Phase-conjugate reflection by degenerate four-wave mixing in a nematic liquid crystal in the isotropic phase

We report the generation of conjugate wave fronts by degenerate four-wave mixing in the isotropic phase of the nematic substance p-methoxy-benzylidene p-n-butylaniline. The temporal and spatial properties of the conjugate wave fronts are verified. The dependence of the nonlinear reflectivity on the pump-wave power and the temperature of the medium is discussed

Generation of amplitude-squeezed light from a room-temperature Fabry-Perot semiconductor laser

Amplitude-squeezed light with intensity fluctuations 29% below the standard quantum limit (SQL) is produced from a pump-suppressed room-temperature semiconductor laser, corresponding to 41% below the SQL after correction for detection efficiency. Excess noise, which degrades the observed squeezing, appears to be associated with the presence of weak longitudinal side modes

The intrinsic electrical equivalent circuit of a laser diode

The basic electrical equivalent circuit of a laser diode is derived. The effects of spontaneous emission and self-pulsations are included. It is found that self-pulsations are represented by a negative resistance in the model. Application of this model suggests purely electronic methods of suppressing relaxation oscillations in laser diodes

Large-Area, Low-Noise, High Speed, Photodiode-Based Fluorescence Detectors with Fast Overdrive Recovery

Two large-area, low noise, high speed fluorescence detectors have been built. One detector consists of a photodiode with an area of 28 mm x 28 mm and a low noise transimpedance amplifier. This detector has a input light-equivalent spectral noise density of less than 3 pW/Hz^1/2, can recover from a large scattered light pulse within 10 us, and has a bandwidth of at least 900 kHz. The second detector consists of a 16 mm diameter avalanche photodiode and a low-noise transimpedance amplifier. This detector has an input light-equivalent spectral noise density of 0.08 pW/Hz^1/2, also can recover from a large scattered light pulse within 10 us, and has a bandwidth of 1 MHz.Comment: Submitted to Review of Scientific Instrument

Single-growth embedded epitaxy AlGaAs injection lasers with extremely low threshold currents

A new type of strip-geometry AlGaAs double-heterostructure laser with an embedded optical waveguide has been developed. The new structure is fabricated using a single step of epitaxial growth. Lasers with threshold currents as low as 9.5 mA (150 µm long) were obtained. These lasers exhibit operation in a single spatial and longitudinal mode, have differential quantum efficiencies exceeding 45%, and a characteristic temperature of 175° C. They emit more than 12 mW/facet of optical power without any kinks

Optimised Fabry-Perot (AlGa)As quantum well lasers tunable over 105 nm

Uncoated, Fabry-Perot (AlGa)As semiconductor lasers are tuned over 105nm in a grating-coupled external cavity. Broadband tunability is achieved by optimising the resonator loss so as to invoke lasing from both the first and second quantised states of the single quantum well active region

Analysis of Optical Pulse Propagation with ABCD Matrices

We review and extend the analogies between Gaussian pulse propagation and Gaussian beam diffraction. In addition to the well-known parallels between pulse dispersion in optical fiber and CW beam diffraction in free space, we review temporal lenses as a way to describe nonlinearities in the propagation equations, and then introduce further concepts that permit the description of pulse evolution in more complicated systems. These include the temporal equivalent of a spherical dielectric interface, which is used by way of example to derive design parameters used in a recent dispersion-mapped soliton transmission experiment. Our formalism offers a quick, concise and powerful approach to analyzing a variety of linear and nonlinear pulse propagation phenomena in optical fibers.Comment: 10 pages, 2 figures, submitted to PRE (01/01

Gallium Arsenide Monolithic Optoelectronic Circuits

The optical properties of GaAs make it a very useful material for the fabrication of optical emitters and detectors. GaAs also possesses electronic properties which allow the fabrication of high speed electronic devices which are superior to conventional silicon devices. Monolithic optoelectronic circuits are formed by the integration of optical and electronic devices on a single GaAs substrate. Integration of many devices is most easily accomplished on a semi-insulating (SI) sub-strate. Several laser structures have been fabricated on SI GaAs substrates. Some of these lasers have been integrated with Gunn diodes and with metal semiconductor field effect transistors (MESFETs). An integrated optical repeater has been demonstrated in which MESFETs are used for optical detection and electronic amplification, and a laser is used to regenerate the optical signal. Monolithic optoelectronic circuits have also been constructed on conducting substrates. A heterojunction bipolar transistor driver has been integrated with a laser on an n-type GaAs substrate

Quantum state preparation and control of single molecular ions

Preparing molecules at rest and in a highly pure quantum state is a long standing dream in chemistry and physics, so far achieved only for a select set of molecules in dedicated experimental setups. Here, a quantum-limited combination of mass spectrometry and Raman spectroscopy is proposed that should be applicable to a wide range of molecular ions. Excitation of electrons in the molecule followed by uncontrolled decay and branching into several lower energy states is avoided. Instead, the molecule is always connected to rotational states within the electronic and vibrational ground-state manifold, while a co-trapped atomic ion provides efficient entropy removal and allows for extraction of information on the molecule. The outlined techniques might enable preparation, manipulation and measurement of a large multitude of molecular ion species with the same instrument, with applications including, but not limited to, precise determination of molecular properties and fundamental tests of physics.Comment: 12 pages, 2 figures, reformatted for resubmissio

Confinement effects on the stimulated dissociation of molecular BECs

We show that a molecular BEC in a trap is stabilized against stimulated dissociation if the trap size is smaller than the resonance healing length $(\hbar^2/2mg\sqrt{n})^{1/2}$. The condensate shape determines the critical atom-molecule coupling frequency. We discuss an experiment for triggering dissociation by a sudden change of coupling or trap parameters. This effect demonstrates one of the unique collective features of 'superchemistry' in that the yield of a chemical reaction depends critically on the size and shape of the reaction vessel.Comment: 4 pages, 4 figure