Volume 88, Issue 6, 06 February 2006
- lasers, optics, and optoelectronics
- plasmas and electrical discharges
- structural, mechanical, thermodynamic, and optical properties of condensed matter
- electronic transport and semiconductors
- magnetism and superconductivity
- dielectrics and ferroelectricity
- nanoscale science and design
- device physics
- applied biophysics
- interdisciplinary and general physics
Index of content:
A single-emitter multiple-input transistor laser has been realized and demonstrated in signal mixing, yielding in the stimulated-recombination region near laser threshold frequency conversion with simultaneously an electrical and optical output signal. In the unique nonlinear region of compression of the transistor characteristics (, ), input signals and are converted into ranging from . Stimulated emission (enhanced recombination) changes the transistor into a special form of nonlinear element, a special form of electronic processor or “switch.”
- LASERS, OPTICS, AND OPTOELECTRONICS
88(2006); http://dx.doi.org/10.1063/1.2172400View Description Hide Description
We fabricate 50-mm-long direct-bonded quasi-phase-matched ridge waveguides for difference frequency generation in the wavelength range. Conversion efficiency of 40%/W is achieved using a pump and a signal, and a 0.26-mW output is obtained. We also use the device to demonstrate methane gas detection at around .
88(2006); http://dx.doi.org/10.1063/1.2171652View Description Hide Description
We demonstrate room temperature optically and electrically controllable group delay using population oscillation in a quantum-dot (QD) semiconductor optical amplifier (SOA). A reduction of the group index up to 10% with a bandwidth of 13 GHz is achieved under different configurations of injection current and optical pump intensity. Our theoretical results based on population pulsation agree well with experimental data. We extract the linewidth enhancement factor and effective carrier diffusion coefficient of the QD SOA. We also observe slow light when the injection current is increased.
88(2006); http://dx.doi.org/10.1063/1.2172070View Description Hide Description
Electrically tunable photonic band gap(PBG)structures hold the potential to become a versatile and compact backbone for optical signal processing. In this letter we report electrical tuning of silicon-based two-dimensional PBGstructures infiltrated with liquid crystals. An improved electrode configuration is used to avoid electric field screening by the conductive silicon walls. Electrical tuning using fields well below is demonstrated experimentally using both polarized light microscopy and reflectance PBG measurements. The structures can be operated with any electro-opticmaterials and lead to fast and efficient modulators, routers, and tunable filters.
88(2006); http://dx.doi.org/10.1063/1.2172024View Description Hide Description
An approach for wafer bonding based on thiourea treatment was presented. The bonding energy reaches the InP fracture energy by annealing at . An multiple quantum well(MQW) structure grown on InP was transferred onto GaAs substrate via the bonding process. X-ray diffraction and photoluminescence reveal that crystal quality of the bonded MQW was preserved. A thin sulfide layer with thickness of about at the bonding interface was detected. X-ray photoelectron spectroscopy analyses indicate that the formation of In–S and Ga–S bond at thiourea treatedsurface is responsible for the strong fusion obtained at such low temperature.
88(2006); http://dx.doi.org/10.1063/1.2172409View Description Hide Description
We report on the realization of polariton quantum boxes in a semiconductor microcavity under strong coupling regime. The quantum boxes consist of mesas, etched on the top of the spacer of a microcavity, that confine the cavity photon. For mesas with sizes of the order of a few microns in width and nanometers in depth, we observe quantization of the polariton modes in several states, caused by the lateral confinement. We evidence the strong exciton-photon coupling regime through a typical anticrossing curve for each quantized level. Moreover, the growth technique permits one to obtain high-quality samples, and opens the way for the conception of new optoelectronic devices.
88(2006); http://dx.doi.org/10.1063/1.2172410View Description Hide Description
Low-threshold and narrow-linewidth lasing from dye-doped holographic polymer-dispersed liquid crystal transmission gratings88(2006); http://dx.doi.org/10.1063/1.2172161View Description Hide Description
Optically pumped lasing with low threshold and narrow linewidth was observed in a 4-dicyanomethylene-2-methyl-6-p-dimethylaminostyryl-4H-pyran dye-doped holographic polymer-dispersed liquid crystal transmission grating structure. The results showed that the lasing peak centered at about 609 nm, with a full width at half maximum of about only 1.8 nm. The threshold pumping intensity was about under the excitation of a frequency-doubled Nd:yttrium–aluminum–garnet laser operating at a wavelength of 532 nm. Theoretical calculation showed that the lasing from this structure happened at the band edge of the photonic band gap. The lasing modes were also investigated. The transmission grating investigated enjoys a much larger gain length compared to the reflection one.
88(2006); http://dx.doi.org/10.1063/1.2172293View Description Hide Description
A high-power optically pumped semiconductor laser operating around 970 nm has been used as a pumping source for an upconversion laser based on an doped crystal. Nearly 0.5 W of continuous wave (cw) output power and 0.8 W peak power at a 50% pump duty cycle could be achieved at a wavelength of 552 nm. This represents the highest output power from a room temperature upconversion laser ever reported. Laser threshold and slope efficiency were measured to be below 100 mW of absorbed pump power and 30%, respectively. This experiment could be an important step along the route to realizing a compact and efficient upconversion laser emitting in the Watt level power regime.
88(2006); http://dx.doi.org/10.1063/1.2172297View Description Hide Description
Time and frequency gating of molecular spontaneous emission at a less than one photon per mode level is achieved using phase matching properties of sum frequency generation in a 3 mm type I BBO crystal. The results of time and frequency resolved fluorescence measurements from a vibrational wavepacket in diatomic potassium molecules are presented. The experimental arrangement is simplified compared to the classical setup which uses a short crystal and monochromator. Both the signal and the signal to noise ratio increase.
88(2006); http://dx.doi.org/10.1063/1.2172299View Description Hide Description
We describe a directed vertical alignment (VA) display mode based on a nematic liquid crystal (LC)doped with a chiraldopant and confined between two substrates, one of which is pretreated, say, by unidirectional rubbing or photoalignment. The design allows one to eliminate umbilical defects that appear during switching of the conventional VA cells and thus to obtain better contrast. Switching is faster than for VA cells when optimized concentration of a chiraldopant is added and LC molecules at one of the substrates are slightly tilted from the cell normal due to the unidirectional surface treatment.
88(2006); http://dx.doi.org/10.1063/1.2172406View Description Hide Description
We present results of nanosecond laser ablation of silicon over a broad range of laser intensities, investigated by studying the time evolution of the ablation plume ejection, which, as measured by transmission of a probe beam, consists of a fast ejection phase followed by a delayed slow ejection phase. Experimental results indicate that different physical processes dominate at different ablation stages. The laser intensity threshold for the appearance of the slow ejection is . The plume kinetics parameters extracted from our experiments agree well with estimations based on blast wave and homogeneous nucleation theories, providing a physical explanation for the observed ablation rate dependence on the laser light intensity.
88(2006); http://dx.doi.org/10.1063/1.2170435View Description Hide Description
This letter describes the design and operation of a liquid-core liquid-cladding optical waveguide composed of a thermal gradient across a compositionally homogeneous liquid flowing in a microfluidic channel at low Reynolds number. Two streams of liquid at a higher temperature (the cladding) sandwich a stream of liquid at a lower temperature (the core). This temperature difference results in a contrast in refractive index across the width of the channel that is sufficient to guide light. The use of a single homogeneous liquid in this system simplifies recycling, and facilitates closed-loop operation. Furthermore, with radiative and inline heating of the liquids, it should be possible to reconfigure this optical system with considerable flexibility.
88(2006); http://dx.doi.org/10.1063/1.2171488View Description Hide Description
We present an experimental study of the propagation of the THz Zenneck surface wave on an aluminum sheet, now more commonly denoted as the THz surface plasmon (TSP). Here, the TSP pulse is generated by coupling the THz pulse from a metal parallel-plate waveguide onto the aluminum sheet; the propagated TSP pulse is detected at the output end of the sheet using a standard photoconductive dipole antenna. We separate the associated free-space THz pulse from the TSP pulse using a curved sheet. The observed weakly guided TSP propagation has the expected low group velocity dispersion, but also has anomalously high attenuation and much tighter binding to the metal surface than predicted by Zenneck theory.
88(2006); http://dx.doi.org/10.1063/1.2172291View Description Hide Description
We report the use of continuous wave spectralhole burning to perform high-resolution spectroscopy of the homogeneous linewidth of self-assembled InGaAs-GaAs quantum dots at low temperature. We use this technique to examine the power broadening behavior of the homogeneous InGaAs-GaAs quantum dot line. We find that at a temperature of 9.8 K and over the majority of the pump powers considered, the spectral hole signal is well fit by a single Lorentizian line shape. Analysis of the power broadening yields a full width at half maximum of for the homogeneous linewidth and a corresponding coherence time of 1.76 ns.
Effect of the lossy layer thickness of metal cylindrical waveguide wall on the propagation constant of electromagnetic modes88(2006); http://dx.doi.org/10.1063/1.2172735View Description Hide Description
Based on the dispersion equation of electromagnetic mode, the propagation problem in a lossy cylindrical waveguide is studied. The analytic formula of propagation constant for any mode in the waveguide is presented, which includes the effect of the lossy layer thickness on the waveguide wall. The analysis with the analytic formula shows that the lossy layer thickness has great effect on the propagation constant when the thickness is 1.5 times smaller than the skin depth of good conductor .
Demonstration of quasi-phase-matched nonreciprocal polarization rotation in III-V semiconductor waveguides incorporating magneto-optic upper claddings88(2006); http://dx.doi.org/10.1063/1.2172648View Description Hide Description
The demonstration of quasi-phase-matched nonreciprocal polarization rotation in a waveguide comprising a conventional III-V semiconductor core and lower cladding is reported. The approach, which is achieved through the incorporation of a periodic upper cladding that alternates between magneto-optic and nonmagneto-optic media, overcomes many of the problems traditionally encountered when transferring the principles of free-space Faraday-effect optical isolators into waveguide geometries. An enhancement of polarization rotation many times greater than that achievable in the absence of phase matching is observed. Additionally, the technique facilitates an ability to select and/or manipulate individual modes from multimode waveguides.
88(2006); http://dx.doi.org/10.1063/1.2172649View Description Hide Description
We experimentally demonstrate the ability of a self-guided laser beam to induce waveguides with sharp bends. The beam is a two-dimensional photorefractive screening-photovoltaic bright spatial soliton generated inside a biased lithium-niobate crystal shaped as a prism. The soliton robustness against total internal reflections is shown to leave place to a low-loss unimodal waveguide undergoing multiple zero-radius 90° turns.
88(2006); http://dx.doi.org/10.1063/1.2172144View Description Hide Description
We investigate a peculiar optical instability (blinking) phenomena associated with spatial inhomogeneity in single quantum well systems. We studied the time dependence of this dynamic phenomenon and tested a “quantum jump” single exponential model on the system. A comparative analysis of the behavior of different samples suggests that indium-rich localized centers participate in the mechanism of blinking and that the instability behavior differs with the excitation wavelength. Our study indicates that the trapping and de-trapping process between the localized-luminescent centers and surrounding less luminous regions plays important roles in the carrier recombination mechanism.
Monte Carlo simulation of hot phonon effects in resonant-phonon-assisted terahertz quantum-cascade lasers88(2006); http://dx.doi.org/10.1063/1.2172225View Description Hide Description
We study the influence of nonequilibrium optical phonons on the electron transport in resonant-phonon-assisted terahertz (THz) quantum-cascade lasers (QCLs). The hot phonon effect is included in the Monte Carlo simulation by introducing a time constant accounting for the decay of polar optical phonons into other phonon modes. We find that nonequilibrium polar optical phonons may modify the electron-phonon interaction, affect the electron distribution in different subbands, and consequently change the device current. We conclude that the hot phonon effect should be taken into account in the study of the transport properties of resonant-phonon-assisted THz QCLs.
Use of a long-duration ns pulse for efficient emission of spectral lines from the laser ablation plume in water88(2006); http://dx.doi.org/10.1063/1.2172235View Description Hide Description
The effect of pulse duration upon the line profile of Cu I emission observed by laser ablation of a copper metal plate immersed in water has been examined. By irradiating a pulse with the duration longer than 40 ns the spectral profile with clear narrow emission lines of Cu atoms is obtained, while the emission spectra always suffer from broadening and self-absorption by the irradiation of the 20 ns pulse for the ablation. The results show that the use of a long-duration pulse enables in situ elemental analysis of the solid surface in contact with a bulk liquid.