The design,fabrication and performance of narrow-band rugate minus filters are investigated in this paper.A method of fabricating graded-index coatings by rapidly alternating deposition of low(Si O_(2))and high(Al_(2)...The design,fabrication and performance of narrow-band rugate minus filters are investigated in this paper.A method of fabricating graded-index coatings by rapidly alternating deposition of low(Si O_(2))and high(Al_(2)O_(3))refractive index materials is presented to fabricate a rugate structure.The narrow-band rugate minus filter design and fabrication approaches are discussed in detail.The experimental results,including transmittance spectrum,surface damage test and damage morphology investigated with a scanning electron microscope,demonstrate the high performance of the as-fabricated spatial filter and confirm the feasibility of the fabrication method for narrow-band rugate minus filters.展开更多
We study a non-Hermitian two-level system with square-wave modulated dissipation and coupling.Based on the Floquet theory,we achieve an effective Hamiltonian from which the boundaries of the PT diagram are captured ex...We study a non-Hermitian two-level system with square-wave modulated dissipation and coupling.Based on the Floquet theory,we achieve an effective Hamiltonian from which the boundaries of the PT diagram are captured exactly.Two kinds of PT symmetry broken phases are found,whose effective Hamiltonians differ by a constant ω/2.For the time-periodic dissipation,a vanishingly small dissipation strength can lead to the PT symmetry breaking in the (2k-1)-photon resonance(△=(2k-1)ω),with k=1,2,3…It is worth noting that such a phenomenon can also happen in 2k-photon resonance(△=2kω),as long as the dissipation strengths or the driving times are imbalanced,namely γo≠-γ1orT0≠T1.For the time-periodic coupling,the weak dissipation induced$\mathcal{PT}$symmetry breaking occurs at △eff=kω,where △eff=(△0T0+△1 T1)/T.In the high frequency limit,the phase boundary is given by a simple relation γeff=±△eff.展开更多
基金Project supported by the Postdoctoral Science Foundation of China(Grant Nos.2016M592528 and 2016M602517)the Natural Science Foundation of Guangdong Province,China(Grant No.2017A030310130)the National Natural Science Foundation of China(Grant No.11705259)
文摘The design,fabrication and performance of narrow-band rugate minus filters are investigated in this paper.A method of fabricating graded-index coatings by rapidly alternating deposition of low(Si O_(2))and high(Al_(2)O_(3))refractive index materials is presented to fabricate a rugate structure.The narrow-band rugate minus filter design and fabrication approaches are discussed in detail.The experimental results,including transmittance spectrum,surface damage test and damage morphology investigated with a scanning electron microscope,demonstrate the high performance of the as-fabricated spatial filter and confirm the feasibility of the fabrication method for narrow-band rugate minus filters.
基金Supported by the National Natural Science Foundation of China(Grant Nos.11674285 and 11834005)the National Key Research and Development Program of China(Grant No.2017YFA0303002).
文摘We study a non-Hermitian two-level system with square-wave modulated dissipation and coupling.Based on the Floquet theory,we achieve an effective Hamiltonian from which the boundaries of the PT diagram are captured exactly.Two kinds of PT symmetry broken phases are found,whose effective Hamiltonians differ by a constant ω/2.For the time-periodic dissipation,a vanishingly small dissipation strength can lead to the PT symmetry breaking in the (2k-1)-photon resonance(△=(2k-1)ω),with k=1,2,3…It is worth noting that such a phenomenon can also happen in 2k-photon resonance(△=2kω),as long as the dissipation strengths or the driving times are imbalanced,namely γo≠-γ1orT0≠T1.For the time-periodic coupling,the weak dissipation induced$\mathcal{PT}$symmetry breaking occurs at △eff=kω,where △eff=(△0T0+△1 T1)/T.In the high frequency limit,the phase boundary is given by a simple relation γeff=±△eff.
