An assembly includes a first electrical circuitry for providing a first electrical signal containing data and a transmitting arrangement, connected with the first electrical circuitry, for receiving the first electrical signal and for converting the first electrical signal into an electromagnetic signal containing at least a portion of the data. The electromagnetic signal has a carrier frequency greater than 300 GHz. The assembly also includes a receiving arrangement for receiving the electromagnetic signal and for converting the electromagnetic signal into a second electrical signal containing at least some of the portion of the data, and a second electrical circuitry connected with the receiving arrangement and configured for receiving the second electrical signal.

Terahertz interconnect system and applications

The increasing interest in vertical-cavity surface-emitting lasers (VCSEL's) requires the corresponding development of circuit-level VCSEL models for use in the design and simulation of optoelectronic applications. Unfortunately, existing models lack either the computational efficiency or the comprehensiveness warranted by circuit-level simulation. Thus, in this paper we present a comprehensive circuit-level model that accounts for the thermal and spatial dependence of a VCSEL's behavior. The model is based on multimode rate equations and empirical expressions for the thermal dependence of the active-layer gain and carrier leakage, thereby facilitating the simulation of VCSEL's in the context of an optoelectronic system. To confirm that our model is valid, we present sample simulations that demonstrate its ability to replicate typical dc, small-signal, and transient operation, including temperature-dependent light-current (LI) curves and modulation responses, multimode behavior, and diffusive turn-off transients. Furthermore, we verify our model against experimental data from four devices reported in the literature. As the results will show, we obtained excellent agreement between simulation and experiment.

A comprehensive circuit-level model of vertical-cavity surface-emitting lasers

With desktop computers requiring ever more communication bandwidth, fiber-optics has become an essential part of the Local Area Network (LAN).

Low-Cost Multimode WDM for Local Area Networks

Current local area network (LAN) bandwidth demands of >1 Gb/s are pushing the limit of the bandwidth-distance product of multimode fiber, the predominant fiber in LAN backbones. In order to overcome these limitations, a low-cost and compact wavelength division multiplexing scheme is demonstrated. Aggregate bit rates of 5 and 10 Gb/s are achieved through 300 and 100 m of 62.5/125-/spl mu/m multimode fiber, respectively. Four vertical-cavity surface-emitting lasers are used at wavelengths of 820, 835, 850, and 865 nm with each operating at a bit rate of 1.25 or 2.5 Gb/s. This technology provides a practical solution for reaching bit rates up to 10 Gb/s in the LAN.

Low-cost multimode WDM for local area networks up to 10 Gb/s

We measured the increase in threshold currents due to lateral carrier diffusion in InGaAs/AlGaAs quantum‐well ridge‐waveguide laser diodes. The ridge stripes were fabricated by using both in situ monitored pure Cl2 reactive ion etching and selective wet etching to completely eliminate the spreading current in the conductive upper cladding layer while keeping the ridge sidewalls straight. After comparing the threshold data with a theoretical model, the ambipolar diffusion coefficient is found to be 22 cm2/s in the population‐inverted InGaAs layer. This model is based on the calculated optical gain curve and the ambipolar carrier transport in the quantum‐well and waveguiding layers. The dependence of carrier lifetime on the local carrier concentration is included in the calculation. Moreover, from another set of devices with the portions of the active layer outside the ridge stripes etched away, the surface recombination velocity is found to be around 1–2×105 cm/s.

Lateral carrier diffusion and surface recombination in InGaAs/AlGaAs quantum‐well ridge‐waveguide lasers

We stress the importance of considering the effect of lateral leakage current on the material gain/current-density characteristics measured from ridge-waveguide diode lasers. It is found that the inclusion of lateral leakage current is crucial to obtaining a self-consistent result. An experimental demonstration has been performed on an In/sub 0.2/Ga/sub 0.8/As/AlGaAs strained single quantum-well laser sample, from which a gain curve with transparency current density of 53.8 A/cm/sup 2/ was obtained. By using devices of different geometries, the variation of leakage currents is measured and the accuracy of the resultant gain curves is discussed. >

The effect of lateral leakage current on the experimental gain/current-density curve in quantum-well ridge-waveguide lasers

A low cost, high speed WDM optical link which employs a circular array of VCSEL emitters directly coupled to a multi-mode fiber through which multiple simultaneously optical transmissions are sent to an optical detector comprising a circular array of RCPD detectors receiving the multiple simultaneous transmissions. The emitters and detectors within each array are fabricated with a double-absorber design which avoids position sensitivity related to the cavity standing wave and eliminates the need for in-situ cavity-mode adjustment. In addition, a coupled-cavity structure is presented to achieve passbands with flat tops and steep sides to approach the ideal square-shape photoresponse and to ensure proper channel alignment.

Direct-coupled multimode WDM optical data links with monolithically-integrated multiple-channel VCSEL and photodetector

We report on the design and implementation of a novel multiple-wavelength optical data link for low-cost multimode wavelength-division multiplexing (WDM) local-area network applications. This link utilizes a monolithically integrated multiple-wavelength vertical-cavity laser array and a narrow-band resonant-cavity photodetector array to transmit multiple channels of information simultaneously via a single multimode fiber. A detailed analysis on wavelength tuning and threshold characteristics of different laser cavity designs is presented. Theoretical results are compared to our experimental data. On the receiver part, both Schottky and p-i-n photodetectors with a single- or coupled-cavity structure are discussed. A novel p-i-n resonant-cavity photodetector design with a partially oxidized front mirror for linewidth control is proposed. Moreover, we also demonstrate preliminary measurements on the optical link built with our multiple-wavelength vertical-cavity laser array and photodetector array. Finally, the feasibility of constructing a multiwavelength optical data link with a single dual-core multimode fiber and an integrated laser/detector array is evaluated.

Multimode WDM optical data links with monolithically integrated multiple-channel VCSEL and photodetector arrays

Direct-coupled multimode WDM optical data links with monolithically-integrated multiple-channel VCSEL and photodetector arrays

Significant reduction of threshold currents in InGaAs-GaAs quantum-well ridge-waveguide lasers has been achieved by using silicon-induced disordering to provide lateral confinement. Room-temperature threshold currents as low as 0.7 mA for pulsed operation and 0.9 mA for cw operation have been obtained from an uncoated 137-/spl mu/m-long and 0.3-/spl mu/m-wide device. In addition, the effects of high-temperature annealing on the various device characteristics, such as the gain curve, internal loss, and quantum efficiency, have been investigated. >

S.Y. Hu

Papers

The effect of lateral leakage current on the experimental gain/current-density curve in quantum-well ridge-waveguide lasers

Direct-coupled multimode WDM optical data links with monolithically-integrated multiple-channel VCSEL and photodetector

Multimode WDM optical data links with monolithically integrated multiple-channel VCSEL and photodetector arrays

Direct-coupled multimode WDM optical data links with monolithically-integrated multiple-channel VCSEL and photodetector arrays

Submilliampere-threshold InGaAs-GaAs quantum-well ridge-waveguide lasers with lateral confinement provided by impurity-induced disordering