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Tunable continuous wave emission via phase-matched second harmonic generation in a ZnSe microcylindrical resonator.

Vukovic N, Healy N, Sparks JR, Badding JV, Horak P, Peacock AC - Sci Rep (2015)

Bottom Line: Whispering gallery mode microresonators made from crystalline materials are of great interest for studies of low threshold nonlinear phenomena.Visible red light is observed when pumped with a telecommunications band source by a process that is phase-matched between different higher order radial modes, possible due to the good spatial overlap between the pump and signal in the small volume resonator.By exploiting the geometrical flexibility offered by the fibre platform together with the ultra-wide 500-22000 nm transmission window of the ZnSe material, we expect these resonators to find use in applications ranging from spectroscopy to quantum information systems.

View Article: PubMed Central - PubMed

Affiliation: Optoelectronics Research Centre, University of Southampton, Southampton SO17 1BJ, UK.

ABSTRACT
Whispering gallery mode microresonators made from crystalline materials are of great interest for studies of low threshold nonlinear phenomena. Compared to amorphous materials, crystalline structures often exhibit desirable properties such as high indices of refraction, high nonlinearities, and large windows of transparency, making them ideal for use in frequency comb generation, microlasing and all-optical processing. In particular, crystalline materials can also possess a non-centrosymmetric structure which gives rise to the second order nonlinearity, necessary for three photon processes such as frequency doubling and parametric down-conversion. Here we report a novel route to fabricating crystalline zinc selenide microcylindrical resonators from our semiconductor fibre platform and demonstrate their use for tunable, low power continuous wave second harmonic generation. Visible red light is observed when pumped with a telecommunications band source by a process that is phase-matched between different higher order radial modes, possible due to the good spatial overlap between the pump and signal in the small volume resonator. By exploiting the geometrical flexibility offered by the fibre platform together with the ultra-wide 500-22000 nm transmission window of the ZnSe material, we expect these resonators to find use in applications ranging from spectroscopy to quantum information systems.

No MeSH data available.


Related in: MedlinePlus

Harmonic power scaling and phase-matching.(a) Measured second harmonic power collected in the TLF as a function of the fundamental power dropped into the resonator. (b) Calculated difference between the resonance positions (ΔλWGM) for mode pairs in our microcylindrical resonators near phase-matching. (c) Tuning the mode height to obtain ΔλWGM = 0; blue curve is position of pump resonance and red is for the second harmonic resonance.
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f3: Harmonic power scaling and phase-matching.(a) Measured second harmonic power collected in the TLF as a function of the fundamental power dropped into the resonator. (b) Calculated difference between the resonance positions (ΔλWGM) for mode pairs in our microcylindrical resonators near phase-matching. (c) Tuning the mode height to obtain ΔλWGM = 0; blue curve is position of pump resonance and red is for the second harmonic resonance.

Mentions: To confirm the second harmonic nature of the process, Fig. 3(a) shows a logarithmic plot of the collected second harmonic power () as a function of the power dropped into the resonator (), where it can be seen that the minimum coupled power at which we recorded a measurable harmonic signal was 250 μW. Fitting the data with a linear curve we obtain a slope of 1.95 ± 0.10, which is in good agreement with the expected quadratic dependence. Using this value we can then extract the external efficiency as . Significantly, this external efficiency is comparable to what has been obtained via a similar modal phase-matching method in a smaller, 3.8 μm diameter microresonator fabricated from AlGaAs15 (a material with a larger second order nonlinearity24); a good indication that the overall efficiency of our system is substantial. It is also worth noting that in contrast to previous reports in GaAs-based micro-disks1415, our measurements do not show any evidence of a roll-off in second harmonic power associated with thermal shifting of the pump resonance. We attribute this behaviour, or lack of, to the order of magnitude lower thermo-optic coefficient of the ZnSe material compared to GaAs, which makes it more suitable for high power pumping.


Tunable continuous wave emission via phase-matched second harmonic generation in a ZnSe microcylindrical resonator.

Vukovic N, Healy N, Sparks JR, Badding JV, Horak P, Peacock AC - Sci Rep (2015)

Harmonic power scaling and phase-matching.(a) Measured second harmonic power collected in the TLF as a function of the fundamental power dropped into the resonator. (b) Calculated difference between the resonance positions (ΔλWGM) for mode pairs in our microcylindrical resonators near phase-matching. (c) Tuning the mode height to obtain ΔλWGM = 0; blue curve is position of pump resonance and red is for the second harmonic resonance.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4488835&req=5

f3: Harmonic power scaling and phase-matching.(a) Measured second harmonic power collected in the TLF as a function of the fundamental power dropped into the resonator. (b) Calculated difference between the resonance positions (ΔλWGM) for mode pairs in our microcylindrical resonators near phase-matching. (c) Tuning the mode height to obtain ΔλWGM = 0; blue curve is position of pump resonance and red is for the second harmonic resonance.
Mentions: To confirm the second harmonic nature of the process, Fig. 3(a) shows a logarithmic plot of the collected second harmonic power () as a function of the power dropped into the resonator (), where it can be seen that the minimum coupled power at which we recorded a measurable harmonic signal was 250 μW. Fitting the data with a linear curve we obtain a slope of 1.95 ± 0.10, which is in good agreement with the expected quadratic dependence. Using this value we can then extract the external efficiency as . Significantly, this external efficiency is comparable to what has been obtained via a similar modal phase-matching method in a smaller, 3.8 μm diameter microresonator fabricated from AlGaAs15 (a material with a larger second order nonlinearity24); a good indication that the overall efficiency of our system is substantial. It is also worth noting that in contrast to previous reports in GaAs-based micro-disks1415, our measurements do not show any evidence of a roll-off in second harmonic power associated with thermal shifting of the pump resonance. We attribute this behaviour, or lack of, to the order of magnitude lower thermo-optic coefficient of the ZnSe material compared to GaAs, which makes it more suitable for high power pumping.

Bottom Line: Whispering gallery mode microresonators made from crystalline materials are of great interest for studies of low threshold nonlinear phenomena.Visible red light is observed when pumped with a telecommunications band source by a process that is phase-matched between different higher order radial modes, possible due to the good spatial overlap between the pump and signal in the small volume resonator.By exploiting the geometrical flexibility offered by the fibre platform together with the ultra-wide 500-22000 nm transmission window of the ZnSe material, we expect these resonators to find use in applications ranging from spectroscopy to quantum information systems.

View Article: PubMed Central - PubMed

Affiliation: Optoelectronics Research Centre, University of Southampton, Southampton SO17 1BJ, UK.

ABSTRACT
Whispering gallery mode microresonators made from crystalline materials are of great interest for studies of low threshold nonlinear phenomena. Compared to amorphous materials, crystalline structures often exhibit desirable properties such as high indices of refraction, high nonlinearities, and large windows of transparency, making them ideal for use in frequency comb generation, microlasing and all-optical processing. In particular, crystalline materials can also possess a non-centrosymmetric structure which gives rise to the second order nonlinearity, necessary for three photon processes such as frequency doubling and parametric down-conversion. Here we report a novel route to fabricating crystalline zinc selenide microcylindrical resonators from our semiconductor fibre platform and demonstrate their use for tunable, low power continuous wave second harmonic generation. Visible red light is observed when pumped with a telecommunications band source by a process that is phase-matched between different higher order radial modes, possible due to the good spatial overlap between the pump and signal in the small volume resonator. By exploiting the geometrical flexibility offered by the fibre platform together with the ultra-wide 500-22000 nm transmission window of the ZnSe material, we expect these resonators to find use in applications ranging from spectroscopy to quantum information systems.

No MeSH data available.


Related in: MedlinePlus