IET Optoelectronics
Volume 12, Issue 4, August 2018
Volumes & issues:
Volume 12, Issue 4
August 2018
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- Author(s): Piotr Martyniuk ; Paweł Madejczyk ; Małgorzata Kopytko ; Aleksandra Magdalena Henig ; Kacper Grodecki ; Waldemar Gawron ; Jarosław Rutkowski
- Source: IET Optoelectronics, Volume 12, Issue 4, p. 161 –167
- DOI: 10.1049/iet-opt.2017.0161
- Type: Article
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161
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This study reports on photoelectrical performance of the long-wave infrared HgCdTe high operating temperature (200–230 K) detector for the fast response time operating under unbiased conditions. The detailed analysis of the response time as a function of device architecture was conducted pointing out optimal working conditions and structure. The response time of the long-wave (x Cd = 0.19) HgCdTe detector for temperatures reached by thermoelectrical cooling (200–230 K) was estimated at the level of τ s < 0.6 ns for unbiased condition while responsivity Ri ∼ 1.8 A/W and detectivity was assessed at the level of D * ∼ 1.6 × 1010 cm Hz1/2/W. It was shown that extra series resistance R series < 10 Ω (resistance–capacitance time constant) plays a decisive role in order to reach τ s < 1 ns meaning that device processing is much more important rather than fundamental limitations imposed by physics.
- Author(s): Jitendra Bahadur Maurya and Yogendra Kumar Prajapati
- Source: IET Optoelectronics, Volume 12, Issue 4, p. 168 –175
- DOI: 10.1049/iet-opt.2018.0008
- Type: Article
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p.
168
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The nature of dielectric constant and its thickness placed between metal layer and prism base is analysed. The attributes of reflectance curve which defines the performance of the surface plasmon resonance sensor are shift in resonance angle, minimum reflection intensity, and half width at half maxima. These attributes are plotted according to the refractive index (RI) and extinction coefficient (EC) of the adhesion layer or buffer layer placed between metal layer and prism base. Further, these attributes are plotted according to the thickness of adhesion layer at different combination of RI and EC.
- Author(s): Shuvra Dey and Sourangshu Mukhopadhyay
- Source: IET Optoelectronics, Volume 12, Issue 4, p. 176 –179
- DOI: 10.1049/iet-opt.2017.0138
- Type: Article
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176
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Pauli-Y type of quantum gate is a significant name in the logic family of quantum gates, as this gate deals with complex qubits. It has many significant applications in quantum computing. In this study, the authors propose a new method of generation of Pauli-Y gate by the proper uses of optical polarisation encoding and phase encoding jointly. This quantum gate can be implemented by dibit and tribit mechanisms instead of single qubit system, where tribit-based system deals with the high degree of error sensitivity.
- Author(s): Ahmed H.H. Al-Masoodi ; Fauzan Ahmad ; Mahmoud H.M. Ahmed ; Abtisam H.H. Al-Masoodi ; Ibrahim A.M. Alani ; Hamzah Arof ; Sulaiman Wadi Harun
- Source: IET Optoelectronics, Volume 12, Issue 4, p. 180 –184
- DOI: 10.1049/iet-opt.2017.0134
- Type: Article
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p.
180
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Q-switched and mode-locked fibre lasers have been successfully demonstrated in ytterbium-doped fibre laser cavity by taking an advantage of the optical absorption of antimony telluride (Sb2Te3) material. The Sb2Te3 was embedded into polyvinyl alcohol to function as a saturable absorber (SA). A Q-switching pulses train was obtained by incorporating the SA into the laser ring cavity configured with 3 dB coupler. The Q-switching pulse repetition rate increases from 24.4 to 55 kHz as the pump power is increased from the threshold of 75.4–96.2 mW. The maximum pulse energy of 252.6 nJ is obtained at 82.3 mW pump power. On the other hand, by changing the output coupler to 10 dB coupler, a stable self-started mode-locking operation was then generated at pump power range from 47.8 to 89.4 mW with a fixed repetition rate of 24.2 MHz. At 89.4 mW pump power, the maximum output power and pulse energy are obtained to be around 18.6 mW and 0.8 nJ, respectively. The authors results display that the Sb2Te3 material could also be developed as an effective SA for both Q-switched and mode-locked fibre lasers.
- Author(s): Sonu Bishnoi and Saurabh Kumar Pandey
- Source: IET Optoelectronics, Volume 12, Issue 4, p. 185 –190
- DOI: 10.1049/iet-opt.2017.0135
- Type: Article
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185
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A comprehensive numerical analysis for a lead-free perovskite solar cell (PSC) has been carried out using device simulation software. Various factors affecting the solar cell's performance have been investigated for device optimisation; more specifically optimisation of device buffer and the absorber layer. Different design strategies for optimising the power conversion efficiency (PCE) through solar cell capacitance simulator numerical simulation have been proposed. Enumerated study of the effects of thickness, band gap, light illumination and defect area on the PCE is carried out. In this study, two types of configurations (La0.7Sr0.3MnO3/zinc oxide and La0.7Sr0.3MnO3/Nb:SrTiO3) are simulated which gives highest conversion efficiency of 11% at 600 nm and 32% at 350 nm wavelength. The impact of defect density has also been addressed to analyse the performance of cell module. The optimisation of device parameters pinpoints enormous potential for the enhancement of conversion efficiency of high-efficient PSC.
- Author(s): Ahmad Mohebzadeh-Bahabady and Saeed Olyaee
- Source: IET Optoelectronics, Volume 12, Issue 4, p. 191 –195
- DOI: 10.1049/iet-opt.2017.0174
- Type: Article
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191
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In this study, a small size, low power, simple and high contrast ratio (CR) structure was designed and simulated to use in photonic crystal-based all-optical logic gates. This structure can be used for both all-optical logic NOT and XOR gates. The suggested structure is composed of three waveguides and a nano-resonator. The nano-resonator was designed by removing two dielectric rods. For use as an optical NOT logic gate, one of the input ports enters the control signal. In this case, the CR between logic levels ‘0’ and ‘1’ is 20.53 dB, which is higher than that of the provided gates based on structures published recently. The CR for the XOR gate is 19.95 dB. The response time to the input signal of the designed gate is 0.466 ps. The simplicity of the structure, small size, and high CR are the advantages of this structure compared to previously provided logic gates. The results have proven a superior prospect for the proposed structure to use in all optical integrated circuits.
- Author(s): Hitoshi Obara
- Source: IET Optoelectronics, Volume 12, Issue 4, p. 196 –201
- DOI: 10.1049/iet-opt.2017.0096
- Type: Article
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196
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Two principal two-stage switch architectures (cascaded and parallel), both of which are composed of two identical optical crossbar switches with an extra set of inputs and outputs, are compared in terms of their number of crosspoints, switch control complexities, and key optical performances, such as insertion loss and crosstalk power, through theoretical analysis. The authors begin by briefly introducing a known N × N cascaded optical crossbar switch with N 2/2 crosspoints, where N is the switch size, and present a new functional perspective based on quasi-bitonic sorting. Subsequently, the authors derive two types of two-stage parallel optical crossbar switches with reduced crosspoints from a conventional single-stage parallel crossbar switch with N 2 + 2N crosspoints. The first type uses two N/2 × N asymmetric switches in parallel, both of which are embedded in a single N/2 × N/2 crossbar switch. It has (N 2 + 2N)/2 crosspoints and suffers from a complex switch control of O(N 2). The second type is equivalent to a three-stage Benes network and exploits bidirectional transmission to reduce the number of switching stages. It requires (N 2 + 3N)/2 crosspoints, but has a dramatically reduced switch control complexity of O(N), and significantly improved optical performance.
- Author(s): Festus Idowu Oluwajobi ; Nguyen Dong-Nhat ; Amin Malekmohammadi
- Source: IET Optoelectronics, Volume 12, Issue 4, p. 202 –207
- DOI: 10.1049/iet-opt.2018.0032
- Type: Article
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A novel advanced modulation format based on Manchester signalling is proposed and assessed for high-speed optical communication systems. The new advanced modulation format known as modified Manchester derived from the combination of Manchester and vestigial sideband (VSB) techniques. Its performance assessed and compared in terms of spectral efficiency, chromatic dispersion tolerance and receiver sensitivity against conventional Manchester, return-to-zero (RZ) and non-RZ (NRZ) (with the same spectral width). The optimisation of the optical filter that performed the VSB filtering on the Manchester signal and its detuning frequency results in the compression of the spectral width of the Manchester signal and thereby enhanced the spectral efficiency of the modified Manchester to about 31.3%. This results in the improvement of dispersion tolerance to ∼140 ps/nm. In comparison with conventional modulation formats, the proposed system can improve the dispersion tolerance by three times more than conventional Manchester, which is 44 ps/nm, and twice more than NRZ, which is 51.8 ps/nm and has a better dispersion tolerance of 31 ps/nm than RZ with dispersion tolerance of 109 ps/nm at a bit-error-rate of 10−9. The improvement in the proposed modulation performance achieved without utilisation of any dispersion compensation module or electronic equalisation.
- Author(s): Vineeta Dubey ; Devi Chadha ; Vinod Chandra
- Source: IET Optoelectronics, Volume 12, Issue 4, p. 208 –214
- DOI: 10.1049/iet-opt.2017.0123
- Type: Article
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The authors investigate the performance and reliability improvement of multiple relay cooperative free space optical (FSO) communication over direct link. Multiple gain combiner (MGC) method has been introduced as a diversity combining method which assures to provide a close to optimum performance as compared to maximal ratio combining (MRC). As compared to MRC, the proposed MGC technique does not require prior channel information and adaptive gain adjustment. Bit error rate (BER) performance improvement with different combining techniques, including MGC, in cooperative FSO system for different channel environments has been included in this study. BER performance for multiple relays for various combining techniques: selection combining, equal gain combining, MRC and MGC have been compared and it is seen that the performance of MGC is close to optimum MRC. High availability of the system is achieved by using multiple relays in the cooperative system. Markov model analysis for availability and mean time between failures of FSO systems in multiple relays cooperative communication has been done to verify the reliability improvement of a cooperative system with increasing number of relays.
- Author(s): Chunchao Yu ; Lihui Sun ; Huafeng Zhang ; Fang Chen
- Source: IET Optoelectronics, Volume 12, Issue 4, p. 215 –219
- DOI: 10.1049/iet-opt.2018.0033
- Type: Article
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The optical bistability (OB) in the quantum dot molecules with four energy levels in a unidirectional ring cavity has been investigated. The authors find that the OB behaviour in the proposed system can be controlled by the system's different parameters such as electronic cooperation parameter, Rabi frequency of the two coupling laser field, decay rate, three frequency detuning, in which the parameters sensitivity is studied. The proposed system can be used for all optical switching and logic.
Theoretical simulation of the thermoelectrically cooled HgCdTe LWIR detector for fast response operating under unbiased conditions
Influence of adhesion layer on performance of surface plasmon resonance sensor
Implementation of all-optical Pauli-Y gate by the integrated phase and polarisation encoding
Q-switched and mode-locked ytterbium-doped fibre lasers with Sb2Te3 topological insulator saturable absorber
Device performance analysis for lead-free perovskite solar cell optimisation
All-optical NOT and XOR logic gates using photonic crystal nano-resonator and based on an interference effect
Cascaded versus parallel architectures of two-stage optical crossbar switches with an extra set of inputs and outputs
Modified Manchester modulation format for high-speed optical transmission systems
High availability cooperative free space optical communication link with various diversity combining methods
Controllable optical bistability in double quantum dot molecule
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