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Room temperature excitons are necessary to make many devices employing the quantum confined Stark effect. We investigate the degradation of room temperature excitonic absorptions in InGaAs/InP quantum wells under growth conditions used to make integrated photonic and opto-electronic devices involving multiple regrowths. We describe various conditions of temperature and time under which we have observed these excitons to survive or degrade, and offer suggestions for device construction.

We report a high-voltage integrated optical-to-electrical power converter, or photogenerator, operating in the long-wavelength (1480-1650 nm) regime for use in fiber-optic networks. These devices deliver power at voltages in excess of 10 V, which is sufficient to operate switches, micromechanical devices, electronic controllers, optoelectronic circuits and other electrical devices. The high-voltage photogenerator enables provisioning and protection at unpowered nodes in fiber-optic networks, using only the long wavelength light present in the optical fiber as the power source. We also demonstrated its use with a MEMS optical shutter to construct a novel optical power limiter.

Summary form only given. Infinera has commercialized the first digital transport network (DTN) systems as a highly reliable, small footprint system to the telecommunications carriers. The key technology in the DTN is optical-electrical-optical (O-E-O) digital signal processing. O-E-O processing allows the carriers to install systems at more locations, which translates into more entry points into the network. The photonic integrated circuit, or PIC, enables cost-effective O-E-O processing. While research had been ongoing for several decades, Infinera systems are the first to incorporate large-scale photonic integration. Infinera's commercially deployed PICs operate at 100 Gb/s on 10 channels (10Gb/s per channel). Each transmit PIC channel consists of a tunable DFB, modulator, power monitor and variable optical attenuator (VOA). The PIC has been deployed worldwide, demonstrating an excellent reliability track-record. The challenges met in commercializing this chip, including the tradeoff between performance, reliability, and a robust processing methodology, will be discussed as well the latest development results, wherein we have demonstrated transmitter chips integrating over 240 elements with a aggregate capacity of 1.6 Tb/s.

We demonstrate a 16-channel waveguide grating router (WGR) in the InP-based material system. The channel spacing of the WGRs is 100 GHz and the maximum interchannel crosstalk is -28 dB. The polarization related (TE-TM modal) wavelength shift is approximately 0.08 nm and the polarization dependent variation in peak signal is less than 0.2 dB. 2.60-/spl mu/m-wide /spl times/1.90-/spl mu/m-thick raised-stripe InGaAsP Quaternary (/spl lambda//sub g/=1.17 /spl mu/m) waveguides on an n-type InP substrate make up the basis paths of the WGR. In this letter, we describe the design, fabrication and the results of measurement of the 16-channel polarization-insensitive WGR.

A 3/spl times/3 array of series-connected InGaAs photodetectors was used as a photogenerator to optically power a remotely-located microwatt-power optical shutter intended for use in a lightwave network. The conversion efficiency of the photogenerator was 7/spl times/10/sup -3/ A/W when the device was illuminated at 1550 nm from the output of a single-mode fiber; the open-circuit voltage was 2 V with 300 /spl mu/W of incident power.

Detailed measurements of sensitivity and crosstalk under two-wavelength, multichannel operation of an eight-channel receiver array in an optically preamplified, wavelength division multiplexed (WDM) system are reported. The average sensitivity of the system measured at the EDFA input for an individual channel at 2.5 Gb/s is -39.6 dBm for a bit-error rate of 10/sup -9/. Measurement results indicate that the primary contribution to the crosstalk sensitivity penalty is electrical crosstalk between the receiver array preamplifier circuit outputs, with a negligible contribution from optical crosstalk in the WGR.

In this work, we investigate the performance of our receiver array in the realistic environment of an eight-wavelength wavelength-division multiplexed (WDM) testbed. The experiments were performed as a deliverable for the ARPA MONET multi-wavelength optical network program.

We have investigated luminescence processes in high purity In0.53Ga0.47As grown by liquid phase epitaxy on InP substrate. The origins of luminescence processes have been determined by studying the dependence of emission intensity and spectrum on temperature. We show that exciton-ionized donor complex dominates the luminescence at 2K. With increasing temperature, the luminescence spectrum is dominated by donor-valence band and free electron-free hole recombination. Spectrum and bandgap energy are found to be dependent on the excitation position.

Back-illuminated PIN photodiodes with active areas 1 mm in diameter have been made from LPE-grown InGaAs/InP. The diodes have photoresponse, leakage and stability properties which suggest that they may be superior to germanium photodiodes for many general-purpose long-wavelength applications.

High-speed operation of a long-wavelength (1.0µm ≲ λ ≲ 1.65µm) avalanche photodiode (APD) has been achieved with a heterojunction structure consisting of a wide-bandgap (InP) multiplication region and a narrow-bandgap (InGaAs) absorption region separated by an intermediate-bandgap (InGaAsP) "grading" layer. Previous InP/InGaAs APD's without the "grading" layer (SAM-APD structure) have exhibited low dark current and high avalanche gain, but they have not performed well at high bit rates because the bandwidth is restricted by hole trapping at the valence band discontinuity of the InP/InGaAs interface. In this paper we demonstrate that the incorporation of a "grading" layer results in a dramatic improvement in the speed of response while maintaining low dark current, good quantum efficiency, and high avalanche gain. By incorporating one of these APD's into a high-speed optical receiver, sensitivity measurements have been obtained for 1.3µm and 1.5µm wavelengths at bit rates of 420 Mb/s and 1 Gb/s.

The fabrication and device characteristics of back-illuminated InP/InGaAs n-p-n heterojunction phototransistors will be described. These devices consist of a "wide-bandgap" InP emitter with smaller bandgap InGaAs base and collector layers. Uniform spectral response is observed in the wavelength range from 0.95 µm to 1.6 µm. The DC optical gain increases from approximately 40 at an input power of 1 nW to over 1000 for an input power level of 5 µW. The small-signal gain is characteristically 2 to 3 times higher than the EC gain. The cut-off frequency f T is an increasing function of the incident light level; for 1 µW of incident power f T ≃ 300 MHz. The possible applications of these phototransistors in fiber optic systems will be discussed.

Experiments with photodiodes for use in the 1 to 1.3 µm wavelength region, fabricated from LPE double-heterostructure InGaAsP/InP wafers, have shown that the avalanche multiplication in mesa-configuration devices was limited to values of 10 or less. The results of careful measurement of the photoresponse, quantum efficiency and reverse-bias I-V characteristics suggest that the gain was limited by microplasma breakdown.

Light-emitting diodes with the high-radiance Burrus configuration have been made with an internal PNPN structure which causes an S-type negative resistance. The devices were double heterostructures using InGaAsP material. By using the proper external load impedance and bias voltage, the negative resistance can be used to obtain bistable operation with switching from low current to high current triggered by a small current (e.g. 1 µA). Light coupled into the center junction can be used as the source of Signal current. Triggering has been achieved with a 3 µW light pulse.

A 16-channel 100-GHz spacing WDM spectral equalizer having athermal grating multiplexer/demultiplexers and MEMS variable attenuators was demonstrated with 50 dB dynamic range and autonomous power regulation using self-powered optical limiters incorporating InGaAs photogenerators.

We report on an optically powered optical power limiter for use in lightwave networks. Our device is a hybrid consisting of a MEMS variable attenuator specially designed for operation at low voltages operated in conjunction with an InGaAs photogenerator. Our resulting device is fast, small, inexpensive, fiber connectorized and requires no external circuitry or source of electrical power. We believe that it represents a practical power limiter, which will be easily implemented in lightwave systems.