MQW Electroabsorption Modulator Research Articles

Butt-coupled MOVPE growth for high-performance electro-absorption modulator integrated with a DFB laser

A novel butt-joint coupling scheme is proposed to improve the coupling efficiency for the integration of a GaInAsP MQW distributed feedback (DFB) laser with an MQW electro-absorption modulator (EAM). The proposed method gives more than 90% coupling efficiency, being much higher than the 26% coupling efficiency of the common MQW–MQW coupling technique. The differential quantum efficiency of the MQW–bulk–MQW coupled device is also much higher than that of the MQW–MQW device, 0.106 mW/mA versus 0.02 mW/mA. The EAM–DFB devices fabricated by the proposed method exhibit a very high modulation efficiency (12 dB/V) from 0 to 1 V. By adopting a high-mesa ridge waveguide and buried polyimide, the capacitance of the modulator is reduced to about 0.28 pF. The experimental results demonstrate that the method can replace the conventional MQW–MQW coupling technique to fabricate high-quality integrated photonic devices.

Experimental study of NRZ format wavelength conversion using electroabsorption modulator

In this paper, NRZ format wavelength conversion using cross absorption modulation (XAM) in InGaAsP MQW electroabsorption modulator (EAM) is investigated experimentally in detail for the first time, to the best of our knowledge. The influence of two key operating parameters, input signal power and bias voltage of EAM, on wavelength conversion performance is studied. Experimental results indicate that there exists optimal bias voltage for fixed input signal power and that there exists also optimal input signal power for fixed bias voltage and the lowest power penalty of 0.9dB is obtained by optimizing these two parameters. The physical explanations are given for these results based on operating characteristic of EAM device. Finally, the probe light wavelength dependence of wavelength conversion is studied for span of 1530–1560nm.

Uncooled performance of 10-Gb/s laser modules with InGaAlAs-InP and InGaAsP-InP MQW electroabsorption Modulators integrated with semiconductor amplifiers

Uncooled operation of long-reach high performance C-band 10 Gb/s of optical modulator modules is presented. Modules consisting of a distributed feedback laser and a chip with a monolithically integrated electroabsorption modulator and semiconductor optical amplifier based on multiquantum-well structures of both InGaAsP-InP and InGaAlAs-InP material systems are presented. Dispersion penalty of 1 dB over 94-km transmission, output power above 0 dBm, and low extinction ratio variation are demonstrated over an 80/spl deg/C temperature range. A simple analysis of the quantum confined Stark effect is employed to explain the temperature-dc bias voltage dependence.

New Design of InGaAs–InGaAlAs MQW Electroabsorption Modulator for High-Speed All-Optical Wavelength Conversion

We have optimized the structure of InGaAlAs multiple quantum-well electroabsorption modulators for all-optical signal processing. As wavelength conversion is a key function for all-optical telecommunication network, we have based our optimization upon the main parameters of this function, namely, polarization insensitivity, exciton saturation, and photogenerated carrier sweep-out time. Four samples have been studied with different well tensile strain and barrier height. We find low polarization dependence over a range of applied bias. Less than 10-ps absorption-saturation recovery time at lower biases and smaller saturation power than in the literature are reported.

Measurement-Based Model for Cross-Absorption Modulation in an MQW Electroabsorption Modulator

A model for cross-absorption modulation in a multiple-quantum-well electroabsorption modulator is developed based on measurements of the escape time of photogenerated carriers, the dependence of the modulator absorption on the power and wavelength of the pump and probe signals, and the dependence of the /spl alpha/ parameter of the wavelength-converted signal on the power and wavelength of the pump and probe signals. Good agreement between calculated and measured results is demonstrated for static, small-signal and large-signal conditions. The accuracy and computational efficiency of the model in describing the intensity and phase modulation properties of a wavelength-converted signal make it suitable for computer simulations aimed at system design and performance evaluation.

80 Gbit∕s wavelength conversion using MQW electroabsorption modulator in delayed-interferometric configuration

Absorption recovery time and cross-phase modulation characteristics of an MQW electroabsorption modulator (EAM) were experimentally analysed. 80 Gbit/s error-free operation of a wavelength converter using the MQW EAM in a delayed-interferometer configuration was demonstrated for the first time.

Concise RF equivalent circuit model for electroabsorption modulators

An equivalent RF circuit model for electroabsorption modulators (EAMs) is proposed and verified. Circuit parameters extracted from measured S/sub 11/ values for an MQW EAM are used to model the modulator E/O responses. Which are found to be consistent with the measurement. The model clarifies the effect of optical power to the EAM impedance and modulation bandwidth.

Linearity enhancement of electroabsorption optical modulator by absorption variation in propagation direction

We propose a new electroabsorption modulator (EAM) structure where the linearity is improved by means of appropriately changing the absorption profile along the device length. As a practical implementation, a selective-area-grown MQW–EAM was investigated. Compared with a conventional EAM, the linearity was improved by 3 dB reduction in IMD2 and 5 dB reduction in IMD3. ©1999 John Wiley & Sons, Inc. Microwave Opt Technol Lett 22: 30–35, 1999.

Evidence of deep-level defects in an MQW electroabsorption modulator through current-voltage and electrical noise characterization

We present experimental and theoretical results concerning the current-voltage and electrical noise characteristics of an integrated electroabsorption modulator without illumination. Two components were studied: a device whose current-voltage and electrical noise characteristics were representative of the expected behavior and one exhibiting much higher leakage currents and different noise spectra. The first part of the paper contains a detailed description of the structure of the studied components. In the second part, the dark current of modulators is modeled using a thermal or phonon-assisted tunneling current process via electron traps thought to be localized at the multiquantum-well interfaces of the modulator's active layer. This model allows us to deduce the energy levels of the traps involved and demonstrates that the concentrations of the electron traps can vary by several orders of magnitude between the components. In the third part, measurements of electrical noise and the modeling of these measurements allow us to show that the current generation mechanisms involve deep levels of carriers with a continuous energy distribution which is of different width in the two components. In the fourth part, the dynamic chirp of the modulator is analyzed. The characteristic of the Henry modulator parameter (/spl alpha//sub H/) as a function of the applied voltage is given for each of these two components. The difference between the two curves can he attributed to deep levels of carriers.

Low-loss 1.3-/spl mu/m MQW electroabsorption modulators for high-linearity analog optical links

Low-loss InAsP-GaInP multiquantum-well electroabsorption waveguide modulators have been developed for transmitting microwaves as subcarriers over optical fibers. The fiber-to-fiber insertion loss is only 5 dB at 1.32-/spl mu/m wavelength. The electrooptic slope efficiency of an 185-/spl mu/m-long 11-GHz bandwidth device is equivalent to a Mach-Zehnder modulator with a V/sub /spl pi// of 2.2 V. The linearity performance was characterized for a test link without any form of amplification. A RF-to-RF link efficiency of -25.5 dB, noise figure of 27 dB and suboctave spurious-free dynamic range of 114 dB.Hz/sup 4/5/ have been achieved with 16 mW input optical carrier power. The measured 3-dB electrical bandwidth exceeds 20 GHz for a 90-/spl mu/m-long device.

38 GHz bandwidth 1.3 [micro sign]m MQW electroabsorption modulators for RF photonic links

High-speed 1.3 µm MQW electroabsorption waveguide modulators have been developed for high-fidelity transmission of microwaves via fibre optic links. Their high-frequency performance was characterised for a test link without any form of amplification. An RF-to-RF link efficiency of –32 dB, noise figure of 33 dB, and suboctave spurious-free dynamic range of 105 dB·Hz2/3 have been achieved.

MQW electroabsorption modulator integrated with a tapered waveguide vertical interconnect

The integration of a GaAs/AlGaAs multi-quantum well electroabsorption modulator and a tapered waveguide vertical direction optical interconnect has been performed without the complicated regrowth process. Zn impurity-induced layer disordering of MQW layer is used to achieve the energy transfer between SQW and MQW regions. Light coupled into a SQW region was transferred to an MQW region and an intensity modulation of 10 dB extinction ratio was demonstrated.

Low polarisation sensitivity electroabsorption modulators for 160 Gbit/s networks

Packaged low polarisation sensitivity InGaAs/InAlAs MQW electroabsorption modulators employing a novel ridged deeply etched buried heterostructure design are described. The feasibility of using them in 160 Gbit/s OTDM systems is experimentally assessed.

High-performance and low-consumption 10 Gb/s GaAs PHEMT driver for external modulation transmitter

This letter describes the realization of a high-performance GaAs PHEMT driver for 10 Gb/s transmitter with external coding in long haul optical transmission systems. It is shown that with an appropriate design for both IC and packaging, gain up to 14 dB, 2.5 Vp-p output drive-voltage and 1.5 W power consumption can be achieved, with adequate switching times for bit rates up to 12.5 Gb/s. The module has been successfully tested with a 18 GHz bandwidth polarization-independant pigtailed MQW electroabsorption modulator.

Polarization and wavelength insensitive MQW electroabsorption optical gates for WDM switching systems

We propose using MQW electroabsorption (EA) modulators as optical gates in wavelength-division-multiplexing (WDM) switching systems. A fabricated MQW-EA gate with integrated waveguides showed a high extinction ratio (>30 dB), a low polarization-dependent loss (0.3 dB), and a low wavelength-dependent loss (1.1 dB) within the gain band (1545-1560 nm) of erbium doped fiber amplifiers (EDFAs). Ultra-high-speed (<40 ps) switching of a WDM signal was demonstrated.

STUDY ON THE QUANTUM CONFINED STARK EFFECT OF InGaAs/InAlAs MULTIPLE QUANTUM WELL STRUCTURES

The quantum confined stark effect of InGaAs/InAlAs MQW heterostructures lattice-matched to InP substrate, grown by Chinese-built molecular beam epitaxy (MBE) system, is observed by absorption photocurrent spectra measurements, as well as the anisotropic elec-troabsorption of MQWs. The structure parameters of the epitaxied materials, which can be used to fabricate waveguide MQW electroabsorption modulators, were determined from double crystal X-ray diffraction measurements and computer simulations. The theoretical calculations of absorption-edge red shift compared with experimental results shows that the built-in-potential of the p-i-n junction can not be neglected.

Frequency-domain measurement of carrier escape times in MQW electro-absorption optical modulators

Frequency-domain measurement of carrier escape times in reverse-biased multiple-quantum wells (MQW's) is proposed and demonstrated. Measurement and analysis of opto-to-electrical (OE) frequency response give the escape times of both electrons and holes with excellent time resolution. Using this technique, we measured escape times in an InGaAs-InAlAs MQW electro-absorption modulator and estimated the carrier density in the wells during optical input. This measurement can clarify the optical saturation effect in optical devices such as MQW electro-absorption modulators.

Strongly improved frequency response at high-optical input powers from InGaAsP compensated strain MQW electroabsorption modulators

InGaAsP MQW electroabsorption modulators with and without compensated strain were fabricated and tested. Compensated strain was employed to reduce the valence band discontinuity between the well and barrier, which decreased the heavy-hole carrier escape time. A short optical pulse coupled into the modulator was used to measure the enhancement in carrier escape time from strained compensated InGaAsP quantum wells, for the first time. As a result, the strained MQW sample demonstrated an improved frequency response when operated at high optical input powers and low fields.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Soliton transmission at 20 Gbit/s over 2 000 km in Tokyo metropolitan optical network

Experimental field transmissions of solitons at 20 Gbit/s over 2 000 km have been successfully demonstrated using part of the Tokyo metropolitan optical network consisting of conventional dispersion-shifted fibre cables. The soliton pulse width was 10 ps and a polarisation-insensitive MQW electroabsorption modulator was used for demultiplexing. The power penalty at a BER of 10-10 was ~3.5 dB.

Generation and coding of a 100 Gbit/s signal by an InP-based optical multiplexer integrated with modulators

The authors demonstrate a novel InP-based optical multiplexer integrated with MQW electroabsorption modulators for 100 Gbit/s transmission. A 100 GHz optical pulse train is generated and coded with a pseudorandom NRZ pattern.