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The problem of the propagation of ultrashort pulses, including both two-dimensional and three-dimensional pulses, in a Fermi liquid is considered with the help of representations of the duality of gauge gravitation. The electromagnetic field is considered classically on the basis of the Maxwell equations. The effective equation so obtained is analyzed numerically and the dynamics of the state of the electromagnetic field are elucidated in the planar case, and also when it is localized in two/three spatial dimensions. [ABSTRACT FROM AUTHOR]

Coherent mode-locking (CML) uses self-induced transparency (SIT) soliton formation to achieve, in contrast to conventional schemes based on absorption saturation, the pulse durations below the limit allowed by the gain line width. Despite the great promise it is difficult to realize it experimentally because a complicated setup is required. In all previous theoretical considerations CML is believed to be non-self-starting. In this paper we show that if the cavity length is selected properly, a very stable (CML) regime can be realized in an elementary two-section ring-cavity geometry, and this regime is self-developing from the non-lasing state. The stability of the pulsed regime is the result of a dynamical stabilization mechanism arising due to finite-cavity-size effects. [ABSTRACT FROM AUTHOR]

A time-domain nonlinear model representing the propagation of ultra-short optical pulses in dispersive materials containing second order nonlinearity is presented. The model accounts for material dispersion through Lorentz model in addition to the spatiotemporal coupling between the pulsed fundamental and second harmonic beams. Numerical results for the generated second harmonic pulse clearly demonstrate the pulse break-up phenomenon. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1097–1100, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24213 [ABSTRACT FROM AUTHOR]

The accelerating integration of microwave and optical components in modern optoelectronic systems stimulates comprehensive investigations of device operation and efficiency. This paper studies the optoelectronic conversion capabilities of sub-micron GaAs active devices in response to ultra-short illumination pulses. The physical phenomena involved in the photo-electronic effects are appropriately accounted for using a physical device model based on the solution of the Boltzmann’s transport equations. The study targets important optical performance indicators including terminal photocurrent peak value and switching time. A figure-of-merit is defined to quantify the overall response. Results show that operating and geometrical conditions can play important roles in the device design, operation and optimization process. [ABSTRACT FROM AUTHOR]

We have analyzed the four-wave mixing (FWM) characteristics in semiconductor optical amplifiers (SOAs) with optimum time-delays between pump and probe pulses by the finite-difference beam propagation method. This study is very important to achieve the high FWM conversion efficiency and to clarify the timing jitter. From the simulations, we have clarified that the FWM conversion efficiency increases with optimum time-delays between pump and probe pulses in SOA for short optical pulses. In the experiment, we have found the similar tendency. Therefore, we have obtained an excellent agreement between the simulation and experimental results of high FWM conversion efficiency in SOAs with optimum time-delays between pulses. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1182–1185, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22389 [ABSTRACT FROM AUTHOR]

The authors compare analytical and numerical estimates, showing that the nonlinear phase noise of short optical pulses associated with the coupling between amplified spontaneous emission noise and fiber nonlinearity may be controlled by adjusting the duty cycle of the return-to-zero (RZ) signal modulation format. The impact of this effect in the optimization of the performance of 10-Gb/s dispersion-managed wavelength division multiplexed (WDM) systems using RZ-differential phase-shift keying (DPSK) modulation is discussed. By extensive numerical simulations, it is shown that the transmission quality of ultradense WDM systems using the RZ-DPSK modulation format may be significantly enhanced by optimizing the duty cycle of the RZ pulses [ABSTRACT FROM PUBLISHER]

In this paper, we investigate the feasible schemes to generate periodic optical pulses of width between several picoseconds (ps) and tens ps. Gain-switched semiconductor laser diodes are shown to be more suitable for avionics applications than mode-locked laser diodes. In the experiment, we use a low-cost Fabry-Perot laser diode to generate short optical pulse streams. A simple optical injection-locking scheme is then used to reduce the timing jitter and frequency chirp in such laser diodes, which in turn can improve the transmission performance of the generated optical pulses. It is expected that the use of gain-switched semiconductor lasers can meet the requirement of high-speed airborne communication networks or ground supporting systems at airports. Moreover, we discuss the possibility of using the pulsed semiconductor lasers to generate millimetre-wave (mm-wave) signals for future applications to airborne high-resolution, mm-wave radars. [ABSTRACT FROM PUBLISHER]

The Darmstadt IR FEL is designed to generate wavelengths between 3 and 10 μm and driven by the superconducting electron linear accelerator. The pulsed electron beam has a peak current of 2.7 A leading to a small signal gain of 5%. Currently, investigations of the energy transfer process inside the undulator are performed using the 1D time-dependent simulation code FAST1D-OSC. We present simulation results for the power vs. different desynchronization and tapering parameters as well as a comparison with experimental data from the S-DALINAC IR-FEL. Furthermore, a compact autocorrelation system assuring a background-free measurement of the optical pulse length is described. In a first test experiment at FELIX, the autocorrelator has been tested at wavelengths 5.7⩽λ⩽9.0 μm. The frequency doubling in a 2 mm-long ZnGeP2-crystal resulted in a time resolution of 300 fs and a conversion efficiency of 5%. [Copyright &y& Elsevier]

Many properties of an optically interconnected system can be improved through the use of a modelocked laser. The short pulse duration, high peak power, wide spectral bandwidth, and low timing jitter of such a laser lead to these benefits. Timing advantages include simplified synchronization across large chip areas, receiver latency reduction, and data resynchronization. Lower power dissipation may be achieved through improved receiver sensitivity. Additional applications of short optical pulses include time-division multiplexing, single-source wavelength-division multiplexing, and precise time-domain testing of circuits. Several of these concepts were investigated using a high-speed chip-to-chip optical interconnect demonstration link. The link employs a modelocked laser and surface-normal optoelectronic modulators that were flip-chip bonded to silicon CMOS circuits. This paper outlines experiments that were performed on or simulated for the link, and discusses the important benefits of ultrashort optical pulses for optical interconnection. [ABSTRACT FROM PUBLISHER]

We present a new method of latency reduction in optical interconnects: using very low duty cycle return-to-zero encoding (i.e., subpicosecond pulses). An analytical comparison of three different receiver architectures, including transimpedance, integrating, and totem-pole diode pair, is presented. For all three receivers, we demonstrate that using short pulses instead of nonreturn-to-zero (NRZ) shortens the circuit delay. We also experimentally demonstrate a ∼65% reduction in latency of a transimpedance receiver by using short optical pulses. Finally, we show that the latency of optical interconnects can be comparable to or even less than electrical interconnects for global on-chip communication. [ABSTRACT FROM PUBLISHER]

We present ultrafast slotted optical time-division multiplexed networks as a viable means of implementing a highly capable next-generation all-optical packet-switched network. Such a network is capable of providing simple network management, the ability to support variable quality-of-service, self-routing of packets, scalability in the number of users, and the use of digital regeneration, buffering, and encryption. We review all-optical switch and Boolean logic gate implementations using an ultrafast nonlinear interferometers (UNIs) that are capable of stable, pattern-independent operation at speeds in excess of 100 Gb/s. We expand the capability provided by the UNI beyond switching and logic demonstrations to include system-level functions such as packet synchronization, address comparison, and rate conversion. We use these advanced all-optical signal processing capabilities to demonstrate a slotted OTDM multiaccess network testbed operating at 112.5 Gb/s line rates with inherent scalability in the number of users and system line rates. We also report on long-haul propagation of short optical pulses in fiber and all-optical 3R regeneration as a viable cost-effective means of extending the long-haul distance of our OTDM network to distances much greater than 100 km. [ABSTRACT FROM PUBLISHER]

A novel phase-locked coherent demodulator, based on a sampling phase-locked loop, is presented and investigated theoretically. The demodulator is capable of operating at high frequencies, by using optical sampling to downconvert the high-frequency input radio-frequency signal to the frequency range of the baseband loop. We develop a detailed theoretical model of the (sampling) phase-locked coherent demodulator and perform detailed numerical simulations. The simulation results show that the operation of the sampling demodulator resembles the operation of the baseband demodulator for very short optical pulses (<2 ps). Furthermore, we investigate how the signal-to-noise ratio of the demodulator is affected by timing and amplitude jitter of the pulsed optical source [ABSTRACT FROM PUBLISHER]

The gain dynamics of a symmetrical multiple-quantum-well semiconductor optical amplifier (SOA) with wide gain-bandwidth are measured by a two-color heterodyne pump-probe technique. Short optical pulses are generated by using optical filters to select spectral components from compressed supercontinuum optical pulses. To maintain durations of the order of 100 fs over the entire gain bandwidth of the SOA, the pulse broadening caused by frequency shifters is compensated by fibers with lengths optimized for respective wavelengths. We measure the wavelength dependences of the recovery time of carrier heating (CH) and the gain reduction due to CH. The gain reduction caused by spectral hole burning is observed. [ABSTRACT FROM PUBLISHER]

A new technique for generating millimeter-wave (mm-wave) signals from a semiconductor laser without an intracavity saturable absorber, is presented, The method multiplies the signal frequency by using optical injection of short optical pulses at a subharmonic of the cavity round-trip frequency to drive the laser oscillating at its resonant frequency. A 34.64 GHz signal is generated using a multisection semiconductor laser operated under continuous wave conditions, by injecting optical pulses at a repetition rate equal to the fourth subharmonic (8.66 GHz). The generated millimeter-wave signal exhibits a large subharmonic suppression ratio (>17 dB), large frequency detuning range (>300 MHz), low levels of phase-noise (-77.5 dBc/Hz), and large locking range (>400 MHz) [ABSTRACT FROM PUBLISHER]

We demonstrate data resynchronization in a multichannel chip-to-chip free-space optical interconnect for complementary metal-oxide-semiconductor (CMOS) using short optical pulses. Operation of the system is shown at speeds of 82 Mb/s per channel, limited by the repetition rate of the mode-locked laser used. We show explicitly the ability to resynchronize parallel channels and eliminate timing fluctuations; we remove up to ±3/8 of a bit period of interchannel skew and single channel jitter from the transmitted signals in a complete interconnect link that includes optical transmission, reception, and retransmission of digital data [ABSTRACT FROM PUBLISHER]

We analyze intrachannel nonlinear effects in high-bit-rate transmission systems based on short optical pulses that are dispersion compensated. We perform an analytical study of a generic example with two pulses, in which case the nonlinearity shifts the pulses in time and results in the generation of leading and trailing pulse echoes. We show that in all the relevant range of parameters, the magnitude of the nonlinear impairments reduces monotonically with the reduction of pulse width and with the increase of the dispersion coefficient [ABSTRACT FROM PUBLISHER]

With the consideration of fast gain saturation, an approximate analytical solution of nondegenerate four-wave mixing between short optical pulses in a semiconductor optical amplifier is presented. It is simple and agrees well with the rigorous solution. In addition, conditions for the optimum pump input energy and the time delay between the pulses are also investigated [ABSTRACT FROM PUBLISHER]