Simultaneous Wavelength Conversion and Signal Detection in a Traveling-wave Electroabsorption Modulator Hsu-Feng Chou and John E. Bowers Department of Electrical and Computer Engineering University of California, Santa Barbara Chip-Scale WDM Program University of California Santa Barbara 04/25/2003

Objective » Investigate integration of traveling-wave electroabsorption modulator (TW-EAM) into InP platform  Integrated SOA for total loss compensation  Integrated mode-converter for coupling loss reduction » Investigate wavelength conversion using TW-EAM with electrical monitoring capability  Adding monitoring capabilities to the two-stage SOA-IWC » Investigate integration of traveling-wave electroabsorption modulator (TW-EAM) into InP platform  Integrated SOA for total loss compensation  Integrated mode-converter for coupling loss reduction » Investigate wavelength conversion using TW-EAM with electrical monitoring capability  Adding monitoring capabilities to the two-stage SOA-IWC Chip-Scale WDM Program University of California Santa Barbara 1

Two-Stage SOA-IWC 2 University of California Chip-Scale WDM Program Santa Barbara 2

TW-EAM as 1st stage WC with electrical monitoring capability Two-Stage SOA-IWC TW-EAM as 1st stage WC with electrical monitoring capability Chip-Scale WDM Program University of California Santa Barbara 2

Traveling-Wave Electroabsorption Modulator (TW-EAM) » Traveling-wave Electrodes: -Overcome RC Limitation -Longer Device, Higher Extinction Ratio, Lower Driving Power -Flexible Microwave Design » Characteristics: > 20 dB/V Between 0V and 2V > 47 dB Maximum Extinction Ratio < 1 Vpp Driving Voltage for 10 Gb/s Active Waveguide Length: 300 mm Chip-Scale WDM Program University of California Santa Barbara 3

Prior Art of Wavelength Conversion Using Lumped-Element EAM » Utilize Cross-Absorption Modulation (XAM) induced by photo- generated carriers through screening of the external electrical field and band filling » High input power (16~20dBm) required to saturate < 100 mm device » Extracted RF signal was demonstrated to recover electrical clock* *T. Miyazaki et al., OFC’99, paper WM53-1 Chip-Scale WDM Program University of California Santa Barbara 4

Photocurrent-Assisted Wavelength Conversion in TW-EAM New Mechanism » Problems of Prior Art:  High input power is required to saturate absorption (XAM)  Electrical monitoring of signal was not demonstrated » New Mechanism for WC:  Saturation is not required for XAM (lower input power)  Capability of electrical signal monitoring » Problems of Prior Art:  High input power is required to saturate absorption (XAM)  Electrical monitoring of signal was not demonstrated » New Mechanism for WC:  Saturation is not required for XAM (lower input power)  Capability of electrical signal monitoring Photocurrent-Assisted Wavelength Conversion in TW-EAM NEW Chip-Scale WDM Program University of California Santa Barbara 5

Photocurrent-Assisted Wavelength Conversion Principle of Operation Photocurrent-Assisted Wavelength Conversion Chip-Scale WDM Program University of California Santa Barbara 6

How can it be possible? 7 » Typical Values Input NRZ Power: 10 mW Responsivity: 0.4 A/W Impedance: 25 Ohm Modulation Efficiency: 24 dB/V » Extinction = 10 mW * 2 * 0.4 A/W * 25 Ohm * 24 dB/V = 200 mV * 24 dB/V = 4.8 dB Chip-Scale WDM Program University of California Santa Barbara 7

2.5 Gb/s NRZ Conversion: Configurations (Sampling Scope) = -0.45V Open Open Termination 50 Ohm Termination Chip-Scale WDM Program University of California Santa Barbara 8

2.5 Gb/s NRZ from LiNbO3 modulator 2.5 Gb/s NRZ Conversion: Input Eye Diagram 2.5 Gb/s NRZ from LiNbO3 modulator Chip-Scale WDM Program University of California Santa Barbara 9

2.5 Gb/s NRZ Conversion: Output Eye Diagram Chip-Scale WDM Program University of California Santa Barbara 10

Summary and Future Work » Integration of TW-EAM into InP platform and adding electrical monitoring capability to two-stage SOA-IWC » Preliminary result shows proof of principle of photo- current-assisted wavelength conversion in TW-EAM at 2.5 Gb/s » Issues and future works:  Improve efficiency and extinction ratio  Reduce pattern dependence  Investigate fundamental limitations  BER measurements at 2.5 Gb/s RZ and NRZ  Analog performance testing Chip-Scale WDM Program University of California Santa Barbara 11