Overview of photothermal characterization of optical thin film coatings

Wu, Zhouling; Thomsen, Marshall; Kuo, P. K.; Lu, Yajie; Stolz, Christopher J.; Kozlowski, Mark R.

doi:10.1117/12.240409

Cited by 9 publications

(7 citation statements)

References 12 publications

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“…As one of the photothermal techniques, surface thermal lensing technique 21,22,23,24,25 was developed into a high-sensitive apparatus for weak absorption test. A continuous-wave 1064 nm Nd:YAG laser and a He-Ne laser were employed as pump source and probe source, respectively.…”

Section: Weak Absorption Detectionmentioning

confidence: 99%

Laser thin films with very high damage threshold

Shao

Zhang

2005

SPIE Proceedings

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New developments of laser thin films for high power laser systems were reviewed. Special attention was paid to several key coatings which bottlenecked the higher power laser system, such as pick-off mirrors, large aperture polarizer and YAG harmonic wavelength splitter, as well as AR coatings.Defects were deemed to be the initial and essential source of laser-induced damage. The investigation of the original control of defects was focused on the deposition process control, such as substrate cleaning, purity of deposition materials, deposition temperature, oxygen pressure in vacuum chamber and so on. Several methods of evaluation of laser damage were employed, which included Laser Induced Damage Threshold (LIDT) determination and absorption detection based on Surface Thermal Lensing (STL) technique, as well as Total Integrated Scattering (TIS) measurement.The LIDT of pick-off mirrors reached to 20 J/cm 2 (1064 nm, 1 ns), meanwhile the LIDT of the ultraviolet coatings did to 8 J/cm 2 (355 nm, 1 ns) because of its comprehensive mechanism. The LIDT of third harmonic mirror could be improved effectively with post-treatment methods, such as oxygen-plasma post-treatment and vacuum annealing.Actually the situation of the laser thin films with very high damage threshold was complicated due to their uniformity of optical properties and stress induced surface deformation in the large aperture.

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Section: Weak Absorption Detectionmentioning

confidence: 99%

Laser thin films with very high damage threshold

Shao

Zhang

2005

SPIE Proceedings

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“…In this way the detector monitors intensity changes at the center of the probe beam, which is proportional to the optical absorptance of the sample. To convert the PTD signal into absorptance data, the traditional calibration method for PTD is used, where the calibration coefficient is achieved by measuring the PTD signal of a calibration thin film sample with known absorptance [2,3,7].…”

Section: Methodsmentioning

confidence: 99%

“…The photothermal deflection (PTD) technique appears suited for this low absorptance application [1][2][3]. The technique has high sensitivity, uses a low to moderate power laser, and the coating may be tested at its design wavelength by selecting the appropriate pump laser.…”

Section: Introductionmentioning

confidence: 99%

<title>High reflector absorptance measurements by the surface thermal lensing technique</title>

Chow

Taylor

et al. 1997

SPIE Proceedings

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November 4, 1996This is a preprint of a paper intended for publication in a journal or proceedings. Since changes may be made before publication, this preprint is made available with the understanding that it will not be cited or reproduced without the permission of the author. PREPRINTThis paper was prepared for submittal to the DISCLAIMER This document was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor the University of California nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or the University of California, and shall not be used for advertising or product endorsement purposes. ABSTRACTSurface thermal lensing is an alternate configuration of a photothermal deflection system that was used to measure low levels of optical absorption. The thermal lensing configuration facilitated the alignment of the pump and probe laser beams by using a larger diameter probe beam. This technique was applied to high performance optical coatings, specifically high reflectors at 511 nm, zero degrees angle of incidence. The absorptance of these coatings was previously measured using a high power copper vapor laser system. A high power copper laser beam is focused onto a ~2 mm diameter spot. A thermal camera senses the temperature rise with respect to the rest of the coating. The temperature change, power density and beam diameter were used with an empirical formula that yields optical absorption. The surface thermal lensing technique was able to resolve absorption levels lower than that achieved with the copper laser method.

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“…To convert the PTD signal into absorptance da@ the traditional calibration method for PTD is used, where the calibration coefficient is determined horn the PTD signal of a thin film sample with known absorptance [2,3,8].…”

Section: Photothermal Deformationmentioning

confidence: 99%

“…The photothermal deflection (PTD) technique appears suited for this absorptance application [1][2][3]. The technique has high sensitivity, uses low to moderate power lasers, and the coating may be tested at its design wavelength by selecting the appropriate pump laser.…”

Section: Introductionmentioning

confidence: 99%