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IEEE Journal of Quantum Electronics
Journal Prestige (SJR): 0.65

Citation Impact (citeScore): 2
Number of Followers: 19

Hybrid journal (It can contain Open Access articles)
ISSN (Print) 0018-9197
Published by IEEE

[228 journals]

Experiments on an AM Mode-Locked Laser as an Arbitrary Optical Function
Generator
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  Authors: Masataka Nakazawa;Masato Yoshida;Toshihiko Hirooka;
  Pages: 1 - 18
  Abstract: We show experimentally that various optical pulses can be generated from an AM mode-locked laser by employing a 10 GHz harmonically and regeneratively mode-locked erbium fiber laser. A software-controlled liquid crystal on silicon (LCoS) optical filter device, which can control the amplitude and phase of the input signal as a function of optical frequency, was employed to implement a specific filter function. The filter was characterized by the Fourier transformed spectral profile $A(omega )$ of the output pulse $a(t)$ , $A(omega +Omega _{m}), $ and $A(omega -Omega _{m})$ . Here, $Omega _{m}$ is the AM modulation angular frequency. The filter resolution was set at 10 GHz. By installing a specific filter in the laser cavity, we succeeded in generating various pulses such as Gaussian, secant hyperbolic (sech), double-sided and single-sided exponential, parabolic, triangular, and Nyquist pulses with an arbitrary roll-off factor as with an optical function generator. It is interesting to note that we could experimentally generate very precise transform-limited (TL) optical pulses, which were originally designed by calculating the filter function. The generated spectral profile agreed well with the numerical results even below −40 dB, which also agreed with the theory. As we have shown theoretically, we could generate sech and parabolic pulses without fiber nonlinearity. An asymmetric single-sided pulse can also be generated by incorporating a complex filter function with phase information, where a small amount of phase rotation of $sim pi $ /60 in each round trip played an important role in generating the asymmetric pulse. Without the phase change, the pulse became symmetric and was no longer the designed pulse. A clean triangular pulse was difficult to generate since parabolic pulse shaping on the top of a sinusoidal intensity modulation is ineffective in creating a sharp peak.
  PubDate: June 2022
  Issue No: Vol. 58, No. 3 (2022)
Experiments on an FM Mode-Locked Laser as an Arbitrary Optical Function
Generator
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  Authors: Masataka Nakazawa;Masato Yoshida;Toshihiko Hirooka;
  Pages: 1 - 16
  Abstract: We describe experimentally that an FM mode-locked laser can generate various optical pulses such as Gaussian, secant hyperbolic (sech), double-sided exponential, rectangular, parabolic, triangular, and Nyquist pulses like an optical function generator. The experiments were carried out by employing a 10 GHz actively FM mode-locked erbium fiber laser, where a specific filter was installed in the laser cavity. The specific filter was characterized by the Fourier transformed spectrum $A(omega )$ of an output pulse $a(t)$ and $A(omega $ + $nOmega _{m})$ with $n=- infty sim + infty $ . Here, $Omega _{m}$ is the angular modulation frequency. We employed a software-controlled liquid crystal on silicon (LCoS) optical filter, which can control the amplitude and the phase of the input signal as a function of optical frequency. Therefore, we were able to generate various optical pulses by simply changing the filter shape using the software. The filter resolution was 10 GHz. The generated optical pulses agreed well with the theory, where the spectral profile even below −40 dB coincided well with the theoretical profile. We proved experimentally from the product of $Delta nu Delta tau $ at −3 dB that the output pulses have none of the frequency chirp that would inevitably occur with conventional FM mode-locking. It was not possible to generate an asymmetric single-sided pulse as we pointed out theoretically. We we-e also able to generate parabolic and triangular intensity pulses as we predicted in a previous paper. Finally, we compared the possibilities of generating various pulses with AM and FM mode-locking techniques.
  PubDate: June 2022
  Issue No: Vol. 58, No. 3 (2022)
Three-Variable Reduction of the Spin-Flip Model for Spin-VCSELs
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  Authors: Mike Adams;Nianqiang Li;Yu Huang;Pei Zhou;Ian Henning;
  Pages: 1 - 8
  Abstract: Recent increased interest in spin-polarised vertical-cavity surface-emitting lasers (spin-VCSELs) as potential high-speed sources has spurred research into the analysis of their dynamics. This has often been explored by combining the spin-flip model (SFM) with numerical methods. However, numerical simulation does not readily expose key dependencies and to date there is a lack of accessible closed-form analytical results for the steady-state solutions and dynamic stability boundaries. Thus in the present contribution we address this and show that, for zero dichroism, the five rate equations of the SFM can be reduced to a set of three. These can be solved in the steady-state in terms of the intensity and polarisation of the pump (optical or electrical), and the ellipticity of the output. Additionally, a small-signal analysis leads to analytic results for the boundaries between stable and unstable operation in the plane of pump ellipticity versus pump intensity. Comparison of the results from these expressions with those from numerical bifurcation and continuation methods shows very good agreement. The accuracy of the reduced set of equations is confirmed by comparing the results with those from the full set of SFM equations. In the limiting case of very high birefringence, as would be required for a potential THz source, a simple algebraic relation is derived for the spin relaxation rate in terms of other parameters. Hence we find that the range of spin relaxation rates to achieve THz oscillations is very limited. The relative simplicity of the present approach thus offers a rapid, intuitive and convenient route to study the dynamics of spin-VCSELs.
  PubDate: June 2022
  Issue No: Vol. 58, No. 3 (2022)
Dislocation Evolvement in Metamorphic In0.83Ga0.17As/InP Photodetectors
Through Ex-Situ Rapid Thermal Annealing
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  Authors: Songyang Wang;Yingjie Ma;Yage Liu;Hongzhen Wang;Shuangyan Deng;Yi Gu;Bowen Liu;Tao Li;Xiumei Shao;Xue Li;Haimei Gong;
  Pages: 1 - 7
  Abstract: Ex-situ rapid thermal treatments of 1–2.5 $mu text{m}$ extended wavelength In0.83Ga0.17As/In0.83Al0.17As photodetector epiwafers on InP substrate were investigated. Enhanced photoluminescence intensities, narrower and stronger x-ray diffraction peaks, and decreased dislocation defect densities were observed with the increase of the rapid annealing temperature from 650°C to 750°C. Monotonically decreased dark current, dark noise and climbed peak detectivity for the photodetectors were attained. The cut-off wavelength remain unchanged after thermal treatments. The crystal lattice was irreversibly damaged and the device failed once the temperature was risens to 800°C. These results indicate that the ex-situ thermal treatment can serve as an effectively route to improve the qualities of metamorphic InxGa1−xAs materials as well as devices.
  PubDate: June 2022
  Issue No: Vol. 58, No. 3 (2022)
Low Dark Current Deep UV AlGaN Photodetectors on AlN Substrate
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  Authors: Lakshay Gautam;Junhee Lee;Gail Brown;Manijeh Razeghi;
  Pages: 1 - 5
  Abstract: We report high quality, low dark current, deep Ultraviolet AlGaN/AlN Photodetectors on AlN substrate. AlGaN based Photodetectors are grown and fabricated both on AlN and Sapphire substrates with the same epilayer structure. Subsequently, electrical characteristics of both photodetectors on AlN substrate and Sapphire are compared. A reduction of 4 orders of magnitude of dark current density is reported in UV detectors grown on AlN substrate with respect to Sapphire substrate.
  PubDate: June 2022
  Issue No: Vol. 58, No. 3 (2022)
Dead Time Duration and Active Reset Influence on the Afterpulse
Probability of InGaAs/InP Single-Photon Avalanche Diodes
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  Authors: Anton V. Losev;Vladimir V. Zavodilenko;Andrey A. Koziy;Alexandr A. Filyaev;Kristina I. Khomyakova;Yury V. Kurochkin;Alexander A. Gorbatsevich;
  Pages: 1 - 11
  Abstract: We have performed a detailed study of the dependence of afterpulse probability in InGaAs/InP sine-gated SPAD on the dead time and the existing approach for its implementation. We demonstrated an electrical scheme combining sinusoidal gating and active reset. We have shown when such solutions are beneficial from the key distribution point of view, and enough to use a simple scheme with a snatching comparator. We have also proposed a precise method for measuring the afterpulse and presented a model describing the non-markovian dynamic of this effect. We have demonstrated that our afterpulsing measurement approach makes these measurements less dependent on the parameters of the flow of the diode and the laser pulses’ power changes, in contrast to the other methods considered in this paper.
  PubDate: June 2022
  Issue No: Vol. 58, No. 3 (2022)
Efficient Second-Harmonic Generation in an Embedded ABC-Metamaterial
Waveguide
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  Authors: Mohsen Heidari;Babak Janjan;Shahram Bahadori-Haghighi;Vahid Faramarzi;Mohammad Mahdi Mehrnegar;Mohammad R. Khosravi;
  Pages: 1 - 7
  Abstract: ABC-metamaterial, structured by repeating atomic layer deposition of three dielectric material-stack layers, opens the new possibility for creating second-order nonlinearity in CMOS-compatible photonics platforms. Here, the design and simulation of Si3N4 waveguide with embedded ABC-metamaterial for generating second-harmonic (SH) of 1.55 ${mu }text{m}$ wave is presented. High-overlap-integral modal phase matching between the fundamental mode of the fundamental frequency and second-order mode of the SH is attained by properly engineering the waveguide geometry. Numerical analyzes show an absolute efficiency of 0.013% for 10 mW pump power in the straight waveguide which can be enhanced to at least 13.4% by employing a microring resonator.
  PubDate: June 2022
  Issue No: Vol. 58, No. 3 (2022)