Gap In Transmission Research Articles

Accelerating to zero: Closing the gap in detection, cure, and transmission to achieve malaria eradication

Accelerating to zero: Closing the gap in detection, cure, and transmission to achieve malaria eradication

Transmission measurement of the photonic band gap of GaN photonic crystal slabs

A high-contrast-ratio (30 dB) photonic band gap in the near-infrared transmission of hole-type GaN two-dimensional photonic crystals (PhCs) is reported. These crystals are deeply etched in a 650 nm thick GaN layer grown on sapphire. A comparison of the measured spectrum with finite difference time domain simulations gives quantitative agreement for the dielectric band and qualitative agreement for the air band. The particular behavior of the air band arises from the relatively low index contrast between the GaN layer and the sapphire substrate. Our results call for extension of the operation of GaN PhCs to the visible range.

Indirect transitions, free and impurity-bound excitons in gallium phosphide: A revisit with modulation and photoluminescence spectroscopy

The momentum conserving indirect excitonic transitions, from the Γ15 valence band maximum to the conduction band minima close to the X1 point in the Brillouin zone have been measured for GaP in piezo-modulated transmission. At 6 K, excitonic signatures due to phonon emission are observed at Egx+ℏωph for TA(X), LA(X), and TO(X) phonons (Egx=free exciton band gap), whereas at 120 K signatures for both absorption and emission of LA(X) and TA(X) phonons appear. These observations yield Egx=2.3301(4) eV at 6 K. In several GaP specimens, signatures A and/or C for excitons bound to sulfur (S) and/or nitrogen (N) impurities, respectively, are observed in the piezo-modulated transmission. A parallel investigation of the spectra of recombination radiation reveals emission lines for excitons bound to S and N as well as their phonon sidebands. The phonon replicas of N consist of sharp lines in combination with the zone center optical phonons observed in the first order Raman spectrum (LOΓ and TOΓ). In addition, broader replicas are observed for the A line in combination with acoustic and optical phonon branches (A-LA, A-TA, A-X). The phonon energies obtained from both piezo-modulation and photoluminescence experiments are compared with those reported in the literature. Finally, the suppression of S diffusion from a GaP substrate into a GaP epilayer achieved with an intervening GaP/AlGaP superlattice is demonstrated in both modulation and photoluminescence experiments.

A surgical and anatomical classification using a polyethylene tube prosthesis in stapes surgery.

The success of operative mobilization of the stapes for otosclerotic deafness depends upon restoration of sound conduction via the ossicular chain to the cochlea. The conductive impairment of sound in cases of otosclerosis is due to ankylosis of the stapes. In the past, improved hearing would result through surgery of the stapes only if the footplate were loosened and remained in continuity with the crura. This meant that there could not be a break in the transmission of sound from the tympanic membrane to the cochlea if improved hearing was to be obtained. Unfortunately, since the degree of stapes fixation and its anatomic structure vary, its delicate crura would separate from the footplate before it could be mobilized; thus, even if the footplate were mobilized, the gap in sound transmission prevented all possibility of improved hearing. This, briefly, was the reason for the operative failure in so many patients who