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Polarization Insensitive Electroabsorption Modulators for High-Speed Optical Gating
Koji YAMADA Koji NAKAMURA Hitoshi MURAI Tatsuo KUNII Yoh OGAWA
IEICE TRANSACTIONS on Electronics
Publication Date: 1997/01/25
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Devices, Packaging Technology, and Subsystems for the Optical Access Network)
optical gating, electroabsorption modulator, polarization insensitivity, large optical confinement,
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Polarization insensitive discrete electroabsorption modulators have been designed as an optical gating device. It reveals the first finding, to our knowledge, that the ratio of the optical confinement factor (Γ) to the differential of the values (ΔΓ) between TE and TM polarized lights decides polarization dependence of attenuation. The ratio ΔΓ/Γ is significantly reduced by increasing core thickness. Large optical confinement structures combining a thick InGaAsP bulk absorption layer and polyimide-buried mesa-ridge waveguide have fabricated. The ratio ΔΓ/Γ of the high-mesa structure was estimated to be less than 0.05 in the gain-region of an erbium-doped fiber amplifier (EDFA), which enable us extremely low polarization sensitivity less than 1 dB up to 20 dB extinction. Proper waveguide length of the structure allowed low insertion loss ( 9.3 dB), small loss-change ( 1.8 dB) and sufficient modulation depth ( 30 dB) simultaneously in the EDFA's gain region. The low-mesa structure provided low insertion loss around 7 dB with small deviation in the wavelength region. High modulation band-width and a polarization-insensitive optical gating waveform have also demonstrated.