5 research outputs found
Thermo-optical dynamics of a nonlinear GaInP photonic crystal nanocavity depend on the optical mode profile
We measure the dynamics of the thermo-optical nonlinearity of both a mode-gap
nanocavity and a delocalized mode in a
GaInP photonic crystal membrane. We model
these results in terms of heat transport and thermo-optical response in the
material. By step-modulating the optical input power we push the nonlinear
resonance to jump between stable branches of its response curve, causing
bistable switching. An overshoot of the intensity followed by a relaxation tail
is observed upon bistable switching. In this way, the thermal relaxation of
both the localized resonance and the delocalized resonance is measured.
Significant difference in decay time is observed and related to the optical
mode profile of the resonance. We reproduce the observed transient behavior
with our thermo-optical model, implementing a non-instantaneous nonlinearity,
and taking into account the optical mode profile of the resonance, as
experimentally measured
Mode mapping Q > 500 000 photonic crystal nanocavities using free carrier absorption
We demonstrate a nonlinear photomodulation spectroscopy method to image the
mode profile of a high-Q photonic crystal resonator (PhCR). This far-field
imaging method is suitable for ultrahigh-Q cavities which we demonstrate on a Q
= 619000 PhCR. We scan the PhCR surface with a 405 nm pump beam that modulates
the refractive index by local thermal tuning, while probing the response of the
resonance. We enhance resolution by probing at high power, using the
thermo-optical nonlinearity of the PhCR. Spatial resolution of the
thermo-optical effect is typically constrained by the broad thermal profile of
the optical pump. Here we go beyond the thermal limit and show that we can
approach the diffraction limit of the pump light. This is due to free carrier
absorption that heats up the PhCR only when there is overlap between the
optical pump spot and the optical mode profile. This is supported with a
thermo-optical model that reproduces the high-resolution mode mapping. Results
reveal that the observed enhanced resolution is reached for surprisingly low
carrier density
Mode Mapping Photonic Crystal Nanocavities with Q>5Ć105 Using Free-Carrier Absorption
We demonstrate a nonlinear photomodulation spectroscopy method to image the mode profile of a high-Q photonic crystal resonator (PhCR). This far-field imaging method is suitable for ultrahigh-Q cavities which we demonstrate on a Q=619000 PhCR. We scan the PhCR surface with a 405-nm pump beam that modulates the refractive index by local thermal tuning, while probing the response of the resonance. We enhance resolution by probing at high power, using the thermo-optical nonlinearity of the PhCR. Spatial resolution of the thermo-optical effect is typically constrained by the broad thermal profile of the optical pump. Here we go beyond the thermal limit and show that we can approach the diffraction limit of the pump light. This is due to free carrier absorption that heats up the PhCR only when there is overlap between the optical pump spot and the optical mode profile. This is supported with a thermo-optical model that reproduces the high-resolution mode mapping. Results reveal that the observed enhanced resolution is reached for surprisingly low carrier density
Thermo-optical dynamics of a nonlinear GaInP photonic crystal nanocavity depend on the optical mode profile
We measure the dynamics of the thermo-optical nonlinearity of both a mode-gap nanocavity and a delocalized mode in a Ga0.51In0.49P photonic crystal membrane. We model these results in terms of heat transport and thermo-optical response in the material. By step-modulating the optical input power we push the nonlinear resonance to jump between stable branches of its response curve, causing bistable switching. An overshoot of the intensity followed by a relaxation tail is observed upon bistable switching. In this way, the thermal relaxation of both the localized resonance and the delocalized resonance is measured. Significant difference in decay time is observed and related to the optical mode profile of the resonance. We reproduce the observed transient behavior with our thermo-optical model, implementing a non-instantaneous nonlinearity, and taking into account the optical mode profile of the resonance, as experimentally measured
Mode Mapping Photonic Crystal Nanocavities with Q>5Ć105 Using Free-Carrier Absorption
We demonstrate a nonlinear photomodulation spectroscopy method to image the mode profile of a high-Q photonic crystal resonator (PhCR). This far-field imaging method is suitable for ultrahigh-Q cavities which we demonstrate on a Q=619000 PhCR. We scan the PhCR surface with a 405-nm pump beam that modulates the refractive index by local thermal tuning, while probing the response of the resonance. We enhance resolution by probing at high power, using the thermo-optical nonlinearity of the PhCR. Spatial resolution of the thermo-optical effect is typically constrained by the broad thermal profile of the optical pump. Here we go beyond the thermal limit and show that we can approach the diffraction limit of the pump light. This is due to free carrier absorption that heats up the PhCR only when there is overlap between the optical pump spot and the optical mode profile. This is supported with a thermo-optical model that reproduces the high-resolution mode mapping. Results reveal that the observed enhanced resolution is reached for surprisingly low carrier density