| Budget Amount *help |
¥3,800,000 (Direct Cost: ¥3,800,000)
Fiscal Year 2000: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1999: ¥3,200,000 (Direct Cost: ¥3,200,000)
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| Research Abstract |
Recently, there has been a surging interest in the use of ultra-high-speed optical modulators for broad band networks and microwave photonic systems. However, low-driving voltage and high-speed operation contradict each other for lumped modulators that is a key point in practical use because high-speed electrical amplifiers are needless. At present, 40 Gbit/s large-signal (2Vpp) modulation is the best data. We propose a new electroabsorption modulator based on a parallel-electric field that will overcome the above limit in addition to full negative chirp operation and very high allowability of incidental optical power.
A proposed modulator consisting of transverse p-i-n structure enables us to apply electric field parallel to multiple quantum well (MQW) layers. The exciton resonance peak can easily broaden and disappear at fields 〜10^3 V/cm, much lower than that of the perpendicular field previously used. On the other hand, i-region width between an n- and p-doped region can be designed
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to optimize the field intensity, device capacitance and coupling efficiency between an optical fiber and the modulator. Transmission loss and sample length required for 15 and 20 dB extinction ratios are only 2〜3dB and 20〜60 μm long, respectively. Chirp parameters are negative for short wavelengths even under the small field intensity where modulators operate at low transmission loss. This indicates that full negative chirp operation can be expected for this proposed modulator. This structure will be superior to the previous perpendicular-field for the allowability of incidental optical power, because created photo-carriers can transit parallel to the hetero-barriers smoothly for the former, whereas they cannot easily run perpendicular to the barriers for the latter. The 3 dB bandwidth is estimated to be over 200 GHz assurning that the speed is limited by the device capacitance.
Moreover, we propose and demonstrate a new method for evaluating the inser-tion loss of electroabsorption modulators using absorbed photocurrent and extinction ratios Less
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