K.W. Goossen

GaAs MQW modulators integrated with silicon CMOS

We demonstrate integration of GaAs-AlGaAs multiple quantum well modulators to silicon CMOS circuitry via flip-chip solder-bonding followed by substrate removal. We obtain 95% device yield for 32/spl times/32 arrays of devices with 15 micron solder pads. We show operation of a simple circuit composed of a modulator and a CMOS transistor.<<ETX>>

Direct demonstration of a misfit strain‐generated electric field in a [111] growth axis zinc‐blende heterostructure

We report the first direct demonstration of a strain‐generated built‐in electric field in a (111) oriented strained‐layer heterostructure. We present a model which describes the accommodation of the misfit strain in a lattice‐mismatched quantum well, and the resulting generation of a longitudinal electric field via the piezoelectric effect. On a (111)B GaAs substrate, we grew the quantum well in the intrinsic region of a p‐i‐n diode such that the strain‐generated electric field in the quantum well opposes the weaker built‐in electric field of the diode. Under reverse bias operation, photoconductivity measurements show a quadratic blue shift of the quantum well electroabsorption peaks, in contrast to the red shifts normally observed in the quantum‐confined Stark effect. The measured blue shifts demonstrate an electric field strength of 1.7×105 V/cm, which agrees with theory to within the accuracy of the measured sample characteristics.

Silicon modulator based on mechanically-active anti-reflection layer with 1 mbit/sec capability for fiber-in-the-loop applications

We present a micromechanical modulator for fiber-in-the-loop applications with projected optical bandwidths from 1.3 to 1.55 /spl mu/m and data rates of several Mbits/sec. The device behaves as a damped oscillator. We have made a device with a ringing frequency of 1.1 MHz and a damping time constant of 1 /spl mu/s. We indicate that with an appropriate linear filter the device could operate digitally with data rates of 1 Mbit/sec.<<ETX>>

Fiber Bragg grating sensors toward structural health monitoring in composite materials: challenges and solutions.

Nowadays, smart composite materials embed miniaturized sensors for structural health monitoring (SHM) in order to mitigate the risk of failure due to an overload or to unwanted inhomogeneity resulting from the fabrication process. Optical fiber sensors, and more particularly fiber Bragg grating (FBG) sensors, outperform traditional sensor technologies, as they are lightweight, small in size and offer convenient multiplexing capabilities with remote operation. They have thus been extensively associated to composite materials to study their behavior for further SHM purposes. This paper reviews the main challenges arising from the use of FBGs in composite materials. The focus will be made on issues related to temperature-strain discrimination, demodulation of the amplitude spectrum during and after the curing process as well as connection between the embedded optical fibers and the surroundings. The main strategies developed in each of these three topics will be summarized and compared, demonstrating the large progress that has been made in this field in the past few years.

Optoelectronic-VLSI: photonics integrated with VLSI circuits

Optoelectronic-VLSI (OE-VLSI) technology represents the intimate integration of photonic devices with silicon VLSI electronics. We review the motivations and status of emerging OE-VLSI technologies and examine the performance of OE-VLSI technology versus conventional wire-bonded OE packaging. The results suggest that OE-VLSI integration offers substantial power and speed improvements even when relatively small numbers of photonic devices are driven with commodity complementary metal-oxide-semiconductor logic technologies.

Vertical-cavity surface-emitting lasers flip-chip bonded to gigabit-per-second CMOS circuits

We describe the first integration of vertical-cavity surface-emitting laser arrays with gigabit-per-second CMOS circuits via flip-chip bonding.

Observation of room‐temperature blue shift and bistability in a strained InGaAs‐GaAs 〈111〉 self‐electro‐optic effect device

We have observed room‐temperature exciton blue shift with applied voltage in a 〈111〉 In0.1Ga0.9As‐GaAs p‐i‐n multiple quantum well modulator. We have also observed optically induced bistability in a symmetric self‐electro‐optic effect device circuit composed of these modulators. Very large (2.5:1) ratios of photocurrent were obtained with only 0–3 V applied bias.

Grating enhanced quantum well detector

An infrared detector based on the excitation of carriers out of a modulation‐doped quantum well is theoretically investigated. The efficiency of the detector is increased by using a grating to enhance the fields in the well. Scattering effects are taken into account by designing the quantum well so that upon excitation carriers will escape in a short time compared to the time it takes to scatter back into the well. Despite this constraint, a quantum efficiency of 90% is shown to be possible for a GaAs‐AlGaAs quantum well with a carrier density of 1012 cm−2.

A tunable dispersion compensating MEMS all-pass filter

A tunable dispersion compensating filter based on a multistage optical all-pass filter with a microelectromechanical (MEM) actuated variable reflector and a thermally tuned cavity is described. A two-stage device was demonstrated with a tuning range of /spl plusmn/100 ps/nm, 50-GHz passband and a group delay ripple less than /spl plusmn/3 ps. The device has negligible polarization dependence and is suitable for single or multiple channel compensation. An off-axis, two-fiber package with an excess loss <2 dB/stage avoids the need for a circulator. By cascading four stages, a passband to channel spacing ratio of 0.8 is obtained that allows both 40 Gb/s nonreturn-to-zero (NRZ) and return-to-zero (RZ) signals to be compensated.

Micromechanical fiber-optic attenuator with 3 /spl mu/s response

Optomechanical fiber-optic attenuators are bulky and slow. The mechanical antireflection switch (MARS) modulator offers a high-speed alternative for applications including dynamic gain control in fiber amplifiers. This paper describes a compact electrically controlled variable attenuator using a micromechanical device where electrostatic deflection of a silicon nitride quarter-wave dielectric layer suspended over a silicon substrate creates a variable reflectivity mirror. This device is packaged with two fibers in one ceramic ferrule placed in contact with a gradient index (GRIN) collimation lens, so that the input light reflects from the modulator in the collimated beam plane and couples into the output fiber. Using a 300 /spl mu/m diameter MARS attenuator and a 500 /spl mu/m diameter collimation lens, the total insertion loss at 1550 nm was 3.0 dB with no applied voltage, increasing to 31 dB at 35.2 V. The polarization dependent loss was less than 0.06 dB. Full attenuation with more than 100 mW input power produced no damage. The response time was 2.8 /spl mu/s to move from maximum to minimum transmission and 1.1 /spl mu/s to return to maximum transmission.