Eun Soo Nam

Channel estimation and synchronization for polarization-division multiplexed CO-OFDM using subcarrier/polarization interleaved training symbols.

We propose and demonstrate the use of subcarrier/polarization-interleaved training symbols for channel estimation and synchronization in polarization-division multiplexed (PDM) coherent optical orthogonal frequency-division multiplexed (CO-OFDM) transmission. The principle, the computational efficiency, and the frequency-offset tolerance of the proposed method are described. We show that the use of subcarrier/polarization interleaving doubles the tolerance to the frequency offset between the transmit laser and the receivers optical local oscillator as compared to conventional schemes. Using this method, we demonstrate 43-Gb/s PDM CO-OFDM transmission with 16-QAM subcarrier modulation over 5,200-km of ultra-large-area fiber.

0.34

A large GaN-Schottky barrier diode (SBD) with a recessed dual anode metal is proposed to achieve improved the forward characteristics without a degradation of the reverse performances. Using optimized dry etch condition for a large device, the electrical characteristics of the device are demonstrated when applying the recessed dual anode metal and changing the recess depths. The device size and channel width are 4 mm2 and 63 mm, respectively. The 16-nm recessed dual anode metal SBD has a turn-ON voltage of 0.34 V, a breakdown voltage of 802 V, and a reverse leakage current of 1.82 μA/mm at -15 V. The packaged SBD exhibits a forward current of 6.2 A at 2 V and a reverse recovery charge of 11.54 nC.

\text{V}_{\mathrm {T}}

We demonstrate a kink and beam steering free operation of 0.98-/spl mu/m GaInAs-GaInP high-power ridge waveguide (RW) lasers utilizing channel ion implantation. The ion-implanted regions along the both sides of the ridge effectively suppressed the excitation of higher order lateral modes, which causes beam steering and kink. The maximum power without beam steering and kink has been achieved over 250 mW for channel ion-implanted RW lasers with 1.8-3.7-/spl mu/m ridge width, compared to 120-mW maximum power without the channel ion implantation.

AlGaN/GaN-on-Si Large Schottky Barrier Diode With Recessed Dual Anode Metal

We propose a simple, full-range carrier frequency offset (CFO) algorithm for coherent optical orthogonal frequency division multiplexing (CO-OFDM) systems. By applying the Chinese remainder theorem (CRT) to training symbol of single frequency, the proposed CFO algorithm has wide range with shorter training symbol. We numerically and experimentally demonstrate the performance of CRT-based algorithms in a 16-ary quadrature amplitude modulation (QAM) CO-OFDM system. The results show that the estimation range of the CRT-based algorithm is full-range corresponding to the sampling frequency. Also, the bit error ratio (BER) degradation of the proposed algorithm with one training symbol is negligible. These results indicate that the proposed algorithm can be used as a wide range CFO estimator with an increased data rate in high speed CO-OFDM systems.

Improvement of kink and beam steering characteristics of 0.98-μm GaInAs-GaInP high-power lasers utilizing channel ion implantation

We propose a computationally efficient and frequency-offset-tolerant channel estimation and synchronization method for polarization-division-multiplexed (PDM) coherent optical OFDM (CO-OFDM). Using this method, we demonstrate a 43-Gb/s PDM CO-OFDM transmission with 16-QAM subcarrier modulation over 5,200-km of ultra-large-area fiber.

Simple full-range carrier frequency offset estimation for high speed CO-OFDM

The microstructural degradation of a lattice‐matched Ga0.28In0.72As0.61P0.39/InP heterointerface induced by Zn diffusion has been investigated using transmission electron microscopy. The localized interfacial stress caused by intermixing appears to create stacking faults in the Ga‐mixed InP substrate, and dislocation tangles in the In‐mixed GaInAsP layer. The observed results are attributed to the contrasted effect of tensile and compressive stresses upon the nucleation of dislocations from both sides of the GaInAsP/GaInP interface. As an evidence of the interface nucleation, we find a stacking fault at the tensile interface, which is bounded by a pair of partials having opposite Burgers vectors. A model is proposed to explain the strain relaxation in the intermixed region in terms of nucleation and splitting mechanisms of the paired dislocations.

An efficient and frequency-offset-tolerant channel estimation and synchronization method for PDM CO-OFDM transmission

We report a 1.5 μm and 10 Gb s−1 etched mesa buried heterostructure λ/4-shifted distributed feedback laser diode (DFB-LD) for the low-cost application of WDM–based datacenter networks. To reduce the threshold current and improve the modulation bandwidth in a conventional p-/n-/p-InP current blocking structure, a thin undoped-InP (u-InP) layer was inserted between the side walls of the active region and the p-InP layer (i.e., a u-/p-/n-/p-InP structure), and the region containing the active region and the current blocking structures was etched in a mesa form (i.e., an etched mesa). From this work, it was found that a 300 μm long anti-reflection (AR)-AR DFB-LD with a mesa width of 8 μm is reduced by about 25% while a side mode suppression ratio is >50 dB and a 3 dB bandwidth is >10 GHz at a current of 40 mA; in addition, it shows a clear eye-opening with a dynamic extinction ratio of >4.5 dB at 10 Gb s−1, and a power penalty of <1 dB after a 2 km transmission.

FORMATION OF MISFIT DISLOCATIONS DURING ZN-DIFFUSION-INDUCED INTERMIXING OF A GAINASP/INP HETEROSTRUCTURE

The electroplating and screen printing are widely used in the micro-electric industry but they have disadvantages of a complicated series of bumping process, equipments and materials. Furthermore, they are not suitable for the fine pitch bumping technology. To overcome these weak points, a maskless bumping technology using SBM has been developed. Solder Bump Masker (SBM) technology does not need any special equipment and mask tools. It is composed of solder powder and a resin. The solder is Sn58Bi and the resin is designed to have low viscosity for theological characteristics of the solder droplets. In this paper, we optimized the bumping condition with controlling the process time. After bumping, the coining process, which the various loads were applied, has been investigated to get the bump with the extremely uniform heights. Finally, low-volume bumps with the excellent uniformity were successfully achieved.

1.5-μm and 10-Gb s−1 etched mesa buried heterostructure DFB-LD for datacenter networks

The microstructural degradation of a lattice-matched Ga 0.28 In 0.72 As 0.61 P 0.39 /InP heterointerface during atomic intermixing induced by Zn diffusion has been investigated using high-resolution transmission electron microscopy and Auger electron spectroscopy. The localized interfacial stress caused by intermixing appears to create stacking faults in the Ga-mixed InP substrate, and dislocation tangles in the In-mixed GalnAsP layer. The results are attributed to the contrasted effect of tensile and compressive stresses upon the nucleation of partial dislocations from both sides of the intermixed interface. A qualitative model is proposed for the homogeneous nucleation of misfit dislocations from the locally stressed interface.

Solder Bump Maker with coining process on TSV chips for 3D packages

Bonding-pad electrode-area-etched AlGaN/GaN on a Si-based Schottky barrier diode (SBD) is fabricated. Electrode mesa etching leads to reverse bias leakage current about one order of magnitude lower than that of SBD without electrode mesa etching, but forward currents do not vary greatly, compared with that in conventional SBD, which has no electrode mesa etching.