High-performance dual-step evanescently coupled uni-traveling-carrier photodiodes

Y. S. Wu, J. W. Shi, P. H. Chiu, Wei Lin

Research output: Contribution to journalArticlepeer-review

19 Scopus citations


In this letter, we discuss a dual-step evanescently coupled photodiode (PD), which is composed of an improved evanescently coupled optical waveguide and a uni-traveling-carrier PD (UTC-PD). The hitherto serious dependence of the responsivity on the coupling length, which is determined by the cleaving process, or the necessity of a long (∼700 μm) passive waveguide with a complex tapered structure, can be eliminated. The optimization of the waveguide structure, and the doping profile of the p-type absorption layer, allow the integrated UTC-PD to achieve a high responsivity (0.9 A/W, 1.04 A/W), with a large cleaving tolerance (∼50 μm), a wide invariable electrical 3-dB bandwidth (60 GHz, 40 GHz) from a low (∼0.5 mA) to a high output current (>13 mA), and a high saturation current-bandwidth product (around 780 mA ·GHz) simultaneously under a load of 50 Ω.

Original languageEnglish
Pages (from-to)1682-1684
Number of pages3
JournalIEEE Photonics Technology Letters
Issue number20
StatePublished - Oct 2007


  • Evanescent coupling
  • High efficiency
  • High-power photodiode
  • Optical receivers
  • Photodiode (PD)


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