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Optics Express

Optics Express

  • Editor: Michael Duncan
  • Vol. 11, Iss. 20 — Oct. 6, 2003
  • pp: 2497–2501
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Integrated photothermal microscope and laser damage test facility for in-situ investigation of nanodefect induced damage

Annelise During, Mireille Commandré, Caroline Fossati, Bertrand Bertussi, Jean-Yves Natoli, Jean-Luc Rullier, Hervé Bercegol, and Philippe Bouchut  »View Author Affiliations


Optics Express, Vol. 11, Issue 20, pp. 2497-2501 (2003)
http://dx.doi.org/10.1364/OE.11.002497


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Abstract

An integrated setup allowing high resolution photothermal microscopy and laser damage measurements at the same wavelength has been implemented. The microscope is based on photothermal deflection of a transmitted probe beam : the probe beam (633 nm wavelength) and the CW pump beam (1.06 µm wavelength) are collinear and focused through the same objective. In-situ laser irradiation tests are performed thanks to a pulsed beam (1.06 µm wavelength and 6 nanosecond pulse). We describe this new facility and show that it is well adapted to the detection of sub-micronic absorbing defects, that, once located, can be precisely aimed and irradiated. Photothermal mappings are performed before and after shot, on metallic inclusions in dielectric. Results obtained on gold inclusions of about 600 nm in diameter embedded in silica are presented.

© 2003 Optical Society of America

Laser-induced damage in optical materials has long been widely acknowledged as a localized phenomenon associated with the presence of micrometer and nanometer-sized defects, such as scratches, polishing residues and, more generally, impurities, contaminants or bulk inhomogeneities [1

1. N. Bloembergen, “Role of cracks, pores, and absorbing inclusions on laser induced damage threshold at surfaces of transparent dielectrics,” Appl. Opt. 12, 661–664 (1973). [CrossRef] [PubMed]

5

5. J.Y. Natoli, L. Gallais, H. Akhouayri, and C. Amra, “Laser induced damage of materials in bulk, thin films and liquid forms,” Appl. Opt. 41, 3156–3166 (2002). [CrossRef] [PubMed]

]. All these defects can be responsible for local variations of optical, thermal or thermo-optical properties. Absorbing defects are suspected to induce thermal effects that lead to damage, but, as many attempts have shown, the correlation between defect absorption and laser damage is not easy to demonstrate.

To solve these problems, a new facility has been implemented, allowing in-situ, high resolved investigation of laser damage. It is constituted of an integrated setup of photothermal microscopy and laser damage measurements. The scheme of the setup is shown on Fig. 1.

Fig. 1. Experimental setup.

We implemented a photothermal deflection microscope in the collinear configuration: the pump and probe beams are parallel and focused through the same optics. The pump laser is a YAG laser with 1.064 µm wavelength and the probe laser a He-Ne laser. The details of the experimental realization and characterization of the photothermal microscope have already been described [11

11. A. During, C. Fossati, and M. Commandré, “Development of a photothermal deflection microscope for multiscale studies of defects,” in Laser-induced damage in optical materials: 2001, G. J. Exarhos, A. H. Guenther, K. L. Lewis, M. J. Soileau, and C. J. Stolz, eds., Proc. SPIE4679, 400–409 (2002). [CrossRef]

]. In order to maximize the sensitivity of the setup, we optimized the position and the focus length of the lens which focuses the probe beam on the position sensor (lens L). We showed that with a pump beam diameter of 1 µm, obtained thanks to a microscope objective, a resolution of 1 µm was reached on non-isolated defects.

The sample is visualized by an imaging system, which permits a real time observation of the irradiated zone. This system is composed of a CCD camera and a set of long working distance objectives. The resolution obtained with the higher magnification is about 1 µm. The sample observation is performed in dark field mode. “Damage” is defined as having occurred when a visible modification is detected.

To demonstrate the practicability of this new setup for the detection of sub-micronic absorbing defects, that, once located, can be precisely aimed and irradiated, we use special samples prepared by CEA/LETI. They are constituted of gold inclusions, covered by an evaporated ultra-pure silica layer. The structure of the samples is described on Fig. 2.

The thickness of the upper layer is 2 µm and the size of the gold inclusions, deduced from the height of domes that cover them and measured by AFM ranges from 400 nm to 800 nm. An example of sample topography by AFM measurement is presented on figure 3.

The low damage threshold of the silica film, measured avoiding gold inclusions, and using 1 on 1 procedure, is evaluated to T=52 J/cm2.

Fig. 2. Studied samples scheme.
Fig. 3. Sample topography by AFM measurement.

The samples are studied by photothermal microscopy, before and after shot at various fluences, below T. The results obtained on a 600 nm gold inclusion are presented on Fig. 4, and the corresponding photothermal values are summed up in Table 1.

Fig. 4. Photothermal (top) and refraction (bottom) measurement of the same gold inclusion before shot (a.), after shot at 2 J/cm2 (b.) and after shot at 10 J/cm2 (c.), mapped area: 20 µm×20 µm.

Two kinds of mappings are presented: on one hand photothermal mappings representing absorption and on the other hand, “refraction” mappings representing surface profile variations. These mappings are acquired simultaneously to photothermal mappings and the signal is the probe deflection but measured at frequency 0. This signal is proportional to the refraction angle

Table 1. Photothermal values corresponding to Fig. 4, in arbitrary units.

table-icon
View This Table

The results obtained before shot are presented on figure 4a. We can perfectly detect the gold inclusion and the corresponding dome of the silica layer on the photothermal and refraction mappings. These results show that gold inclusions are highly absorbing: the ratio between maximum signal and noise level is about 103. Thus, the possibility of the melting of gold during photothermal measurement, by interaction between the pump beam and the inclusion is not negligible. To check that gold is not melted during photothermal measurement, we perform two successive photothermal mappings of the same gold inclusion. To quantify the likeness of the 2 mappings, we calculate their correlation coefficient [10

10. A. During, C. Fossati, and M. Commandré, “Multi-wavelength imaging of defects in UV optical materials,” Appl. Opt. 41, 3118–3126 (2002). [CrossRef] [PubMed]

]. It is equal to 97.6%, which corresponds to a very good repeatability and shows that no modification of the gold inclusion occurred during photothermal measurement.

A shot with a fluence of 2 J/cm2 is performed on this gold inclusion. Given the aiming error of the irradiation laser, the absolute value of fluence is determined with a 10% error. The results are presented on Fig. 4(b). The comparison with fig. 4(a) shows that we are well positioned since the gold inclusion and the corresponding dome are still visible. However, absorption has partially decreased, though the refraction mapping is not significantly modified, showing no damage of the sample surface. Then, a shot with a fluence of 10 J/cm2 is performed. As shown on figure 4c, absorption is no more detectable, and the structure of the dome has changed, revealing that a surface damage has occurred. The low value of fluence leading to damage on gold inclusion (10 J/cm2 instead of 52 J/cm2 on pure silica), shows that these inclusions behave as laser damage precursors.

In conclusion, we showed that this new facility, constituted of an integrated photothermal microscopy and laser damage setup, is well adapted to the detection of sub-micronic absorbing defects and to the study of their behavior under laser irradiation. Photothermal mappings, performed before and after shot on gold inclusions, permit to study the evolution of localized absorption under irradiation before surface damage appearance. Refraction mappings, performed simultaneously, give information about the surface profile. It is also possible to precisely associate laser damage with the absorption level of gold inclusions. Then, systematic work, taking into account the size and nature of such inclusions will permit to established the correlation between laser damage threshold and defect absorption. Moreover, these inclusions behaving as precursor of laser damage, this new setup appears of great interest for the study of damage initiation mechanisms. Study of smaller inclusions will be possible and further work on inclusions of different size and nature at different wavelength (UV for example) seems really promising.

References and links

1.

N. Bloembergen, “Role of cracks, pores, and absorbing inclusions on laser induced damage threshold at surfaces of transparent dielectrics,” Appl. Opt. 12, 661–664 (1973). [CrossRef] [PubMed]

2.

M.R. Kozlowski and R. Chow, “The role of defects in laser damage of multilayer coatings,” in Laser-induced damage in optical materials: 1993, H.E. Bennett, L. Chase, A.H. Guenther, B.E. Newnam, and M.J. Soileau, eds., Proc. SPIE2114, 640–649 (1994). [CrossRef]

3.

J. Dijon, T. Poiroux, and C. Desrumaux, “Nano absorbing centers : A key point in laser damage of thin films,” in Laser-induced damage in optical materials: 1996, H.E. Bennett, A.H. Guenther, M.R. Kozlowski, B.E. Newnam, and M.J. Soileau, eds., Proc. SPIE2966, 315–325 (1997). [CrossRef]

4.

F.Y. Genin, A. Salleo, T.V. Pistor, and L.L. Chase, “Role of light intensification by cracks in optical breakdown on surfaces,” J. Opt. Soc. Am. A 18, 2607–2616 (2001). [CrossRef]

5.

J.Y. Natoli, L. Gallais, H. Akhouayri, and C. Amra, “Laser induced damage of materials in bulk, thin films and liquid forms,” Appl. Opt. 41, 3156–3166 (2002). [CrossRef] [PubMed]

6.

M. Commandré and P. Roche, “Characterization of optical coatings by photothermal deflection,” Appl. Opt. 35, 5021–5034 (1996). [CrossRef] [PubMed]

7.

E. Welsch and M. Reichling, “Micrometer resolved photothermal displacement inspection of optical coatings,” J. Mod. Opt. 40, 1455–1475 (1993). [CrossRef]

8.

M. Reichling, E. Welsch, A. Duparré, and E. Matthias, “Photothermal absorption microscopy of defects in ZrO2 and MgF2 single layer films,” Opt. Eng. 33, 1334–1342 (1994). [CrossRef]

9.

A. Gatto and M. Commandré, “Multiscale mapping technique for the simultaneous estimation of absorption and partial scattering in optical coatings,” Appl. Opt. 41, 225–234 (2002). [CrossRef] [PubMed]

10.

A. During, C. Fossati, and M. Commandré, “Multi-wavelength imaging of defects in UV optical materials,” Appl. Opt. 41, 3118–3126 (2002). [CrossRef] [PubMed]

11.

A. During, C. Fossati, and M. Commandré, “Development of a photothermal deflection microscope for multiscale studies of defects,” in Laser-induced damage in optical materials: 2001, G. J. Exarhos, A. H. Guenther, K. L. Lewis, M. J. Soileau, and C. J. Stolz, eds., Proc. SPIE4679, 400–409 (2002). [CrossRef]

12.

D. Boyer, P. Tamarat, A. Maali, B. Loumis, and M. Orrit, “Photothermal imaging of nanometer-sized metal particles among scaterrers,” Science 297, 1160–1163 (2002). [CrossRef] [PubMed]

13.

A. During, M. Commandré, C. Fossati, J.Y. Natoli, J.L. Rullier, H. Bercegol, and P. Bouchut, “Development of a photothermal deflection microscope for multi-scale studies of defects,” in Laser-induced damage in optical materials: 2001, G. J. Exarhos, A. H. Guenther, N. Kaiser, K. L. Lewis, M. J. Soileau, and C. J. Stolz, eds., Proc. SPIE4932, 374–384 (2003). [CrossRef]

14.

A. Fornier, C. Cordillot, D. Bernardino, O. Lam, A. Roussel, C. Amra, L. Escoubas, G. Albrand, and M. Commandré, “Characterization of optical coatings: damage threshold/local absorption correlation,” in Laser-induced damage in optical materials: 1996, H.E. Bennett, A.H. Guenther, M.R. Kozlowski, B.E. Newnam, and M.J. Soileau, eds., Proc. SPIE2966, 292–305 (1997). [CrossRef]

15.

A.B. Papandrew, C.J. Stolz, Z.L. Wu, G.E. Loomis, and S. Falabella, “Laser conditioning characterization and damage threshold prediction of hafnia/silica multilayer mirrors by photothermal microscopy,” in Laser-induced damage in optical materials: 2000, G.J. Exarhos, A.H. Guenther, M.R. Kozlowski, K.L. Lewis, and M.J. Soileau, eds., Proc. SPIE4347, 53–61 (2001). [CrossRef]

16.

M. Reichling, A. Bodemann, and N. Kaiser, “Defect induced laser damage in oxide multilayer coatings for 248 nm,” Thin Solid Films 320, 264–279 (1998). [CrossRef]

17.

E. Welsch, H.G. Walther, D. Schafer, and R. Wolf, “Measurement of optical losses and damage resistance of ZnS-Na3/AlF6 and TiO2 laser mirrors depending on coatings design,” Thin Solid Films 152, 433–442 (1988). [CrossRef]

OCIS Codes
(110.0180) Imaging systems : Microscopy
(140.3330) Lasers and laser optics : Laser damage
(300.1030) Spectroscopy : Absorption
(350.5340) Other areas of optics : Photothermal effects

ToC Category:
Research Papers

History
Original Manuscript: September 4, 2003
Revised Manuscript: September 16, 2003
Published: October 6, 2003

Citation
Annelise During, Mireille Commandre, Caroline Fossati, Bertrand Bertussi, Jean-Yves Natoli, Jean-Luc Rullier, Herve Bercegol, and Philippe Bouchut, "Integrated photothermal microscope and laser damage test facility for in-situ investigation of nanodefect induced damage," Opt. Express 11, 2497-2501 (2003)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-11-20-2497


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References

  1. N. Bloembergen, �??Role of cracks, pores, and absorbing inclusions on laser induced damage threshold at surfaces of transparent dielectrics,�?? Appl. Opt. 12, 661-664 (1973). [CrossRef] [PubMed]
  2. M.R. Kozlowski and R. Chow, �??The role of defects in laser damage of multilayer coatings,�?? in Laser-induced damage in optical materials: 1993, H.E. Bennett, L. Chase, A.H. Guenther, B.E. Newnam and M.J. Soileau, eds. Proc. SPIE 2114, 640-649 (1994). [CrossRef]
  3. J. Dijon, T. Poiroux and C. Desrumaux, �??Nano absorbing centers : A key point in laser damage of thin films,�?? in Laser-induced damage in optical materials: 1996, H.E. Bennett, A.H. Guenther, M.R. Kozlowski, B.E. Newnam and M.J. Soileau, eds., Proc. SPIE 2966, 315-325 (1997). [CrossRef]
  4. F.Y. Genin, A. Salleo, T.V. Pistor and L.L. Chase, �??Role of light intensification by cracks in optical breakdown on surfaces,�?? J. Opt. Soc. Am. A 18, 2607-2616 (2001). [CrossRef]
  5. J.Y. Natoli, L. Gallais, H. Akhouayri and C. Amra, �??Laser induced damage of materials in bulk thin films and liquid forms,�?? Appl. Opt. 41, 3156-3166 (2002). [CrossRef] [PubMed]
  6. M. Commandre and P. Roche, �??Characterization of optical coatings by photothermal deflection,�?? Appl. Opt. 35, 5021-5034 (1996). [CrossRef] [PubMed]
  7. E. Welsch and M. Reichling, �??Micrometer resolved photothermal displacement inspection of optical coatings,�?? J. Mod. Opt. 40, 1455-1475 (1993). [CrossRef]
  8. M. Reichling, E. Welsch, A. Duparre and E. Matthias, �??Photothermal absorption microscopy of defects in ZrO2 and MgF2 single layer films,�?? Opt. Eng. 33, 1334-1342 (1994). [CrossRef]
  9. A. Gatto and M. Commandre, �??Multiscale mapping technique for the simultaneous estimation of absorption and partial scattering in optical coatings,�?? Appl. Opt. 41, 225-234 (2002). [CrossRef] [PubMed]
  10. A. During, C. Fossati and M. Commandre, �??Multi-wavelength imaging of defects in UV optical materials,�?? Appl. Opt. 41, 3118-3126 (2002). [CrossRef] [PubMed]
  11. A. During, C. Fossati and M. Commandre, �??Development of a photothermal deflection microscope for multiscale studies of defects,�?? in Laser-induced damage in optical materials: 2001, G. J. Exarhos, A. H. Guenther, K. L. Lewis, M. J. Soileau and C. J. Stolz, eds., Proc. SPIE 4679, 400-409 (2002). [CrossRef]
  12. D. Boyer, P. Tamarat, A. Maali, B. Loumis, M. Orrit, �??Photothermal imaging of nanometer-sized metal particles among scaterrers,�?? Science 297, 1160-1163 (2002 [CrossRef] [PubMed]
  13. A. During, M. Commandre, C. Fossati, J.Y. Natoli, J.L. Rullier, H. Bercegol, P. Bouchut, �??Development of a photothermal deflection microscope for multi-scale studies of defects,�?? in Laser-induced damage in optical materials: 2001, G. J. Exarhos, A. H. Guenther, N. Kaiser, K. L. Lewis, M. J. Soileau and C. J. Stolz, eds., Proc. SPIE 4932, 374-384 (2003). [CrossRef]
  14. A. Fornier, C. Cordillot, D. Bernardino, O. Lam, A. Roussel, C. Amra, L. Escoubas, G. Albrand and M. Commander, �??Characterization of optical coatings: damage threshold/local absorption correlation,�?? in Laser-induced damage in optical materials: 1996, H.E. Bennett, A.H. Guenther, M.R. Kozlowski, B.E. Newnam and M.J. Soileau, eds., Proc. SPIE 2966, 292-305 (1997). [CrossRef]
  15. A.B. Papandrew, C.J. Stolz, Z.L. Wu, G.E. Loomis, S. Falabella, �??Laser conditioning characterization and damage threshold prediction of hafnia/silica multilayer mirrors by photothermal microscopy,�?? in Laser-induced damage in optical materials: 2000, G.J. Exarhos, A.H. Guenther, M.R. Kozlowski, K.L. Lewis and M.J. Soileau, eds., Proc. SPIE 4347, 53-61 (2001). [CrossRef]
  16. M. Reichling, A. Bodemann and N. Kaiser, �??Defect induced laser damage in oxide multilayer coatings for 248 nm,�?? Thin Solid Films 320, 264-279 (1998). [CrossRef]
  17. E. Welsch, H.G. Walther, D. Schafer and R. Wolf, �??Measurement of optical losses and damage resistance of ZnS-Na3/AlF6 and TiO2 laser mirrors depending on coatings design,�?? Thin Solid Films 152, 433-442 (1988). [CrossRef]

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