• ETRI Journal
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• v.27 no.1
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• pp.95-101
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• 2005

Waveguide structures of the stand-alone electroabsorption (EA) modulator and the electroabsorption modulated laser (EML) are investigated using the 3D beam propagation method. The EA waveguide structures with InP-based passivation layers show saturation in the extinction ratio (ER) due to the stray light traveling through the passivation layers. This paper demonstrates that narrower passivation layers suppress stray-light excitation in the EA waveguide, increasing the ER. A taper structure in the isolation section of the EML waveguide can reduce the mode mismatch and suppress the excitation of the stray light, increasing the ER further. Low-index-polymer passivation layers can confine the mode more tightly in the active waveguide, yielding an even higher ER.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.8
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• pp.53-61
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• 1998

Dynamic characteristics of widely tunable SGDBR/SSGDBR laser diodes integrated with an electroabsorption modulator is inestigated using an improved large-signal timef-domain model. First, wide tunning properties of a SGDBR laser diode and a SSGDBR laser diode are analyzed respectively and compared with each other. And, intensity-modulation characteristics of a SGDBR laser diode incorprating an electroabsorption modulator are investigated. It is shown that an external modulation has the lower frequency chirp by 1/20 for almost same extinction ratios than a direct modulation, and a nearly transform-limited pulse train can be generated using the optical gating of an electroabsorption modulator.

• ETRI Journal
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• v.35 no.3
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• pp.459-468
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• 2013

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.

• JSTS:Journal of Semiconductor Technology and Science
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• v.4 no.1
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• pp.74-81
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• 2004

We propose a novel scheme to transmit high center frequency RF signals using electroabsorption devices (EADs) as frequency converters at the transmitter and the receiver. In this approach frequency heterodyning is employed for obtaining high center frequency. With the EAD as a detector/mixer at the receiver we demonstrated a smaller conversion loss than that of the conventional modulator/mixer. With EAD as a modulator/mixer at the transmitter and with two heterodyned lasers to generate an optical local oscillator (LO), we demonstrated a large reduction (${\sim}23dB$) in conversion loss, and the transmission is not limited by the optical saturation of the EAD. This transmission scheme has optical single-side-band transmission feature which greatly relieves the fiber dispersion effect.

• Electrical & Electronic Materials
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• v.11 no.11
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• pp.28-36
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• 1998

Widely tunable diodes integrated with periodically sampled and chirped DBR(distributed Bragg reflector) and an EA(electroabsorption) modulator are analyzed dynamically using the improved largesinal time-domain model. The tuning characteristics of sampled- and chirped-grating DBR laser diodes are demonstrated theoretically. The results of the simulation agree well with those of the experiment. And the intensity-modulation properties of the laser diodes integrated with an EA modulator are calculated. It is shown that the external modulation has the lower frequency chirp by 1/20 for the same extinction ratio than the direct modulation, and also the short pulse train can be generated using the optical gating of an EA modulator.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.6
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• pp.293-297
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• 2005

Linearity is an important property of optical devices for analog communications. In this paper, we study the 3rd-order interrnodulation distortion (IMD3) of an Inp/InGaAsP multiple-quantum-well (MQW) traveling-wave type electroabsorption modulator (TW-EAM). We observe abnormal notches in the IMD3 results those were different from notches by general transfer curve of electroabsorption modulators (EAMs). We analyze the phenomena through absorption coefficients according to wavelengths and bias voltages to verify appearance of the abnormal notchs, where it can be known to result from Stark-shift and broadening. We propose the method to enhance linearity of MQW-EAMs by using these effects.

• ETRI Journal
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• v.31 no.6
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• pp.765-769
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• 2009

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.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.11a
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• pp.817-820
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• 2002

In this letter, we developed a 400Gb/s optical transmitter using an electroabsorption modulator and measured its characteristics. As a result, the extinction ratio, the output power and the wavelength are varied while DC bias voltage and temperature of an electroabsorption modulator are changed. Based upon these experimental results, a design of 400Gb/s optical transmitter can be optimized.

• Journal of the Optical Society of Korea
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• v.1 no.1
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• pp.44-47
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• 1997

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.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.7
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• pp.37-45
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• 2002

In this paper, the microwave characteristics of traveling-wave electroabsorption coplanar waveguide modulator have been analyzed and optimized precisely by using the 3-dimensional finite-difference time-domain method (FDTD). Microwave characteristics are affected by the thickness of intrinsic layer, the width of meas, and the distance between signal electrode and ground electrode on traveling-wave type structure. In case that intrinsic layers are composed of InAsP/InGaP (1.3Q), the optimized distance between signal electrode and ground electrode, the optimized intrinsic region thickness and the width of waveguide are founded to be $3{\mu}m,\;039{\mu}m\;and\;2{\mu}m$, respectively, to minimize microwave loss and to obtain velocity and impedance matched structure. By using the FDTD, we could design the traveling-wave electroabsorption modulator more precisely.