Reference UVC LED Source

A compact reference UVC source based on commercially available LED has been developed. The article presents the design and results of the study of the optical characteristics of the radiation of the reference UVC LED source. The source provides a power density of radiation up to 400 μW/cm2 on area of 3×3 mm with inhomogeneity of 1.5 %.The emission band of a source with a maximum of 265 nm is predominantly 97 % in the UV-C spectrum region, and a small part of it is inUV-B and UV-A regions, 2.7 % and 0.3 %, respectively. The use of ComboSource for laser diodes allowed to precisionally stabilize the injection current and temperature of the LED. It is shown that overheating of the active region of the selected UV LED is only 10°C - 25°C at the recommended injection currents due to the peculiarities of its design. This results in a low degradation rate of the UV LED. Possible ways to improve the characteristics of the reference UVCsource are discussed.

A pulse amplitude modulation scheme based on in-line semiconductor optical amplifiers (SOAs) for optical soliton systems

<p>The objective of this work is to simulate a pulse amplitude modulation (PAM) scheme based on in-line semiconductor optical amplifiers for optical soliton systems. The max. power for soliton systems, based on various bits/symbol PAM modulation schemes after a fiber length of 100 km, is simulated and clarified. In addition to the max. Q factor for soliton systems, PAM modulation schemes with various in-line SOA injection currents and a fiber length of 100 km are also simulated and demonstrated in the results. The total electrical power after photo-detectors for soliton systems, based on PAM modulation schemes with various in-line SOA injection currents and a fiber length of 100 km, is also simulated and clarified in the results. The study emphasizes that the higher the SOA injection current, the higher the electrical power and the lower the Q factor that can be achieved in the soliton system.</p>

Hexagonal transverse-coupled-cavity VCSEL redefining the high-speed lasers

Vertical-cavity surface-emitting lasers (VCSELs) have emerged as a vital approach for realizing energy-efficient and high-speed optical interconnects in the data centers and supercomputers. Indeed, VCSELs are the most suitable mass production lasers in terms of cost-effectiveness and reliability. However, there are still key challenges that prevent achieving modulation speeds beyond 30s GHz. Here, we propose a novel VCSEL design of a hexagonal transverse-coupled-cavity adiabatically coupled through a central cavity. Following this scheme, we show a prototype demonstrating a 3-dB roll-off modulation bandwidth of 45 GHz, which is five times greater than a conventional VCSEL fabricated on the same epiwafer structure. This design harnesses the Vernier effect to increase the laser’s aperture and therefore is capable of maintaining single-mode operation of the laser for high injection currents, hence extending the dynamic roll-off point and offering increases power output. Simultaneously, extending both the laser modulation speed and output power for this heavily deployed class of lasers opens up new opportunities and fields of use ranging from data-comm to sensing, automotive, and photonic artificial intelligence systems.

Wave-shaped temperature dependence characteristics of the electroluminescence peak energy in a green InGaN-based LED grown on silicon substrate

This study aimed to investigate temperature dependencies at different injection currents (ICs) of the electroluminescence (EL) spectra from a green InGaN/GaN light-emitting diode (LED) based on multiple quantum wells (MQWs) grown on a Si substrate in a wide range of ICs (0.001–350 mA) and temperatures (6–350 K). The results show that the temperature-changing characteristic of the EL peak energy gradually evolves from an approximately V-shaped temperature dependence into a wave-shaped (three-step blueshift) dependence with increasing IC. Finally, it emerges as an approximately inverted V-shaped temperature dependence. The behavior reflects the fact that the emission related to InGaN is significantly influenced by the changing recombination dynamics of carriers with rising temperature or IC. This is attributed to the presence in the MQW active region of a stronger carrier localization effect across three zones with different average In contents. Moreover, with the decline of the temperature at lower ICs, the temperature behavior of the external quantum efficiency (EQE) value is dominated by the deactivated non-radiative centers. This phenomenon occurs not only in the higher temperature range but also at lower temperatures due to more In-content-induced structural defects, which are confirmed by measurements of the integrated EL intensity as well as the EQE dependence on IC.

Rising of charge stability of gate dielectric of MIS structure by phosphorus doping

In the paper we demonstrate that the thermal doping of SiO2 film by phosphorus, causing formation of thin film of phospho-silicate glass on its surface, allows to rise charge stability of gate dielectric of MIS structure. We have ascertained that a presence of the film of phospho-silicate glass has given a possibility to significantly lower local injection currents flowing within defects because of electron capturing by traps located in the film of phospho-silicate glass what results in the rising of energy barrier. As a result, amount of the structures that comes to a state of breakdown at low values of charge injected into the dielectric under high fields noticeably reduces. We show that heating processes of injected electrons lowers in the films of phospho-silicate glass and this results in increasing of charge stability of the gate dielectric under high-field injection.

A Monolithically Integrated Laser-Photodetector Chip for On-Chip Photonic and Microwave Signal Generation

An Indium-phosphide-based monolithically integrated photonic chip comprising of an amplified feedback laser (AFL) and a photodetector was designed and fabricated for on-chip photonic and microwave generation. Various waveforms including single tone, multi-tone, and chaotic signal generation were demonstrated by simply adjusting the injection currents applied to the controlling electrodes. The evolution dynamics of the photonic chip was characterized. Photonic microwave with frequency separation tunable from 26.3 GHz to 34 GHz, chaotic signal with standard bandwidth of 12 GHz were obtained. An optoelectronic oscillator (OEO) based on the integrated photonic chip was demonstrated without using any external electrical filter and photodetector. Tunable microwave outputs ranging from 25.5 to 26.4 GHz with single sideband (SSB) phase noise less than −90 dBc/Hz at a 10-kHz offset from the carrier frequency were realized.

Влияние примеси самария на локальную структуру халькогенидного стеклообразного полупроводника Se-=SUB=-95-=/SUB=-Te-=SUB=-5-=/SUB=- и механизм прохождения тока через структуры Al-Se-=SUB=-95-=/SUB=-Te-=SUB=-5-=/SUB=-<Sm>-Te

Effect of samarium doping on the local structure and morphological features of films surface of the Se95Te5 chalcogenide glassy semiconductor system have been investigated by X-ray analysis and atomic force microscopy methods, and the influence of doping on the current passing mechanism through the Al-Se95Te5 <Sm> -Te structures have been also considered by measuring the current-voltage characteristics in a stationary mode. The results obtained are interpreted on the basis of the theory of Lampert injection currents, the Elliott void-cluster model and the Mott and Street charged defect model proposed for chalcogenide glasses.