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Group velocity mismatch-absent nonlinear frequency conversions for mid-infrared femtosecond pulses generation.

Zhong H, Zhang L, Li Y, Fan D - Sci Rep (2015)

Bottom Line: The system employs MgO-doped periodically poled LiNbO3 as the nonlinear medium.Desired group-velocity dispersion would be obtained via appropriately temperature regulation.Compared with the conventional scheme of type-0 QPM, the quantum-efficiency can be more than doubled with nearly unlimited bandwidth.

View Article: PubMed Central - PubMed

Affiliation: SZU-NUS Collaborative Innovation Center for Optoelectronic Science &Technology, Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China.

ABSTRACT
A novel group velocity mismatch (GVM) absent scheme for nonlinear optical parametric procedure in mid-infrared was developed with type-I quasi phase matching by use of an off-digital nonlinear optical coefficient d31. This was achieved by matching of the group velocities of the pump and the signal waves, while the phase velocities were quasi phase matched. The system employs MgO-doped periodically poled LiNbO3 as the nonlinear medium. Desired group-velocity dispersion would be obtained via appropriately temperature regulation. To demonstrate its potential applications in ultrafast mid-infrared pulses generation, aiming at a typical mid-infrared wavelength of ~3.2 μm, design examples of two basic nonlinear frequency conversion procedures are studied for both the narrow-band seeding mid-IR optical parametric amplification (OPA) and the synchronously pumped femtosecond optical parametric oscillation (SPOPO). Compared with the conventional scheme of type-0 QPM, the quantum-efficiency can be more than doubled with nearly unlimited bandwidth. The proposed GVM- absent phase matching design may provide a promising route to efficient and broadband sub-100 fs mid-infrared ultrafast pulses generation without group-velocity walk-off.

No MeSH data available.


Related in: MedlinePlus

(a) Dependence of the photon conversion efficiency of SPOPO on pump intensities, for both type-I and type-0 QPM designs. To show the plots clearly, different pump intensity scales were utilized for distinct pump durations. The paler part in the solid curve correspond the cases when pulse distortion exists. (b) The calculated maximum conversion efficiency versus various pump durations without compromising on the quality of mid-IR output.
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f6: (a) Dependence of the photon conversion efficiency of SPOPO on pump intensities, for both type-I and type-0 QPM designs. To show the plots clearly, different pump intensity scales were utilized for distinct pump durations. The paler part in the solid curve correspond the cases when pulse distortion exists. (b) The calculated maximum conversion efficiency versus various pump durations without compromising on the quality of mid-IR output.

Mentions: Figure 6 (a) presents the simulated dependence of quantum efficiency with different pump intensities. In this figure, two specific examples are given, where the pump duration is 80 fs and the shorter 40 fs respectively. For comparison, the widely used type-0 QPM is included as well. In the calculations, incident pump wave is taken to be Gaussian in temporal. Under the ideal situation of ignoring the influence of material dispersion, if we want to obtain same conversion efficiency for both type-I and type-0 QPM interactions, a shorter crystal length will be needed for the type-0 cases under the same pump intensity, due to its larger effective nonlinear coefficient of ~16 pm/V33. In our simulations, ~1 mm and ~5.5 mm MgO:PPLN were chosen for the type-0 and type-I QPM designs respectively, the ratio of which is just the inverse proportion of their nonlinear coefficients. Accordingly, ~0.5 and 2.7 mm-thick Ge plates were inserted inside the cavity to compensate the negative GVD of MgO:PPLN. In the circumstances, taking the detrimental GVD and GVM into account, the performance of different OPOs would be reflected in their conversion efficiencies and spectral bandwidths. As can be seen, for the proposed GVM-absent design with a 5.5 mm type-I QPM MgO:PPLN crystal, maximum photon efficiency of ~80% is obtained at the pump intensity of ~0.9 GW/cm2 while the pump duration is 80 fs. Comparatively, the maximum conversion efficiency would be less than 60% at ~0.7 GW/cm2 for the conventional type-0 QPM situation. It should be noted that, in the numerical simulations, the pulse slipping between the pump and signal waves had been compensated before the next pump pulse arrive, which can be realized by slightly modulating the cavity length in practice.


Group velocity mismatch-absent nonlinear frequency conversions for mid-infrared femtosecond pulses generation.

Zhong H, Zhang L, Li Y, Fan D - Sci Rep (2015)

(a) Dependence of the photon conversion efficiency of SPOPO on pump intensities, for both type-I and type-0 QPM designs. To show the plots clearly, different pump intensity scales were utilized for distinct pump durations. The paler part in the solid curve correspond the cases when pulse distortion exists. (b) The calculated maximum conversion efficiency versus various pump durations without compromising on the quality of mid-IR output.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4477408&req=5

f6: (a) Dependence of the photon conversion efficiency of SPOPO on pump intensities, for both type-I and type-0 QPM designs. To show the plots clearly, different pump intensity scales were utilized for distinct pump durations. The paler part in the solid curve correspond the cases when pulse distortion exists. (b) The calculated maximum conversion efficiency versus various pump durations without compromising on the quality of mid-IR output.
Mentions: Figure 6 (a) presents the simulated dependence of quantum efficiency with different pump intensities. In this figure, two specific examples are given, where the pump duration is 80 fs and the shorter 40 fs respectively. For comparison, the widely used type-0 QPM is included as well. In the calculations, incident pump wave is taken to be Gaussian in temporal. Under the ideal situation of ignoring the influence of material dispersion, if we want to obtain same conversion efficiency for both type-I and type-0 QPM interactions, a shorter crystal length will be needed for the type-0 cases under the same pump intensity, due to its larger effective nonlinear coefficient of ~16 pm/V33. In our simulations, ~1 mm and ~5.5 mm MgO:PPLN were chosen for the type-0 and type-I QPM designs respectively, the ratio of which is just the inverse proportion of their nonlinear coefficients. Accordingly, ~0.5 and 2.7 mm-thick Ge plates were inserted inside the cavity to compensate the negative GVD of MgO:PPLN. In the circumstances, taking the detrimental GVD and GVM into account, the performance of different OPOs would be reflected in their conversion efficiencies and spectral bandwidths. As can be seen, for the proposed GVM-absent design with a 5.5 mm type-I QPM MgO:PPLN crystal, maximum photon efficiency of ~80% is obtained at the pump intensity of ~0.9 GW/cm2 while the pump duration is 80 fs. Comparatively, the maximum conversion efficiency would be less than 60% at ~0.7 GW/cm2 for the conventional type-0 QPM situation. It should be noted that, in the numerical simulations, the pulse slipping between the pump and signal waves had been compensated before the next pump pulse arrive, which can be realized by slightly modulating the cavity length in practice.

Bottom Line: The system employs MgO-doped periodically poled LiNbO3 as the nonlinear medium.Desired group-velocity dispersion would be obtained via appropriately temperature regulation.Compared with the conventional scheme of type-0 QPM, the quantum-efficiency can be more than doubled with nearly unlimited bandwidth.

View Article: PubMed Central - PubMed

Affiliation: SZU-NUS Collaborative Innovation Center for Optoelectronic Science &Technology, Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China.

ABSTRACT
A novel group velocity mismatch (GVM) absent scheme for nonlinear optical parametric procedure in mid-infrared was developed with type-I quasi phase matching by use of an off-digital nonlinear optical coefficient d31. This was achieved by matching of the group velocities of the pump and the signal waves, while the phase velocities were quasi phase matched. The system employs MgO-doped periodically poled LiNbO3 as the nonlinear medium. Desired group-velocity dispersion would be obtained via appropriately temperature regulation. To demonstrate its potential applications in ultrafast mid-infrared pulses generation, aiming at a typical mid-infrared wavelength of ~3.2 μm, design examples of two basic nonlinear frequency conversion procedures are studied for both the narrow-band seeding mid-IR optical parametric amplification (OPA) and the synchronously pumped femtosecond optical parametric oscillation (SPOPO). Compared with the conventional scheme of type-0 QPM, the quantum-efficiency can be more than doubled with nearly unlimited bandwidth. The proposed GVM- absent phase matching design may provide a promising route to efficient and broadband sub-100 fs mid-infrared ultrafast pulses generation without group-velocity walk-off.

No MeSH data available.


Related in: MedlinePlus