Compound heterozygosity for a frame shift mutation and a likely pathogenic sequence variant in the planar cell polarity­ciliogenesis gene WDPCP in a girl with polysyndactyly, coarctation of the aorta, and tongue hamartomas.

We report on a young girl with polysyndactyly, coarctation of the aorta, and tongue hamartomas. These features are similar to those reported in individuals with variant forms of orofaciodigital syndrome known as congenital heart defects, hamartomas of the tongue and polysyndactly (CHDHTP: OMIM 217085) [Örstavik et al., 1992] and orocardiodigital syndrome [Digilio et al., 1996]. Whole exome sequencing revealed that she is a compound heterozygote for a frame shift mutation and a likely pathogenic sequence variant in WDPCP, a gene that regulates planar cell polarity and ciliogenesis. Results of genotyping in her parents and unaffected siblings were consistent with autosomal recessive inheritance of the mutation and the WDPCP variant. These results suggest that disruption of planar cell polarity and ciliogenesis may result in this unusual form of orofaciodigital syndrome.

Terahertz bandwidth all-optical modulation and logic using multiexcitons in semiconductor nanocrystals.

Optical pumping of semiconductor nanocrystals with femtosecond pulse sequences was performed in order to modulate multiexciton populations. We show for the first time that control of multiexciton populations produces high speed modulation of stimulated emission. Upon the basis of the speed of multiexcitonic processes in nanocrystals, we show modulation rates approaching 1 THz by virtue of strong quantum confinement effects. Employing femtosecond optical pulse sequences, we demonstrate all-optical logic using these nanocrystals in two forms: an AND gate, and an inverter, a key step toward all optical signal processing.

Two-color two-dimensional electronic spectroscopy using dual acousto-optic pulse shapers for complete amplitude, phase, and polarization control of femtosecond laser pulses.

We demonstrate a dual pulse-shaper setup capable of independent polarization, phase, and amplitude control over each pulse. By using active phase stabilization, we achieve a phase stability of ~λ/314 between the two pulse shapers, making the dual-shaper setup suitable for both two-quantum and one-quantum measurements. The setup is compact and easily switchable between pump-probe and collinear geometries. We further illustrate the functionality of the dual-shaper setup by performing two-color 2D visible spectroscopy on colloidal CdSe quantum dots in pump-probe geometry.

A microscopic picture of surface charge trapping in semiconductor nanocrystals.

Several different compositions of semiconductor nanocrystals are subjected to numerous spectroscopic techniques to elucidate the nature of surface trapping in these systems. We find a consistent temperature-dependent relationship between core and surface photoluminescence intensity and marked differences in electron-phonon coupling for core and surface states based on ultrafast measurements and Resonance Raman studies, respectively. These results support a minimal model of surface charge trapping applicable to a range of nanocrystal systems involving a single surface state in which the trapped charge polarization leads to strong phonon couplings, with transitions between the surface and band edge excitonic states being governed by semiclassical electron-transfer theory.

Controlling piezoelectric response in semiconductor quantum dots via impulsive charge localization.

By direct observation of coherent acoustic phonons, we demonstrate a novel extrinsic piezoelectric response in colloidal CdSe semiconductor quantum dots. This response is driven by the migration of charges to the surface of the quantum dot on a vibrationally impulsive time scale. Surface- and fluence-dependent studies reveal that the observed carrier capture based piezo response is controllable and is at least an order of magnitude larger than the intrinsic piezo response of wurtzite CdSe.

Recording the sound of musical instruments with FBGs: the photonic pickup.

Fiber Bragg gratings (FBGs) have previously found many applications as strain and vibration sensors. Here we demonstrate that they may also be employed as pickups for musical instruments and, specifically, for acoustic guitars and solid-body electric guitars. By fixing the FBG to a vibrating part of the instrument's body, e.g., near the bridge of an acoustic guitar or on the headstock of a solid-body guitar, a number of sound recordings were made and compared to those obtained with either piezoelectric pickups or with magnetic induction pickups. The change in attenuation at the FBG's midreflection point is found to be correlated to the amplitude of vibration of the vibrating structure of the instrument. Acoustic frequency spectrum analysis supports the observation that the FBG acoustic transducer has a frequency response range that is comparable to those of commercial piezoelectric pickups. The recordings made with FBG pickups were of comparable quality to those obtained with other recording methods.

Control of phonons in semiconductor nanocrystals via femtosecond pulse chirp-influenced wavepacket dynamics and polarization.

The realistic electronic structure of semiconductor nanocrystals is characterized by excitonic fine structure and atomistic symmetry breakings that are challenging to resolve experimentally. Exciton-phonon coupling is one of the most sensitive measures of the excitonic wave functions of the nanocrystals. Here, we exploit this sensitivity via chirped pulse and polarization resolved femtosecond pump/probe spectroscopy of colloidal CdSe nanocrystals. Pulse chirp measurements and simulations are used to explore the contributions of excited- and ground-state vibrational wavepackets to the observed coherent phonons in the pump/probe signals. Polarization resolved pump/probe spectroscopy is used to explore electronic and vibrational polarization anisotropies. We find no electronic polarization anisotropy, whereas vibrational anisotropy is preserved.

Ultrafast electron trapping at the surface of semiconductor nanocrystals: excitonic and biexcitonic processes.

Aging of semiconductor nanocrystals (NCs) is well-known to attenuate the spontaneous photoluminescence from the band edge excitonic state by introduction of nonradiative trap states formed at the NC surface. In order to explore charge carrier dynamics dictated by the surface of the NC, femtosecond pump/probe spectroscopic experiments are performed on freshly synthesized and aged CdTe NCs. These experiments reveal fast electron trapping for aged CdTe NCs from the single excitonic state (X). Pump fluence dependence with excitonic state-resolved optical pumping enables directly populating the biexcitonic state (XX), which produces further accelerated electron trapping rates. This increase in electron trapping rate triggers coherent acoustic phonons by virtue of the ultrafast impulsive time scale of the surface trapping process. The observed trapping rates are discussed in terms of electron transfer theory.