Monolithically integrated optical differential amplifiers forapplications in smart pixel arrays

The design, fabrication, and characterization of monolithically integrated single- and dual-stage cascadable optical differential amplifiers (ODAs) are presented. The circuits are realized with photodiodes (PDs), metal-semiconductor field-effect transistors (MESFETs) and light-emitting diodes (LEDs) in the GaAs-AlGaAs system. They are fabricated with a process which uses trench technology for the separation of the devices. The single-stage switching energy of 2.5 pJ is reduced to 0.4 pJ by the addition of a second stage, thereby increasing the bandwidth from 2 to 12 MHz., The output power is 30 μW, and the measured contrast ratio is approximately 1000. Switching is possible over an input power range of more than 5 decades, with a lower limit of 15 pW. We measure an optical open-loop gain of 2·10⁶ and a power dissipation of 15-20 mW     

Wavelength conversion from 1.3 to 1.55 mu m using split contact optical amplifiers

Wavelength conversion of data from an optical carrier at a wavelength of 1.31 mu m to an optical carrier within the 1.5- mu m telecommunications window was demonstrated using a split-contact semiconductor nonlinear Fabry-Perot optical amplifier. Conversion was achieved by modulating the amplifier gain seen by a 1.55- mu m continuous-wave signal by saturating an absorber section using a modulated 1.31- mu m signal. Data transfer was possible from 1.31 mu m up to wavelengths between 1.53 and 1.585 mu m for bit-rates of up to 400 Mb/s. The maximum output contrast ratio was 3:1 and the minimum power at 1.31 mu m required for switching was approximately 60 mu W. By optically pumping the amplifier to above the lasing threshold using the 1.31- mu m signal, conversion was obtained to a fixed multiwavelength output with a 10-dB contrast ratio.<>     

A 3-Gb/s optical detector in standard CMOS for 850-nm optical communication

This paper presents a monolithic optical detector, consisting of an integrated photodiode and a preamplifier in a standard 0.18-/spl mu/m CMOS technology. A data rate of 3 Gb/s at BER <10/sup -11/ was achieved for /spl lambda/=850 nm with 25-/spl mu/W peak-peak optical power. This data rate is more than four times than that of current state-of-the-art optical detectors in standard CMOS reported so far. High-speed operation is achieved without reducing circuit responsivity by using an inherently robust analog equalizer that compensates (in gain and phase) for the photodiode roll-off over more than three decades. The presented solution is applicable to various photodiode structures, wavelengths, and CMOS generations.     

Ultrafast all-optical pattern matching using differential spin excitation and its application to bypass/drop self-routing for asynchronous optical packets

This paper presents a novel scheme for ultrafast all-optical pattern matching using the differential spin excitation in semiconductor multiple quantum wells (MQWs). In a demonstration of an all-optical pattern matching between two 100-Gb/s 16-bit optical packets, the contrast ratio of the photodiode (PD) output from the pattern matcher, between the pattern matched and the pattern-unmatched cases, was more than four for packets with a 2-dB power fluctuation. As an application of the pattern matcher to optical-packet-switched ring networks, bypass/drop self-routing is demonstrated for asynchronous 100-Gb/s 32-bit optical packets with 8-bit labels. In the experiment, a label of an incoming packet was compared to a local address (LA) given to a node in the optical domain. By changing the pattern of the LA packet instead of that of the incoming packet, the pattern matching was carried out for packets with various kinds of patterns. The contrast ratio of the PD output was more than six for all patterns.     

Long wavelength vertical-cavity semiconductor optical amplifiers

This paper overviews the properties and possible applications of long wavelength vertical-cavity semiconductor optical amplifiers (VCSOAs). A VCSOA operating in the 1.3-μm wavelength region is presented. The device was fabricated using wafer bonding; it was optically pumped and operated in reflection mode. The reflectivity of the VCSOA top mirror was varied in the characterization of the device. Results are presented for 13 and 12 top mirror periods. By reducing the top mirror reflectivity, the amplifier gain, optical bandwidth, and saturation output power were simultaneously improved. For the case of 12 top mirror periods, rye demonstrate 13-dB fiber-to-fiber gain, 0.6 nm (100 GHz) optical bandwidth, a saturation output power of -3.5 dBm and a noise figure of 8.3 dB. The switching properties of the VCSOA are also briefly investigated. By modulating the pump laser, we have obtained a 46-dB extinction ratio in the output power, with the maximum output power corresponding to 7-dB fiber-to-fiber gain. All results are for continuous wave operation at room temperature     

VCSOA动态开关特性的理论研究

区别于常规的法布里-珀罗（F—P）腔增益公式,本文结合传输矩阵和载流子速率方程从理论上研究了垂直腔半导体光放大器（VCSOA）的动态开关特性。模拟结果发现,VCSOA作为光开关应用时,可以达到ns级的开关延时和15dB以上的消光比;在满足增益需求的前提下减小顶部分布布拉格反射镜（DBR）的膜层周期,以及正确设置关状态下的抽运电流密度值略高于增益截止区水平,是同时得到较好的开关延时和输出消光比的重要因素。     

1-Gb/s 80-dB/spl Omega/ fully differential CMOS transimpedance amplifier in multichip on oxide technology for optical interconnects

A 1-Gb/s differential transimpedance amplifier (TIA) is realized in a 0.25-/spl mu/m standard CMOS technology, incorporating the regulated cascode input configuration. The TIA chip is then integrated with a p-i-n photodiode on an oxidized phosphorous-silicon (OPS) substrate by employing the multichip-on-oxide (MCO) technology. The MCO TIA demonstrates 80-dB/spl Omega/ transimpedance gain, 670-MHz bandwidth for 1-pF photodiode capacitance, 0.54-/spl mu/A average input noise current, -17-dBm sensitivity for 10/sup -12/ bit-error rate (BER), and 27-mW power dissipation from a single 2.5-V supply. It also shows negligible switching noise effect from an embedded VCO on the OPS substrate. Furthermore, a four-channel MCO TIA array is implemented for optical interconnects, resulting in less than -40-dB crosstalk between adjacent channels.     

Multiple quantum well directional coupler as a self-electro-optic effect device

A report is made here on results obtained with a GaAs/AlGaAs multiple quantum well directional coupler configured as a SEED device. A robust optical switching operation is demonstrated with a high contrast ratio and constant output power.<>     

An area-efficient maximum-ratio-combining diversity receiver in 90 nm CMOS for free-space optical links

This paper presents a low-power imaging diversity front-end receiver employing the maximum-ratio-combining algorithm for free-space optical communication. It consists of seven signal channels and an output stage, each channel has a front-end transimpedance amplifier, a signal-to-noise ratio (SNR) estimator and a variable gain amplifier (VGA). The imaging receiver circuit was implemented in a 90 nm CMOS process. The maximum-ratio weighting is achieved with the SNR estimator and variable gain amplifier (VGA), which provides the signal with a gain proportional to the signal amplitude. The maximum ratio combining feature was demonstrated with two channels driven by photodiode emulation circuits for electrical characterization. The power dissipation for the whole chip is 43 mW from a single 1.2 V supply.     

Nonlinear optical limiter and digital optical switch by cascadednonlinear couplers: analysis

In this paper, an all-optical digital switch and a limiter are proposed and analyzed, both of which consist of several nonlinear directional couplers in series. These two devices utilize the nonlinear restraining effect of the nonlinear coherent coupler on its input power. In the devices, the OFF-ON extinction ratio, the output power fluctuation and the dynamic switching range all decrease with the number of the couplers in series increasing, and the output power level can be adjusted by varying the coupling length. The characteristics of these devices with different structures are discussed, and the numerical results show that the OFF-ON extinction ratio and the dynamic switching range of the optical switches can be less than -90 dB and 0.03P_c /100, respectively, and that the fluctuation of the limiting output power of the optical limiter can be less than 10^-7P _c     

The bipolar mode field effect transistor (BMFET) as an opticallycontrolled switch: numerical and experimental results

The use of the optically controlled devices is very attractive in power applications where serious problems can occur when high voltage control is required. In this context, optical switching of electronic devices is instrumental for the electrical insulation between control and power circuits. On this line of argument we have demonstrated the possibility of optically switching a BMFET (bipolar mode field effect transistor) by means of a low power laser diode. After carrying out a detailed theoretical and numerical analysis of the optically controlled BMFET, we have performed different experimental measurements. In particular, by using a BMFET that can block 1300 V and conducts peak drain currents up to 10 A, we have been able to switch an electrical power up to 1 kW by a laser diode of 25 mW operating at 830 nm. This corresponds to a power gain G_P (defined as the ratio between the switched electrical power and the optical power) equal to about to 40000. Both experimental and numerical results have shown that, for optical switching application, the BMFET works much better than an electrically equivalent bipolar junction transistor (BJT)     

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     

应用于10Gb/s光接收机的全差分CMOS跨阻前置电路设计

设计了一种的低成本、低功耗的10 Gb/s光接收机全差跨阻前置放大电路。该电路由跨阻放大器、限幅放大器和输出缓冲电路组成,其可将微弱的光电流信号转换为摆幅为400 mVpp的差分电压信号。该全差分前置放大电路采用0.18 m CMOS工艺进行设计,当光电二极管电容为250 fF时,该光接收机前置放大电路的跨阻增益为92 dB,-3 dB带宽为7.9 GHz,平均等效输入噪声电流谱密度约为23 pA/(0~8 GHz)。该电路采用电源电压为1.8 V时,跨阻放大器功耗为28 mW,限幅放大器功耗为80 mW,输出缓冲器功耗为40 mW,其芯片面积为800 m1 700 m。     

1Gb/s CMOS调节型共源共栅光接收机

基于特许0.35μm EEPROM CMOS标准工艺设计了一种单片集成光接收机芯片,集成了双光电探测器(DPD)、调节型共源共栅(RGC)跨阻前置放大器(TIA)、三级限幅放大器(LA,limiting amplifier)和输出电路,其中RGCTIA能够隔离光电二极管的电容影响,并可以有效地扩展光接收机的带宽。测试结果表明,光接收机的3dB带宽为821MHz,在误码率为10-9、灵敏度为-11dBm的条件下,光接收机的数据传输速率达到了1Gb/s;在3.3V电压下工作,芯片的功耗为54mW。     

Amorphous silicon/silicon carbide superlattice avalanchephotodiodes

An a-Si/SiC:H superlattice avalanche photodiode (SAPD) has been successfully fabricated on an ITO/glass substrate by plasma-enhanced chemical vapor deposition. The room-temperature electron and hole impact ionization rates, α and β, have been determined for the a-Si/SiC:H superlattice structure by photocurrent multiplication measurements. The ratio α/β is 6.5 at a maximum electric field of 2.08×10⁵ V/cm. Avalanche multiplications in the superlattice layer yields an optical gain of 184 at a reverse bias V_R=20 V and an incident light power P_in=5 μW. An LED-SAPD photocouple exhibited a switching time of 4.5 μs at a load resistance R-1.8 kΩ     

A 10-Gb/s optical transmitter module with a monolithicallyintegrated electroabsorption modulator with a DFB laser

A compact 10-Gb/s optical transmitter module with small-chirp output was developed by using a monolithically integrated electroabsorption modulator with a distributed-feedback laser. This module can be operated at a bit rate of more than 10 Gb/s at 1.55 μm, and shows a high modulated output power of ~1 dBm with a low optical coupling loss of 3.2 dB between chip and fiber. A multifunctional and compact optical isolator with a monitor photodiode was also developed to decrease noise     

A normal amorphous silicon-based separate absorption andmultiplication avalanche photodiode (SAMAPD) with very high optical gain

A normal amorphous silicon-based separate absorption and multiplication avalanche photodiode (SAMAPD) with very high optical gain of the avalanche photodiode has been developed successfully by plasma-enhanced chemical vapor deposition (PECVD). Based on experimental results, using undoped α-Si:H as avalanche layer material and α-Si_1-xGe_x:H as absorption layer material, the hole-injection (HI) type SAMAPD yields a very high optical gain of 686 at a reverse bias of 16 V under an incident light power of P_in =1 μW and has a rise time of 145 μs at a load resistance R=10 kΩ. Thus the amorphous silicon-based SAMAPD is a good candidate for the long-range optical communication applications     

All-optical bistable switching in an active InGaAs quantum-well waveguide

The authors have observed low-power optical bistability in an active strained InGaAs single-quantum-well waveguide which is biased with a quasi-constant current injection 20% below the threshold current. Although the output power measured after the output collecting lens is half of the peak input power measured before the input focusing lens, it is believed that this is mainly due to the inefficient coupling into a slab mode, and that optical switching occurs with net gain in the device. A channel waveguide with a similar active medium would operate with constant DC electrical bias and should provide significant overall gain.<>     

Maximum loss budget criteria for subcarrier multiplex broadcast passive optical networks

Analytic criteria for the laser optical modulation index and avalanche photodiode gain which maximise the loss budget of subcarrier multiplexed, broadcast, passive optical networks are described for the first time. A theoretical loss budget approaching 40 dB is predicted for 16.5 dB carrier-to-noise ratio in 36 MHz bandwidth for each of 120 channels under optimum conditions with <1 pA/ square root (Hz) thermal noise III-V avalanche photodiode receivers, 0 dBm laser launch power and <0.1% laser nonlinearity.<>     

High-gain and very sensitive photonic switching device byintegration of heterojunction phototransistor and laser diode

A photonic switching device with very large gain and high sensitivity has been developed by the vertical and direct integration of a heterojunction phototransistor and a laser diode. The device switches on with very low input power of ~10 nW and emits output power of ~4 mW under continuous-wave conditions at room temperature. The minimum energy for switching on is estimated to be as low as 80 fJ. The internal optical feedback of the device is quantitatively discussed to interpret the low-power operation for the switch-on