OSA's Digital Library

Optics Express

Optics Express

  • Editor: Andrew M. Weiner
  • Vol. 21, Iss. 4 — Feb. 25, 2013
  • pp: 4591–4597
« Show journal navigation

Inscription of first-order sapphire Bragg gratings using 400 nm femtosecond laser radiation

Tino Elsmann, Tobias Habisreuther, Albrecht Graf, Manfred Rothhardt, and Hartmut Bartelt  »View Author Affiliations


Optics Express, Vol. 21, Issue 4, pp. 4591-4597 (2013)
http://dx.doi.org/10.1364/OE.21.004591


View Full Text Article

Acrobat PDF (1806 KB)





Browse Journals / Lookup Meetings

Browse by Journal and Year


   


Lookup Conference Papers

Close Browse Journals / Lookup Meetings

Article Tools

Share
Citations

Abstract

The paper describes the implementation of fiber Bragg gratings inscribed by femtosecond laser pulses with a wavelength of 400 nm. The use of a Talbot interferometer for the inscription process makes multiplexing practicable. We demonstrate the functionality of a three-grating multiplexing sensor and the temperature stability up to 1200 °C for a single first-order Bragg grating.

© 2013 OSA

1. Introduction

Fiber Bragg gratings (FBGs) are sensor elements often used in harsh environments such as extreme temperatures, strong electromagnetic fields or chemically aggressive conditions, because they are not influenced by electromagnetic radiation, have limited cross talk from many environmental influences and are very flexible. Due to their small size, they can easily be embedded in compound materials. Typical applications are temperature and strain sensing. There are limitations, however, for the use of such gratings in silica fibers for temperatures beyond 300 °C or 1000 °C. Fiber gratings based on color center effects bleach out at temperatures higher than 200 °C – 300 °C. With additional heat treatment known as thermal regeneration it is possible to stabilize the gratings and, thus, expand the temperature range up to 1000 °C [1

1. S. Bandyopadhyay, J. Canning, M. Stevenson, and K. Cook, “Ultrahigh-temperature regenerated gratings in boron-codoped germanosilicate optical fiber using 193 nm,” Opt. Lett. 33(16), 1917–1919 (2008). [CrossRef] [PubMed]

,2

2. E. Lindner, C. Chojetzki, S. Brückner, M. Becker, M. Rothhardt, and H. Bartelt, “Thermal regeneration of fiber Bragg gratings in photosensitive fibers,” Opt. Express 17(15), 12523–12531 (2009). [CrossRef] [PubMed]

] or, for short-term measurements, even up to 1200 °C [3

3. Y. Li, M. Yang, D. N. Wang, J. Lu, T. Sun, and K. T. V. Grattan, “Fiber Bragg gratings with enhanced thermal stability by residual stress relaxation,” Opt. Express 17(22), 19785–19790 (2009). [CrossRef] [PubMed]

] near the glass transition point of fused silica. The softening of the silica glass then defines the ultimate temperature for which such sensors can be applied. There is, however, great interest to use such sensors for even higher temperatures, e.g. for temperature sensing and material monitoring in gas turbines or melting furnaces. Fibers made of single crystalline sapphire are a good option to overcome the temperature limit of fused silica, because the material melting point is at temperatures beyond 2040 °C [4

4. D. Grobnic, S. Mihailov, C. Smelser, and H. Ding, “Sapphire Fiber Bragg Grating Sensor Made Using Femtosecond Laser Radiation for Ultrahigh Temperature Applications,” IEEE Photon. Technol. Lett. 16(11), 2505–2507 (2004). [CrossRef]

6

6. T. Elsmann, E. Lindner, M. Becker, W. Ecke, M. Rothhardt, and H. Bartelt, “Erzeugung von Faser-Bragg-Gittern (FBGs) in Saphirfasern für die Hochtemperatursensorik,” in DGaO-proceeding, A28, (2011).

]. Single Bragg gratings in sapphire fibers have been reported for sensing applications up to 1745 °C [4

4. D. Grobnic, S. Mihailov, C. Smelser, and H. Ding, “Sapphire Fiber Bragg Grating Sensor Made Using Femtosecond Laser Radiation for Ultrahigh Temperature Applications,” IEEE Photon. Technol. Lett. 16(11), 2505–2507 (2004). [CrossRef]

7

7. S. J. Mihailov, D. Grobnic, and C. W. Smelser, “High-temperature multiparameter sensor based on sapphire fiber Bragg gratings,” Opt. Lett. 35(16), 2810–2812 (2010). [CrossRef] [PubMed]

]. Thin film temperature sensors on a sapphire fiber tip have also been described [8

8. J. Wang, E. M. Lally, B. Dong, J. Gong, and A. Wang, “Fabrication of a miniaturized thin-film temperature sensor on a sapphire fiber tip,” IEEE Sens. J. 11(12), 3406–3408 (2011). [CrossRef]

]. Femtosecond (fs)-laser pulses were used for inscription of the FBGs, since they provide high peak intensities and multi-photon processes to provide a permanent change of the refractive index.

FBGs are formed by a spatial periodic change of the refractive index achieved by special illumination techniques [9

9. A. Othonos, “Fiber Bragg gratings,” Rev. Sci. Instrum. 68(12), 4309–4341 (1997). [CrossRef]

]. The most common techniques are point-by-point fabrication [10

10. B. Malo, K. O. Hill, F. Bilodeau, D. C. Johnson, and J. Albert, “Point-by-point fabrication of micro-Bragg gratings in photosensitive fibre using single excimer pulse refractive index modification techniques,” Electron. Lett. 29(18), 1668–1669 (1993). [CrossRef]

] and phase mask exposure [11

11. K. O. Hill, B. Malo, F. Bilodeau, D. C. Johnson, and J. Albert, “Bragg gratings fabricated in monomode photosensitive optical fiber by UVexposure through a phase mask,” Appl. Phys. Lett. 62(10), 1035 (1993). [CrossRef]

]. For the point-by-point method, the inscription laser is focused into the fiber to change the refractive index locally and then the grating is built up by scanning the fiber. The phase mask technique uses the interference pattern directly located behind a phase mask, which is designed so that the interference pattern forms the whole grating structure. Another technique uses a phase mask as a beam-splitting element. The spatially separated beams are then superimposed to form an interference pattern with great geometrical flexibility. Such an interferometer of the Talbot type is used in our experiments [12

12. M. Becker, J. Bergmann, S. Brückner, M. Franke, E. Lindner, M. W. Rothhardt, and H. Bartelt, “Fiber Bragg grating inscription combining DUV sub-picosecond laser pulses and two-beam interferometry,” Opt. Express 16(23), 19169–19178 (2008). [CrossRef] [PubMed]

].

Although the potential applicability of FBGs in sapphire fibers for high temperature sensing has been experimentally shown, the realization of the gratings still suffers from limitations. Until now, only the phase mask method has been applied successfully for the inscription of fiber Bragg gratings in sapphire fibers. The use of an interferometric inscription concept could simplify considerably the implementation of wavelength-multiplexed arrays of gratings.

A second limitation in the inscription process is the wavelength used. From the simplified Bragg condition (Eq. (1)) for perpendicular incidence
m·λBragg=2·neff·Λgrating
(1)
the Bragg wavelength λBragg depends on the effective refractive index neff of the reflected mode, the order of diffraction m and the period of the phase grating Λgrating. Because sapphire has a very high refractive index of about 1.74, the grating period for a first-order grating with a λBragg of 1550 nm in the standard C-band has to be in the order of 440 nm. This is much smaller than the current inscription wavelength of 800 nm. To overcome this physical limitation, gratings of higher order [4

4. D. Grobnic, S. Mihailov, C. Smelser, and H. Ding, “Sapphire Fiber Bragg Grating Sensor Made Using Femtosecond Laser Radiation for Ultrahigh Temperature Applications,” IEEE Photon. Technol. Lett. 16(11), 2505–2507 (2004). [CrossRef]

7

7. S. J. Mihailov, D. Grobnic, and C. W. Smelser, “High-temperature multiparameter sensor based on sapphire fiber Bragg gratings,” Opt. Lett. 35(16), 2810–2812 (2010). [CrossRef] [PubMed]

] were inscribed e.g. for a doubled reflection wavelength (3100 nm) but used in second diffraction order for 1550 nm. In this case the reflection efficiency might be reduced especially in case of non-perfect grating structures.

In the following we describe the implementation of multiplexed fiber Bragg gratings inscribed by an interferometric setup. We show that, by use of the second harmonic wave from a Titanium:Sapphire laser, we can inscribe fiber Bragg gratings also in first-order. This method is then easily applied to realize multiplexed arrays of gratings.

2. Inscription and characterization of the Bragg gratings

For the inscription of FBGs we used a femtosecond laser system. This system provides pulses with a wavelength of 800 nm, a pulse duration of 135 fs and an averaged power of 3 W with a repetition rate of 1 kHz. These pulses pass a nonlinear crystal to generate the second harmonic of the pump wave. The transformed pulses with a wavelength of 400 nm have an averaged power of 1 W. Femtosecond laser pulses were used for inscription of the FBGs, since they provide high peak intensities and multi-photon processes for a permanent change of the refractive index. We also tested the third harmonic with a resulting wavelength of 266 nm, but there was no power regime found that enabled a permanent change of the sapphires' refractive index without destroying the fiber.

The averaged power for inscription with the second harmonic was reduced from the maximum of 1 W to 550 mW, and an external dynamic iris diaphragm was used to reduce the mean repetition rate in order to avoid a material ablation of the fiber due to local heating. We did not observe any erasing effect of the gratings due to the heating of the fiber during the inscription process itself [12

12. M. Becker, J. Bergmann, S. Brückner, M. Franke, E. Lindner, M. W. Rothhardt, and H. Bartelt, “Fiber Bragg grating inscription combining DUV sub-picosecond laser pulses and two-beam interferometry,” Opt. Express 16(23), 19169–19178 (2008). [CrossRef] [PubMed]

]. The iris diaphragm was opened for 0.01 s with 0.5 Hz, so that on average a number of 20 pulses per second reached the fiber. Due to the shorter inscription wavelength, the averaged laser power was nearly halved, and a destruction of the fiber became less likely compared to an inscription wavelength of 800 nm.

The FBG was fabricated using the interference pattern of a Talbot interferometer (see Fig. 1
Fig. 1 Talbot interferometer (schematic).
) [12

12. M. Becker, J. Bergmann, S. Brückner, M. Franke, E. Lindner, M. W. Rothhardt, and H. Bartelt, “Fiber Bragg grating inscription combining DUV sub-picosecond laser pulses and two-beam interferometry,” Opt. Express 16(23), 19169–19178 (2008). [CrossRef] [PubMed]

]. Inside the interferometer the beam is divided by a phase mask. This phase mask has a period of 888 nm and was optimized for an inscription wavelength of λinscription = 400 nm to suppress the zero order (which was additionally blocked). The two diffracted beams were reflected by the mirrors and then interfered under the angle ϑ. The fiber was placed exactly perpendicular to the interference pattern in the field of superposition. Additionally, a cylindrical lens (focal length of 221 mm) was used in front of the interferometer to increase the local intensity at the place of the fiber. Since the sapphire fibers were used as air-clad fibers with a large core diameter of 100 µm, the cylindrical lens was moved to scan through the full diameter with a velocity of 0.1 µm/s. Because of the very short pulses in the fs-regime, all beam paths have to be aligned with a tolerance of less than 50 microns.

For multiplexing of gratings the mirrors were turned symmetrically. This leads to a change in the angle ϑ. Considering the Bragg condition with respect to the interferometric inscription, the design wavelength can be calculated from the following Eq. (2):

λBragg=(neff·λinscription)/sinϑ.
(2)

Commercial single crystalline sapphire fibers (MicroMaterials Inc.) fabricated by laser-heated pedestal growth to lengths up to one meter were used [13

13. V. Phomsakha, R. S. F. Chang, and N. Djeu, “Novel implementation of laser heated pedestal growth for the rapid drawing of sapphire fibers,” Rev. Sci. Instrum. 65(12), 3860–3861 (1994). [CrossRef]

,14

14. R. K. Nubling and J. A. Harrington, “Optical properties of single-crystal sapphire fibers,” Appl. Opt. 36(24), 5934–5940 (1997). [CrossRef] [PubMed]

]. Attenuation data for Sapphire fibers vary from 0.5 to 4 dB/m at 1550 nm, dependent on fiber diameter, preparation, or annealing procedures [13

13. V. Phomsakha, R. S. F. Chang, and N. Djeu, “Novel implementation of laser heated pedestal growth for the rapid drawing of sapphire fibers,” Rev. Sci. Instrum. 65(12), 3860–3861 (1994). [CrossRef]

, 14

14. R. K. Nubling and J. A. Harrington, “Optical properties of single-crystal sapphire fibers,” Appl. Opt. 36(24), 5934–5940 (1997). [CrossRef] [PubMed]

]. Sapphire fibers guide the light in a large multimode core with an index difference of 0.74 relative to air. Because of this fact, several hundred modes can propagate through the fiber, which results in a very broad reflection spectrum of the FBG of about more than 8 nm. To always measure the same form of the spectrum, the light of a superluminescent diode (SLD) was mode-mixed in a 50 µm graded index fiber and coupled via a commercial APC connector to the sapphire fiber (see Fig. 2
Fig. 2 Spectral characterization setup (schematic).
). To suppress strong back reflection from the coupling, the sapphire fiber end was polished to an angle of 8° to match the APC fused silica fiber. We expected some losses especially for the coupling from 100µm sapphire to the 50µm supply fiber, but this setup achieved a well measurable signal output. The reflected light coming from the grating was then analyzed in a commercial Ibsen Photonics interrogator [15]. With this setup a spectral range from 1510 nm up to 1596 nm could be evaluated.

3. Experimental results

At first a fiber with a single grating was evaluated. Figure 3
Fig. 3 Characterization of a single FBG. Spectral response of the grating (black crosses) with a strong background signal (orange line), and the corrected reflection signal from the grating (green points), fit of a Gaussian function (blue line) and an asymmetric peak function (red dash-dotted line) to the corrected grating signal.
shows the reflection spectrum at 100 °C. A strong signal background is observed, belonging to the reflected light at the fiber end having the spectrum of the light source itself.

The real reflection peak was discernible as an offset coming from the grating. The background was subtracted to obtain the reflection spectrum of the grating itself. As the sapphire fiber is a multimode fiber, the reflected modes result in a wider peak compared to single mode fiber. The Bragg wavelength λBragg was derived as the center of a fitted Gaussian function. For the Bragg grating of Fig. 3, a reflection wavelength of λBragg = (1530.310 ± 0.072) nm was found to have a full width at half maximum (FWHM) of 9.44 nm. This would correspond to a numerical aperture of NA = 0.18 in accordance with observations in other experiments [5

5. M. Busch, W. Ecke, I. Latka, D. Fischer, R. Willsch, and H. Bartelt, “Inscription and characterization of Bragg gratings in single-crystal sapphire optical fibres for high-temperature sensor applications,” Meas. Sci. Technol. 20(11), 115301 (2009). [CrossRef]

]. The reflectivity could not be estimated, because it was not possible to measure a reference intensity due to the connection losses of the sapphire fiber. However, the reflectivity is high enough for sensor applications, so that all of the inscribed gratings could be used in the heating experiments. The length of the grating itself is limited by the diameter of the inscription laser beam, which was 8 mm for a 1/e limit.

Due to the multimodal reflection characteristic of the FBGs, an asymmetric Gaussian-like function [5

5. M. Busch, W. Ecke, I. Latka, D. Fischer, R. Willsch, and H. Bartelt, “Inscription and characterization of Bragg gratings in single-crystal sapphire optical fibres for high-temperature sensor applications,” Meas. Sci. Technol. 20(11), 115301 (2009). [CrossRef]

] would describe the reflection spectrum better (red dash-dotted line in Fig. 3) than a Gaussian function. We heated up a grating to various temperatures between room temperature and 1200°C, stabilizing the temperature for at least 5 min before the spectra were measured. It turned out that the form of the grating spectrum is unaffected by a change of temperature. Therefore the temperature dependency of the Bragg wavelength showed almost the same parameters for the fitting using the Gaussian function, (25.7 ± 0.2) pm/K, and the asymmetric Gaussian function, (25.9 ± 0.2) pm/K. Since the resulting temperature dependencies were almost identical, we therefore used the Gaussian function for further experiments to evaluate the spectra, because of the simpler calculation procedure.

The spectra of different gratings inscribed with the same parameters are reproducible with high accuracy. However, the amplitude and therefore the reflectivity strength may vary. This could be explained by the shape of the fiber itself, because single crystalline sapphire has a rounded hexagonal cross section. The orientation of the fiber was not adjusted in the experimental setup.

For high temperature investigations, fibers were also heated up to 1200 °C. The Fig. 4
Fig. 4 Temperature dependency of the Bragg wavelength for different peak identifications (crosses) and the fitted temperature sensitivity.
shows the temperature dependency of the Bragg wavelength. The reflected intensity was constant during the whole heating process. This demonstrates that, with 400 nm fs-pulses, the material modifications induced in sapphire cause the gratings to be stable also at temperatures beyond 1000 °C and that way to be applicable for measurements in high temperature regimes. The average temperature sensitivity for the fiber of Fig. 4 was (27.2 ± 0.4) pm/K. In Fig. 4, a slight deviation from a linear slope can be observed. The slope, and therefore the sensitivity, slightly increases monotonously with increasing temperature. Over the whole temperature range of 1200 K variation of +/−2.9 pm/K can be found for the local slope of a linear fit. This behavior is already known and especially reported for sapphire fibers in reference [5

5. M. Busch, W. Ecke, I. Latka, D. Fischer, R. Willsch, and H. Bartelt, “Inscription and characterization of Bragg gratings in single-crystal sapphire optical fibres for high-temperature sensor applications,” Meas. Sci. Technol. 20(11), 115301 (2009). [CrossRef]

].

The grating with the highest reflection wavelength was only observable up to 500 °C, because of the maximally possible evaluable wavelength determined by the light source and interrogator used. In general, the wide wavelength shift in case of extreme temperature variations results in some limitation for the number of possible multiplexed gratings within a certain spectral range. Within a temperature range of 1000 °C, the Bragg wavelength shifts by nearly 30 nm. If the spectral separations of the gratings are about 10 nm (no cross talk between two different gratings), three gratings could be used within a spectral range of about 100 nm. The multiplexing capacity could be increased in case of a more restricted temperature measurement range. Further optimization concerning the number of multiplexed sensors would be possible by selective generation of only the fundamental fiber mode [7

7. S. J. Mihailov, D. Grobnic, and C. W. Smelser, “High-temperature multiparameter sensor based on sapphire fiber Bragg gratings,” Opt. Lett. 35(16), 2810–2812 (2010). [CrossRef] [PubMed]

] or by a sapphire fiber structure with a smaller number of allowed propagating modes.

4. Conclusion

We have demonstrated the applicability of femtosecond pulses with a wavelength of 400 nm to inscribe first-order FBGs in sapphire fibers. An external, additional, dynamic iris diaphragm was used to avoid heating up or destroying the fiber during the inscription process. Single gratings as well as three multiplexed gratings were fabricated using the Talbot interferometer. The gratings showed a nearly linear wavelength dependency of the maximum of reflection. Sapphire fibers are stable up to temperatures of 2000 °C. The high temperature stability of the reported gratings has been experimentally tested for temperatures up to 1200 °C.

Acknowledgments

Funding by the German Federal Ministry of Economics and Technology under contract 13INE036, and the Thuringian Ministry of Education, Science and Culture (EFRE program) is gratefully acknowledged.

References and links

1.

S. Bandyopadhyay, J. Canning, M. Stevenson, and K. Cook, “Ultrahigh-temperature regenerated gratings in boron-codoped germanosilicate optical fiber using 193 nm,” Opt. Lett. 33(16), 1917–1919 (2008). [CrossRef] [PubMed]

2.

E. Lindner, C. Chojetzki, S. Brückner, M. Becker, M. Rothhardt, and H. Bartelt, “Thermal regeneration of fiber Bragg gratings in photosensitive fibers,” Opt. Express 17(15), 12523–12531 (2009). [CrossRef] [PubMed]

3.

Y. Li, M. Yang, D. N. Wang, J. Lu, T. Sun, and K. T. V. Grattan, “Fiber Bragg gratings with enhanced thermal stability by residual stress relaxation,” Opt. Express 17(22), 19785–19790 (2009). [CrossRef] [PubMed]

4.

D. Grobnic, S. Mihailov, C. Smelser, and H. Ding, “Sapphire Fiber Bragg Grating Sensor Made Using Femtosecond Laser Radiation for Ultrahigh Temperature Applications,” IEEE Photon. Technol. Lett. 16(11), 2505–2507 (2004). [CrossRef]

5.

M. Busch, W. Ecke, I. Latka, D. Fischer, R. Willsch, and H. Bartelt, “Inscription and characterization of Bragg gratings in single-crystal sapphire optical fibres for high-temperature sensor applications,” Meas. Sci. Technol. 20(11), 115301 (2009). [CrossRef]

6.

T. Elsmann, E. Lindner, M. Becker, W. Ecke, M. Rothhardt, and H. Bartelt, “Erzeugung von Faser-Bragg-Gittern (FBGs) in Saphirfasern für die Hochtemperatursensorik,” in DGaO-proceeding, A28, (2011).

7.

S. J. Mihailov, D. Grobnic, and C. W. Smelser, “High-temperature multiparameter sensor based on sapphire fiber Bragg gratings,” Opt. Lett. 35(16), 2810–2812 (2010). [CrossRef] [PubMed]

8.

J. Wang, E. M. Lally, B. Dong, J. Gong, and A. Wang, “Fabrication of a miniaturized thin-film temperature sensor on a sapphire fiber tip,” IEEE Sens. J. 11(12), 3406–3408 (2011). [CrossRef]

9.

A. Othonos, “Fiber Bragg gratings,” Rev. Sci. Instrum. 68(12), 4309–4341 (1997). [CrossRef]

10.

B. Malo, K. O. Hill, F. Bilodeau, D. C. Johnson, and J. Albert, “Point-by-point fabrication of micro-Bragg gratings in photosensitive fibre using single excimer pulse refractive index modification techniques,” Electron. Lett. 29(18), 1668–1669 (1993). [CrossRef]

11.

K. O. Hill, B. Malo, F. Bilodeau, D. C. Johnson, and J. Albert, “Bragg gratings fabricated in monomode photosensitive optical fiber by UVexposure through a phase mask,” Appl. Phys. Lett. 62(10), 1035 (1993). [CrossRef]

12.

M. Becker, J. Bergmann, S. Brückner, M. Franke, E. Lindner, M. W. Rothhardt, and H. Bartelt, “Fiber Bragg grating inscription combining DUV sub-picosecond laser pulses and two-beam interferometry,” Opt. Express 16(23), 19169–19178 (2008). [CrossRef] [PubMed]

13.

V. Phomsakha, R. S. F. Chang, and N. Djeu, “Novel implementation of laser heated pedestal growth for the rapid drawing of sapphire fibers,” Rev. Sci. Instrum. 65(12), 3860–3861 (1994). [CrossRef]

14.

R. K. Nubling and J. A. Harrington, “Optical properties of single-crystal sapphire fibers,” Appl. Opt. 36(24), 5934–5940 (1997). [CrossRef] [PubMed]

15.

www.ibsen.dk/im

16.

W. J. Tropf, M. E. Thomas, and T. J. Harris, Handbook of Optics (McGraw-Hill, 1995), Vol. 2, Chap. 33.

OCIS Codes
(060.2370) Fiber optics and optical communications : Fiber optics sensors
(230.1480) Optical devices : Bragg reflectors
(060.3735) Fiber optics and optical communications : Fiber Bragg gratings

ToC Category:
Fiber Optics and Optical Communications

History
Original Manuscript: December 5, 2012
Revised Manuscript: January 18, 2013
Manuscript Accepted: February 5, 2013
Published: February 14, 2013

Citation
Tino Elsmann, Tobias Habisreuther, Albrecht Graf, Manfred Rothhardt, and Hartmut Bartelt, "Inscription of first-order sapphire Bragg gratings using 400 nm femtosecond laser radiation," Opt. Express 21, 4591-4597 (2013)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-21-4-4591


Sort:  Author  |  Year  |  Journal  |  Reset  

References

  1. S. Bandyopadhyay, J. Canning, M. Stevenson, and K. Cook, “Ultrahigh-temperature regenerated gratings in boron-codoped germanosilicate optical fiber using 193 nm,” Opt. Lett.33(16), 1917–1919 (2008). [CrossRef] [PubMed]
  2. E. Lindner, C. Chojetzki, S. Brückner, M. Becker, M. Rothhardt, and H. Bartelt, “Thermal regeneration of fiber Bragg gratings in photosensitive fibers,” Opt. Express17(15), 12523–12531 (2009). [CrossRef] [PubMed]
  3. Y. Li, M. Yang, D. N. Wang, J. Lu, T. Sun, and K. T. V. Grattan, “Fiber Bragg gratings with enhanced thermal stability by residual stress relaxation,” Opt. Express17(22), 19785–19790 (2009). [CrossRef] [PubMed]
  4. D. Grobnic, S. Mihailov, C. Smelser, and H. Ding, “Sapphire Fiber Bragg Grating Sensor Made Using Femtosecond Laser Radiation for Ultrahigh Temperature Applications,” IEEE Photon. Technol. Lett.16(11), 2505–2507 (2004). [CrossRef]
  5. M. Busch, W. Ecke, I. Latka, D. Fischer, R. Willsch, and H. Bartelt, “Inscription and characterization of Bragg gratings in single-crystal sapphire optical fibres for high-temperature sensor applications,” Meas. Sci. Technol.20(11), 115301 (2009). [CrossRef]
  6. T. Elsmann, E. Lindner, M. Becker, W. Ecke, M. Rothhardt, and H. Bartelt, “Erzeugung von Faser-Bragg-Gittern (FBGs) in Saphirfasern für die Hochtemperatursensorik,” in DGaO-proceeding, A28, (2011).
  7. S. J. Mihailov, D. Grobnic, and C. W. Smelser, “High-temperature multiparameter sensor based on sapphire fiber Bragg gratings,” Opt. Lett.35(16), 2810–2812 (2010). [CrossRef] [PubMed]
  8. J. Wang, E. M. Lally, B. Dong, J. Gong, and A. Wang, “Fabrication of a miniaturized thin-film temperature sensor on a sapphire fiber tip,” IEEE Sens. J.11(12), 3406–3408 (2011). [CrossRef]
  9. A. Othonos, “Fiber Bragg gratings,” Rev. Sci. Instrum.68(12), 4309–4341 (1997). [CrossRef]
  10. B. Malo, K. O. Hill, F. Bilodeau, D. C. Johnson, and J. Albert, “Point-by-point fabrication of micro-Bragg gratings in photosensitive fibre using single excimer pulse refractive index modification techniques,” Electron. Lett.29(18), 1668–1669 (1993). [CrossRef]
  11. K. O. Hill, B. Malo, F. Bilodeau, D. C. Johnson, and J. Albert, “Bragg gratings fabricated in monomode photosensitive optical fiber by UVexposure through a phase mask,” Appl. Phys. Lett.62(10), 1035 (1993). [CrossRef]
  12. M. Becker, J. Bergmann, S. Brückner, M. Franke, E. Lindner, M. W. Rothhardt, and H. Bartelt, “Fiber Bragg grating inscription combining DUV sub-picosecond laser pulses and two-beam interferometry,” Opt. Express16(23), 19169–19178 (2008). [CrossRef] [PubMed]
  13. V. Phomsakha, R. S. F. Chang, and N. Djeu, “Novel implementation of laser heated pedestal growth for the rapid drawing of sapphire fibers,” Rev. Sci. Instrum.65(12), 3860–3861 (1994). [CrossRef]
  14. R. K. Nubling and J. A. Harrington, “Optical properties of single-crystal sapphire fibers,” Appl. Opt.36(24), 5934–5940 (1997). [CrossRef] [PubMed]
  15. www.ibsen.dk/im
  16. W. J. Tropf, M. E. Thomas, and T. J. Harris, Handbook of Optics (McGraw-Hill, 1995), Vol. 2, Chap. 33.

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  |  Next Article »

OSA is a member of CrossRef.

CrossCheck Deposited