Intimate Monolithic integration of Chip-scale Photonic Circuits

Cataloged from PDF version of article.In this paper, we introduce a robust monolithic integration technique for fabricating photonic integrated circuits comprising optoelectronic devices (e.g., surface-illuminated photodetectors, waveguide quantum-well modulators, etc.) that are made of completely separate epitaxial structures and possibly reside at different locations across the wafer as necessary. Our technique is based on the combination of multiple crystal growth steps, judicious placement of epitaxial etch-stop layers, a carefully designed etch sequence, and self-planarization and passivation steps to compactly integrate optoelectronic devices. This multigrowth integration technique is broadly applicable to most III-V materials and can be exploited to fabricate sophisticated, highly integrated, multifunctional photonic integrated circuits on a single substrate. As a successful demonstration of this technique, we describe integrated photonic switches that consume only a 300 x 300 mu m footprint and incorporate InGaAs photodetector mesas and InGaAsP/InP quantum-well modulator waveguides separated by 50 mu m on an InP substrate. These switches perform electrically-reconfigurable optically-controlled wavelength conversion at multi-Gb/s data rates over the entire center telecommunication wavelength band

Ultrafast Differential Sample and Hold using Low Temperature grown GaAs MSM for Photonic A/D Conversion

: We demonstrate an ultrafast sample and hold circuit using optically triggered metal-semiconductor-metal (MSM) switches made of low temperature (LT) grown GaAs for use in a photonic A/D conversion system. We incorporate a differential configuration to reduce feedthrough noise. Many proposed photonic A/D conversion systems consist of an input electrical signal biasing an optical modulator whose output is optically de-multiplexed to an array of electrical A/D converters [1,2]. However, the speed and linearity of the optical modulator limit the performance of these systems. To circumvent this problem, we propose a sample and hold scheme utilizing LT grown GaAs MSM switches. The short recombination lifetime and high mobility of LT grown GaAs allow high-speed operation with good sensitivity [3]. Optically triggered by a short pulse laser, the switches would be attached to a transmission line and would sample the input electrical signal onto a hold capacitor. One potential drawback of this ..

Observation of wavelength-converting optical switching at 2.5 GHz in a surface-normal illuminated waveguide

Abstract: We demonstrate proof-of-principle switching of a continuous wave (CW) signal that propagates in a p-i-n multiple quantum well waveguide illuminated from above with a modulated control beam. We observe modulation of the CW signal at 2.5 GHz using ~ 1mW control beam powers. Desirable features in optically-controlled optical switches include fast operating speeds, high contrast ratios, low switching power, and NxN scalability. Normally, waveguide modulators provide large contrast ratios but provide only 1xN scalability. By having surface-normal control of planar (waveguided) signals, NxN arrays could be achieved. Several groups have simply electrically interconnected surface-normal photodetectors with waveguide switches to achieve such a configuration [1-3]. In this paper we demonstrate an optically controlled waveguide switch that combines the detection and modulation function into a single device [4-5] that, in principle, can provide all of the above features. In addition to optically invoked modulation, we can enable (or disable) the device with an appropriate applied electrical bias. We demonstrate wavelength conversion capability of this device by employing different wavelengths for the control and signal beams (822 nm and 868 nm, respectively). The device is a multiple quantum well p-i-n diode with a waveguide structure, as seen in Fig. 1. The control beam is coupled into the diode through surface normal illumination while the CW signal is coupled in through the waveguiding direction of the device. Upon detection of the control beam, the absorption properties of the multiple quantum wells in the device are changed, which in turn modulates the CW signal. Consequently, data from the control beam can be encoded onto the CW signal. Thus, switching is achieved by performing detection of the control beam and modulation of the input signal with the same device. Because the detection and modulation occur in the same space, power consumption is decreased and electrical interconnection issues are eliminated. CW Signal (868 nm

Ultrafast optoelectronic sample-and-hold using low-temperaturegrown GaAs MSM

Abstract—We demonstrate 20-GHz input bandwidth of an optoelectronic sample-and-hold circuit using optically triggered metal–semiconductor–metal switches made of low-temperature-grown GaAs. Linearity 4 effective-number-of-bits and an estimated 3-dB bandwidth of up to 63 GHz are observed for the sample-and-hold process, making the device a potential candidate for moderate resolution, high-speed sampling applications. Index Terms—Analog-to-digital (A/D) conversion, low-temperature (LT)-grown GaAs, metal–semiconductor–metal (MSM) devices, optical data processing, sample-and-hold circuits. I