In this thesis we study ultrafast all-optical switching of microcavities. We employ the electronic Kerr effect to switch the resonance frequency of microcavities operating at telecom wavelengths. We observe the fastest possible switching of a microcavity resonance within 300 fs. The switching speed is only determined by the cavity storage time; only limited by the speed of light and not by material related relaxation properties. For the first time, we derive and measure the non-degenerate three-photon absorption coefficient of GaAs. Using the measured nondegenerate two- and three-photon absorption coefficients we estimate that the trigger laser only lose 22 aJ/µm2 at each switch event, which is a record level of minimum energy loss per switch event. We achieve repeated switching of microcavities within 700 fs, corresponding to THz rates. Therefore to best of our knowledge, we have broken the THz clock rate barrier experimentally using semiconductor cavities for the first time. The THz clock rate that we achieve can be a solution for information technology that is exploring ways to meet the growth rate of the computational demand. The color of light is a main visual perception of light for humans. Indeed, a simple measure for the color of light is given by its frequency since frequency of light is invariant from one medium to another. Although the propagation of light is strongly modified using nanostructures such as photonic crystals and microcavities, the frequency of light stays constant in these structures as well. The color of light can be changed in a nonlinear process or by absorption and re-emission. Using microcavities light is conveniently confined in space and then by dynamical control the medium can be changed to act as a nonlinear medium for light. Remarkably, we show that during the switching of cavities we achieve both up and down frequency conversion of light. The frequency conversion that we observe is a result of the instantaneous refractive index change achieved using the electronic Kerr effect. We achieve repeated frequency conversion at THz rates and generate blue- and red-shifted light pulses at this rate.
In this thesis we study ultrafast all-optical switching of microcavities. We employ the electronic Kerr effect to switch the resonance frequency of microcavities operating at telecom wavelengths. We observe the fastest possible switching of a microcavity resonance within 300 fs. The switching speed is only determined by the cavity storage time; only limited by the speed of light and not by material related relaxation properties. For the first time, we derive and measure the non-degenerate three-photon absorption coefficient of GaAs. Using the measured nondegenerate two- and three-photon absorption coefficients we estimate that the trigger laser only lose 22 aJ/µm2 at each switch event, which is a record level of minimum energy loss per switch event. We achieve repeated switching of microcavities within 700 fs, corresponding to THz rates. Therefore to best of our knowledge, we have broken the THz clock rate barrier experimentally using semiconductor cavities for the first time. The THz clock rate that we achieve can be a solution for information technology that is exploring ways to meet the growth rate of the computational demand. The color of light is a main visual perception of light for humans. Indeed, a simple measure for the color of light is given by its frequency since frequency of light is invariant from one medium to another. Although the propagation of light is strongly modified using nanostructures such as photonic crystals and microcavities, the frequency of light stays constant in these structures as well. The color of light can be changed in a nonlinear process or by absorption and re-emission. Using microcavities light is conveniently confined in space and then by dynamical control the medium can be changed to act as a nonlinear medium for light. Remarkably, we show that during the switching of cavities we achieve both up and down frequency conversion of light. The frequency conversion that we observe is a result of the instantaneous refractive index change achieved using the electronic Kerr effect. We achieve repeated frequency conversion at THz rates and generate blue- and red-shifted light pulses at this rate.
We have repeatedly and reproducibly switched a GaAs-AlAs planar microcavity operating in the "original" telecom band by exploiting the virtually instantaneous electronic Kerr effect. We achieve repetition times as fast as 300 fs, thereby breaking the terahertz modulation barrier. The rate of the switching in our experiments is only determined by optics and not by material-related relaxation. Our results offer opportunities for fundamental studies of cavity quantum electrodynamics and optical information processing in the subpicosecond time scale.
Changing the color of light in a small mode volume is essential for applications that require on-chip operation. Microcavities are profound structures given their property to confine light in a small mode volume. Here, I numerically investigate the frequency conversion of light in a microcavity and show that the frequency converted light intensity is distinguished from an open medium such as an optical fiber or a nonlinear crystal. I observe that the frequency converted light intensity increases with increased rate of change of the refractive index of the microcavity. Notably, this study shows that the intensity of the frequency converted light is maximized when the duration of the index perturbation is matched to the cavity storage time. The results provide a set of optimum parameters for increasing frequency conversion efficiency inside a microcavity.
Ever since the advent of nonlinear optics, the generation of light by frequency-conversion is drawing continued attention, and leading to emerging applications such as supercontinuum sources for ultra stable clocks and advanced microscopy. A modern approach to frequency-conversion is to switch light confined in micro- and nanocavity resonances to enable on-chip operation. Supposedly, nonlinear frequency conversion in such confined media differs from traditional non-linear optics in three key features regarding output spectrum, frequency shift, and critical time scale. Therefore, we switch GaAs-AlAs microcavities by the electronic Kerr effect, and study a range of quality factors to bridge the confined and the traditional non-linear regimes. We uncover the key role of the density of vacuum fluctuations, i.e., the local density of optical states (LDOS) for newly generated frequencies, a concept inspired by cavity quantum electrodynamics (cQED). As a result, we succeed to establish a framework, which not only describes nonlinear optics both in traditional bulk and in confined media but also opens a new control dimension in changing the color of light.
Focus Serial: Frontiers of Nonlinear Optics Nonlinear photonic-crystal microresonators offer unique fundamental ways of enhancing a variety of nonlinear optical processes. This enhancement improves the performance of nonlinear optical devices to such an extent that their corresponding operation powers and switching times are suitable for their implementation in realistic ultrafast integrated optical devices. Here, we review three different nonlinear optical phenomena that can be strongly enhanced in photonic crystal microcavities. First, we discuss a system in which this enhancement has been successfully demonstrated both theoretically and experimentally, namely, a photonic crystal cavity showing optical bistability properties. In this part, we also present the physical basis for this dramatic improvement with respect to the case of traditional nonlinear devices based on nonlinear Fabry-Perot etalons. Secondly, we show how nonlinear photonic crystal cavities can be also used to obtain complete second-harmonic frequency conversion at very low input powers. Finally, we demonstrate that the nonlinear susceptibility of materials can be strongly modified via the so-called Purcell effect, present in the resonant cavities under study.
The ability to control and manipulate light with light is crucial for optical information and communication technology. However, all-optical information processing is hindered by the absence of interactions between photons in linear materials. Nonlinear materials mediate effective photon-photon interactions, but require large light intensity. Optical resonators store and confine light for many optical cycles, which increases the interaction time and reduces the nonlinearity threshold. However, monolithic optical resonators have limited variability of the intra-cavity medium. Instead, a wide variety of materials can be easily integrated in tunable open-access microcavities, making them an ideal platform for exploring novel materials for nonlinear optics. In this thesis, we present experiments using coherently driven tunable open-access microcavities hosting either oil or a perovskite semiconductor. In Chapter 2 we demonstrate steady-state room-temperature superfluidity of photons in an oil-filled cavity, and reveal how the fluid dynamics are influenced by the nonlocality of the effective interactions mediated by the oil. Chapters 3 and 4 describe experiments using a halide perovskite semiconductor in an open-access microcavity in a closed-cycle cryostat. We demonstrate continuous-wave nonlinearity in the halide perovskite material through optical bistability, and reveal signatures of a phase transition in the temperature dependence of the nonlinearity strength. Next we investigate the emergence of irreversibility in the bistable switching of our perovskite cavity. Finally, we present in Chapter 5 experimental observations of fast nonlinearity-enabled oscillations in the light intensity, that occur despite the slowness of thermal nonlinearity of the oil.
Impressive progress has been achieved in controlling the spontaneous emission rate for emitters in Nanophotonic structures, such as microcavities, photonic crystals and nano-antennas. In all cases, however, the modification of the emission is stationary in time. Thus, the emission rate is time-independent and the distribution of photon emission times are stochastic and follow an exponential distribution in the weak coupling regime. In this paper, by using fast all-optical switching of a microcavity, the cavity resonance is tuned within tens of picosesonds. This drastically changes the local optical density of states at the emission frequency within the emission lifetime of the emitters. This paper theoretically studied an ensemble of two-level sources with a time dependent decay rate and have derived the excited state population and emitted intensity as a function of time for continuous wave and pulsed excitation. Deterministic bursts of dramatically enhanced or inhibited emission intensity within short intervals. Thereby, we control the photon distribution to show behavior that strongly deviates from single exponential decay. This can be used to protect quantum information systems against decoherence and to realize non-Markovian dynamics in cavity quantum electrodynamics.