Resonant enhancement by a factor of over 20 of direct two-photon absorption from the ground state $^{7}\mathrm{F}_{6}$ to the excited state $^{5}\mathrm{G}_{6}$ of the 4 ${f}^{8}$ configuration of the ${\mathrm{Tb}}^{3+}$ ion at 40 200 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ has been observed in time-resolved experiments with two separate pulsed lasers. The results provide clear evidence for resonant enhancement of two-photon absorption in rare-earth compounds and imply a similar enhancement for Raman scattering and nonlinear-optical mixing. Two separate contributions to the direct transition moment were observed. When a single laser frequency was used, the intermediate states which made the largest contribution were from excited configurations of opposite parity; those intermediate states were far from resonance. Detailed two-frequency experiments showed, however, that near a single photon $^{7}\mathrm{F}_{6}$ ${\mathrm{\ensuremath{-}}}^{5}$ ${\mathrm{D}}_{4}$ resonance, a much stronger contribution arose from the 4 ${f}^{8}$ configuration $^{5}\mathrm{D}_{4}$ intermediate state. Two-photon absorption was clearly isolated from two-step (incoherent) excitation by varying the timing of two separately triggered lasers.Resonant enhancement by a factor of over 20 of direct two-photon absorption from the ground state $^{7}\mathrm{F}_{6}$ to the excited state $^{5}\mathrm{G}_{6}$ of the 4${f}^{8}$ configuration of the ${\mathrm{Tb}}^{3+}$ ion at 40 200 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ has been observed in time-resolved experiments with two separate pulsed lasers. The results provide clear evidence for resonant enhancement of two-photon absorption in rare-earth compounds and imply a similar enhancement for Raman scattering and nonlinear-optical mixing. Two separate contributions to the direct transition moment were observed. When a single laser frequency was used, the intermediate states which made the largest contribution were from excited configurations of opposite parity; those intermediate states were far from resonance. Detailed two-frequency experiments showed, however, that near a single photon $^{7}\mathrm{F}_{6}$${\mathrm{\ensuremath{-}}}^{5}$${\mathrm{D}}_{4}$ resonance, a much stronger contribution arose from the 4${f}^{8}$ configuration $^{5}\mathrm{D}_{4}$ intermediate state. Two-photon absorption was clearly isolated from two-step (incoherent) excitation by varying the timing of two separately triggered lasers.

Physical review. B, Condensed matterApr 1, 198920 citations

Two-photon resonance in spaced coherent fields

Sergiy I. Zub, A. S. Kleiman

Radiophysics and Quantum ElectronicsApr 1, 19790 citations

Nonlinear switching mechanism in nanostructures doped in photonic crystals

Mahi R. Singh

We have investigated the nonlinear switching mechanism in nanostructures doped in photonic crystals. The nonlinear phenomenon studied in this paper is the two-photon absorption process. A probe laser field is applied between the ground state and the next excited state of the nanoparticles to measure the two-photon absorption spectrum. A coupling field is applied between the two excited states of nanoparticles to control the two-photon process. It is found that when the decay resonance energy lies away from the photonic band edge the inhibition of two-photon absorption is observed. However, when the probe field is not resonance, the inhibition of two photons absorption is not observed. An interesting result is observed when the decay resonance energy lies near the band edge. It is found that the inhibition of the two-photon absorption disappears. It means that the phenomenon of two-photon absorption can be switched on and off by tuning the resonance energy within the lower band of the crystal. This mechanism can be used to make a new type of photonic switching devices using photonic crystals.We have investigated the nonlinear switching mechanism in nanostructures doped in photonic crystals. The nonlinear phenomenon studied in this paper is the two-photon absorption process. A probe laser field is applied between the ground state and the next excited state of the nanoparticles to measure the two-photon absorption spectrum. A coupling field is applied between the two excited states of nanoparticles to control the two-photon process. It is found that when the decay resonance energy lies away from the photonic band edge the inhibition of two-photon absorption is observed. However, when the probe field is not resonance, the inhibition of two photons absorption is not observed. An interesting result is observed when the decay resonance energy lies near the band edge. It is found that the inhibition of the two-photon absorption disappears. It means that the phenomenon of two-photon absorption can be switched on and off by tuning the resonance energy within the lower band of the crystal. This mechanism can be used to make a new type of photonic switching devices using photonic crystals.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIEJun 21, 20070 citations

Absorption Changes Induced by Off-Resonance Driving a Degenerate Two-Level System

Jin Sheng Cai, Haitao Zhou, Wenqi Wang +3 more

The alteration of atomic absorption via quantum coherence is observed in the degenerate two-level atomic system. It is shown that when the detuning of coupling field equals to that of probe light, i.e. two-photon resonance, the reduction of atomic absorption via electromagnetically induced transparency occurs. However, when we tune the coupling field to two-photon off-resonance, the enhancement of absorption is obtained for the probe field. The influences of one-photon detuning and intensity of coupling field on absorption are also experimentally demonstrated.The alteration of atomic absorption via quantum coherence is observed in the degenerate two-level atomic system. It is shown that when the detuning of coupling field equals to that of probe light, i.e. two-photon resonance, the reduction of atomic absorption via electromagnetically induced transparency occurs. However, when we tune the coupling field to two-photon off-resonance, the enhancement of absorption is obtained for the probe field. The influences of one-photon detuning and intensity of coupling field on absorption are also experimentally demonstrated.

Chinese Physics LettersMay 29, 20084 citations

Two-photon absorption in strong fields

Moorad Alexanian, S. Bose

Journal of LuminescenceNov 1, 19995 citations

Resonant enhancement by a factor of over 20 of direct two-photon absorption from the ground state

^{7}\mathrm{F}_{6}

to the excited state

^{5}\mathrm{G}_{6}

of the 4

{f}^{8}

configuration of the

{\mathrm{Tb}}^{3+}

ion at 40 200 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ has been observed in time-resolved experiments with two separate pulsed lasers. The results provide clear evidence for resonant enhancement of two-photon absorption in rare-earth compounds and imply a similar enhancement for Raman scattering and nonlinear-optical mixing. Two separate contributions to the direct transition moment were observed. When a single laser frequency was used, the intermediate states which made the largest contribution were from excited configurations of opposite parity; those intermediate states were far from resonance. Detailed two-frequency experiments showed, however, that near a single photon

^{7}\mathrm{F}_{6}

${\mathrm{\ensuremath{-}}}^{5}$

{\mathrm{D}}_{4}

resonance, a much stronger contribution arose from the 4

{f}^{8}

configuration

^{5}\mathrm{D}_{4}

intermediate state. Two-photon absorption was clearly isolated from two-step (incoherent) excitation by varying the timing of two separately triggered lasers.