低波长漂移的电吸收调制DFB激光器

采用端面有效反射率法,从理论上计算了单片集成电吸收调制DFB激光器（Electroabsorption Modulated DFB Laser,EML）的腔面反射率、耦合强度（κL）对其波长漂移的影响.同时在实验中通过改变腔面的反射率来验证计算结果.理论与实验的结果表明：为提高EML的模式稳定性,必须减小调制器一端的反射率,同时增加DFB激光器的κL.最终我们采用选择区域生长（Selective Area Growth,SAG）的方法,制作了低光反馈出光面的单脊条形EML,在2.5Gb/s的非归零(NRZ)码调制下,经过280km的标准光纤传输后,没有发现色散代价.     

Fabrication and Packaging of 40-Gb/s AlGaInAs Multiple-Quantum-Well Electroabsorption Modulated Lasers Based on Identical Epitaxial Layer Scheme

High-speed AlGaInAs multiple-quantum-well (MQW) electroabsorption modulated lasers (EMLs) based on an identical epitaxial layer (IEL) integration scheme are developed for 40-Gb/s optical fiber communication systems. A self-aligned planarization technique has been adopted to reduce the capacitance of the electroabsorption modulator (EAM). The IEL structure EML chips exhibit a small signal modulation bandwidth around 40 GHz. The influence of residual reflection at the modulator facet on the small signal modulation response is investigated. Submount containing a grounded coplanar waveguide (GCPW) transmission line is used for packaging the EML chips into transmitter modules. The optimization of the GCPW structure to suppress resonances in frequency response due to parallel-plate modes is presented. Clear eye opening under 40-Gb/s nonreturn-to-zero (NRZ) modulation has been demonstrated for the packaged EML module.     

High-speed electroabsorption modulator with strip-loaded GaInAsP planar waveguide

We describe fabrication and characterization of an electroabsorption (EA) light modulator (LM) with a strip-loaded GaInAsP planar waveguide. The EA LM's were fabricated from hydride vapor-phase-epitaxy (VPE) grown wafers. The electroabsorption, the insertion loss, the electrical properties, and the modulation characteristics were investigated for the EA LM's. The drive voltage at a 99-percent modulation depth has been noticeably reduced to 4.5 V by optimizing the thicknesses of the epitaxial layers. The total capacitance of 1.5 pF was obtained by inserting an insulating film under the wire-bonding pad and by improving the mount design. Consequently, a 3-dB bandwidth of 3.8 GHz has been achieved and a pulse modulation operation under 2 Gbit/s nonreturn-to-zero (NRZ) pseudorandom pattern has also been confirmed. Moreover, the dynamic spectra of the EA modulators were measured for the first time. A spectral broadening factor α has been determined to be 1-4 from a relative strength of the sideband to the carrier and it has been experimentally found to decrease with increasing the electric field inside the absorptive waveguide. As the other measures of merit for the EA LM's, the extinction ratio over 23 dB and the insertion loss of 10-14 dB including a coupling loss due to an end-fire method were obtained. As a whole, these results have exhibited that the EA LM is a promising external modulator which will be monolithically integrated into a gigabit per second optical source with a dynamic single-mode laser.     

40 Gb/s Traveling‐Wave Electroabsorption Modulator‐Integrated DFB Lasers Fabricated Using Selective Area Growth

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.     

多量子阱电吸收调制DFB激光器的一种新型LP-MOCVD对接生长方法

提出了一种提高多量子阱电吸收调制DFB LD集成器件(EML)耦合效率的对接生长方法.采用LP MOCVD外延方法,制作了对接方法不同的三种样片,通过扫描电镜研究它们的表面及对接界面形貌,发现新对接结构的样片具有更好的对接界面.制作出相应的三种EML管芯,从测量所得到的出光功率特性曲线,计算出不同对接方法下EML管芯的耦合效率和外量子效率.实验结果表明,这种对接生长方案,可以获得光滑的对接界面,显著提高了激光器和调制器之间的耦合效率(从常规的17%提高到78% )及EML器件的外量子效率(从0 0 3mW /mA提高到0 15mW /mA) .     

端面反射对集成光源高频特性的影响及其抑制

研究了分布反馈型半导体激光器（DFB-LD）与电吸收（EA）调制器集成光源中调制器端面残余反射对器件高频特性的影响及其消除。针对在DFB-LD／EA集成光源小信号调制响应曲线低频段观察到的异常起伏,测量了DFB-LD的强度噪声谱,比较了不同反向偏压下EA调制器的调制响应。实验结果表明,对集成器件调制响应的干扰主要是来自于EA调制器端面的残余反射而不是微波调制信号的串扰。为了抑制调制器端面的光反射,优化了抗反镀膜工艺,基本消除了调制响应的异常起伏,有效改善了集成器件的高频调制特性。     

Proposal and Analysis of Distributed Reflector‐Laser Diode Integrated with an Electroabsorption Modulator

A novel integrated laser, that is, a distributed reflector laser diode integrated with an electroabsorption modulator, is proposed to improve the output efficiency, single‐mode stability, and chirp. The proposed laser can be realized using the selective metalorganic vapor phase epitaxy technique (that is, control of the width of the insulating mask), and its fabrication process is almost the same as the conventional electroabsorption modulated laser (EML) process except for the asymmetric coupling coefficient structure along the cavity. For our analysis, an accurate time‐domain transfer‐matrix‐based laser model is developed. Based on this model, we perform steady‐state and large‐signal analyses. The performances of the proposed laser, such as the output power, extinction ratio, and chirp, are compared with those of the EML. Under 10‐Gbps NRZ modulation, we can obtain a 30% higher output power and about 50% lower chirp than the conventional EML. In particular, the simulation results show that the chirp provided by the proposed laser can appear to have a longer wavelength side at the leading edge of the pulse and a shorter wavelength side at the falling edge.     

10-Gb/s, 80-km SMF Transmission From 0 to 80 $^{circ}$C by Using L-Band InGaAlAs-MQW Electroabsorption Modulated Laser With Twin Waveguide Structure

A 10-Gbit/s, 1.58-mu m, InGaAlAs electroabsorption modulator (EAM) integrated distributed-feedback (DFB) laser (EML) with a twin waveguide (TWG) structure is operated experimentally over a wide temperature range of 0 to 80degC. We introduce an InGaAlAs multi-quantum well (MQW) system for both LD and EAM MQWs, because this material has temperature-tolerant characteristics. These layers are grown using single step epitaxial growth, and the device was fabricated with a very simple process. Moreover, successful transmission through an 80-km single-mode fiber (SMF) was achieved with the device running at up to 80degC. These results confirm the suitability of this type of laser for use as a cost-effective and low-power consumption light source in 10-Gbit/s optical network systems.     

Discrete electroabsorption modulators with enhanced modulationdepth

In this paper, we present an investigation into factors that limited the median modulation depth of a batch of packaged discrete waveguide EA modulators to 23 dB at a wavelength of 1.55 μm. Results from detailed measurements of the DC absorption and photocurrent spectra are used to show how stray parasitic light can perturb the absorption characteristic and reduce the modulation depth of these high-speed multiple-quantum-well modulators. A novel ridged deeply etched buried heterostructure EA modulator design is presented in which stray light is removed from the immediate vicinity of the guided mode. The key structural difference between these and the previous devices is that they employ a much thicker Fe-doped InP current blocking layer that was grown by atmospheric pressure MOVPE using PCl₃ for planarization. Detailed measurements of the DC absorption spectra of a packaged ridged deeply etched buried heterostructure device confirm that stray light causes only a minor perturbation on its absorption characteristics. Consequently the new batch of EA modulator modules have a higher median modulation depth of 40 dB, as well as lower fiber-to-fiber insertion losses and picosecond pulse generation capabilities that are very similar to the previous devices which were used in 40 Gb/s optically time division multiplexed experiments     

Investigating the Role of Emissive Layer Architecture on the Exciton Recombination Zone in Organic Light‐Emitting Devices

An experimental approach to determine the spatial extent and location of the exciton recombination zone in an organic light‐emitting device (OLED) is demonstrated. This technique is applicable to a wide variety of OLED structures and is used to examine OLEDs which have a double‐ (D‐EML), mixed‐ (M‐EML), or graded‐emissive layer (G‐EML) architecture. The location of exciton recombination in an OLED is an important design parameter, as the local optical field sensed by the exciton greatly determines the efficiency and angular distribution of far‐field light extraction. The spatial extent of exciton recombination is an important parameter that can strongly impact exciton quenching and OLED efficiency, particularly under high excitation. A direct measurement of the exciton density profile is achieved through the inclusion of a thin, exciton sensitizing strip in the OLED emissive layer which locally quenches guest excitons and whose position in the emissive layer can be translated across the device to probe exciton formation. In the case of the G‐EML device architecture, an electronic model is developed to predict the location and extent of the exciton density profile by considering the drift, diffusion, and recombination of charge carriers within the device.     

Anisotropic electroabsorption and optical modulation in InGaAs/InAlAs multiple quantum well structures

The first measurements to be made of large anistropic electroabsorption and modulation of long-wavelength light propagating along the plane of InGaAs/InAlAs multiple quantum well (MQW) structures grown by molecular beam epitaxy (MBE) are reported. Photocurrent response of waveguide p-i-n diodes is studied for incident light polarization parallel and perpendicular to the MQW layers. Photocurrent increase with reverse bias throughout the entire photoresponse spectrum is observed for both polarizations. The MQW p-in optical modulator shows a capacitance-limited pulse response of 250 ps and the modulation depth is 14 percent.     

Physical Media Dependent Prototype for 10‐Gigabit‐Capable PON OLT

In this work, we study the physical layer solutions for 10‐gigabit‐capable passive optical networks (PONs), particularly for an optical link terminal (OLT) including a 10‐Gbit/s electroabsorption modulated laser (EML) and a 2.5‐Gbit/s burst mode receiver (BM‐Rx) in a novel bidirectional optical subassembly (BOSA). As unique features, a bidirectional mini‐flat package and a 9‐pin TO package are developed for a 10‐gigabit‐capable PON OLT BOSA composed of a 1,577‐nm EML and a 1,270‐nm avalanche photodiode BM‐Rx, including a single‐chip burst mode integrated circuit that is integrated with a transimpedance and limiting amplifier. In the developed prototype, the 10‐Gbit/s transmitter and 2.5‐Gbit/s receiver characteristics are evaluated and compared with the physical media dependent (PMD) specifications in ITU‐T G.987.2 for XG‐PON1. By conducting the 10‐Gbit/s downstream and 2.5‐Gbit/s upstream transmission experiments, we verify that the developed 10‐gigabit‐capable PON PMD prototype can operate for extended network coverage of up to a 40‐km fiber reach.     

GaInAsP buried channel ea modulator for 13?m fibre links

Double-heterostructure (DH) GaInAsP/InP buried channel waveguide electroabsorption (EA) modulators are demonstrated. They are designed for external intensity modulation of 1·3 ?m laser light and direct coupling to single-mode fibre. For a 650?m-long device, a 30 dB on/off ratio has been achieved at a bias voltage of ? 9 V. The substrate light is found to be a limiting factor of the measured extinction ratio for short modulators, but not for long (1·8 mm) modulators     

单脊条形可调谐电吸收调制DFB激光器

报道了一种波长可热调谐的电吸收调制分布反馈激光器(Electroabsorptionmodulateddistributedfeedbacklaser,EML)。在激光器条形的侧面淀积一薄膜加热器,EML实现了 2 2nm的连续调谐。在调谐范围内,激光器输出功率的变化小于 3dB。采用端面有效反射率方法和耦合波理论的计算表明:采用相调制方法,可实现调谐范围达3 2nm的EML。如果热调谐与相调谐方法结合,可在较宽范围内实现波长快速调谐的EML     

平板波导光谱仪中光栅多次衍射杂散光的抑制

平板波导光谱仪是一种紧凑型光谱仪,其光栅多次衍射杂散光大,需要进行抑制。首先研究了多次衍射杂散光的形成过程,并通过TracePro软件详细分析了多次衍射杂散光的传播路径和大小。然后根据杂散光的空间特性和波长特性对其进行分类,采取不同的抑制方法。在不改变原有光学结构的基础上提出了利用滤光片和挡光板来抑制多次衍射杂散光的方法,滤光片的参数和位置需要精心选择以达到最好的抑制效果。最后对增加抑制结构前后的杂光系数进行对比分析。结果表明,多次衍射杂散光得到了很好的抑制,最大杂光系数从5.3%降到0.033%,平均杂光系数从1.9%降到0.0018%。     

Degradation Mechanism of Perovskite Light‐Emitting Diodes: An In Situ Investigation via Electroabsorption Spectroscopy and Device Modelling

The past few years have seen a significant improvement in the efficiency of organometal halide‐perovskite‐based light‐emitting diodes (PeLEDs). However, poor operation stability of the devices still hinders the commercialization of this technology for practical applications. Despite extensive studies on the degradation mechanisms of perovskite thin films, it remains unclear where and how degradation occurs in a PeLED. Electroabsorption (EA) spectroscopy is applied to study the degradation process of PeLEDs during operation and directly evaluates the stability of each functional layer (i.e., charge transporting layers and light‐emitting layer) by monitoring their unique optical signatures. The EA measurements unambiguously reveal that the degradation of the PeLEDs occurs predominantly in the perovskite layer. With finite‐element method‐based device modeling, it is further revealed that the degradation may initiate from the interface between the perovskite and hole transporting layers and that vacancy, antisite, or interstitial defects can further accelerate this degradation. Inspired by these observations, a surface‐treatment step is introduced to passivate the perovskite surface with phenethylammonium iodide. The passivation leads to a drastic enhancement of the PeLED stability, with the operation lifetime increased from 1.5 to 11.3 h under a current density of 100 mA cm^?2.     

3D Micromolding of Arrayed Waveguide Gratings on Upconversion Luminescent Layers for Flexible Transparent Displays without Mirrors,Electrodes, and Electric Circuits

A new technique for the fabrication of arrayed waveguide gratings on upconversion luminescent layers for flexible transparent displays is reported. Ho³⁺‐ and Yb³⁺‐codoped NaYF₄ nanoparticles are synthesized by hydrothermal techniques. Transparent films consisting of two transparent polymers on the NaYF₄ nanoparticle films exhibit mechanical flexibility and high transparence in visible region. Patterned NaYF₄ nanoparticle films are fabricated by calcination‐free micromolding in capillaries. Arrayed waveguide gratings consisting of the two transparent polymers are formed on the patterned NaYF₄ nanoparticle films by micromolding in capillaries. Green and red luminescence is observed from the upconversion luminescent layers of the NaYF₄ nanoparticle films in the arrayed waveguide gratings under excitation at 980 nm laser light. Arrayed waveguide gratings on the upconversion luminescent layers are fabricated with Er³⁺‐doped NaYF₄ nanoparticles which can convert two photons at 850 and 1500 nm into single photon at 550 nm. These results demonstrate that flexible transparent displays can be fabricated by constructing arrayed waveguide gratings on upconversion luminescent layers, which can operate in nonprojection mode without mirrors, transparent electrodes, and electric circuits.     

选择区域生长高质量InGaAsP多量子阱材料

采用LP-MOVPE在SiO2掩膜的InP衬底上实现了高质量的InGaAsP多量子阱(MQW)的选择区域生长(SAG).通过改变生长温度和生长压力,MQW的适用范围由C波段扩展至L波段,即MQW的光致发光波长从1546nm延展至1621nm.光致发光（PL）测试表明：在宽达75nm的波长范围内,MQW的质量与非选择生长的MQW质量相当,并成功制作出电吸收调制DFB激光器（EML）.     

选择区域生长高质量InGaAsP多量子阱材料

采用 L P- MOVPE在 Si O2 掩膜的 In P衬底上实现了高质量的 In Ga As P多量子阱 (MQW)的选择区域生长(SAG) .通过改变生长温度和生长压力 ,MQW的适用范围由 C波段扩展至 L 波段 ,即 MQW的光致发光波长从15 46 nm延展至 16 2 1nm.光致发光 (PL)测试表明 :在宽达 75 nm的波长范围内 ,MQW的质量与非选择生长的MQW质量相当 ,并成功制作出电吸收调制 DFB激光器 (EML) .     

Measurement of facet reflectivity of antireflection-coatedelectroabsorption modulator using induced photocurrent

A new method to measure the facet reflectivity of an antireflection (AR)-coated electroabsorption (EA) modulator in the region of operating wavelengths is proposed. First, by measuring the induced photocurrent and reflectance simultaneously at the front facet of an EA waveguide, the cleaved facet reflectivity and propagation loss are determined. After coating the facet with AR, the residual reflectivity of AR-coated facet is obtained from the measured photocurrent spectra and the predetermined facet reflectivity. We demonstrate the reflectivity of a double-layer AR-coated EA modulator can be measured to be ~4×10^-4 at 1.55 μm for TE polarization by using the proposed technique