A theoretical comparison of the breakdown behavior of In0.52Al0.48As and InP near-infrared single-photon avalanche photodiodes

We study the breakdown characteristics and timing statistics of InP and In0.52Al0.48As single-photon avalanche photodiodes (SPADs) with avalanche widths ranging from 0.2 to 1.0 mu m at room temperature using a random ionization path-length model. Our results show that, for a given avalanche width, the breakdown probability of In0.52Al0.48As SPADs increases faster with overbias than InP SPADs. When we compared their timing statistics, we observed that, for a given breakdown probability, InP requires a shorter time to reach breakdown and exhibits a smaller timing jitter than In0.52Al0.48As. However, due to the lower dark count probability and faster rise in breakdown probability with overbias, In0.52Al0.48As SPADs with avalanche widths <= 0.5 mu m are more suitable for single-photon detection at telecommunication wavelengths than InP SPADs. Moreover, we predict that, in InP SPADs with avalanche widths <= 0.3 mu m and In0.52Al0.48As SPADs with avalanche widths <= 0.2 mu m, the dark count probability is higher than the photon count probability for all applied biases

A proposed minimum skill set for university graduates to meet the informatics needs and challenges of the "-omics" era

10.1186/1471-2164-10-S3-S36BMC Genomics10SUPPL. 3BGME

A STUDY OF MUSCLE FATIGUE FOR PROLONGED STANDING USING SURFACE ELECTROMYOGRAM: A CASE STUDY

The purpose of this study is to use surface Electromyogram (sEMG) for the investigation of muscle activities in the lower limbs of human subjects during prolonged standing. It has been suggested that prolonged standing leads to muscle fatigue. This is a single-subject investigation that involves a healthy female subject, performing 8 similar quiet standing trials for one hour on separate days. sEMG methods were used to record myoelectric activity from the Tibialis Anterior (TA), Peroneus Longus (PE) and Gastrocnemius muscles (GA). In the preliminary analysis, a progressive decrease in the median frequency curve has been observed in all muscle groups investigated and the trend was statistically significant (p < 0.05). The results of this study confirmed that muscle fatigue sets in during prolonged standing

Avalanche Breakdown Timing Statistics for Silicon Single Photon Avalanche Diodes

CCBY Silicon-based Single Photon Avalanche Diodes (SPADs) are widely used as single photon detectors of visible and near infrared photons. There has however been a lack of models accurately interpreting the physics of impact ionization (the mechanism behind avalanche breakdown) for these devices. In this work, we present a statistical simulation model for silicon SPADs that is capable of predicting breakdown probability, mean time to breakdown and timing jitter. Our model inherently incorporates carriers & #x0027; dead space due to phonon scattering and allows for non-uniform electric fields. Model validation included avalanche gain, excess noise factor, breakdown voltage, breakdown probability, and timing statistics. Simulating an n on-p and a p-on-n SPAD design using our model, we found that the n-on-p design offers significantly improved mean time to breakdown and timing jitter characteristics. For a breakdown probability of 0.5, mean time to breakdown and timing jitter from the n-on-p design were 3 and 4 times smaller compared to those from the p on n design. The data reported in this paper is available from the ORDA digital repository (DOI: 10.15131/shef.data.4823248)

Effects of carrier injection profile on low noise thin Al0.85Ga0.15As0.56Sb0.44 avalanche photodiodes

Avalanche photodiodes (APDs) with thin avalanche regions have shown low excess noise characteristics and high gain-bandwidth products, so they are suited for long-haul optical communications. In this work, we investigated how carrier injection profile affects the avalanche gain and excess noise factors of Al0.85Ga0.15As0.56Sb0.44 (lattice-matched to InP substrates) p-i-n and n-i-p diodes with total depletion widths of 145-240 nm. Different carrier injection profiles were achieved by using light with wavelengths of 420, 543 and 633nm. For p-i-n diodes, shorter wavelength light produces higher avalanche gains for a given reverse bias and lower excess noise factors at a given gain, compared to longer wavelength light. Thus, using 420 nm light on the p-i-n diodes, corresponding to pure electron injection conditions, gave the highest gain and lowest excess noise. In n-i-p diodes, pure hole injection yields significantly lower gain and higher excess noise, compared to mixed carrier injection. These show that the electron ionization coefficient, α, is higher than the hole ionization coefficient, β. Using pure electron injection, excess noise factor characteristics with effective ionization ratios, keff, of 0.08-0.1 were obtained. This is significantly lower than those of InP and In0.52Al0.48As, the commonly used avalanche materials combined with In0.53Ga0.47As absorber. The data reported in this paper is available from the ORDA digital repository (DOI: 10.15131/shef. DATA: 5787318)

Continuous-variable quantum teleportation of entanglement

Entangled coherent states can be used to determine the entanglement fidelity for a device that is designed to teleport coherent states. This entanglement fidelity is universal, in that the calculation is independent of the use of entangled coherent states and applies generally to the teleportation of entanglement using coherent states. The average fidelity is shown to be a poor indicator of the capability of teleporting entanglement; i.e., very high average fidelity for the quantum teleportation apparatus can still result in low entanglement fidelity for one mode of the two-mode entangled coherent state.Comment: 5 pages, 1 figure, published versio

Therapeutic capsule endoscopy: Opportunities and challenges

10.1260/2040-2295.2.4.459Journal of Healthcare Engineering24459-47

Neuro-ophthalmic complications of vestibular schwannoma resection : current perspectives

Vestibular schwannomas (VSs), also called acoustic neuromas, are benign intracranial neoplasms of the vestibulocochlear (VIII) cranial nerve. Management options include “wait-and-scan,” stereotactic radiosurgery and surgical resection. Due to the proximity of the VIII nerve to the facial (VII) nerve in the cerebello-pontine angle, the VII nerve is particularly vulnerable to the effects of surgical resection. This can result in poor eye closure, lagophthalmos and resultant corneal exposure post VS resection. Additionally, compression from the tumor or resection can cause trigeminal (V) nerve damage and a desensate cornea. The combination of an exposed and desensate cornea puts the eye at risk of serious ocular complications including persistent epithelial defects, corneal ulceration, corneal vascularization, corneal melting and potential perforation. The abducens (VI) nerve can be affected by a large intracranial VS causing raised intracranial pressure (a false localizing sign) or as a result of damage to the VI nerve at the time of resection. Other types of neurogenic strabismus are rare and typically transient. Contralaterally beating nystagmus as a consequence of vestibular dysfunction is common post-operatively. This generally settles to pre-operative levels as central compensation occurs. Ipsilaterally beating nystagmus post-operatively should prompt investigation for post-operative cerebrovascular complications. Papilledema (and subsequent optic atrophy) can occur as a result of a large VS causing raised intracranial pressure. Where papilledema follows surgical resection of a VS, it can indicate that cerebral venous sinus thrombosis has occurred. Poor visual function following VS resection can result as a combination of all these potential complications and is more likely with larger tumors

Trapping and cooling single atoms with far-off resonance intracavity doughnut modes

We investigate cooling and trapping of single atoms inside an optical cavity using a quasi-resonant field and a far-off resonant mode of the Laguerre-Gauss type. The far-off resonant doughnut mode provides an efficient trapping in the case when it shifts the atomic internal ground and excited state in the same way, which is particularly useful for quantum information applications of cavity quantum electrodynamics (QED) systems. Long trapping times can be achieved, as shown by full 3-D simulations of the quasi-classical motion inside the resonator.Comment: 18 pages, 18 figures, RevTe

Cooling of a single atom in an optical trap inside a resonator

We present detailed discussions of cooling and trapping mechanisms for an atom in an optical trap inside an optical cavity, as relevant to recent experiments. The interference pattern of cavity QED and trapping fields in space makes the trapping wells distinguishable from one another. This adds considerable flexibility to creating effective trapping and cooling conditions and to detection possibilities. Friction and diffusion coefficients are calculated in and beyond the low excitation limit and full 3-D simulations of the quasiclassical motion of a Cs atom are performed.Comment: One more figure and one more autho