Frontiers of Optoelectronics

This paper reviews our recent progress on silicon (Si) pn junction light emitting diodes with locally doping engineered carrier potentials. Boron implanted Si diodes with dislocation loops have electroluminescence (EL) quantum efficiency up to 0.12%, which is two orders of magnitude higher than those without dislocations. Boron gettering along the strained dislocation lines produces locally p-type spike doping at the dislocations, which have potential wells for bounding spatially indirect excitons. Thermal dissociation of the bound excitons releases free carriers, leading to an anomalous increase of the band to band luminescence with increasing temperature. Si light emitting diodes with external quantum efficiency of 0.2% have been also demonstrated by implementation of pnpn modulation doping arrays.

This paper experimentally investigated slow light effect in cascaded silicon-on-insulator (SOI) microring resonators. Double channel and single channel side-coupled integrated spaced sequence of resonators (SCISSOR) devices were fabricated with electron beam lithography and dry etching technology. The delay performances of the SCISSOR devices were demonstrated using non-return-to-zero (NRZ) and return-to-zero (RZ) signals at different bit rates. Group delays and bandwidths of cascaded microrings are significantly enhanced compared with single microring.

In this paper, a new simple structure of index-guiding photonic crystal fiber (PCF) is designed and presented. In this PCF, dispersion, confinement loss, and effective mode area characteristics are investigated in the second communication window (1.55 μm). Since 1.55 μm wavelength is widely used in optical communication systems, we try to optimize the PCF characteristics in this wavelength by designing an index-guiding PCF and three versions of optimized PCF. The results show that the dispersion is obtained very close to zero around 4.6×10−4 ps/(nm·km). Also, the confinement loss is 2.303×10−6 dB/km and effective mode area is as small as 2.6 μm2.

In this paper, we proposed quantum dot (QD) based structure for implementation of white light emitting diode (WLED) based on InGaN/GaN. The proposed structure included three layers of InGaN QD with box shapes and GaN barriers. By using of single band effective mass method and considering strain effect, piezoelectric and spontaneous polarizations internal fields, then solving Schrödinger and Poisson equations self consistently, we obtained electron and hole eigen energies and wave functions. By evaluating dipole moment matrix elements for interband transitions, the output intensity was calculated due to the interband transition between two energy levels with highest emission probability. We adjusted QDs dimensions and material compositions so that the output light can be close to the ideal white light in chromaticity diagrams. Finally, effects of temperature variations on output spectrum and chromaticity coordinates were studied. We demonstrated that temperature variations in the range of 100 to 400 K decrease output intensity, broaden output spectral profile and cause a red shift in three main colors spectrums. This temperature variation deviates (x, y) are coordinated in the chromaticity diagram, but the output color still remains close to white.

A 3-input all-optical priority encoder is designed. Proof-of-concept experiment is performed at 40-Gbit/s based on a cross-gain modulation (XGM) in two parallel semiconductor optical amplifiers (SOAs). Output logic signals with over 10-dB extinction ratios (ERs) and clear open eye diagrams are obtained. No additional input light beam is used. The proposed scheme may be a promising candidate for future ultrafast all-optical digital signal processing circuits and computing systems.

The use of cavity to manipulate photon emission of quantum dots (QDs) has been opening unprecedented opportunities for realizing quantum functional nanophotonic devices and quantum information devices. In particular, in the field of semiconductor lasers, QDs were introduced as a superior alternative to quantum wells (QWs) to suppress the temperature dependence of the threshold current in vertical-external-cavity surfaceemitting lasers (VECSELs). In this work, a review of properties and development of semiconductor VECSEL devices and QD laser devices is given. Based on the features of VECSEL devices, the main emphasis is put on the recent development of technological approach on semiconductor QD VECSELs. Then, from the viewpoint of both single QD nanolaser and cavity quantum electrodynamics (QED), a single-QD-cavity system resulting from the strong coupling of QD cavity is presented. In this review, we will cover both fundamental aspects and technological approaches of QD VECSEL devices. Lastly, the presented review here has provided deep insight into useful guideline for the development of QD VECSEL technology, future quantum functional nanophotonic devices and monolithic photonic integrated circuits (MPhICs).

Slow light in planar photonic structures has attracted for some years an increasing interest due to amazing physical effects it allows or reinforces and to the degrees of freedom it raises for designing new optical functions. Controlling light group velocity is achieved through the use of periodical optical media obtained by nano-structuration of semiconductor wafers at the scale of light wavelength: the so-called photonic crystals. This article reviews present achievements realized in the field of slow light photonic bandgap structures, including the physical principles of slow light to the description of the most advanced integrated optical devices relying on it. Challenges and current hot topics related to slow light are discussed to highlight the balance between the advantages and drawbacks of using slow waves in integrated photonic structures. Then, future trends are described, which is focused on the use of slow wave slot waveguides for nonlinear optics and bio-photonic applications.

The mode-field half widths of two kinds of single-mode waveguides are investigated. Based on the maximal matching efficiency method, the relationship between the mode-field half width and normalized frequency is analyzed. Furthermore, two equations of mode-field half widths as a function of normalized frequency are proposed through mathematical modeling and the curve fitting method. Numerical calculations indicate that they are accurate within a parameter range.

In this article, the fabrication technologies of photonic crystal fibers (PCFs) and their applications at home and abroad were formulated at length, especially in fields such as large mode-area active PCFs, fiber lasers, birefringence fibers, sensors, high nonlinear PCFs, frequency transformation, dispersion compensation PCFs, wideband communication for optical network systems, and photonic band-gap fibers. Finally, according to the above analysis, the prospects and developing trends of PCFs were presented.