Coherent detection of metal-metal terahertz quantum cascade lasers with improved emission characteristics

Coherent detection of emission from quantum cascade lasers with metal-metal waveguides is demonstrated through free-space coupling of a THz pulse to the sub-wavelength waveguide. We implement a simple, monolithic planar horn antenna design on the metal-metal waveguide that reduces the impedance mis-match to the waveguide. The resulting devices show up to 10 times more directed output power than conventional metal-metal waveguides. This enhanced coupling to free-space allows a more efficient injection of broad-band THz pulses into the waveguide. Through this, we are able to seed the laser emission and coherently detect the laser emission by electro-optic sampling

Predictive closed-loop service automation in O-RAN based network slicing

Network slicing provides introduces customized and agile network deployment for managing different service types for various verticals under the same infrastructure. To cater to the dynamic service requirements of these verticals and meet the required quality-of-service (QoS) mentioned in the service-level agreement (SLA), network slices need to be isolated through dedicated elements and resources. Additionally, allocated resources to these slices need to be continuously monitored and intelligently managed. This enables immediate detection and correction of any SLA violation to support automated service assurance in a closed-loop fashion. By reducing human intervention, intelligent and closed-loop resource management reduces the cost of offering flexible services. Resource management in a network shared among verticals (potentially administered by different providers), would be further facilitated through open and standardized interfaces. Open radio access network (O-RAN) is perhaps the most promising RAN architecture that inherits all the aforementioned features, namely intelligence, open and standard interfaces, and closed control loop. Inspired by this, in this article we provide closed loop and intelligent resource provisioning scheme for O-RAN slicing to prevent SLA violations. In order to maintain realism, a real-world dataset of a large operator is used to train a learning solution for optimizing resource utilization in the proposed closed-loop service automation process. Moreover, the deployment architecture and the corresponding flow that are cognizant of the O-RAN requirements are also discussed

Atomic Layer-controlled Nonlinear Terahertz Valleytronics in Dirac Semi-metal and Semiconductor PtSe2

Platinum diselenide (PtSe2) is a promising two-dimensional (2D) material for the terahertz (THz) range as, unlike other transition metal dichalcogenides (TMDs), its bandgap can be uniquely tuned from a semiconductor in the near-infrared to a semimetal with the number of atomic layers. This gives the material unique THz photonic properties that can be layer-engineered. Here, we demonstrate that a controlled THz nonlinearity - tuned from monolayer to bulk PtSe2 - can be realised in wafer size polycrystalline PtSe2 through the generation of ultrafast photocurrents and the engineering of the bandstructure valleys. This is combined with the PtSe2 layer interaction with the substrate for a broken material centro-symmetry permitting a second order nonlinearity. Further, we show layer-dependent circular dichroism, where the sign of the ultrafast currents and hence the phase of the emitted THz pulse can be controlled through the excitation of different bandstructure valleys. In particular, we show that a semimetal has a strong dichroism that is absent in the monolayer and few layer semiconducting limit. The microscopic origins of this TMD bandstructure engineering is highlighted through detailed DFT simulations and show that circular dichroism can be controlled when PtSe2 becomes a semimetal and when the K-valleys can be excited. As well as showing that PtSe2 is a promising material for THz generation through layer controlled optical nonlinearities, this work opens up new class of circular dichroism materials beyond the monolayer limit that has been the case of traditional TMDs, and impacting a range of domains from THz valleytronics, THz spintronics to harmonic generation

Tunable and compact dispersion compensation of broadband THz quantum cascade laser frequency combs

Miniaturized frequency combs (FCs) can be self-generated at terahertz (THz) frequencies through four-wave mixing in the cavity of a quantum cascade laser (QCL). To date, however, stable comb operation is only observed over a small operational current range in which the bias-depended chromatic dispersion is compensated. As most dispersion compensation techniques in the THz range are not tunable, this limits the spectral coverage of the comb and the emitted output power, restricting potential applications in, for example, metrology and ultrashort THz pulse generation. Here, we demonstrate an alternative architecture that provides a tunable, lithographically independent, control of the free-running coherence properties of THz QCL FCs. This is achieved by integrating an on-chip tightly coupled mirror with the QCL cavity, providing an external cavity and hence a tunable Gires Tournois interferometer (GTI). By finely adjusting the gap between the GTI and the back-facet of an ultra-broadband, high dynamic range QCL, we attain wide dispersion compensation regions, where stable and narrow (~3 kHz linewidth) single beatnotes extend over an operation range that is significantly larger than that of dispersion-dominated bare laser cavity counterparts. Significant reduction of the phase noise is registered over the whole QCL spectral bandwidth (1.35 THz). This agile accommodation of a tunable dispersion compensator will help enable uptake of QCL-combs for metrological, spectroscopic and quantum technology−oriented applications

Measuring the sampling coherence of a terahertz quantum cascade laser

The emission of a quantum cascade laser can be synchronized to the repetition rate of a femtosecond laser through the use of coherent injection seeding. This synchronization defines a sampling coherence between the terahertz laser emission and the femtosecond laser which enables coherent field detection. In this letter the sampling coherence is measured in the time-domain through the use of coherent and incoherent detection. For large seed amplitudes the emission is synchronized, while for small seed amplitudes the emission is non-synchronized. For intermediate seed amplitudes the emission exhibits a partial sampling coherence that is time-dependent

Mid-infrared ultrashort pulse generation

International audienc

Large-area photoconductive switches as emitters of terahertz pulses with fully electrically controlled linear polarization

International audienc

Ultrafast Pulse Generation from Quantum Cascade Lasers

Quantum cascade lasers (QCLs) have broken the spectral barriers of semiconductor lasers and enabled a range of applications in the mid-infrared (MIR) and terahertz (THz) regimes. However, until recently, generating ultrashort and intense pulses from QCLs has been difficult. This would be useful to study ultrafast processes in MIR and THz using the targeted wavelength-by-design properties of QCLs. Since the first demonstration in 2009, mode-locking of QCLs has undergone considerable development in the past decade, which includes revealing the underlying mechanism of pulse formation, the development of an ultrafast THz detection technique, and the invention of novel pulse compression technology, etc. Here, we review the history and recent progress of ultrafast pulse generation from QCLs in both the THz and MIR regimes

The Exploration of CRISPR within Infectious and Genetic Disease Research, Diagnoses, and Treatments

Prokaryotes, such as bacteria, have evolved defense mechanisms that protect them from foreign bodies invading and harming them.1 One of these mechanisms is the clustered regularly interspaced short palindromic repeats (CRISPR), alongside their accompanying CRISPR-associated (Cas) proteins.1 This system functions as an immune response that protects prokaryotes from viruses (and other harmful bodies) by detecting foreign genetic material invading them and disabling their functionality and ability to spread.2 Understanding the underlying mechanism of this immune response allowed scientists around the world to develop CRISPR and adapt it to various uses in gene editing, agriculture, and most recently, diagnosis of infectious and noninfectious diseases.2  The discovery of CRISPR as a biomedical disease detection tool has revolutionized modern day medicine and its accessibility. Infectious diseases are those that are caused by microorganisms and easily passed from one human to another. Currently, CRISPR--specifically the Cas13 protein system--is being utilized for disease detection and diagnosis through the detection and cleavage of specific ssRNA molecules. SHERLOCK, Specific High-sensitivity Enzymatic Reporter unLOCKing, is a specific breed of CRISPR Cas13a disease detection technology that has been deployed in West African countries to combat infectious disease such as Lassa Fever-- a disease caused by the zoonotic virus Lassa mammarenavirus that originates from the Mastomys natalensis rodent group.5 SHERLOCK’s ability to succeed in the detection and diagnosis of Lassa fever in West African countries that lack proper infrastructure relies on SHERLOCK’s accessibility and efficiency. Cas13a’s specificity and sensitivity in the detection of viral nucleic acids caters to the fact that Lassa Fever has high genetic diversity and requires highly sensitive tools to detect the disease.8 Moreover, genetic diseases are those caused by an error in the DNA of a person. The three main types include monogenic, complex, and chromosomal; the treatment and causes of the diseases are different for each type.17 There are still many obstacles when it comes to curing genetic diseases, yet scientists are using powerful tools such as CRISPR to help those who suffer from these diseases.18 The CRISPR Cas9 enzyme is one powerful system that can be used to disrupt, delete, or insert genes to help edit any errors in the genome and treat genetic diseases.23 It is comprised of the CRISPR-associated (Cas) enzyme and the guide RNA (gRNA), which work together to act as a scissor for the DNA.19 Adrenoleukodystrophy (ALD) is an X-linked genetic disease that is primarily due to a mutation within the ABCD1 gene. Currently, the Cas9 system provides a disease model in order to study the pathogenesis of ALD and target (and repair) the mutation causing this genetic disease

Assessment of accuracy and reliabilty of measurements obtained on 3D scanned models to conventional models

Aims and Objectives: To conclude on superior method of model fabrication and compare accuracy and the reliability of measurements obtained on 3D scanned models to conventional models. Materials and Methods: A total of 20 orthodontic study models were obtained from the department of orthodontics and dentofacial orthopaedics with a full set of permanent teeth from the right first molar to the left first molar and no anomalies of the crown. The plaster models were measured to the nearest 0.01 mm using the Aerospace Electronic Digital Caliper. Identical plaster models were scanned by placing each arch on the integrated rotary table (dental wings 3SERIES) .The acquired data was then processed and exported in stereo lithographic format using DWOS CAD/CAM software. Digital casts were later measured to the nearest 0.123 mm using 3D-Tool 64-Bit Free Viewer V13. Results: indicated that all measurements for the arch and tooth size measurements for both methods were highly correlated (r . 0.99; P\0.05).Cronbach α value of the data at T1 and T2 from incisal segment ,canine segment and the molar segment measured using the two methods was very close to the ideal value of 1, indicating high intraobserver reliability