Evanescently-coupled Photodiodes Research Articles

Design of novel three port optical gates scheme for the integration of large optical cavity electroabsorption modulators and evanescently-coupled photodiodes

This paper presents a novel scheme to monolithically integrate an evanescently-coupled uni-travelling carrier photodiode with a planar short multimode waveguide structure and a large optical cavity electroabsorption modulator based on a multimode waveguide structure. By simulation, both electroabsorption modulator and photodiode show excellent optical performances. The device can be fabricated with conventional photolithography, reactive ion etching, and chemical wet etching.

36 GHz bandwidth optoelectronic integrated circuit with flip-chip-assembled InP HBT/evanescently coupled photodiode

An optoelectronic integrated circuit (OEIC) with flip-chip technology for 1.55-µm wavelength application is demonstrated. The presented flip-chip OEIC comprises an InP chip and the carrier substrate. The InP chip consists of an evanescently coupled photodiode (ECPD), an InP/InGaAs heterojunction bipolar transistor (HBT) and bonding pads. The semi-insulating GaAs carrier consists of a coplanar waveguide, bias resistances, interconnects and pads (DC, RF and bonding pads). The flip-chip technology is used to reduce InP chip size and thus save cost. The fabricated ECPD exhibits a responsivity of 0.3 A/W and an f−3 dB of 30 GHz. The OEIC demonstrates an f−3 dB of 36 GHz with a transimpedance gain of 32 dB Ω. This is the first ECPD/HBT with flip-chip technology ever reported for OEIC.

High-power evanescently-coupled waveguide photodiodes

Evanescently-coupled photodiodes were realised for high-power operation at a wavelength of 1.55 µm and wide-band operation beyond 30 GHz. Evanescent coupling allows for uniform carrier generation, which avoids electrical breakdown at the beginning of the active waveguide. The evanescently-coupled photodiodes, with an active length of 70 µm, reach a bandwidth of 40 GHz. Their average photocurrent at the −1 dB saturation point is 14 mA at 40 GHz. The evanescently-coupled photodiodes, with an active length of 120 µm, reach a bandwidth of 30 GHz. Their average photocurrent at the −1 dB saturation point is 22 mA at 40 GHz. The dual-depletion active region allows for reduced capacitance, and therefore higher bandwidth. The measured polarisation dependent loss is, on average, 1.2 dB on the 30 GHz devices. More work is needed to understand this high value, compared with the low theoretical value of 0.01 dB.

37-GHz bandwidth monolithically integrated InP HBT/evanescently coupled photodiode

In this letter, we demonstrate a monolithically integrated optoelectronic integrated circuit (OEIC) for 1.55-mum wavelength application. The presented OEIC consists of an evanescently coupled photodiode (ECPD) and a single-stage common-base InP-InGaAs heterojunction bipolar transistor (HBT) amplifier. The guide structure was grown first by metal-organic chemical vapor deposition and pin/HBT was then regrown by molecular beam epitaxy. The ECPD exhibits a responsivity of 0.3 A/W and a -3-dB electrical bandwidth of 30 GHz. The photoreceiver demonstrates a -3-dB electrical bandwidth of 37 GHz with a transimpedance gain of 32 dBmiddotOmega. This is, to our knowledge, the first ECPD/HBT ever reported for a monolithically integrated OEIC

High-performance evanescently edge coupled photodiodes with partially p-doped photoabsorption layer at 1.55-/spl mu/m wavelength

In this letter, we demonstrate a high-performance evanescently coupled photodiode (ECPD) with the partially p-doped photoabsorption layer. As compared to the control ECPD with the traditional intrinsic photoabsorption layer, the demonstrated device can exhibit much higher output saturation current (power) and electrical bandwidth without sacrificing the quantum efficiency performance. By properly designing the geometry size and epilayer structures of the partially p-doped ECPD, very high responsivity (1.01 A/W), high electrical bandwidth (around 50 GHz), and high saturation current bandwidth product (920 mA/spl middot/GHz, at 40 GHz) have been achieved simultaneously at 1.55-/spl mu/m wavelength.