Scott M. Hendrickson

Observation of two-photon absorption at low power levels using tapered optical fibers in rubidium vapor.

Nonlinear optical effects can be enhanced in tapered optical fibers with diameters less than the wavelength of the propagating light. Here we report on the observation of two-photon absorption using tapered fibers in rubidium vapor at power levels of less than 150 nW. Transit-time broadening produces two-photon absorption spectra with sharp peaks that are very different from conventional line shapes.

All-optical-switching demonstration using two-photon absorption and the Zeno effect

Low-contrast all-optical Zeno switching has been demonstrated in a silicon nitride microdisk resonator coupled to a hot atomic vapor. The device is based on the suppression of the field build-up within a microcavity due to non-degenerate two-photon absorption. This experiment used one beam in a resonator and one in free-space due to limitations related to device physics. These results suggest that a similar scheme with both beams resonant in the cavity would correspond to input power levels near 20 nW.

Analysis of enhanced two-photon absorption in tapered optical fibers

We analyze the rate of two-photon absorption in tapered optical fibers with diameters less than the wavelength of the incident light. The rate of two-photon absorption is shown to be enhanced due to the small mode volume of the tapered fiber and the relatively large overlap of the evanescent field with an atomic vapor that surrounds the tapered region. The two-photon absorption rate is optimized as a function of the diameter of the tapered region.

Integrated nonlinear photonics. Emerging applications and ongoing challenges - A mini review

We provide a review of recent progress in integrated nonlinear photonics with a focus on emerging applications in all-optical signal processing, ultra-low-power all-optical switching, and quantum information processing.

Enhanced two-photon absorption using entangled states and small mode volumes

We calculate the rate of two-photon absorption for frequency-entangled photons in a tapered optical fiber whose diameter is comparable to the wavelength of the light. The confinement of the electric field in the transverse direction increases the intensity associated with a single photon, while the two-photon absorption rate is further enhanced by the fact that the sum of the frequencies of the two photons is on resonance with the upper atomic state, even though each photon has a relatively broad linewidth. As a result, the photons are effectively confined in all three dimensions and the two-photon absorption rate for frequency-entangled photons in a tapered fiber was found to be comparable to that for unentangled photons in a microcavity with a small mode volume.

Holey Fiber Microcavities

Microcavities have been formed by placing mirrors on the ends of a short section of holey fiber. The resonant behavior of these devices was analyzed and their suitability for use in nonlinear-optics experiments was evaluated.

Microcavities Using Holey Fibers

Microcavities consisting of microstructured holey fibers and separate end mirrors have been constructed and tested. These devices exhibit excellent transverse-mode confinement and the ability to control the percentage of power guided outside of the fiber core. As a result, these devices may be a useful tool for enhancing the interaction between light and an atomic medium.

Portable non-invasive brain-computer interface: challenges and opportunities of optical modalities

The development of portable non-invasive brain computer interface technologies with higher spatio-temporal resolution has been motivated by the tremendous success seen with implanted devices. This talk will discuss efforts to overcome several major obstacles to viability including approaches that promise to improve spatial and temporal resolution. Optical approaches in particular will be highlighted and the potential benefits of both Blood-Oxygen Level Dependent (BOLD) and Fast Optical Signal (FOS) will be discussed. Early-stage research into the correlations between neural activity and FOS will be explored.

Observation of Low-Contrast All-Optical Switching in Silicon Nitride Microdisks Based on the Zeno Effect

Low-contrast all-optical Zeno switching has been demonstrated in a Silicon Nitride microdisk resonator surrounded by hot Rubidium vapor. The device is based on the suppression of the cavity field buildup due to non-degenerate two-photon absorption.

Observation of low-contrast all-optical switching based on the Zeno effect

Low-contrast all-optical Zeno switching has been demonstrated in a Silicon Nitride microdisk resonator coupled to hot Rubidium vapor. The device is based on the suppression of cavity power buildup due to non-degenerate two-photon absorption.