Abstract: In analyzing radiation from a sample, single-quanta counting can be used to advantage especially at low levels of radiation energy, e.g. in the detection of fluorescent radiation. Preferred detection techniques include methods in which (i) fluorescence-stimulating radiation is intensity-modulated in accordance with a preselected code, (ii) wherein it is the fluorescent radiation which is intensity-modulated with the preselected code, and (iii) wherein modulation with a preselected code is applied to a sample to influence a property which functionally affects emitted fluorescent radiation. For registration of the signals from a sensing element of a single-photon detector, time of arrival is recorded, optionally in conjunction with registration of time intervals. Advantageously, in the interest of minimizing the number of pulses missed due to close temporal spacing of pulses, D-triggers can be included in counting circuitry.

Abstract: In analyzing radiation from a sample, single-quanta counting can be used to advantage especially at low levels of radiation energy, e.g. in the detection of fluorescent radiation. Preferred detection techniques include methods in which (i) fluorescence-stimulating radiation is intensity-modulated in accordance with a preselected code, (ii) wherein it is the fluorescent radiation which is intensity-modulated with the preselected code, and (iii) wherein modulation with a preselected code is applied to a sample to influence a property which functionally affects emitted fluorescent radiation. For registration of the signals from a sensing element of a single-photon detector, time of arrival is recorded, optionally in conjunction with registration of time intervals. Advantageously, in the interest of minimizing the number of pulses missed due to close temporal spacing of pulses, D-triggers can be included in counting circuitry.

Abstract: A load sharing system which minimizes overall costs by assigning segments of a divisible load to distributed processor platforms based on the resource utilization cost of each processor platform. The distributed processor platforms are connected via data links which also have associated resource utilization costs. A controller divides a divisible load or task and assigns each segment of the load or task to a processor platform based on the processor platform's resource utilization cost and data link cost. After the initial allocation, an optimizing reallocation is performed to reduce the overall monetary cost processing the load or task. The optimization can be performed using a pair-wise swapping technique.

Abstract: Structured materials for photonic devices, at wavelengths of X-ray, ultraviolet, visible, infrared and microwave radiation, can be made using layer growth techniques. Such a structure can be made layer by layer, by homogeneous deposition followed by localized modification for refractive index differentiation. Alternatively, the structure can be made by simultaneous growth of regions whose refractive index differs. The structures can be used as selective bandpass filters, and in photovoltaic solar cells, for example.

Abstract: For multicolor fluorescence detection or spectroscopy with low signal-to-noise ratio and rapid readout, signals from multiple sensors are combined in analog form so that only one signal per fluorescent response needs to be read from a sensor array. The contributions of sensors in the array to a given output signal are programmable, for exclusive selection of the desired information. As the contributions of sensors to output signals are electronically programmed, the energy of the light source can be filtered electronically. Such devices can be programmed in real time for adaptive measurements.

Abstract: A load sharing system which minimizes overall costs by assigning segments of a divisible load to distributed processors based on the monetary cost of each processor. The distributed processors are connected to a network such as a local area network or the internet. A controller divides a divisible load and assigns each segment of the load to a processor based on the processor's monetary cost which is a function of its operating cost and its processing speed. The allocation is then optimized by transferring portions of the load from the expensive processors to the cheaper processor while maintaining an acceptable finish time for all processing. The optimization can also be performed for minimizing the finish time of the processors within a cost constraint.

Abstract: The present invention is a unique method for identifying the presence, and preferably the identity, of a fluorophore by optically stimulating one or more fluorophores with an optical signal which has been modulated in intensity in the time domain. The stimulated fluorophore produces a resulting fluorescence which is demodulated to produce an electrical signal corresponding to the intensity modulation of the fluorescence. Finally, the electrical signal is compared to the modulation of the optical signal to determine whether or not the fluorophore is present. The present method can be used alone or in conjunction with known methods of optically analyzing fluorescence of fluorophores to determine the presence of fluorophores.

Abstract: The gate electrode of a polysilicon gate MOS transistor--the transistor having either a thin film polysilicon substrate or a bulk monocrystalline substrate--has a pair of contiguous regions: a heavily doped gate electrode region near the source, and a lightly doped gate electrode region near the drain. The gate electrode region near the drain is thus doped significantly more lightly, in order to reduce electric fields in the channel region in the neighborhood of the drain (and hence reduce field induced leakage currents) when voltages are applied to turn transistor OFF. At the same time, sufficient impurity doping is introduced into the gate electrode region near the source in order to enable the transistor to turn ON when other suitable voltages are applied.

Abstract: A Novel method of making a semiconductor device (e.g., a HBT) is disclosed. A semiconductor body that comprises bulk semiconductor material and epitaxial semiconductor material on the bulk material is processed by carrying out a first sequence of processing steps on the epitaxial material. The sequence comprises forming at least first and second contact means on the epitaxial material. The resulting intermediate body is mounted, epitaxial material down, on a carrier body (e.g., a Si wafer with integrated circuitry thereon), such that the first and second contact means are electrically connected to, respectively, third and fourth contact means on the carrier body. Mounting is accomplished, exemplarily, by means of anisotropically conductive adhesive means. Subsequent to mounting of the intermediate body on the carrier body, a second sequence of processing steps is carried out on the intermediate body.

Abstract: The novel bipolar transistor has at least two separated emitter contacts and no base contact, and the emitter/base p-n junction has backward diode characteristics. The transistor can function as a logic device, but can also function as an amplifying device in digital or analog circuits.

Abstract: This application discloses, to the best of our knowledge, the first unipolar laser. An exemplary embodiment of the laser was implemented in the GaInAs/AlInAs system and emits radiation of about 4.2 .mu.m wavelength. Embodiments in other material systems are possible, and the lasers can be readily designed to emit at a predetermined wavelength in a wide spectral region. We have designated the laser the "quantum cascade" (QC) laser. The QC laser comprises a multilayer semiconductor structure that comprises a multiplicity of essentially identical undoper "active" regions, a given active region being separated from an adjoining one by a doped "energy relaxation" region. In a currently preferred embodiment each active region comprises three coupled quantum wells designed to facilitate attainment of population inversion. In the currently preferred embodiment the energy relaxation regions are digitally graded gap regions. However, other energy relaxation regions are possible.

Abstract: The disclosed novel heterojunction bipolar transistor, to be referred to as the enhanced diffusion transistor (EDT), comprises a base of composition selected such that the base bandgap narrows from emitter towards collector in substantially step-wise fashion, resulting in N (N.gtoreq.2) substantially flat levels in the base bandgap. The height .DELTA..sub.j of the steps in the bandgap is greater than kT (typically at least about 30 meV), and also greater than the threshold energy of an appropriate rapid inelastic minority carrier scattering mechanism (e.g., optical phonon scattering, plasmon scattering) in the base material. The presence of the "steps" in the base bandgap of the EDT can, in consequence of the resulting strongly accelerated diffusive minority carrier transport in the base, lead to, e.g., improved high frequency characteristics, as compared to otherwise identical prior art (N=1) transistors.

Abstract: We have discovered that coherent variation of at least two laser parameters can result in improved device performance, e.g., in pure amplitude or frequency modulation at frequencies substantially above 1 GHz, or in previously unattainable modulation frequencies. Among the relevant laser parameters are pumping rate, optical gain coefficient, photon lifetime, confinement factor, effective carrier temperature, output frequency and spontaneous emission factor. Exemplarily, the pumping rate and the optical gain are coherently varied such that the output radiation is free of chirp, or the output frequency and the effective carrier temperature are coherently varied such that the output radiation has constant amplitude.

Abstract: The disclosed heterojunction bipolar transistor, to be referred to as the "coherent" transistor (CT), is capable of providing gain above the conventionally defined cut-off frequencies f.sub.T and f.sub.max. Substantially, mono-energetic (average energy .DELTA.) carriers are injected in beam-like fashion into the base, with kT<.DELTA.<hv.sub.opt, where k, T and h have their conventional meaning, and v.sub.opt is the frequency of the lowest relevant optical phonon in the base of width W.sub.B. Exemplarily, W.sub.B is about 100 nm, .DELTA. is about 20 meV, the CT comprises Si.sub.1-x Ge.sub.x or III/V material, with the base being doped n-type. The CT utilizes substantially collisionless minority carrier transport through the base, and is designed such that, at an operating temperature which typically is .ltorsim.77K, the variance of the average base transit time (.DELTA..tau..sub.B) is much less than the base transit time .tau..sub.B, typically less than 0.5 .tau..sub.B, preferably about .tau..sub.