1,721,032 research outputs found
Laser gyroscope precisely tracks the Earth’s rotation
No full textPrecise measurements of the length of an Earth day are essential for understanding global mass transport phenomena. A ring laser gyroscope provides absolute measurements of variations in the length of the day with a resolution of 5 parts per billion over a 14-day period
PCM aided PICs: a Crucial Migration Towards Cutting-Edge Signal Processing
No full textAdvanced signal processing is paramount in different sectors, including wireless communications, neural networks, artificial intelligence, quantum computing, medical diagnosis, internet of things, etc. With its rapid growth, silicon photonic integrated circuit (PIC) based signal processors are established to be a strong competitor to their electronic counterparts, owing to various advantages like small footprint, low energy consumption, immunity to electromagnetic interference, high speed operation, CMOS compatibility, etc. However, traditional means of realizing programmability, such as thermo-optic and carrier dispersion often suffer from large footprints due to small modulation in refractive index. Further, the volatile nature of such a programming mechanism requires a continuous power supply. In this context, a new generation of low-loss, large index contrast, non-volatile phase change materials (PCMs) are showing great promise towards upscaling the silicon photonic signal processing units. Here, a compact resonator cavity-based signal processing unit is proposed through advantageous integration of a hybrid plasmonic mode in the silicon photonic domain and low-loss PCM. Excellent switching performance with extinction ratio > 30 dB and low energy consumption of 7.6 nJ, highlighting its promise towards different sectors such as telecommunications, neural networks, etc
Parametric analysis of 2D guided-wave photonic band gap structures
Full text linkThe parametric analysis of the electromagnetic properties of 2D guided wave photonic band gap structures is reported with the aim of providing a valid tool for the optimal design. The modelling approach is based on the Bloch-Floquet method. Different lattice configurations and geometrical parameters are considered. An optimum value for the ratio between the hole (or rod) radius and the lattice constant does exist and the calculation demonstrated that it is almost independent from the etching depth, only depending on the lattice type. The results are suitable for the design optimisation of photonic crystal reflectors to be used in integrated optical devices
Coupled ring resonators at fibonacci frequencies
No full textSince the Middle Ages, Fibonacci (FB) numbers have attracted the interest of many scientists. In the recent years, a great research effort has been spent on the applications of FB numbers and sequences. It has been demonstrated that also some properties of resonant electronic systems are related to FB numbers. In this paper, an optical resonant device, with resonant frequencies spaced according to the FB series, is proposed, demonstrating the analogy with coupled electrical resonant cells. The proposed device consists of a silicon-based photonic coupled ring resonators, properly designed such that the resonant frequencies correspond to the sequence: 0.618·ω0,⋯, ω0, ⋯, 1.618·ω0, where ω0 is the operating angular frequency [rad/s]. These features make the device suitable for several applications, e.g. frequency-based quantum cryptography for the transmission of quantum information
Optical modelling of a Si-based DBR laser source using a nanocrystal Si-sensitized Er-doped silica rib waveguide in the C-band
Full text linkThe availability of reliable silicon-based laser sources is at the basis of the integration of photonic and microelectronic devices on a single chip with consequent development of wavelength division multiplexing telecommunication systems. A high efficiency Si-based laser source with good stability at room temperature would encourage and push the large scale of integration of electronic and photonic devices within a single chip.
Several techniques have been proposed for generating light with an internal quantum efficiency some order of magnitude greater than that typical of silicon (10-6) by using either electrical or optical pumping. Among them we mention the improvement of some fabrication process steps, reduction of the channels of non-radiative recombination, quantum confinement, the use of silicon nanocrystals (Si-ncs) incorporated in a silica matrix. This last technique is used in combination with Er3+ doping to generate light emission around 1500 nm in silicon, since Er-doped Si-ncs behave as electron-hole pairs trap, and the presence of Er shifts the emission peak to around 1500 nm. In this paper we have pointed out the optical model of a Si-based DBR laser including a Si-ncs Er-doped SiO2 rib waveguide, working at a wavelength in C-band. In particular, after a brief description of the structural and optical properties of the silicon crystals, we report on the model and design of the Er:Si-nc/SiO2 rib waveguide, of the optical cavity and of the Bragg mirrors. Numerical results are in good agreement with the literature
Resonant optical gyro: Monolithic vs. hybrid integration
No full textSince several decades, angular velocity sensors are considered crucial devices in a wide range of vehicles such as military and civil airplanes, military ships, submarines, satellites, space launchers, and long-range ballistic missiles. The interest towards miniaturized gyroscopes for aerospace and defense industry has given rise to an increasing research effort aiming at the scaling of optical gyros through integrated optical technologies. In particular, the resonant optical gyro (ROG) has been identified as the ideal candidate for a new generation photonic angular velocity sensor. Two technological approaches are available to implement the ROGs, i.e., the hybrid integration of optoelectronic components manufactured on different substrates or the monolithic integration of all components on a single chip. The two options are critically discussed and compared in this paper with a special attention on integrated gyroscopes (gyro-on-a-chip, GoC) in silica on silicon and indium phosphide that have been recently theoretically and experimentally studied, demonstrating promising results
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Modelling and design of an electrically-pumped DFB laser based on an erbium-doped silicon-rich silicon oxide layer embedded in a slot waveguide
No full textThe development of a high-performance DFB laser compatible with the CMOS technology is essential for the future development of silicon photonics. In this paper the preliminary results on modelling and design of a distributed feedback silicon laser are reported. The gain medium, which is a layer of erbium doped silicon-rich silicon oxide, is embedded in a horizontal slot waveguide. The designed device includes a grating with 140 periods and a quarter-wave phase shift at the grating middle. The threshold gain coefficient of the laser is 0.4 cm(-1) and the emission wavelength is very close to 1.55 mu m
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