70 Gbps PAM-4850-nm oxide-confined VCSEL without equalization and pre-emphasis

Directly modulated 850-nm vertical-cavity surface-emitting lasers(VCSELs)with the advantages of low cost,high modulation speed,good reliability,and low power consumption,are the key sources in the optical interconnects with multimode fibers for the supercomputers,data centers,and machine learning applications[1−3].Typically,non-return-tozero(NRZ)modulation format is used.

Design and experimental study of compensation fitting on the angle-tuned filters

For a 100 GHz DWDM angle-tuned filter with low polarization dependent loss,the insertion loss and the Gaussian-transformation tendency of the transmission spectrum will become more serious as the incident angle is increased. It is because of that the optical path and the transmission modes of the thin film filter will change when the incident angle is varied. According to the thin film matrix theory,the analysis model is established,the displacement change of the transmission field is simulated,and a dynamic compensation fitting is also designed and fabricated in the paper. The experimental results show that it can effectively reduce the insertion loss and the phenomenon of Gaussian process. Using the compensation fitting,the tunable range of the filter is at about 20 nm which coincides with the theoretical design.

Four-Channel 1.55μm DFB Laser Array Monolithically Integrated with a 4× 1 Multimode-Interference Combiner Based on Nanoimprint Lithography

A monolithically integrated four-channel λ/4 phase shift distributed feedback （DFB） laser array with a 4 × 1 multimode interference combiner is designed and fabricated using nanoimprint lithography. The threshold currents of the lasers are less than 10mA, which are as good as a discrete DFB laser. Moreover, the side-mode suppression ratio is also better than 50 dB. The channel space is about 200 GHz for dense wavelength division multiplexing applications in an 1.55μm system.

A Multiple Phase-Shifted Distributed Feedback(DFB)Laser Fabricated by Nanoimprint Lithography

Multiple phase-shifted(MPS)diffraction grating is an effective way proposed to overcome the spatial hole burning(SHB)effect in a distributed feedback(DFB)laser.We present two symmetric λ/8 phase-shifted DFB lasers by using nanoimprint lithography(NIL).The threshold current of a typical laser is less than 15 mA.The side mode suppression ratio(SMSR)is still above 42 dB even at 100 mA current injection.To show the versatility of NIL,eight different wavelength MPS-DFB lasers on this single chip are also demonstrated.Our results prove that NIL is a promising tool for fabricating high performance complex grating DFB lasers.

A 16-Channel Distributed-Feedback Laser Array with a Monolithic Integrated Arrayed Waveguide Grating Multiplexer for a Wavelength Division Multiplex-Passive Optical Network System Network

A 16 隧道分布式反馈(DFB ) 有为一个波长部门更复合的一个整体的综合穿的波导栅栏的激光数组复合被动的光网络系统被使用靶子关节金属制作器官的化学蒸汽免职技术和 nanoimpirnt 技术。结果证明阀值水流是在 25 点的大约 2030

Synthesis and Crystal Structure of {4-[2-(9-Hexyl-9H-carbazol-3-yl)vinyl]phenyl} Dimethylamine

The title compound {4-[2-（9-hexyl-9H-carbazol-3-yl）vinyl]phenyl} dimethylamine has been synthesized by the well known Wittig reaction, and its crystal structure was determined by single-crystal X-ray diffraction analysis. It crystallizes in monoclinic, space group P21/c with a = 47.87（2）, b = 10.222（4）, c = 9.612（4）A, β = 92.401（9）°, V = 4699（3）A^3, Z = 8, C28H32N2, Mr = 396.56, Dc = 1.121 g/cm^3, F（000） = 1712 and μ（MoKa） = 0.065 mm^-1. The final R and wR are 0.0793 and 0.1983, respectively for 3524 observed reflections with Ⅰ〉 2σ（Ⅰ）. In the title compound, the bond lengths are normal, and the crystal is stabilized by Van der Waals＇ forces.

High gain optical amplification and lasing performance of the Bi/P co-doped silica fiber in the O-band

In this Letter,the optical amplification characteristics of the home-made Bi/P co-doped silica fiber were systematically explored in the range of 1270–1360 nm.The maximum gain of 24.6 dB was obtained in the single-pass amplification device,and then improved to 38.3 dB in the double-pass amplification device for-30 dBm signal power.In addition,we simultaneously investigated the laser performance of the fiber with the linear cavity.A slope efficiency of 16.4%at~1313 nm was obtained with a maximum output power of about 133 mW under the input pump power of 869 mW at 1240 nm.As far as we know,it is the first laser reported based on the bismuth-doped fiber in China.

Room-temperature continuous-wave electrically pumped InGaN/GaN quantum well blue laser diode directly grown on Si

Current laser-based display and lighting applications are invariably using blue laser diodes(LDs)grown on freestanding GaN substrates,which are costly and smaller in size compared with other substrate materials.1–3 Utilizing less expensive and large-diameter Si substrates for hetero-epitaxial growth of indium gallium nitride/gallium nitride(InGaN/GaN)multiple quantum well(MQW)structure can substantially reduce the cost of blue LDs and boost their applications.To obtain a high crystalline quality crack-free GaN thin film on Si for the subsequent growth of a blue laser structure,a hand-shaking structure was formed by inserting Al-composition step down-graded AlN/AlxGa1−xN buffer layers between GaN and Si substrate.Thermal degradation in InGaN/GaN blue MQWs was successfully suppressed with indium-rich clusters eliminated by introducing hydrogen during the growth of GaN quantum barriers(QBs)and lowering the growth temperature for the p-type AlGaN/GaN superlattice optical cladding layer.A continuous-wave(CW)electrically pumped InGaN/GaN quantum well(QW)blue(450 nm)LD grown on Si was successfully demonstrated at room temperature(RT)with a threshold current density of 7.8 kA/cm^(2).

800 Gbit/s transmission over 1 km single-mode fiber using a four-channel silicon photonic transmitter

We demonstrate the optical transmission of an 800 Gbit/s(4×200 Gbit/s)pulse amplitude modulation-4(PAM-4)signal and a 480 Gbit/s(4×120 Gbit/s)on–off-keying(OOK)signal by using a high-bandwidth(BW)silicon photonic(SiP)transmitter with the aid of digital signal processing(DSP).In this transmitter,a four-channel SiP modulator chip is co-packaged with a four-channel driver chip,with a measured 3 dB BW of 40 GHz.DSP is applied in both the transmitter and receiver sides for pre-/post-compensation and bit error rate(BER)calculation.Back-to-back(B2B)BERs of the PAM-4 signal and OOK signal are first measured for each channel of the transmitter with respect to a variety of data rates.Similar BER performance of four channels shows good uniformity of the transmitter between different channels.The BER penalty of the PAM-4 and OOK signals for 500 m and 1 km standard single-mode fiber(SSMF)transmission is then experimentally tested by using one channel of the transmitter.For a 200 Gbit/s PAM-4 signal,the BER is below the hard-decision forward error correction(HD-FEC)threshold for B2B and below the soft-decision FEC(SD-FEC)threshold after 1 km transmission.For a 120 Gbit/s OOK signal,the BER is below SD-FEC threshold for B2B.After 500 m and 1 km transmission,the data rate of the OOK signal shrinks to 119 Gbit/s and 118 Gbit/s with the SD-FEC threshold,respectively.Finally,the 800 Gbit/s PAM-4 signal with 1 km transmission is achieved with the BER of all four channels below the SD-FEC threshold.

Ultra-low dark count InGaAs/InP single photon avalanche diode

A low noise InGaAs/InP single photon avalanche diode(SPAD) is demonstrated. The device is based on planar type separate absorption, grading, charge and multiplication structure. Relying on reasonably designed device structure and low-damage Zn diffusion technology, excellent low-noise performance is achieved. Due to its importance, the physical mechanism of dark count is analyzed through performance characterization at different temperatures. The device can achieve 20% single photon detection efficiency and 320 Hz dark count rate(DCR) with a low after pulsing probability of 0.57% at 233 K.

1.3-μm uncooled 10 Gb/s directly modulated MQW AlGaInAs/InP laser diodes

In this paper, we report a novel 1.3-μm uncooled AlGaInAs/InP multiple quantum well （MQW） ridge waveguide laser diodes. By optimizing the design of MQW structure and facet coatings, together with the application of reversed-mesa ridge waveguide （RM-RWG） structure, polyimide planarization, and lift-off processes technology, an uncooled 1.3-μm, 10-Gb/s directly modulated MQW ridge waveguide laser diode was successfully fabricated. The threshold current and the slope efficiency were 7 mA and 0.48 mW/mA, respectively. The directly modulated bandwidths of 11 and 9.2 GHz were achieved at room temperature and 80℃, respectively.

Spatial control based quantum well intermixing in InP/InGaAsP structures using ICP

This paper presents a new method based on spatial controlling in quantum well intermixing in InP/InGaAsP structures using ICP technology.The degree of bandgap energy shift in the same wafer can be controlled flexibly using masks with different duty ratios.With an optimal condition including ICP-RIE etching depth, SiO_2 deposition,and RTA process,five different degrees of blue-shift with maximum of 75 nm were obtained in the same sample.The result shows that our method is an effective way to fabricate monolithic integration devices, especially in multi-bandgap structures.

Fault monitoring in passive optical network using code division multiplex-based dual-OTDR traces comparison

A dual optical time domain reflectometry （OTDR） system, which employs two different continuous waves at the optical line terminal and a pair of fiber Bragg gratings at the end of each optical network unit, is proposed in a time-division multiplexing passive optical network （PON）. The proposed scheme accomplishes the fiber fault monitoring by comparing the different wavelength＇s testing curves. Complete complementary code is utilized to measure multiple wavelength signals simultaneously with only one receiver and to improve the dynamic range of this system. The PON system consisting of 20 km feeding fiber and a 1：16 splitter is investigated by the experiments. The experimental results show that the faulty branch can be successfully identified by using our scheme. What is more, we also demonstrate that our scheme can be applied to the multi-stage PON.

High speed and wide temperature range uncooled 1.3-μm ridge waveguide DFB lasers

A 1.3-μm wavelength vertical-mesa ridge waveguide mulitple-quantum-well （MQW） distributed feedback （DFB） laser with high directly modulated bandwidth and wide operation temperature range is reported. With the optimization of the strained-layer MQWs in the active region, the surrounding graded-index separated-confinement-heterostructure waveguide layers, together with the optimization of the detuning and coupling coefficient of the DFB grating, high directly modulation bandwidth of 16 GHz at room temperature and wide working temperature range from -40 to 85 ℃ are obtained. The mean time to failure （MTTF） is estimated to be over 2×10^6 h. The device is suitable as light source of high-bit-rate optical transmitters with small size and reduced cost.

Fabrication of low threshold current monolithic DFB laser with an MMI combiner

We fabricate low threshold current monolithic distributed feedback（DFB） laser with a multi-mode interface（MMI） combiner using butt-joint metal-organic chemical vapor deposition technology with different waveguide structures. Multi-layer mask self-aligned photolithography technology is used to form different waveguides in active and passive regions, respectively. The result shows that the laser threshold current is lower than 10 m A, with 50 d B side-mode suppression ratio.

Thermal radiation effect in near infrared single photon detector

Aminiaturized near infrared single photon detector is demonstrated by integrating a thermoelectric cooler(TEC),a thermistor,and a planar type In Ga As/In P separate absorption,charge and multiplication structure single photon avalanche diode into a butterfly case.The performance of the device at different temperatures is tested.It can achieve 20.3% single photon detection efficiency and 1.38 k Hz dark count rate when the chip is cooled to 223 K.The test results show that even when the chip temperature is kept constant,the dark count rate of the device still increases with the increase of ambient temperature,which is consistent with the carrier generation mechanism of semiconductor materials.The mechanism is researched and it is found that thermal radiation of the high temperature case is the main source of dark count.The deep research on the mechanism is beneficial to developing higher performance devices in the future.

Investigation on wavelength switching of widely tunable SGDBR lasers

The sampled-grating distributed Bragg reflector(SGDBR) laser is a typical and important photonic integrated device,and has potential wide application to agile optical networks.A new dynamic model for this device has been developed,which combines the traveling-wave method for the active region and the transfer-matrix method for the passive sections into a single procedure.The behaviors of wave-length switching of the SGDBR laser,which include the transient spectrum and mode competition,have been studied in detail using this model.A new efficient way has been proposed to improve the wavelength switching performance only by increasing the coupling coefficients without changing the carrier density.

A novel fabrication approach for an athermal arrayed-waveguide grating

A novel method for fabricating an athermal AWG is proposed, using a unique apparatus for ITU-T center wavelength adjustment and optical coupling of two cut-parts. UV adhesive or sticky gel is applied into the gap between the cut-elements and the alignment base substrate by capillary infiltration. The spectrum profiles are almost the same as those of the original chip state, and no deterioration is observed resulting from athermalization. Flat-top athermal AWG modules of 100 GHz × 40 ch are fabricated. Over a temperature range of-40 to 85 ℃, the center wavelength shift is ±22 pm, and the insertion loss change is less than ±0.11 dB.

A new approach for dynamic modeling of widely tunable GCSR lasers

A new dynamic model is developed for simulating the widely tunable grating assisted codirectional coupler with rear sampled grating reflector （GCSR） lasers. The gain section of the device is calculated in timedomain using traveling-wave method, while the transmission spectrum of the coupler and the reflection spectrum of the reflector are firstly simulated in frequency-domain, and then transformed into time-domain via digital filter approach. Both static and dynamic performances based on this model agree well with the published results. Compared with previous works, this new model is more efficient and applicable, especially in the dynamic simulation.

Review on developments of novel specialty fibers： performance, application and process

This paper reviews the development progress of optical fiber, the producing and application of the specialty optical fiber in the world. Finally it states the leading technology of optical fiber of the world. Specialty optical fibers are series of optical fiber which could satisfy special requirements. Recently, the rapidly growing need from fiber to the home （FTTH）, sensors, active optical link, energy conversion and delivery and fiber laser attracts researchers and optical companies to explore more possibilities of optical fiber and some novel specialty optical fibers were invented for the efforts. Bending insensitive optical fiber with the ability of extreme 3 mm bending diameter makes it possible to use the optical fiber as the electric wire in some extremely compact devices. Higher power was achieved in the fiber laser field with the development of rare earth doped fiber. Nanomaterials such as Au particles and ZnO nanostructures were utilized to extend the application in sensors and energy conversion. Pure silica design was commercialized to improve the radiation resistance of sensors based on fiber optics.