Abstract-We introduce a single-loop PLL that operates in a narrower-bandwidth, integer-mode during phase lock and in a wider-bandwidth, fractionalmode during transient. This hybrid PLL, as a generalization of the conventional variable-bandwidth PLL that shifts only its bandwidth, simultaneously achieves the fast-locking advantage of the fractional-PLL and design simplicity of the integer-PLL, and as such, brings benefits in certain important PLL applications. In addition, the frequency division mode switching, unique in the hybrid PLL, enables a new, more digital protocol to execute bandwidth switching. A CMOS IC prototype attests to the validity of the proposed approach.Index Terms-Charge-pump phase-locked loops, fractionalfrequency synthesizers, integer-frequency synthesizers, phaselocked loops.

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 mm 2 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. Index Terms-AlGaN/GaN on Si, Schottky barrier diode (SBD), recess dual anode metal, low turn-on voltage. I. INTRODUCTIONG ALLIUM nitride (GaN) power devices are drawing greater attention in high-power switching applications owing to their superior power density, efficiency, and switching speed [1]. To achieve high efficiency and a small size in a power-conversion system, a low turn-on voltage (V T ), low on-resistance (R on ) and low reverse recovery of the diode are very important [2]. Various technologies to improve the performance of an SBD have recently been studied. Researches to reduce on-resistance and to reduce surface leakage current, such as SiO 2 , SiN x , Al 2 O 3 dielectric film, have been investigated [3]. In addition, studies on recess etching in the anode region and recess depth control have been actively conducted owing to the capability of recessed SBDs to reduce the V T without an increase in the leakage current [4]-[6]. However, for large device fabrication, the dry etch conditions including a uniform etch profile, a reproducible etch rate, and a small amount of plasma damage are very difficult and Manuscript

In this paper, we present the fabrication of 40 Gb/s traveling‐wave electroabsorption modulator‐integrated laser (TW‐EML) modules. A selective area growth method is first employed in 40 Gb/s EML fabrication to simultaneously provide active layers for lasers and modulators. The 3 dB bandwidth of a TW‐EML module is measured to be 34 GHz, which is wider than that of a lumped EML module. The 40 Gb/s non‐return‐to‐zero eye diagram shows clear openings with an average output power of +0.5 dBm.

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 receiver's 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.

A low onset voltage AlGaN/GaN diode with a width of 14 mm is achieved. The recess depth of the AlGaN layer is responsible for the low onset voltage. In comparison with the conventional non-recessed diode, the onset voltage reduces by 45% along with a decrease of reverse leakage current by about one order of magnitude.