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Optics Express

Optics Express

  • Editor: Michael Duncan
  • Vol. 14, Iss. 7 — Apr. 3, 2006
  • pp: 2898–2903
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UV-exposed Bragg gratings for laser applications in silver-sodium ion-exchanged phosphate glass waveguides

Sanna Yliniemi, Jacques Albert, Qing Wang, and Seppo Honkanen  »View Author Affiliations


Optics Express, Vol. 14, Issue 7, pp. 2898-2903 (2006)
http://dx.doi.org/10.1364/OE.14.002898


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Abstract

High reflectivity Bragg gratings have been written by ArF excimer laser through a phase mask into Schott IOG-1 hybrid phosphate glass. After grating exposure, a waveguide was fabricated by silver-sodium ion-exchange. Reflectivities around 80 % at a wavelength of ~ 1535 nm were measured from the waveguide for both quasi-TE and -TM polarizations. Waveguide laser operation with the photowritten waveguide grating as another mirror was demonstrated. Output power of 3.8 mW with a pump power of 199 mW could be extracted from the laser configuration.

© 2006 Optical Society of America

1. Introduction

It would be beneficial, if the Bragg gratings for the waveguide lasers could be formed by using UV-irradiation through a phase mask, as is common in fiber optics [8

8. J.-L. Archambault and S. G. Grubb, “Fiber gratings in lasers and amplifiers,” J. Lightwave Technol. 15, 1378–1390 (1997). [CrossRef]

]. Photosensitivity of phosphorus-doped silicate-glass was reported by Malo et al. [9

9. B. Malo, J. Albert, F. Bilodeau, T. Kitagawa, D. C. Johnson, K. O. Hill, K. Hattori, Y. Hibino, and S. Gujrathi, “Photosensitivity in phosphorus-doped silica glass and optical waveguides,” Appl. Phys. Lett. 65, 394–396 (1994). [CrossRef]

] already in 1994. However, phosphorus-doped silicate glass is very different from phosphate glass, and it was only recently that photoinduced index changes in slab waveguides made by silver ion exchange in Er-doped IOG-1 phosphate glass were demonstrated by irradiation with KrF laser light [10

10. S. Pissadakis, A. Ikiades, P. Hua, A. K. Sheridan, and J. Wilkinson, “Photosensitivity of ion-exchanged Er-doped phosphate glass using 248nm excimer laser radiation,” Opt. Express 12, 3131–3136 (2004). [CrossRef] [PubMed]

]. The estimated refractive index modulation was ~2× 10-3 over a depth of 3μm. It was reported that the index change obtained was 2 orders of magnitude larger in the ion-exchanged region than in the substrate glass alone. This was tentatively attributed to photo-induced silver ion migration and photo-ionization of Ag0 and Ag+ species. Our own experiments with Schott IOG-1 glass have confirmed these observations. However, these gratings are too shallow to provide high enough reflectivity and the stability of the gratings is a concern as well. A shallow surface-like grating with index modulation amplitude below 0.01 would not provide enough optical feedback at the lasing wavelength (1535 nm), since the overlap between the grating and the guided mode is small. In addition, our experiments have revealed that it is rather difficult to fabricate efficient UV-written gratings in active (i.e. Er/Yb-codoped) IOG-1 glass.

In this paper, we present results on high quality UV-written Bragg gratings in passive Schott IOG-1 phosphate glass channel waveguides using a different approach than in Ref [10

10. S. Pissadakis, A. Ikiades, P. Hua, A. K. Sheridan, and J. Wilkinson, “Photosensitivity of ion-exchanged Er-doped phosphate glass using 248nm excimer laser radiation,” Opt. Express 12, 3131–3136 (2004). [CrossRef] [PubMed]

]. We also report on a first demonstration of a distributed Bragg reflector (DBR) waveguide laser using a photowritten grating in a hybrid IOG-1 glass.

2. Fabrication

After grating exposure, the waveguides were fabricated by electric field assisted silver-film ion exchange [14

14. P. Pöyhönen, S. Honkanen, A. Tervonen, and M. Tahkokorpi, “Planar 1/8 splitter in glass by photoresist masked silver film ion exchange,” Electron. Lett. 27, 1319–1320 (1991). [CrossRef]

]. First, the waveguides were patterned onto the glass by standard photolithography. Next, a thin silver film was sputtered on top of the sample. The electric field assisted ion exchange was performed at 90°C with a voltage of 200 V. The residual silver and the photoresist were removed in a NH4OH/H2O2 wet etch. Then the sample was diced and the end facets were polished. Finally, the sample was annealed at 225°C for 90 min during which the silver ions diffused further into the glass and formed a waveguide.

After fabrication, the reflection and transmission spectra of the waveguide grating were measured, and the results are presented in Fig. 1. A narrowband reflection maximum occurs at 1608.63 nm. The grating reflectivity is 44 % for a grating length of 4 mm. This first result demonstrates the feasibility of our approach but the reflectivity is not high enough for laser applications. Thereafter, we wrote a 10 mm long grating using a phase mask with a periodicity matching with the gain peak of 1535 nm of Erbium doped phosphate glass. The grating fabrication procedure was the same as described above with the exception that the gratings were exposed through beam expanders that increase the spatial coherence of the laser irradiation. This resulted in a reduction of the fluence to 140 mJ/cm2. The waveguide fabrication procedure was as described above.

Fig. 1. (a) Reflection and (b) transmission spectrum of a photowritten grating in a silver-sodium ion-exchanged waveguide. The measurement was done with polarized light.

The second grating was fabricated into a passive section of a hybrid phosphate IOG-1 glass. In addition to a 20 mm long passive section, the fabricated hybrid glass waveguide sample contains a 19 mm long erbium-ytterbium doped active section with concentrations of 1.0 × 1020 for erbium and 6.0×1020 ions/cm3 for ytterbium. The active waveguide section provides the gain required in the laser operation, and the UV-written grating exposed into the passive waveguide section provides the optical feedback and the wavelength selection. It also serves as an output coupler for the DBR waveguide laser.

The grating strength for a hybrid sample was measured separately for quasi-TE and -TM polarization modes in transmission geometry and the measured spectra are presented in Fig. ??. At the Bragg wavelength the grating transmission is around 20 % for both polarizations, and the Bragg wavelength for the TE polarized mode is 1534.71 nm while for the TM-mode it is 1534.52 nm.

Fig. 2. Transmission spectra of the waveguide Bragg grating. Red line refers to the quasi-TE-polarization and blue line to the quasi-TM-polarization.

3. Results

The setup for measuring the laser characteristics is presented in Fig. ??. The laser cavity was constructed by using a Corning SMF28 fiber coated with a broadband SiO2/TiO2 dielectric mirror stack with reflectivities close to 100 % at 1550 nm wavelength region and 0 % at a pump (980 nm) wavelength region. The pump power was delivered through this fiber too. The fiber-to-waveguide/waveguide-to-fiber coupling loss is estimated to be approximately 1 dB. The UV-written grating operated as the other, narrowband mirror with a reflectivity around 80 % at ~ 1535 nm as well as an output coupler. The laser output spectrum and the slope efficiency were measured, respectively, by an optical spectrum analyzer (OSA) and by a fiber connected power meter. The OSA resolution is 0.07 nm. A standard single-mode fiber was butt coupled to the waveguide end facet at the passive section.

Fig. 3. Schematic of the set-up for measuring the slope efficiency and the laser spectrum. A fiber-pigtailed pump laser is connected to a fiber with a dielectric mirror on the output end, which is butt-coupled to a waveguide with a grating. The UV-written Bragg grating acts as the other cavity mirror as well as an output coupler. The laser output power is measured by a fiber-coupled detector and a power meter. The output spectrum is measured using an optical spectrum analyzer (OSA). The output fiber can be coupled either to the power meter or to the OSA. The black blocks in the figure represent fiber connectors.
Fig. 4. The measured slope efficiency and the output spectrum of the waveguide laser.

4. Conclusions

We have demonstrated narrowband UV-written volume gratings in passive Schott IOG-1 phosphate glass. Grating reflectivities around 80 % were measured for both quasi-TE- and TM-polarizations after channel waveguide fabrication. The grating survived a long heat treatment at 225°C. Utilizing a hybrid glass we constructed a DBR laser using a photowritten grating as an output coupler. The maximum output power was 3.8 mW with a slope efficiency of 6.1 %. The lasing threshold was 148 mW. We believe that the pump efficiency can still be increased by shortening and by further annealing the sample. However, before proceeding to these experiments, more precise linewidth characteristic measurements will be performed.

Acknowledgments

Support from TRIF (State of Arizona Photonics Initiative) and from the University of Arizona is appreciated. Prof. J. Albert would like to acknowledge the financial support of the Canada Research Chairs Program. S. Yliniemi would also like to thank the Academy of Finland and Magnus Ehrnrooth’s foundation for financial support. This work was performed while S. Yliniemi was with the College of Optical Sciences at the University of Arizona.

References and links

1.

D. L. Veasey, D. S. Funk, N. A. Sanford, and J. S. Hayden, “Arrays of distributed-Bragg-reflector waveguide lasers at 1536 nm in Yb/Er codoped phosphate glass,” Appl. Phys. Lett. 74, 789–791 (1999). [CrossRef]

2.

S. Blaize, L. Bastard, C. Cassagnètes, and J. E. Broquin, “Multiwavelengths DFB waveguide laser arrays in Yb-Er codoped phosphate glass substrate,” IEEE Photon. Tecnhnol. Lett. 15, 516–518 (2003). [CrossRef]

3.

P. Madasamy, G. Nunzi Conti, P. Pöyhönen, M. M. Morrell, D. F. Geraghty, S. Honkanen, and N. Peyghambarian, “Waveguide distributed Bragg reflector laser arrays in erbium doped glass made by dry Ag film ion exchange,” Opt. Eng. 41, 1084–1086 (2002). [CrossRef]

4.

T. Ohtsuki, S. Honkanen, S. I. Najafi, and N. Peyghambarian, “Cooperative upconversion effects on the performance of Er3+-doped phosphate glass waveguide amplifiers,” J. Opt. Soc. Am. B 14, 1838–1845 (1997). [CrossRef]

5.

Y. C. Yan, A. J. Faber, H. de Waal, P. G. Kik, and A. Polman, “Erbium-doped phosphate glass waveguide on silicon with 4.1 dB/cm gain at 1.535 μm,” Appl. Phys. Lett. 71, 2922–2924 (1997). [CrossRef]

6.

F. D. Patel, S. DiCarolis, P. Lum, S. Venkatesh, and J. N. Miller, “A compact high-performance optical waveguide amplifier,” IEEE Photon. Technol. Lett. 16, 2607–2609 (2004). [CrossRef]

7.

B.-C. Hwang, S. Jiang, T. Luo, J. Watson, G. Sorbello, and N. Peyghambarian, “Cooperative upconversion and energy transfer of new hig Er3+- and Yb3+-Er3+-doped phosphate glasses,” J. Opt. Soc. Am. B 17, 833–839 (2000). [CrossRef]

8.

J.-L. Archambault and S. G. Grubb, “Fiber gratings in lasers and amplifiers,” J. Lightwave Technol. 15, 1378–1390 (1997). [CrossRef]

9.

B. Malo, J. Albert, F. Bilodeau, T. Kitagawa, D. C. Johnson, K. O. Hill, K. Hattori, Y. Hibino, and S. Gujrathi, “Photosensitivity in phosphorus-doped silica glass and optical waveguides,” Appl. Phys. Lett. 65, 394–396 (1994). [CrossRef]

10.

S. Pissadakis, A. Ikiades, P. Hua, A. K. Sheridan, and J. Wilkinson, “Photosensitivity of ion-exchanged Er-doped phosphate glass using 248nm excimer laser radiation,” Opt. Express 12, 3131–3136 (2004). [CrossRef] [PubMed]

11.

J. Albert, S. Yliniemi, S. Honkanen, A. Andreyuk, and A. Steele, “UV-written Bragg gratings in silver ion-exchanged phosphate glass channel waveguides,” in Proceedings of the 2005 Topical meeting on Bragg Gratings, Photosensitivity and Poling, B. Eggleton, ed. (Sydney, Australia, 2005) 402–404 (2005).

12.

S. D. Gonzone, J. S. Hayden, D. S. Funk, A. Roshko, and D. L. Veasey, “Hybrid glass substrates for waveguide device manufacture,” Opt. Lett. 26, 509–511 (2001). [CrossRef]

13.

P. Madasamy, S. Honkanen, D. F. Geraghty, and N. Peyghambarian, “Single-mode tapered waveguide laser in Er-doped glass with multimode-diode pumping,” Appl. Phys. Lett. 82, 1332–1334 (2003). [CrossRef]

14.

P. Pöyhönen, S. Honkanen, A. Tervonen, and M. Tahkokorpi, “Planar 1/8 splitter in glass by photoresist masked silver film ion exchange,” Electron. Lett. 27, 1319–1320 (1991). [CrossRef]

15.

D. L. Veasey, D. S. Funk, P. M. Peters, N. A. Sanford, G. E. Obarski, N. Fontaine, M. Young, A. P. Peskin, W.-C. Liu, S. N. Houde-Walter, and J. S. Hayden, “Yb/Er-codoped and Yb-doped waveguide lasers in phosphate glass,” J. Non-Cryst. Solids 263&264, 369–381 (2000). [CrossRef]

OCIS Codes
(130.0130) Integrated optics : Integrated optics
(140.3500) Lasers and laser optics : Lasers, erbium
(230.1480) Optical devices : Bragg reflectors
(230.7380) Optical devices : Waveguides, channeled

ToC Category:
Optical Devices

History
Original Manuscript: January 13, 2006
Revised Manuscript: March 29, 2006
Manuscript Accepted: March 29, 2006
Published: April 3, 2006

Citation
Sanna Yliniemi, Jacques Albert, Qing Wang, and Seppo Honkanen, "UV-exposed Bragg gratings for laser applications in silver-sodium ion-exchanged phosphate glass waveguides," Opt. Express 14, 2898-2903 (2006)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-14-7-2898


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References

  1. D. L. Veasey, D. S. Funk, N. A. Sanford, J. S. Hayden, "Arrays of distributed-Bragg-reflector waveguide lasers at 1536 nm in Yb/Er codoped phosphate glass," Appl. Phys. Lett. 74,789-791 (1999). [CrossRef]
  2. S. Blaize, L. Bastard, C. Cassagnètes, J. E. Broquin, "Multiwavelengths DFB waveguide laser arrays in Yb-Er codoped phosphate glass substrate," IEEE Photon. Tecnhnol. Lett. 15,516-518 (2003). [CrossRef]
  3. P. Madasamy, G. Nunzi Conti, P. Pöyhönen, M. M. Morrell, D. F. Geraghty, S. Honkanen, N. Peyghambarian, "Waveguide distributed Bragg reflector laser arrays in erbium doped glass made by dry Ag film ion exchange," Opt. Eng. 41,1084-1086 (2002). [CrossRef]
  4. T. Ohtsuki, S. Honkanen, S. I. Najafi, N. Peyghambarian, "Cooperative upconversion effects on the performance of Er3+-doped phosphate glass waveguide amplifiers," J. Opt. Soc. Am. B 14,1838-1845 (1997). [CrossRef]
  5. Y. C. Yan, A. J. Faber, H. de Waal, P. G. Kik, A. Polman, "Erbium-doped phosphate glass waveguide on silicon with 4.1 dB/cm gain at 1.535 μm," Appl. Phys. Lett. 71,2922-2924 (1997). [CrossRef]
  6. F. D. Patel, S. DiCarolis, P. Lum, S. Venkatesh, J. N. Miller, "A compact high-performance optical waveguide amplifier," IEEE Photon. Technol. Lett. 16,2607-2609 (2004). [CrossRef]
  7. B.-C. Hwang, S. Jiang, T. Luo, J. Watson, G. Sorbello, N. Peyghambarian, "Cooperative upconversion and energy transfer of new hig Er3+- and Yb3+-Er3+-doped phosphate glasses," J. Opt. Soc. Am. B 17,833-839 (2000). [CrossRef]
  8. J.-L. Archambault, S. G. Grubb, "Fiber gratings in lasers and amplifiers," J. Lightwave Technol. 15,1378-1390 (1997). [CrossRef]
  9. B. Malo, J. Albert, F. Bilodeau, T. Kitagawa, D. C. Johnson, K. O. Hill, K. Hattori, Y. Hibino, S. Gujrathi, "Photosensitivity in phosphorus-doped silica glass and optical waveguides," Appl. Phys. Lett. 65,394-396 (1994). [CrossRef]
  10. S. Pissadakis, A. Ikiades, P. Hua, A. K. Sheridan, J. Wilkinson, "Photosensitivity of ion-exchanged Er-doped phosphate glass using 248nm excimer laser radiation," Opt. Express 12,3131-3136 (2004). [CrossRef] [PubMed]
  11. J. Albert, S. Yliniemi, S. Honkanen, A. Andreyuk, A. Steele, "UV-written Bragg gratings in silver ion-exchanged phosphate glass channel waveguides," in Proceedings of the 2005 Topical meeting on Bragg Gratings, Photosensitivity and Poling, B. Eggleton, ed. (Sydney, Australia, 2005) 402-404 (2005).
  12. S. D. Gonzone, J. S. Hayden, D. S. Funk, A. Roshko, D. L. Veasey, "Hybrid glass substrates for waveguide device manufacture," Opt. Lett. 26,509-511 (2001). [CrossRef]
  13. P. Madasamy, S. Honkanen, D. F. Geraghty, N. Peyghambarian, "Single-mode tapered waveguide laser in Erdoped glass with multimode-diode pumping," Appl. Phys. Lett. 82,1332-1334 (2003). [CrossRef]
  14. P. Pöyhönen, S. Honkanen, A. Tervonen,M. Tahkokorpi, "Planar 1/8 splitter in glass by photoresist masked silver film ion exchange," Electron. Lett. 27,1319-1320 (1991). [CrossRef]
  15. D. L. Veasey, D. S. Funk, P. M. Peters, N. A. Sanford, G. E. Obarski, N. Fontaine, M. Young, A. P. Peskin,W.-C. Liu, S. N. Houde-Walter, J. S. Hayden, "Yb/Er-codoped and Yb-doped waveguide lasers in phosphate glass," J. Non-Cryst. Solids 263,369-381 (2000). [CrossRef]

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