36 research outputs found
Temperature Dependence of a Sub-wavelength Compact Graphene Plasmon-Slot Modulator
We investigate a plasmonic electro-optic modulator with an extinction ratio
exceeding 1 dB/um by engineering the optical mode to be in-plane with the
graphene layer, and show how lowering the operating temperature enables steeper
switching. We show how cooling Graphene enables steeping thus improving dynamic
energy consumption. Further, we show that multi-layer Graphene integrated with
a plasmonic slot waveguide allows for in-plane electric field components, and
3-dB device lengths as short as several hundred nanometers only. Compact
modulators approaching electronic length-scales pave a way for ultra-dense
photonic integrated circuits with smallest footprint
Exceeding octave tunable Terahertz waves with zepto-second level timing noise
Spectral purity of any millimeter wave (mmW) source is of the utmost interest
in low-noise applications. Optical synthesis via photomixing is an attractive
source for such mmWs, which usually involves expensive spectrally pure lasers
with narrow linewidths approaching monochromaticity due to their inherent
fabrication costs or specifications. Here, we report an alternative option for
enhancing the spectral purity of inexpensive semiconductor diode lasers via a
self-injection locking technique through corresponding Stokes waves from a
fiber Brillouin cavity exhibiting greatly improved phase noise levels and large
wavelength tunability of ~1.8 nm. We implement a system with two self-injected
diode lasers on a common Brillouin cavity aimed at difference frequency
generation in the mmW and THz region. We generate tunable sub-mmW (0.3 and 0.5
THz) waves by beating the self-injected two wavelength Stokes light on a
uni-travelling carrier photodiode and characterize the noise performance. The
sub-mmW features miniscule timing noise levels in the zepto-second (zs.Hz^-0.5)
scale outperforming the state of the art dissipative Kerr soliton based
micro-resonator setups while offering broader frequency tunability. These
results suggest a viable inexpensive alternative for mmW sources aimed at
low-noise applications featuring lab-scale footprints and rack-mounted
portability while paving the way for chip-scale photonic integration.Comment: 31 page
The genetics associated with Primary Congenital Glaucoma
Glaucoma is a progressive optic neuropathy; increased intraocular pressure (IOP) is a modifiable risk factor for primary congenital glaucoma (PCG). Increase IOP causes retinal and optic nerve compression and leads to gradual and irreversible loss of eyesight if left untreated. It is the second most leading cause of blindness. PCG mainly affects children up to the age of three years, and symptoms include epiphora, photalgia, swollen eyes, opaque corneas, blepharospasm, rupture in the retina and ocular nerve damage due to IOP. Early detection, management, and treatment are the keys to preventing vision loss from glaucoma. Many mutations have been discovered in Cytochrome P450 1B1 (CYP1B1) gene to be responsible for causing PCG, and there are still a lot of mutations to be discovered. In this review, we will discuss the genetic aspects of PCG and the most frequent mutations responsible for PCG in Pakistani children. PCG can be handled by decreasing IOP either by medication or by surgery. Genetic counselling plays a significant role in the establishment of proper management of PCG.Keywords: Primary Congenital Glaucoma; IOP; Cyp1b1; Mutation
60 Gbps real-time wireless communications at 300 GHz carrier using a Kerr microcomb
Future wireless communication infrastructure will rely on terahertz systems
that can support an increasing demand for large-bandwidth, ultra-fast wireless
data transfer. In order to satisfy this demand, compact, low-power, and low
noise sources of terahertz radiation are being developed. A promising route to
achieving this goal is combining photonic-integrated optical frequency combs
with fast photodiodes for difference frequency generation in the THz. Here, we
demonstrate wireless communications using a 300 GHz carrier wave generated via
photomixing of two optical tones originating from diode lasers that are
injection locked to a dissipative Kerr soliton frequency microcomb. We achieve
transfer rates of 80 Gbps using homodyne detection and 60 Gbps transmitting
simultaneously both data and clock signals in a dual-path wireless link. This
experimental demonstration paves a path towards low-noise and integrated
photonic millimeter-wave transceivers for future wireless communication
systems