Proton exchanged waveguides in LiNbO&lt;inline-formula&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;/inline-formula&gt; and LiTaO&lt;inline-formula&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;/inline-formula&gt; for integrated lasers and nonlinear frequency converters

Baldi, Pascal; Micheli, Marc de; Hadi, K. El; Nouh, S.; Cino, Alfonso Carmelo; Aschiéri, Pierre; Ostrowsky, D. B.

doi:10.1117/1.601954

Cited by 73 publications

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“…It is reasonable to conclude that some free charge carriers were formed in the single crystal through electrochemical hydrogen charging. In a previous investigation, a peak at 3280 cm −1 had been observed in the infrared absorption spectra of hydrogen-charged TiO 2 single crystals, 8 which gives a direct evidence for the incorporation of hydrogen in the TiO 2 lattice. As predicted by some theoretical investigations, [3][4][5] hydrogen is a shallow donor in TiO 2 , and it has been proposed that free electrons are formed in the following way:…”

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confidence: 85%

“…When the acidity of the melt in the proton exchange process is high enough, another broad peak at 3280 cm −1 can also be observed, which is only metastable and will disappear through an annealing process. 8 Obviously, these two peaks should correspond to two different states of hydrogen with quite different stabilities. The broad peak should indicate the existence in LiNbO 3 of hydrogen with a much lower stability, which is possibly a deep impurity forming only long and weak bonds to neighboring oxygen sites.…”

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confidence: 99%

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Hydrogen: A metastable donor in TiO2 single crystals

Chen

Wang

Chan

2008

Applied Physics Letters

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The properties of TiO 2 ͑110͒ single crystals are greatly changed after hydrogen is doped into them through electrochemical hydrogen charging, in which the crystals have been placed in 0.01M NaOH solution to deposit hydrogen on their electrodes through the electrolysis of water. The changes in properties, including great increases in leakage current, strong dielectric dispersions over 10 2 -10 6 Hz, and a strong aging phenomenon suggest that hydrogen is a donor in TiO 2 while ionized hydrogen is not bound to an oxygen site by a strong O-H bond. This behavior of hydrogen, which can be characterized as a metastable donor, is different from the usual donor behavior of hydrogen in oxides and should be interesting for a better understanding of the behavior of hydrogen in oxides. © 2008 American Institute of Physics. ͓DOI: 10.1063/1.2900957͔The behavior of hydrogen in oxides has been a topic of extensive investigations. On one hand, hydrogen is a ubiquitous impurity in various oxides. It can be introduced into oxides from precursors, from annealing gases, 1 or even from aqueous vapor in ambient atmosphere.2 On the other hand, hydrogen behaves quite differently from one oxide to another. In some oxides, hydrogen forms deep gap states in all of its three charge states, H + , H 0 , and H − ; while in other oxides, hydrogen gives rise to a shallow level at the conduction band edge and acts as a donor. [3][4][5] As an example, hydrogen has been predicted theoretically 6 and proven experimentally 7 as a shallow donor in ZnO. It must possess a high stability in ZnO to survive high-temperature sintering or crystal growth. As a matter of fact, it is generally believed that as a donor, hydrogen ionizes to H + with the electron being delocalized in the oxide conduction band and then H + forms a single strong O-H bond to an O site; in contrast, when hydrogen is a deep impurity, it will only form some longer, weaker bonds to more than one neighboring oxygen and exist as a metastable interstitial.5 Metastable interstitial hydrogen has been observed in proton-exchanged LiNbO 3 . A sharp peak at around 3500 cm −1 can always be observed in the infrared absorption spectra of proton exchange processtreated LiNbO 3 , which is the characteristic absorption peak for the stretch mode of the O-H bond, as hydrogen has replaced some lithium ions in LiNbO 3 . When the acidity of the melt in the proton exchange process is high enough, another broad peak at 3280 cm −1 can also be observed, which is only metastable and will disappear through an annealing process. Obviously, these two peaks should correspond to two different states of hydrogen with quite different stabilities. The broad peak should indicate the existence in LiNbO 3 of hydrogen with a much lower stability, which is possibly a deep impurity forming only long and weak bonds to neighboring oxygen sites. In a previous investigation, hydrogen has been doped into TiO 2 single crystals through an electrochemical method.9 Presently, a study on the behavior of hydrogen in TiO 2 single crysta...

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confidence: 85%

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confidence: 99%

Hydrogen: A metastable donor in TiO2 single crystals

Chen

Wang

Chan

2008

Applied Physics Letters

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“…For those applications involving non linear optical conversion processes the channel waveguide design is of special relevance since the achievement of high spatial overlap and confinement of both pump and second order waves leads to a strong enhancement in the optical conversion efficiencies. For the same reason, the guided configuration is also advantageous for lasing devices, when low threshold and compact size are required [2]. Among the different methods available for Nd:LiNbO 3 channel waveguide fabrication, Proton Exchanged (PE) waveguides have focused much attention because of the low loss, high index contrast and photorefractive resistant waveguides that can be obtained [3].…”

Section: Introductionmentioning

confidence: 99%

Time resolved confocal luminescence investigations on Reverse Proton Exchange Nd:LiNbO_3 channel waveguides

Jaque¹,

Cantelar²,

Cussó³

et al. 2007

Opt. Express

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Abstract:In this work we report on the time and spatial resolved fluorescence of Neodymium ions in LiNbO 3 channel waveguides fabricated by Reverse Proton Exchange. The analysis of the fluorescence decay curves obtained with a sub-micrometric resolution has evidenced the presence of a relevant fluorescence quenching inside the channel waveguide. From the comparison between diffusion simulations and the spatial dependence of the 4 F 3/2 fluorescence decay rate we have concluded that the observed fluorescence quenching can be unequivocally related to the presence of H + ions in the LiNbO 3 lattice. Nevertheless, it turns out that Reverse Proton Exchange guarantees a fluorescence quenching level significantly lower than in similar configurations based on Proton Exchange waveguides. This fluorescence quenching has been found to be accompanied by a relevant red-shift of the 4 F 3/2 → 4 I 9/2 fluorescence band.

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“…Previous work on ion implanted Nd:YAG waveguides has been done using helium ions and protons with energies of typically 1 to 2 MeV [6,7]. In this crystal as well as in other crystalline materials such as LiNbO 3 and Bi 4 Ge 3 O 12 [8,9] the refractive index in the guiding region increases by a small amount during ion implantation, producing a conventional waveguide profile with an enhanced index. In this case the optical barrier becomes superfluous for the lowest modes, as these can be confined without exhibiting tunneling loss, which normally will be caused by the presence of the optical barrier.…”

Section: Introductionmentioning

confidence: 99%

“…They offer high power densities which are confined in a small volume and can be used for nonlinear applications such as second harmonic generation, four wave mixing, etc. Some of the advantages of optical waveguides are that they can be easily coupled to semiconductor pump lasers and that modest powers are needed to achieve the nonlinear effects [1][2][3].…”

Section: Introductionmentioning

confidence: 99%

Low dose carbon implanted waveguides in Nd:YAG

Vázquez¹,

Rickards²,

Lifante³

et al. 2003

Opt. Express

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Abstract:For the first time to our knowledge, carbon implantation into YAG crystals doped with Nd has been used to produce optical waveguides. A considerable index decrease in the nuclear region (i.e., the region where the energetic ions stop) of ~ 2.5% was obtained with a low dose implant, while giving an index enhancement in the guiding region of ~ 0.35%. After an annealing step necessary to recover the transparency of the crystals, the layer of reduced refractive index produced by implantation is preserved. Spectroscopic studies carried out in a waveguiding configuration show that emission bands coming from the 4 F 3/2 level present a slight broadening, while its associated lifetime is similar to that reported in bulk crystals (240 µs).

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Proton exchanged waveguides in LiNbO<inline-formula><sub>3</sub></inline-formula> and LiTaO<inline-formula><sub>3</sub></inline-formula> for integrated lasers and nonlinear frequency converters

Cited by 73 publications

References 0 publications

Hydrogen: A metastable donor in TiO2 single crystals

Hydrogen: A metastable donor in TiO2 single crystals

Time resolved confocal luminescence investigations on Reverse Proton Exchange Nd:LiNbO_3 channel waveguides

Low dose carbon implanted waveguides in Nd:YAG

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