• Photonics Research
  • Vol. 7, Issue 11, 1345 (2019)
Atri Halder1、*, Vytautas Jukna2, Matias Koivurova3, Audrius Dubietis2, and Jari Turunen1
Author Affiliations
  • 1Department of Physics and Mathematics, University of Eastern Finland, FI-80101 Joensuu, Finland
  • 2Laser Research Center, Vilnius University, LT-10223 Vilnius, Lithuania
  • 3Photonics Laboratory, Physics Unit, Tampere University, FI-33101 Tampere, Finland
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    DOI: 10.1364/PRJ.7.001345 Cite this Article Set citation alerts
    Atri Halder, Vytautas Jukna, Matias Koivurova, Audrius Dubietis, Jari Turunen. Coherence of bulk-generated supercontinuum[J]. Photonics Research, 2019, 7(11): 1345 Copy Citation Text show less

    Abstract

    We have developed a numerical framework that allows estimation of coherence in spatiotemporal and spatiospectral domains. Correlation properties of supercontinuum (SC) pulses generated in a bulk medium are investigated by means of second-order coherence theory of non-stationary fields. The analysis is based on simulations of individual space–time and space–frequency realizations of pulses emerging from a 5 mm thick sapphire plate, in the regimes of normal, zero, and anomalous group velocity dispersion. The temporal and spectral coherence properties are analyzed in the near field (as a function of spatial position at the exit plane of the nonlinear medium) and as a function of propagation direction (spatial frequency) in the far field. Unlike in fiber-generated SC, the bulk case features spectacularly high degrees of temporal and spectral coherence in both the spatial and spatial-frequency domains, with increasing degrees of coherence at higher pump energies. When operating near the SC generation threshold, the overall degrees of temporal and spectral coherence exhibit an axial dip in the spatial domain, whereas in the far field, the degree of coherence is highest around the optical axis.
    E(ρ;t)=0E˜(ρ;ω)exp(iωt)dω.(1)

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    A(κ;t)=1(2π)2E(ρ;t)exp(iκ·ρ)d2ρ(2)

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    A˜(κ;ω)=1(2π)2E˜(ρ;ω)exp(iκ·ρ)d2ρ(3)

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    Γ(ρ1,ρ2;t1,t2)=E*(ρ1;t1)E(ρ2;t2).(4)

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    W(ρ1,ρ2;ω1,ω2)=E˜*(ρ1;ω1)E˜(ρ2;ω2).(5)

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    G(κ1,κ2;t1,t2)=A*(κ1;t1)A(κ2;t2)(6)

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    T(κ1,κ2;ω1,ω2)=A˜*(κ1;ω1)A˜(κ2;ω2).(7)

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    f(x)=limN1Nn=1Nfn(x),(8)

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    γ(ρ1,ρ2;t1,t2)=Γ(ρ1,ρ2;t1,t2)I(ρ1;t1)I(ρ2;t2),(9)

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    μ(ρ1,ρ2;ω1,ω2)=W(ρ1,ρ2;ω1,ω2)S(ρ1;ω1)S(ρ2;ω2),(10)

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    g(κ1,κ2;t1,t2)=G(κ1,κ2;t1,t2)I(κ1;t1)I(κ2;t2),(11)

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    ν(κ1,κ2;ω1,ω2)=T(κ1,κ2;ω1,ω2)S(κ1;ω1)S(κ2;ω2).(12)

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    G(κ1,κ2;t1,t2)=1(2π)4Γ(ρ1,ρ2;t1,t2)×exp[i(κ1·ρ1κ2·ρ2)]dρ1dρ2(13)

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    T(κ1,κ2;ω1,ω2)=1(2π)4W(ρ1,ρ2;ω1,ω2)×exp[i(κ1·ρ1κ2·ρ2)]dρ1dρ2.(14)

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    γ¯2(ρ)=|Γ(ρ,ρ;t1,t2)|2dt1dt2I(ρ;t1)I(ρ;t2)dt1dt2(15)

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    μ¯2(ρ)=0|W(ρ,ρ;ω1,ω2)|2dω1dω20S(ρ;ω1)S(ρ;ω2)dω1dω2.(16)

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    g¯2(κ)=|G(κ,κ;t1,t2)|2dt1dt2I(κ;t1)I(κ;t2)dt1dt2(17)

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    ν¯2(κ)=0|T(κ,κ;ω1,ω2)|2dω1dω20S(κ;ω1)S(κ;ω2)dω1dω2.(18)

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    s^=(sx,sy,sz)=(σ^,sz)=(sinθcosϕ,sinθsinϕ,cosθ)(19)

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    k=(kx,ky,kz)=(κ,kz)=ks^,(20)

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    r=(x,y,z)=(ρ,z)=rs^,(21)

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    E˜()(r;ω)=i2πkszA˜(kσ^;ω)exp(ikr)r,(22)

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    W()(r,r;ω1,ω2)=E˜()*(r;ω1)E˜()(r;ω2).(23)

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    W()(r,r;ω1,ω2)=(2πsz)2ω1ω2c2T(k1σ^,k2σ^;ω1,ω2)×exp[i(k2k1)r]r2,(24)

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    W()(r,r;ω,ω)=S()(r;ω)=(2πkszr)2S(kσ^;ω),(25)

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    μ()(r,r;ω1,ω2)=T(k1σ^,k2σ^;ω1,ω2)S(k1σ^;ω1)S(k2σ^;ω2).(26)

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    E()(r;t)=0E˜()(r;ω)exp(iωt)dω,(27)

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    E()(r;t)=i2πszrc0ωA˜(kσ;ω)×exp[iω(tr/c)]dω,(28)

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    Γ()(r,r;t1,t2)=E()*(r;t1)E()(r;t2),(29)

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    Γ()(r,r;t1,t2)=(2πszrc)20T(k1σ^,k2σ^;ω1,ω2)×ω1ω2exp[ir(k2k1)]×exp[i(ω1t1ω2t2)]dω1dω2.(30)

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    Γ()(r,r;t1,t2)=(2πszk0r)2G(k0σ^,k0σ^;t1,t2).(31)

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    T(k1σ^1,k2σ^2;ω1,ω2)=Tσ(k0σ^1,k0σ^2)Tω(ω1,ω2).(32)

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    A˜(κ,ω;z)z=i[k2(ω)κ2k(ω0)kg(ω0)]×A˜(κ,ω;z)+iω2n(ω)cϵ01[P˜(κ,ω;z)+iJ˜(κ,ω;z)ω].(33)

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    ϵ01P(ρ,t;z)=2n0n2|E(ρ,t;z)|2E(ρ,t;z),(34)

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    ϵ01J(ρ,t;z)=n0c[σB(1+iω0τc)ρe+UgW(ρ,t;z)|E(ρ,t;z)|2(1ρeρnt)]E(ρ,t;z),(35)

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    ρet=(1ρeρnt)×[W(ρ,z;t)+σBUg|E(ρ,z;t)|2ρe]ρeτrec,(36)

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    Atri Halder, Vytautas Jukna, Matias Koivurova, Audrius Dubietis, Jari Turunen. Coherence of bulk-generated supercontinuum[J]. Photonics Research, 2019, 7(11): 1345
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