Traveling-wave photodetectors

The authors propose and analyze the traveling-wave photodetector (TWPD), an edge-coupled photodetector that is capable of both a larger absolute bandwidth and a larger bandwidth-efficiency product than the waveguide photodetector (WGPD). The intrinsic RC bandwidth limitation is increased in the traveling-wave photodetector by providing for controlled transmission of the electrical wave down the device in parallel with the optical wave and by eliminating bandwidth-limiting electrical reflections. It is shown that 1-μm wide, parallel-plate, GaAs/AlGaAs, p-i-n TWPD with open-circuit input termination has a 26% greater potential bandwidth-efficiency product than the comparable WGPD, while a TWPD with matched input termination actually has a worse bandwidth-efficiency product than the WGPD     

110-GHz, 50%-efficiency mushroom-mesa waveguide p-i-n photodiodefor a 1.55-μm wavelength

A mushroom-mesa structure is proposed to reduce the CR-time constant which originates from the waveguide photodiode structure. Experimental results at a 1.55-μm wavelength show that the multimode waveguide p-i-n photodiode with mushroom-mesa structure has an electrical 3-dB bandwidth of more than 75 GHz in the frequency domain and an electrical 3-dB bandwidth of 110 GHz in the time domain. The external quantum efficiency is 50% or 0.63 A/W, which leads to a record bandwidth-efficiency product of 55 GHz for long wavelength p-i-n photodetectors     

Highly efficient 40 GHz waveguide InGaAs p-i-n photodiode employing multimode waveguide structure

The authors describe the design procedure of a highly efficient waveguide p-i-n photodiode. The efficiency of the waveguide InP/InGaAsP ( lambda /sub g/=1.3 mu m)/InGaAs/InGaAsP ( lambda /sub g/=1.3 mu m)/InP p-i-n photodiode is calculated using the step-segment method and overlap-integral between the optical field of a fiber and that of the photodiode. A remarkably high coupling efficiency to a fiber can be obtained by using a multimode waveguide structure. The fabricated device has an external quantum efficiency of 68% as well as 3 dB bandwidth of higher than 40 GHz at a 1.55 mu m wavelength.<>     

一种高效高功率倏逝波耦合型光电探测器的研究

The effects of the multimode diluted waveguide on quantum efficiency and saturation behavior of the evanescently coupled uni-traveling carrier （UTC） photodiode structures are reported. Two kinds of evanescently coupled uni-traveling carrier photodiodes （EC-UTC-PD） were designed and characterized： one is a conventional EC-UTC-PD structure with a multimode diluted waveguide integrated with a UTC-PD; and the other is a compact EC-UTC-PD structure which fused the multimode diluted waveguide and the UTC-PD structure together. The effect of the absorption behavior of the photodiodes on the efficiency and saturation characteristics of the EC-UTC-PDs is analyzed using 3-D beam propagation method, and the results indicate that both the responsivity and saturation power of the compact EC-UTC-PD structures can be further improved by incorporating an optimized compact multimode diluted waveguide.     

A high-efficiency high-power evanescently coupled UTC-photodiode

The effects of the multimode diluted waveguide on quantum efficiency and saturation behavior of the evanescently coupled uni-traveling carrier(UTC)photodiode structures are reported.Two kinds of evanescently coupled uni-traveling carrier photodiodes(EC-UTC-PD)were designed and characterized:one is a conventional EC-UTC-PD structure with a multimode diluted waveguide integrated with a UTC-PD;and the other is a compact EC-UTC-PD structure which fused the multimode diluted waveguide and the UTC-PD structure together.The effect of the absorption behavior of the photodiodes on the efficiency and saturation characteristics of the EC-UTC-PDs is analyzed using 3-D beam propagation method,and the results indicate that both the responsivity and saturation power of the compact EC-UTC-PD structures can be further improved by incorporating an optimized compact multimode diluted waveguide.     

Spectral response of blue-sensitive Si photodetectors in SOI

In this paper, we present a novel blue-sensitive Si photodetector. The detector is realized as a Si diode with a vertical PN junction in the silicon-on-insulator (SOI) thin film for normal incident light. Due to the thin SOI device layer, the photodetector shows a blue-shift spectral response with the peak external quantum efficiency (QE) of 69.6% at wavelength of 480 nm. The photodetector adopts a thin layer of SiO₂ as an antireflection coating and as a blocking layer for shallow ion implantation doping. The isolation trench etched through the SOI thin film to the buried oxide (BOX) provides fully electrical isolation. The device structure is simple and its performance is very high, therefore, it is in favor of monolithically integration with other micro/nanodevices.     

A 1550-nm millimeter-wave photodetector with a bandwidth-efficiencyproduct of 2.4 THz

The monolithic integration of an optical preamplifier and a waveguide p-i-n photodiode has resulted in a 1550-nm photodetector having an external quantum efficiency of 72 (a responsivity of 89 A/W) and an electrical bandwidth of 33.5 GHz. These figures combine to give a bandwidth efficiency product of 2.4 THz, which is approximately one hundred times higher than for any other type of millimeter-wave photodetector published to date. In addition, the preamplifier performance is supplemented by wide optical bandwidth (60 nm), low polarization sensitivity (1 dB), near traveling wave amplification (1-dB maximum gain ripple), and high saturated output power (+11 dBm). The principal advance over work reported earlier is the traveling wave operation of the monolithic optical preamplifier     

谐振腔增强型光探测器的高速响应性能研究

高速长波长光探测器是高速光纤通信系统和网络的关键器件，它要求光探测器具有宽的频率响应带宽和高量子效率。常用的PIN光探测器由于量子效率和高速性能均受到吸收层厚度的牵制，使得二者相互制约，成为一对矛盾。谐振腔增强型(RCE)光探测器为这一矛盾的解决提供了有效的方案。基于谐振腔增强型光探测器的实际设计和制作模型，分析了器件吸收层中的光场分布，并将其运用于载流子的连续方程，从理论上详细地分析了器件的高速响应特性，给出了计算结果。针对研制的高速长波长谐振腔增强型光探测器，进行了理论分析和实际器件测试的结果比较，得到了比较一致的结果。     

Wavelength-selective semiconductor in-line fibre photodetectors

A photodetector which extracts and detects light at a specific wavelength travelling through a fibre is presented. The detector is a semiconductor waveguide evanescently coupled to a single-mode fibre. The full width at half-maximum of the photocurrent response is 1.6 nm, and the external quantum efficiency is 75%     

Modeling O/E characteristics of 40-gb/s InGaAs side-illuminated waveguide photodiode submodule for optical receivers

In this paper, the circuit models of a waveguide photodiode (WGPD) and its submodule were investigated, and the O/E characteristics of a WGPD submodule are examined. Test structures of the WGPD and WGPD submodule were fabricated and microwave return loss (S11) was measured and compared with simulated data to validate the circuit models. With the established submodule model, optical to electrical (O/E) characteristics were measured and compared with the modeled data to analyze the effects of model parameters on the submodule performance. Based on the results, it can be concluded that the suggested submodule model can explain the characteristics of the submodule performance. In addition, parasitic components that originated from the ribbon bonding block can crucially impact on the performance of WGPD submodule.     

Regrowth-free waveguide-integrated photodetector with efficienttotal-internal-reflection coupling

A novel technique utilizing an etched total-internal-reflection mirror for vertical waveguide-to-photodetector coupling is described. An 83% quantum efficiency and 5-GHz bandwidth are achieved at λ=0.84 μ in a GaAs MSM photodetector illuminated by a low-loss (0.5 dB/cm) AlGaAs double-heterostructure (DH) waveguide. A significant advantage of total-internal-reflection coupling is its compatibility with the integration of low-loss active DH waveguide components without requiring epitaxial regrowth. This coupling technique is independent of both optical wavelength and polarization, and permits efficient waveguide coupling to extremely small-area photodetectors     

50 GHz InGaAs edge-coupled PIN photodetector

An edge-coupled PIN photodetector with an InGaAs absorber layer has been designed and fabricated. Values of bandwidth at 1530 nm, with and without bias, have been measured as 50 GHz and 20 GHz, respectively. The external quantum efficiency is as high as 40% using a standard 12 mu m radius lens-ended single-mode fibre.<>     

A silicon-based integrated NMOS-p-i-n photoreceiver

For large-volume optoelectronics applications, the low cost, manufacturability and reliability of silicon MOSFET technology are advantageous. In addition, silicon photodetectors operate quite efficiently at the 850 nm wavelength of economical AlGaAs light sources. In this paper, we report on a silicon-based monolithic optical receiver. The fabrication of the integrated lightwave receiver was carried out on a nominally undoped p-type Si substrate. The p-i-n photodetector was fabricated directly on the high-resistivity substrate so that the thickness of the detector depletion layer was approximately equal to the optical absorption length of 850 nm light in silicon. A more heavily-doped p-well was formed for the NMOSFET fabrication. The silicon photodiodes had a dark current of 20 nA at 5 V, a breakdown voltage greater than 60 V, and a zero-bias capacitance of 40 fF. The external quantum efficiency of the photodiode at 870 nm was approximately 67% at 5 V without an AR coating, and the bandwidth of the device was approximately 1.3 GHz. Frequency response evaluation of the receiver indicated a circuit-design-limited bandwidth of 30 MHz with open eye diagrams demonstrated at 40 MB/s     

Design of ultra-fast dual-wavelength resonant-cavity-enhancedSchottky photodetectors

A systematic optimization procedure for the design of RCE Schottky photodetectors to achieve maximum quantum efficiency and high speed operation at 1.3 and 1.55 μm wavelengths is presented. The quantum efficiency formulation used includes the structural parameters of the photodetector and takes into account the wavelength dependence of the top and bottom mirrors reflectivities. The results have shown that the value of the thickness of the antireflection coating layer has a major influence in selecting the width of the photodetector to simultaneously achieve maximum quantum efficiency and high bandwidth at the two wavelengths. Simulated values of 270 and 40 GHz were obtained, respectively, for the 3-dB carrier-transit time-limited bandwidth and bandwidth-efficiency product for an RCE Schottky photodetector with a 0.02-μm gold layer     

光通信中的主流光电探测器研究

对光通信系统解复用接收部分中的关键器件——主流光电探测器进行综合比较、优缺点分析与展望．分别对PIN光电探测器,普通雪崩二极管,超品格雪崩二极管,波导型光电探测器,振腔增强型光电探测器,金属-半导体-金属光电探测器的原理和特点做了简要概括,并做系统比较,最后对光电探测器发展前景进行展望．     

硅光电探测器阵列

以获得高量子效率的pin硅光电探测器阵列为目标,对影响pin硅光电探测器阵列量子效率和暗电流的重要因素展开了分析,此外针对探测器入射面的抗反射层结构进行了理论分析与模拟的仿真研究.流片测试结果表明,实验样品LPD型硅光电探测器阵列的单像素暗电流为2～7 pA,低于滨松S11212型商用光电探测器;结电容为45 ～ 46 pF,光响应值为0.37～0.39 A/W(仅比S11212型器件低约0.25％).LPD硅光电探测器阵列通过耦合碘化铯晶体并封装之后,放置在物品安检机上进行扫描成像,测试结果表明:LPD硅光电探测器阵列可以在X光机165 kV,0.8 mA时穿透40 mm厚的铅饼清晰成像.LPD硅光电探测器阵列的整体灵敏度和商用S11212型光电探测器性能相当,没有明显区别.     

Design and performance of an erbium-doped silicon waveguide detector operating at 1.5 /spl mu/m

A new concept for an infrared waveguide detector based on silicon is introduced. It is fabricated using silicon-on-insulator material, and consists of an erbium-doped p-n junction located in the core of a silicon ridge waveguide. The detection scheme relies on the optical absorption of 1.5-/spl mu/m light by Er/sup 3+/ ions in the waveguide core, followed by electron-hole pair generation by the excited Er and subsequent carrier separation by the electric field of the p-n junction. By performing optical mode calculations and including realistic doping profiles, we show that an external quantum efficiency of 10/sup -3/ can be achieved in a 4-cm-long waveguide detector fabricated using standard silicon processing. It is found that the quantum efficiency of the detector is mainly limited by free carrier absorption in the waveguide core, and may be further enhanced by optimizing the electrical doping profiles. Preliminary photocurrent measurements on an erbium-doped Si waveguide detector at room temperature show a clear erbium related photocurrent at 1.5 /spl mu/m.     

Vertical integration of a GaAs/AlGaAs quantum-well laser and along-wavelength quantum-well infra-red photodetector

A short-wavelength (~0.8 μm) GaAs/AlGaAs graded-index separate-confinement heterostructure quantum-well laser has been monolithically integrated with a long-wavelength (~8 μm) GaAs/AlGaAs multiple-quantum-well infra-red photodetector on a semi-insulating GaAs substrate by molecular beam epitaxy. The vertical integration method is used and the combined structure is a pinin structure. Both the laser and detector exhibit excellent characteristics. At room temperature, the ridge waveguide laser has an extremely low threshold current of 25 mA and a differential quantum efficiency above 65% with a stripe width of 20 μm. The quantum-well detector has a peak response at 8 μm and a responsivity of 0.7 A/W     

High-speed, self-passivated InGaAs PIN photodiode for microwave fibre links

High-speed, low-dark-current, front-side-illuminated InGaAs PIN photodiodes with a self-passivated-mesa structure have been fabricated on semi-insulating InP substrates. These detectors have a nearly flat frequency response beyond 22GHz. Their quantum efficiency is 65% without AR coating and the dark current is about 5nA at ?10V.     

Extracting Light from Polymer Light‐Emitting Diodes Using Stamped Bragg Gratings

In this paper, we describe a method for increasing the external efficiency of polymer light‐emitting diodes (LEDs) by coupling out waveguided light with Bragg gratings. We numerically model the waveguide modes in a typical LED structure and demonstrate how optimizing layer thicknesses and reducing waveguide absorption can enhance the grating outcoupling. The gratings were created by a soft‐lithography technique that minimizes changes to the conventional LED structure. Using one‐dimensional and two‐dimensional gratings, we were able to increase the forward‐directed emission by 47 % and 70 %, respectively, and the external quantum efficiency by 15 % and 25 %.