D. Carpentier

High performance evanescent edge coupled waveguide unitraveling-carrier photodiodes for >40-gb/s optical receivers

We have demonstrated a low-cost high-bandwidth and high-responsivity evanescent waveguide unitravelling-carrier photodiode (PD) fabricated using all 2-in InP processing including on-wafer mirrors and coating. Optimization of the optical input waveguide was made using the method of the genetic algorithm associated with a beam propagation method. Optical fiber coupling to the PD is based on a diluted multimode waveguide allowing simple material epitaxial growth. The fabricated PDs exhibit simultaneously 0.76-A/W responsivity at 1.55 /spl mu/m, >50-GHz bandwidth, and more than 22-mA average saturation photocurrent at 50 GHz. The light polarization dependence is less than 0.1 dB.

High-Power High-Linearity Uni-Traveling-Carrier Photodiodes for Analog Photonic Links

We have fabricated and characterized two high-power high-linearity uni-traveling-carrier photodiode (UTC-PD) structures. The UTC performances are compared regarding their respective collector design. A -3-dB bandwidth improvement (from 16-25 GHz to 19-32 GHz) is achieved when the collector layer thickness is increased (from 250 to 350 nm, respectively). The bandwidth improvement for large photocurrent is at the origin of a ldquosupra-linearityrdquo effect. Photocurrent saturation effects are investigated and -1-dB compression current measurements at 20 GHz show saturation currents as high as 70 mA at -4 V. We also report third-order intermodulation distortion measurements at 20 GHz. The ldquosupra-linearityrdquo effect enhances the PD linearity with increased photocurrent, leading to a record third-order intercept point of 35 dBm at 40 mA.

High Responsivity and High Power UTC and MUTC GaInAs-InP Photodiodes

We have developed a high-performance uni-traveling-carrier (UTC) and a modified uni-traveling-carrier (MUTC) photodiode (PD). We report a comparison between the two devices comprising both a 1.5- μm-thick absorption layer followed by a 0.5-μm-thick transparent collector layer. Both devices showed simultaneously a high responsivity (larger than 0.92 A/W at 1.55 μm), a high saturation current (larger than 100 mA at 10 GHz), and a high linearity (OIP3 of 35 dBm at 10 GHz). Thanks to a partly depleted absorber, the MUTC-PD is demonstrated to achieve a higher bandwidth (more than 20 GHz at high current), while the UTC-PD is demonstrated to achieve a higher saturation current and a less voltage dependent radio-frequency and linearity characteristics.

High Gain

This letter demonstrates a planar junction GalnAs-AlInAs avalanche photodiode using back-side illumination through thinned InP substrate covered with chemical vapor deposition SiNx antireflection coating. The combined properties of very low dark current (I dark(M = 0) = 17 nA), low excess noise factor (f(M = 10) = 3.5), and high gain x bandwidth product over 140 GHz were simultaneously achieved with a high primary responsivity of 0.95 A/W at 1.55 mum.

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We report two uni-traveling-carrier photodiode (PD) structures, for high-power and high-linearity applications. Using a thick collection layer (500 nm), the fabricated 25-m-diameter PDs achieve a 3-dB bandwidth up to 29 GHz, and a maximum dissipated heat power of about 480 mW, simultaneously. A new collector design with a nonuniform doping profile is proposed to better relax the space charge effect. Its performances are compared to a uniformly doped collector layer. Saturation currents and third-order intermodulation distortion measurements at 20 GHz confirm the advantage of the new collector design for high-power and high-linearity performances: 1-dB saturation current as high as 120 mA and a third-order intercept point in excess of 35 dBm at 70 mA are recorded.

Bandwidth Product Over 140-GHz Planar Junction AlInAs Avalanche Photodiodes

We demonstrate an AlInAs-InGaAs separate absorption, grading, and multiplication avalanche photodiode (APD) with a very thin avalanche layer operating at 1550 nm for 10-Gb/s optical transmission achieving simultaneously high responsivity (0.9 A/W at M = 1), very low excess noise factor (F(M=10) = 3), and very high gain-bandwidth product of 240 GHz. To our knowledge, this is the first time that a back-side illuminated planar junction AlInAs-InGaAs APD achieved such performances.

High-Performance Uni-Traveling-Carrier Photodiodes With a New Collector Design

We demonstrate the monolithic integration of a buried heterostructure semiconductor optical amplifier (SOA) and a deep ridge PIN photodiode for high-speed on-off keying links at 1.55 μm. The structure allows separate optimization of the SOA and the photodiode. The integrated receiver presents simultaneously a peak responsivity of 88 A/W with a low polarization dependence loss (<; 1 dB), a low noise figure (8.5 dB), and a wide 3-dB electrical bandwidth (≈ 50 GHz). This corresponds to a very large gain-bandwidth product of 3.5 THz. To our knowledge, this is the first time that a monolithically integrated SOA-PIN receiver has achieved such performances.

240-GHz Gain-Bandwidth Product Back-Side Illuminated AlInAs Avalanche Photodiodes

High responsivity backside-illuminated uni-traveling-carrier photodiodes (PDs) with a 1.2-mum-thick p-doped absorption layer are demonstrated. The fabricated PDs achieve simultaneously high speed, high responsivity, and good linearity under high-power operation. The measured responsivity at 1.55 mum is larger than 0.83 A/W at low photocurrent and increases up to 1 A/W at 75 mA. The measured bandwidth increases from 9 GHz at 1 mA up to 24 and 29 GHz at 50 mA, for 25- and 20-mum-diameter PDs, respectively. Good linearity is demonstrated with a third-order intercept point of 30 dBm at 10 GHz and 50 mA.

Monolithic Integration of a Semiconductor Optical Amplifier and a High-Speed Photodiode With Low Polarization Dependence Loss

For high speed remote colorless modulation in FTTH technology, a new 10Gbit/s monolithically integrated amplified reflective electroabsorption modulator (R-EAM-SOA) is demonstrated over 50nm spectral range and over 20°C-60°C, with excellent eye diagrams.

Thick Absorption Layer Uni-Traveling-Carrier Photodiodes With High Responsivity, High Speed, and High Saturation Power

Integrated laser modulators are attractive devices for wavelength-division-multiplexing optical systems due to their compactness, high output power, and low cost. Their fabrication simplicity is a way to decrease further the transmitter cost and address new opening markets of short range and metropolitan networks. We report a new integration scheme electroabsorption-modulator distributed feedback (DFB) laser based on well-established industrial solutions for discrete buried ridge (BRS) DFB lasers and discrete shallow ridge modulators. Processing simplification with an identical active layer has been possible due to a good behavior of strongly positively detuned BRS lasers. The integrated devices demonstrated 30-dB extinction ratio with 10-GHz bandwidth and P/sub out/=10 dBm for emission in 1.55-/spl mu/m range.