010.

2.

B. E. Little, J.-P. Laine, and H. A. Haus, “Analytic Theory of Coupling from Tapered Fibers and Half-Blocks into Microsphere Resonators,” J. Lightwave Technol. 17(4), 704–715 (1999). [CrossRef]

3.

Y. S. Park, A. K. Cook, and H. Wang, “Cavity QED with diamond nanocrystals and silica microspheres,” Nano Lett. 6(9), 2075–2079 (2006). [CrossRef] [PubMed]

4.

S. M. Spillane, T. J. Kippenberg, and K. J. Vahala, “Ultralow-threshold Raman laser using a spherical dielectric microcavity,” Nature 415(6872), 621–623 (2002). [CrossRef] [PubMed]

5.

M. Kuwata-Gonokami and K. Takeda, “Polymer whispering gallery mode lasers,” Opt. Mater. 9(1-4), 12–17 (1998). [CrossRef]

6.

C. G. B. Garrett, W. Kaiser, and W. L. Bond, “Stimulated. Emission into Optical Whispering Modes of Spheres,” Phys. Rev. 124(6), 1807–1809 (1961). [CrossRef]

7.

L. Collot, V. Lefevre-Seguin, M. Brune, J. M. Raimond, and S. Haroche, “Very high-Q whispering-gallery mode resonances observed on fused silica microspheres,” Europhys. Lett. 23(5), 327–334 (1993). [CrossRef]

8.

V. Sandoghdar V, F. Treussart, J. Hare, V. Lefèvre-Seguin V, J.-M. Raimond, and S. Haroche, “Very low threshold whispering-gallery-mode microsphere laser,” Phys. Rev. A 54(3), R1777–R1780 (1996). [CrossRef] [PubMed]

9.

M. Cai and K. Vahala, “Highly efficient hybrid fiber taper coupled microsphere laser,” Opt. Lett. 26(12), 884–886 (2001). [CrossRef]

10.

K. Miura, K. Tanaka, and K. Hirao, “Laser oscillation of a Nd3+-doped fluoride glass microsphere,” J. Mater. Sci. Lett. 15(21), 1854–1857 (1996). [CrossRef]

11.

X. Peng, F. Song, S. Jiang, N. Peyghambarian, M. Kuwata-Gonokami, and L. Xu, “Fiber-taper-coupled L-band Er3+-doped tellurite glass microsphere laser,” Appl. Phys. Lett. 82(10), 1497–1499 (2003). [CrossRef]

12.

T. Schweizer, Rare-earth-doped Gallium lanthanum sulphide glasses for mid-infrared fibre lasers (University of Southampton, 2000) http://www.orc.soton.ac.uk/viewpublication.html?pid=1510T

13.

T. Schweizer, D. W. Hewak, D. N. Payne, T. Jensen, and G. Huber, “Rare-earth doped chalcogenide glass laser,” Electron. Lett. 32(7), 666–667 (1996). [CrossRef]

14.

T. Schweizer, B. N. Samson, R. C. Moore, D. W. Hewak, and D. N. Payne, “Rare-earth doped chalcogenide glass fibre laser,” Electron. Lett. 33(5), 414–416 (1997). [CrossRef]

15.

A. K. Mairaj, A. M. Chardon, D. P. Shepherd, and D. W. Hewak, “Laser performance and spectroscopic analysis of optically written channel waveguides in neodymium-doped gallium lanthanum sulphide glass,” IEEE J. Sel. Top. Quantum Electron. 8(6), 1381–1388 (2002). [CrossRef]

16.

P. N. Kumta and S. H. Risbud, “Novel glasses in rare-earth sulphide systems,” Ceramic Bull. 69, 1977–1984 (1990).

17.

D. W. Hewak, “Chalcogenide glasses for photonics device applications”, in Photonic Glasses and Glass Ceramics, editor G.S. Murugan, ed. (Research Signpost, Kerala, India, 2010) Chap. 2 ISBN: 978–81–308–0375–3.

18.

G. R. Elliott, D. W. Hewak, G. S. Murugan, and J. S. Wilkinson, “Chalcogenide glass microspheres; their production, characterization and potential,” Opt. Express 15(26), 17542–17553 (2007). [CrossRef] [PubMed]

19.

G. R. Elliott, Optical microresonators in chalcogenide glass (University of Southampton, 2009) http://www.orc.soton.ac.uk/viewpublication.html?pid=4445

20.

A. Faraon, D. Englund, D. Bulla, B. Luther-Davies, B. J. Eggleton, N. Stoltz, P. Petroff, and J. Vučković, “Local tuning of photonic crystal cavities using chalcogenide glasses,” Appl. Phys. Lett. 92(4), 043123–042125 (2008). [CrossRef]

21.

K. Sasagawa, K. Kusawake, J. Ohta, and M. Nunoshita, “Nd-doped tellurite glass microsphere laser,” Electron. Lett. 38(22), 1355–1357 (2002). [CrossRef]

22.

D. H. Broaddus, M. A. Foster, I. H. Agha, J. T. Robinson, M. Lipson, and A. L. Gaeta, “Silicon-waveguide-coupled high-Q chalcogenide microspheres,” Opt. Express 17(8), 5998–6003 (2009). [CrossRef] [PubMed]

OCIS Codes
(140.3530) Lasers and laser optics : Lasers, neodymium
(140.4780) Lasers and laser optics : Optical resonators
(160.2750) Materials : Glass and other amorphous materials
(230.5750) Optical devices : Resonators

ToC Category:
Chalcogenide Glass

History
Original Manuscript: September 21, 2010
Revised Manuscript: November 7, 2010
Manuscript Accepted: November 23, 2010
Published: December 6, 2010

Virtual Issues
Chalcogenide Glass (2010) Optics Express

Citation
Gregor R. Elliott, G. Senthil Murugan, James S. Wilkinson, Michalis N. Zervas, and Daniel W. Hewak, "Chalcogenide glass microsphere laser," Opt. Express 18, 26720-26727 (2010)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-18-25-26720


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References

  1. J. Tong, A. Liu, H. Lv, Y. Wu, X. Yi, and Q. Li, “Fabrication of glass microspheres using the powders floating method”, in Proceedings of the 2010 Symposium on Photonics and Optoelectronics, Chengdu, China June 19–21, 2010.
  2. B. E. Little, J.-P. Laine, and H. A. Haus, “Analytic Theory of Coupling from Tapered Fibers and Half-Blocks into Microsphere Resonators,” J. Lightwave Technol. 17(4), 704–715 (1999). [CrossRef]
  3. Y. S. Park, A. K. Cook, and H. Wang, “Cavity QED with diamond nanocrystals and silica microspheres,” Nano Lett. 6(9), 2075–2079 (2006). [CrossRef] [PubMed]
  4. S. M. Spillane, T. J. Kippenberg, and K. J. Vahala, “Ultralow-threshold Raman laser using a spherical dielectric microcavity,” Nature 415(6872), 621–623 (2002). [CrossRef] [PubMed]
  5. M. Kuwata-Gonokami and K. Takeda, “Polymer whispering gallery mode lasers,” Opt. Mater. 9(1-4), 12–17 (1998). [CrossRef]
  6. C. G. B. Garrett, W. Kaiser, and W. L. Bond, “Stimulated. Emission into Optical Whispering Modes of Spheres,” Phys. Rev. 124(6), 1807–1809 (1961). [CrossRef]
  7. L. Collot, V. Lefevre-Seguin, M. Brune, J. M. Raimond, and S. Haroche, “Very high-Q whispering-gallery mode resonances observed on fused silica microspheres,” Europhys. Lett. 23(5), 327–334 (1993). [CrossRef]
  8. V. Sandoghdar, F. Treussart, J. Hare, V. Lefèvre-Seguin, J.-M. Raimond, and S. Haroche, “Very low threshold whispering-gallery-mode microsphere laser,” Phys. Rev. A 54(3), R1777–R1780 (1996). [CrossRef] [PubMed]
  9. M. Cai and K. Vahala, “Highly efficient hybrid fiber taper coupled microsphere laser,” Opt. Lett. 26(12), 884–886 (2001). [CrossRef]
  10. K. Miura, K. Tanaka, and K. Hirao, “Laser oscillation of a Nd3+-doped fluoride glass microsphere,” J. Mater. Sci. Lett. 15(21), 1854–1857 (1996). [CrossRef]
  11. X. Peng, F. Song, S. Jiang, N. Peyghambarian, M. Kuwata-Gonokami, and L. Xu, “Fiber-taper-coupled L-band Er3+-doped tellurite glass microsphere laser,” Appl. Phys. Lett. 82(10), 1497–1499 (2003). [CrossRef]
  12. T. Schweizer, Rare-earth-doped Gallium lanthanum sulphide glasses for mid-infrared fibre lasers (University of Southampton, 2000) http://www.orc.soton.ac.uk/viewpublication.html?pid=1510T
  13. T. Schweizer, D. W. Hewak, D. N. Payne, T. Jensen, and G. Huber, “Rare-earth doped chalcogenide glass laser,” Electron. Lett. 32(7), 666–667 (1996). [CrossRef]
  14. T. Schweizer, B. N. Samson, R. C. Moore, D. W. Hewak, and D. N. Payne, “Rare-earth doped chalcogenide glass fibre laser,” Electron. Lett. 33(5), 414–416 (1997). [CrossRef]
  15. A. K. Mairaj, A. M. Chardon, D. P. Shepherd, and D. W. Hewak, “Laser performance and spectroscopic analysis of optically written channel waveguides in neodymium-doped gallium lanthanum sulphide glass,” IEEE J. Sel. Top. Quantum Electron. 8(6), 1381–1388 (2002). [CrossRef]
  16. P. N. Kumta and S. H. Risbud, “Novel glasses in rare-earth sulphide systems,” Ceramic Bull. 69, 1977–1984 (1990).
  17. D. W. Hewak, “Chalcogenide glasses for photonics device applications”, in Photonic Glasses and Glass Ceramics, editor G.S. Murugan, ed. (Research Signpost, Kerala, India, 2010) Chap. 2 ISBN: 978–81–308–0375–3.
  18. G. R. Elliott, D. W. Hewak, G. S. Murugan, and J. S. Wilkinson, “Chalcogenide glass microspheres; their production, characterization and potential,” Opt. Express 15(26), 17542–17553 (2007). [CrossRef] [PubMed]
  19. G. R. Elliott, Optical microresonators in chalcogenide glass (University of Southampton, 2009) http://www.orc.soton.ac.uk/viewpublication.html?pid=4445
  20. A. Faraon, D. Englund, D. Bulla, B. Luther-Davies, B. J. Eggleton, N. Stoltz, P. Petroff, and J. Vučković, “Local tuning of photonic crystal cavities using chalcogenide glasses,” Appl. Phys. Lett. 92(4), 043123–042125 (2008). [CrossRef]
  21. K. Sasagawa, K. Kusawake, J. Ohta, and M. Nunoshita, “Nd-doped tellurite glass microsphere laser,” Electron. Lett. 38(22), 1355–1357 (2002). [CrossRef]
  22. D. H. Broaddus, M. A. Foster, I. H. Agha, J. T. Robinson, M. Lipson, and A. L. Gaeta, “Silicon-waveguide-coupled high-Q chalcogenide microspheres,” Opt. Express 17(8), 5998–6003 (2009). [CrossRef] [PubMed]

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