23,632 research outputs found
Large-signal dynamics of an ultrafast semiconductor laser at digital modulation rates approaching 10 Gbit/s
High-fidelity pseudorandom digital modulation at 8.2 Gbit/s of an ultrahigh speed semiconductor laser is demonstrated. Studies using simple but representative pulse patterns at 10 Gbit/s give insights into the maximum digital modulation rate attainable from a given laser, as well as relations between large-signal digital performance and small-signal analog response
Intermodulation distortion in a directly modulated semiconductor injection laser
A most important quantity in high-frequency analog transmission is the intermodulation distortion product. Experimental studies of the third order intermodulation distortion products in the modulation response of high-speed semiconductor lasers give very low values (< ā60 dB) at low frequencies, an increase at a rate of 40 dB/dec as the modulation frequency is increased, and a leveling off at one-half of the relaxation oscillation resonance frequency. These experimental results can be well explained by a theory based on a perturbative analysis of laser dynamics
Microwave Optical Link In The Frequency Range Of 10-18 Gigahertz By Direct Modulation Of Injection Laser Diode
It is demonstrated that an ultra-high speed window buried heterostructure GaAlAs laser fabricated on semi-insulating substrate can be used as narrow band signal transmitters in the Ku-band frequency range (12-20GHz). The modulation efficiency can be increased over a limited bandwidth by a weak optical feedback. A stronger optical feedback enables one to actively mode-lock the laser diode at a very high repetition rate up to 17.5GHz, producing pulses of = 12ps long
Analog, Digital And Short Pulse Modulation Of Ultrafast Gallium Aluminum Arsenide Semiconductor Lasers
Semiconductor lasers are potentially devices of great importance for optical transmission as well as short pulse generation for various sampling, characteration and dispersion measurements. Since semiconductor lasers are currently driven devices, it is relatively easy to modulate the optical output and to generate short pulses, on the order of 10 ps long, by directly modulating the injection current into the laser. This paper will present some recent developments in injection lasers which are capable of being analog or digitally modulated at rates up to 10 GHz, as well as generating short optical pulses at repetition rates from several hundred megahertz to tens of gigahertz
Self-sustained picosecond pulse generation in a GaAlAs laser at an electrically tunable repetition rate by optoelectronic feedback
We demonstrate that applying optoelectronic feedback to a high-speed, self-pulsing semiconductor laser is an effective and practical means of generating picosecond optical pulses (~10ā20 ps) at a very high repetition rate, between 1 to 5 GHz, which can be electrically tuned. The optical pulses are very stable both on a short term basis with a frequency stability of one part in 10^5, and on the long term basis as a result of the absence of critical optical alignment. This laser system is potentially very useful in high-speed electro-optic signal processing, optical multiplexing, or laser ranging
A theory of longitudinal modes in semiconductor lasers
A theory of longitudinal mode lasing spectrum of semiconductor lasers is developed which takes into account the nonuniform carrier and photon distributions and local gain spectrum shifts inside lasers with low end mirror reflectivities. The theory gives results consistent with observed longitudinal mode behavior in lasers with reduced facet reflectivity
Fluid description of kinetic modes
The classical kinetic modes, such as the Bernstein mode, the loss cone modes, and the Harris dispersion relation are reconstructed from a fluidālike analysis. The analysis begins with a delta function in the equilibrium distribution. By simply calculating the displacement of a single electron exposed to a small signal electric field, the charge perturbation density, and the dispersion relation, immediately follow. The effect of a velocity distribution enters only through a trivial integration of the dispersion relation thus obtained for the monoenergetic plasma. The entire analysis is done in the configuration space. Thus, without explicitly performing the customary integration over the unperturbed orbits in phase space, finite Larmor radius effects to all order have been retained. Possible extensions to nonuniform plasma and to nonuniform magnetic fields are indicated.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70099/2/PHPAEN-1-9-2816-1.pd
Importance of mutual benefits in online knowledge sharing communities
The sustainability of knowledge sharing e-communities is a major issue at present. A hypothesis was
proposed at the outset in the paper that the provision of mutual benefits among participants will lead to positive
participation. Drawing from the economic and social theories, a framework for analysis was developed and tested in
an empirical study. The preliminary results demonstrated a direct relationship between mutual benefits and the level
of participation, and hence supported the hypothesis
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