1064 nm laser-induced defects in pure SiO_2 fibers

Stone, James M.; Wadsworth, William J.; Knight, Jonathan C.

doi:10.1364/ol.38.002717

Cited by 5 publications

(8 citation statements)

References 26 publications

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“…Although the transmission can remain stable for lower powers for a reasonable period of time, 50 μW is generally not sufficient to reach the threshold needed for the observation of nonlinear optical effects in WGRs, such as SRS and hyperparametric oscillation. In contrast to the studies on photodarkening in commercial optical fibers when using high powers (typically a few watts) [37][38][39], the threshold for photodarkening in the nanofibers reported herein was very low (∼50 μW). The most likely explanation is the increased probability of two-photon absorption due to the very high optical intensities (MW∕cm 2 to GW∕cm 2 ) at the waist of the tapered nanofiber.…”

Section: A Photodarkening In Silica Nanofiberscontrasting

confidence: 91%

Blue band nonlinear optics and photodarkening in silica microdevices

Tian¹,

Yu²,

Lei³

et al. 2022

Photon. Res.

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There are extensive studies to date on optical nonlinearities in microcavities at the near and mid-IR wavelengths. Pushing this research into the visible region is equally valuable. Here, we demonstrate a directly pumped, blue band Kerr frequency comb and stimulated Raman scattering (SRS) at 462 nm in a silica nanofiber-coupled whispering gallery microcavity system. Notably, due to the high optical intensities achieved, photodarkening is unavoidable and can quickly degrade the optical quality of both the coupling optical nanofiber and the microcavity, even at very low pump powers. Nonetheless, stable hyperparametric oscillation and SRS are demonstrated in the presence of photodarkening by taking advantage of in-situ thermal bleaching. This work highlights the challenges of silica-based, short wavelength nonlinear optics in high-quality, small mode volume devices and gives an effective method to overcome this apparent limitation, thus providing a baseline for optics research in the blue region for any optical devices fabricated from silica.

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Section: A Photodarkening In Silica Nanofiberscontrasting

confidence: 91%

Blue band nonlinear optics and photodarkening in silica microdevices

Tian¹,

Yu²,

Lei³

et al. 2022

Photon. Res.

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“…In contrast to the available studies on photodarkening in commercial optical fibers when using high powers (typically a few Watts) [46,48,49], the threshold for photodarkening-like effects in the microresonators and nanofibers reported herein is very low (a few mW). The most likely explanation is the increased probability of two-photon absorption due to the very high optical intensities (MW/cm 2 -GW/cm 2 ) in these micro-and nanodevices.…”

Section: Discussioncontrasting

confidence: 69%

“…There are controversies in the literature about the specific generation mechanism of color centers that lead to photodarkening, but it can be generally viewed as being due to oxygen deficiency centers (ODCs) [43], charge transfer band (CT band) transitions [44], or the influence of Tm 3+ impurities [45] in doped fiber. One common color center in pure silica is a partially bound oxygen atom with one free electron, that is the non-bridging oxygen hole center (NBOHC) [46]. This defect often forms as a result of optically induced breaking of a bond in a stressed multiple member Si-O ring [47].…”

Section: Discussionmentioning

confidence: 99%

Blue-band frequency comb and photodarkening in silica whispering gallery microresonators

Tian¹,

Yu²,

Lei³

et al. 2021

Preprint

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In contrast to the generation of optical frequency combs in the near and mid-infrared wavelengths, pushing optical frequency combs into the visible and ultraviolet is equally valuable, for example for direct applications in miniature optical clocks and spectroscopy. Currently, the blue-band is the shortest wavelength region for the generation of Kerr frequency combs, which have been realized using a magnesium fluoride resonator. However, direct comb generation from silica resonators would significantly simplify both the fabrication and integration processes. Here, we demonstrate for the first time, a blue-band Kerr frequency comb directly generated in a silica whispering gallery resonator (WGR) with a silica tapered fiber for optical coupling. A Kerr frequency comb with 13 comb lines is observed using a laser centered around 462 nm with a launched pump power of 30 mW. Significantly, the transmission through the coupling tapered fiber and the optical quality of the whispering gallery modes (WGMs) degrade quickly when pumped with the blue light. This leads to annihilation of the frequency comb, photodarkening being the expected cause. These observations appear to be a significant limiting factor for nonlinear optical processes in silica WGRs and provide a baseline for future nonlinear optics research in WGRs in the blue region.

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“…This can occur also in FRLs, especially with highly germanium-doped fibers (as often used for FRLs), operating at visible wavelengths at high power densities. Thus, for example, photodarkening is known to occur in fibers used for supercontinuum generation at visible wavelengths [7]. However, at longer wavelengths and lower power densities for Raman conversion in fibers longer than 100 m, we expect photodarkening to be negligible.…”

Section: Introductionmentioning

confidence: 99%

High-Power Continuous-Wave Directly-Diode-Pumped Fiber Raman Lasers

et al. 2015

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We describe novel fiber Raman lasers pumped directly by spectrally combined high power multimode laser diodes at ∼975 nm and emitting at ∼1019 nm. With a commercial multimode graded-index fiber, we reached 20 W of laser output power with a record slope efficiency of 80%. With an in-house double-clad fiber, the beam quality improved to M 2 = 1.9, albeit with lower output power and slope efficiency due to higher fiber loss. We believe this is the first publication of a fiber Raman laser cladding-pumped directly by diodes.

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1064 nm laser-induced defects in pure SiO_2 fibers

Cited by 5 publications

References 26 publications

Blue band nonlinear optics and photodarkening in silica microdevices

Blue band nonlinear optics and photodarkening in silica microdevices

Blue-band frequency comb and photodarkening in silica whispering gallery microresonators

High-Power Continuous-Wave Directly-Diode-Pumped Fiber Raman Lasers

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