420 Gbit/s optical signal reception enabled by an inductive gain peaking Ge-Si photodetector with 80†GHz bandwidth.

Based on the commercial silicon photonics (SiPh) process platform, a flat 3 dB bandwidth of 80 GHz germanium-silicon (Ge-Si) photodetector (PD) is experimentally demonstrated at a photocurrent of 0.8 mA. This outstanding bandwidth performance is achieved by using the gain peaking technique. It permits an 95% improvement in bandwidth without sacrificing responsivity and undesired effects. The peaked Ge-Si PD shows the external responsivity of 0.5 A/W and internal responsivity of 1.0 A/W at a wavelength of 1550 nm under -4 V bias voltage. The high-speed large signal reception capability of the peaked PD is comprehensively explored. Under the same transmitter state, the transmitter dispersion eye closure quaternary (TDECQ) penalties of the 60 and 90 Gbaud four-level pulse amplitude modulation (PAM-4) eye diagrams are about 2.33 and 2.76 dB, 1.68 and 2.45 dB for the un-peaked and peaked Ge-Si PD, respectively. When the reception speed increase to 100 and 120 Gbaud PAM-4, the TDECQ penalties are approximatively 2.53 and 3.99 dB. However, for the un-peaked PD, its TDECQ penalties cannot be calculated by oscilloscope. We also measure the bit error rate (BER) performances of the un-peaked and peaked Ge-Si PDs under different speed and optical power. For the peaked PD, the eye diagrams quality of 156 Gbit/s nonreturn-to-zero (NRZ), 145 Gbaud PAM-4, and 140 Gbaud eight-level pulse amplitude modulation (PAM-8) are as good as the 70 GHz Finisar PD. To the best of our knowledge, we report for the first-time a peaked Ge-Si PD operating at 420 Gbit/s per lane in an intensity modulation direct-detection (IM/DD) system. It might be also a potential solution to support the 800 G coherent optical receivers.

Distortion-free amplification of 100†GHz mode-locked optical frequency comb using quantum dot technology.

Semiconductor mode-locked optical frequency comb (ML-OFC) sources with extremely high repetition rates are central to many high-frequency applications, such as dense wavelength-division multiplexing. Dealing with distortion-free amplification of ultra-fast pulse trains from such ML-OFC sources in high-speed data transmission networks requires the deployment of semiconductor optical amplifiers (SOAs) with ultrafast gain recovery dynamics. Quantum dot (QD) technology now lies at the heart of many photonic devices/systems owing to their unique properties at the O-band, including low alpha factor, broad gain spectrum, ultrafast gain dynamics, and pattern-effect free amplification. In this swork, we report on ultrafast and pattern-free amplification of ∼100 GHz pulsed trains from a passively ML-OFC and up to 80 Gbaud/s non-return-to-zero (NRZ) data transmission using an SOA. Most significantly, both key photonic devices presented in this work are fabricated from identical InAs/GaAs QD materials operating at O-band, which paves the way for future advanced photonic chips, where ML-OFCs could be monolithically integrated with SOAs and other photonic components, all originated from the same QD-based epi-wafer.

Experimental demonstration of a 160 Gbit/s 3D-integrated silicon photonics receiver with 1.2-pJ/bit power consumption.

By using the flip-chip bonding technology, a high performances 3D-integrated silicon photonics receiver is demonstrated. The receiver consists of a high-speed germanium-silicon (Ge-Si) photodetector (PD) and a commercial linear transimpedance amplifiers (TIA). The overall 3 dB bandwidth of the receiver is around 38 GHz with appropriate gain. Based on this 3D-integrated receiver, the 56, 64, 90, 100 Gbit/s non-return-to-zero (NRZ) and 112, 128 Gbit/s four-level pulse amplitude (PAM-4) modulation clear openings of eye diagrams are experimentally obtained. The sensitivities of -10, -5.2 dBm and -6.6, -2.7 dBm were obtained for 112 Gbit/s NRZ and 160 Gbit/s PAM-4 at hard-decision forward err correction (HD-FEC,3.8 × 10-3) and KP4 forward err correction (KP4-FEC,2 × 10-4) threshold, respectively. Additionally, the lowest power consumption of this receiver is about 1.2 pJ/bit, which implies its huge potential for short-reach data center applications.

180 Gbit/s Si3N4-waveguide coupled germanium photodetector with improved quantum efficiency.

A high quantum efficiency (QE) and high-speed silicon nitride (Si3N4) waveguide coupled germanium-on-silicon photodetector (Ge-on-Si PD) is presented. The proposed device is fabricated in a commercial 90 nm silicon photonics process platform. By decreasing the spacing between the tapered Si3N4 waveguide and the bottom Si to 200 nm and the Si3N4 thickness to 300 nm, the QE is significantly improved. Although the theoretical responsivity can reach up to 0.92 A/W at 1550 nm, the measured value is calculated to be approximately 0.61 A/W. The maximum experimental responsivity is about 0.9 A/W at 1485 nm. The 3 dB optoelectrical bandwidth of up to 54 GHz is demonstrated at a -3.3V bias. Additionally, the 80, 90, 100, and 105 Gbit/s non-return-to-zero on-off-keying and the 150, 160, 170, and 180 Gbit/s four-level pulse amplitude modulation clear openings of the electrical eye diagrams are attained. Overall, the Si3N4-waveguide coupled Ge-on-Si PD in this work possesses higher QE and operates at the highest data rates reported so far.

High-performance germanium avalanche photodetector for 100 Gbit/s photonics receivers.

A high-bit rate and low-bias voltage waveguide-integrated vertical germanium avalanche photodetector is reported with doping optimization. This scheme alleviates the necessity of complex epitaxial single-crystal silicon layer and multiple ion implantation schemes. The optical absorption and carrier avalanche multiplication gain occur in the same germanium layer. The maximum gain is estimated to be 112.4 at an input power of -30.2dBm. With the input optical power of -16.1dBm, the gain-bandwidth product of nearly 141 GHz is obtained at 7.8 V bias. Meanwhile, a 4.6 dB sensitivity improvement for 60 Gbit/s signal reception is demonstrated with an avalanche gain of 5.1 at a soft-decision forward-error correction threshold (SD-FEC), i.e., bit-error-rate of 2×10-2. The absolute sensitivities of photonics receivers are -21, -18.6, -15.9, and -11.5dBm for 40, 60, 80, and 100 Gbit/s non-return-to-zero signals at the SD-FEC threshold. These demonstrated characteristics enable the reliable and robust on-chip photodetection for energy efficienct silicon photonic interconnects in the future.

High-speed lateral PIN germanium photodetector with 4-directional light input.

We experimentally demonstrate a high-speed lateral PIN junction configuration germanium photodetector (Ge-PD) with 4-directional light input. The typical internal responsivity is about 1.23 A/W at 1550 nm with 98% quantum efficiency and dark current 4 nA at 1V reverse-bias voltage. The equivalent circuit model and theoretical 3-dB opto-electrical (OE) bandwidth of Ge-PD are extracted and calculated, respectively. Compared to the conventional lateral PIN Ge-PD with 1-directional light input, our proposed device features uniform optical field distribution in the absorption region, which will be benefit to realize high-power and high-speed operation. In particular, in the condition of 0.8 mA photocurrent, the measured 3-dB OE bandwidth is about 17 GHz at bias voltage of -8 V which is well matched to the theoretical estimated bandwidth. With additional digital pre-compensations provided by the Keysight arbitrary waveform generator (AWG), the root raised cosine (RRC) filter and roll-off factor of 0.65 are employed at transmitter (TX) side without utilizing any offline digital signal processing (DSP) at receiver (RX) side. The 50 Gbit/s, 60 Gbit/s, 70 Gbit/s, and 80 Gbit/s non-return-to-zero (NRZ), and 60 Gbit/s, 70 Gbit/s, 80 Gbit/s, and 90 Gbit/s four-level pulse amplitude modulation (PAM-4) clear opening of eye diagrams are realized. In order to verify the high-power handling performance in high-speed data transmission, we also investigate the 20 Gbit/s NRZ eye diagram variations with the increasing of photocurrent.

[An investigation of the sexual physiological and psychological development of 2,770 high school students in Yibin].

OBJECTIVE: To investigate the actual condition of the sexual physiological and psychological development of the high school students in Yibin in order to get a reliable basis for sexual education of the teenagers. METHODS: With a proportion of 1% to the whole, 2,770 students were randomly selected from eight high schools in the urban and rural areas of the city. We devised a questionnaire and asked each student to fill in his or her answers presently. RESULTS: So far as sexual physiological and psychological development was concerned, the high school students of Yibin were found rather precocious, with very little sexual knowledge and psychological endurance in sexual affairs and a relative lack of sexual education. CONCLUSION: It is imperative to extend the scope of puberty sexual education in high schools. Teenagers must be taught different kinds of sexual knowledge at different periods of growth as well as how to avoid sexually transmitted diseases and gestation. The sexual knowledge level of the teachers must also be raised. It is a must to establish service or specialist consultation hot lines about sexual knowledge for teenagers. Parents are expected to change their traditional views and assume an active role in the joint efforts of sexual education for their children.