Opto-Electronics Review

In this topic review the results of the X-band electron paramagnetic resonance (EPR) measurements of Mn, Co, Cr, Fe ions in YAlO₃ (YAP) crystals and Fe ions in LiNbO₃ (LNO) crystals and of chromium doped Bi₁₂GeO₂₀ (BGO) and Ca₄GdO(BO₃)₃ single crystals, are presented. It is well known that the oxide crystals (for example:YAP, LNO, BGO) are one of the most widely used host materials for different optoelectronic applications. The nature of point defect of impurities and produced in the oxide crystal after irradiation by bismuth ions and after irradiation by the ²³⁵U ions with energy 9.47 MeV/u and fluency 5 × 10¹¹ cm⁻¹ is discussed. The latter is important for applications of these oxide crystal as laser materials.

This paper presents the current state of a photoconductive semiconductor switch engineering. A photoconductive semiconductor switch is an electric switch with its principle of operation based on the phenomenon of photoconductivity. The wide application range, in both low and high-power devices or instruments, makes it necessary to take design requirements into account. This paper presents selected problems in the scope of designing photoconductive switches, taking into account, i.e. issues associated with the element trigger speed, uniform distribution of current density, thermal resistance, operational lifespan, and a high, local electric field generated at the location of electrodes. A review of semiconductor materials used to construct devices of this type was also presented.

A method for frequency-multiplexed multi-sample gas sensing is presented. It enables measuring multiple samples placed simultaneously in the setup, without any optical or mechanical switching. Samples are measured using heterodyne detection and signal from each sensing path is encoded at different carrier frequency. Subsequently, a signal from particular sample is retrieved through heterodyne beatnote demodulation at unique frequency. This technique is particularly suitable for real-time calibration of the sensor through a sequential (or simultaneous) detection of three signals: from unknown sample, reference sample and baseline. Basic setup is demonstrated and proof-of-concept experiments are presented. Very good agreement with spectra measured using standard tunable diode absorption spectroscopy is obtained.

In this attempt, Two Dimensional Photonic Crystal (2DPC) Quasi Square Ring Resonator (QSRR) based four channel demultiplexer is proposed and designed for Wavelength Division Multiplexing systems. The performance parameters of the demultiplexer such as transmission efficiency, passband width, line spacing, Q factor and crosstalk are investigated. The proposed demultiplexer is composed of bus waveguide, drop waveguide and QSRR. In the proposed demultiplexer, the output ports are arranged separately in odd and even number, where an odd number of ports are located on the right side and even number of ports are located on the left side of the bus waveguide that are used to reduce the channel interference or crosstalk. Further, the refractive index of rods around the center rod is increased linearly one to another in order to improve the signal quality. The resonant wavelengths of the proposed demultiplexer are of 1521.1 nm, 1522.0 nm, 1523.2 nm and 1524.3 nm, respectively. The footprint of the device is of 180.96 μm². Then, a four channel point to point network is designed and the proposed four channel demultiplexer is implemented by replacing a conventional demultiplexer. Finally, functional parameters of the network, namely, BER, receiver sensitivity and Q factor are estimated by varying the link distance. This attempt could create new dimensions of research in the domain of photonic networks.

In recent years, many scientific and industrial centres in the world developed a virtual reality systems or laboratories. The effect of user “immersion” into virtual reality in such systems is largely dependent on optical properties of the system. In this paper, problems of luminance distribution uniformity in CAVE-type virtual reality systems are analyzed. For better characterization of CAVE luminance nonuniformity corner and edge CAVE nonuniformity were introduced. Based on described CAVE-type virtual reality laboratory, named Immersive 3D Visualization Lab (I3DVL) just opened at the Gdansk University of Technology, luminance nonuniformity of the system is evaluated and discussed. Data collection of luminance distribution allows for software compensation of intensity distribution of individual images projected onto the screen (luminance non-uniformity minimization) in the further research.

Optoelectronic technology plays an important role in medical diagnosis. In the paper a review of some optoelectronic sensors for invasive and non-invasive human health test is presented. The main attention is paid on their basic operation principle and medical usefulness. The paper presents also own research related to developing of tools for human breath analysis. Breath sample unit and three gaseous biomarkers analyzer employing laser absorption spectroscopy designed for clinical diagnostics were described. The analyzer is equipped with sensors for CO, CH₄ and NO detection. The sensors operate using multi-pass spectroscopy with wavelength modulation method (MUPASS-WMS) and cavity enhanced spectroscopy (CEAS).

The behaviour of energy levels and optical spectra of a charged particle (electron or hole) confined within a potential well of ellipsoidal shape is investigated as a function of the shape-anisotropy parameter. If two energy levels of the same symmetry intersect in a perturbation-theory approximation, they move apart on direct diagonalization of the appropriate Hamiltonian. The intersection of the energy levels leads to a discontinuity of the corresponding dipole-moment matrix element. The discontinuity of matrix elements is not reflected in the behaviour of transition probabilities which are continuous functions of the shape-anisotropy parameter. The profiles of a spectral line emitted or absorbed by an ensemble of ellipsoidally shaped nanoparticles with a Gaussian distribution of size are calculated and discussed.

In this paper, a low power highly sensitive Triple Metal Surrounding Gate (TM-SG) Nanowire MOSFET photosensor is proposed which uses triple metal gates for controlling short channel effects and III–V compound as the channel material for effective photonic absorption. Most of the conventional FET based photosensors that are available use threshold voltage as the parameter for sensitivity comparison but in this proposed sensor on being exposed to light there is a substantial increase in conductance of the GaAs channel underneath and, thereby change in the subthreshold current under exposure is used as a sensitivity parameter (i.e., I_illumination/I_Dark). In order to further enhance the device performance it is coated with a shell of Al_xGa_1-xAs which effectively passivates the GaAs surface and provides a better carrier confinement at the interface results in an increased photoabsorption. At last performance parameters of TM-SG Bare GaAs Nanowire MOSFET are compared with TM-SG core-shell GaAs/AlGaAs Nanowire MOSFET and the results show that Core-Shell structures can be a better choice for photodetection in visible region.

In this paper, detailed theoretical investigation on the frequency response and responsivity of a strain balanced SiGeSn/GeSn quantum well infrared photodetector (QWIP) is made. Rate equation and continuity equation in the well are solved simultaneously to obtain photo generated current. Quantum mechanical carrier transport like carrier capture in QW, escape of carrier from the well due to thermionic emission and tunneling are considered in this calculation. Impact of Sn composition in the GeSn well on the frequency response, bandwidth and responsivity are studied. Results show that Sn concentration in the GeSn active layer and applied bias have important role on the performance of the device. Significant bandwidth is obtained at low reverse bias voltage, e.g., 200 GHz is obtained at 0.28 V bias for a single Ge_0.83Sn_0.17 layer. Whereas, the maximum responsivity is of 8.6 mA/W at 0.5 V bias for the same structure. However, this can be enhanced by using MQW structure.

Power loss mechanisms in small area monolithic-interconnected photovoltaic modules (MIM) are described and evaluated. Optical and electrical losses are quantified and individual loss components are derived for loss mechanisms of small area radial (radius = 1 mm) pie-shaped six-segment GaAs MIM laser power converter. At low monochromatic homogeneous illumination (G_low = 1.8 W/cm², λ₀ = 809 nm) conversion efficiency of the cell, designed for a low irradiance, is reduced by 3.7%_abs. due to isolation trench optical losses and by 7.0%_abs. due to electrical losses (mainly perimeter recombination). Electrical losses in a device designed for a high irradiance, result in 18%_abs. decrease of output power under homogeneous monochromatic illumination (G_high = 83.1 W/cm², λ₀ = 809 nm), while 11.6%_abs. losses are attributed to optical reasons. Regardless the irradiance level, optical losses further increase if the device is illuminated with a Gaussian instead of an ideal flattop beam profile. In this case, beam spillage losses occur and losses due to isolation trenches and reflections from metallization are elevated. On top of that, additional current mismatch losses occur, if individual MIM’s segments are not equally illuminated. For the studied device, a 29 μm off center misalignment of a Gaussian shaped beam (with 1% spillage) reduces the short circuit current I_sc by 10%_abs. due to the current mismatch between segments.

Four dye-sensitized solar cell devices are designed and fabricated based on natural dyes extracted from Celosia Cristata, Saffron, Cynoglossum, and eggplant peel, as photosensitizers. The UV–vis technique has been served to determine maximum absorption of natural extract and pre-dyed photoanode. The Fourier transform infrared (FT-IR) was employed to cover the presence of functional groups. The cyclic voltammetry method has been employed to assess the possibility of charge transfer from dried natural dyes to the photoelectrode. The performance of natural-based dye-sensitized solar cells is determined subsequently. The highest power conversion efficiency was ca. 1.38%, which belonged to Celosia Cristata extract. The devices were examined for higher efficiencies, individually, co-sensitized arrangement and/or in tandem with each other.

Photoactive nanofilled nematic is proposed. Stable three-component photoresponsive nanocomposite was prepared from photo-insensitive nanofilled nematic by inclusion of 3 wt.% azobenzene-containing photoactive mesogen 4-(4′-ethoxyphenylazo)phenyl hexanoate (EPH). The host nanofilled nematic was produced from the room-temperature nematic liquid crystal 4-n-heptyl cyanobiphenyl (7CB) and 3 wt.% filler of Aerosil 300 hydrophilic silica nanospheres of size 7 nm. Apparent effect of stimulation with a relatively weak continuous illumination by UV light (375 nm wavelength) takes place for both the alternating-current electric field-dependent optical transmittance and the electro-optic amplitude-frequency modulation by thin films (25 µm thick) of the EPH/aerosil/7CB nanocomposite. The light-stimulated electro-optics of EPH-doped aerosil/7CB films and the corresponding reversible light control are achieved through trans-cis-trans photoisomerization of the photoactive agent EPH. As such, the initial electro-optical response of the studied photoactive nanocomposites is recovered with continuous blue-light illumination. The examined EPH/aerosil/7CB nanocomposites exhibit photo-controllable electro-optical response that is of practical interest.

A modified optical fibre based Mach-Zehnder interferometer was applied as a sensor to detect wiretapping in long transmission optical fibre lines. The signal consisting of short pulses (around 1 ns) was launched to the input of the interferometer based on the polarization maintaining fibres and polarization elements. When the sensing line was undisturbed, detectors registered only a single pulse. The additional two side pulses appear, if the wiretapping attempt took place. For robust detection of any alarm situation we proposed two-criteria algorithm to minimize false alarm rate. Moreover, slow environmental fluctuations were continuously monitored and compensated by polarization controllers. We measured frequency characteristics of the sensor and performed a hundred wiretapping attempts, which proved high performance of the sensor.

We demonstrate MW-level, single resonance optical parametric oscillator, based on KTP Type-II crystal with noncritical phase-matching. The OPO is pumped by electro-optically Q-switched Nd:YAG slab laser providing 55 mJ of pulse energy. At the output, we achieved 28 mJ of signal pulse energy at 1.57 μm with 51% conversion efficiency, corresponding to 1.4 MW of peak power.