G. Xia

Computer Model of Time Response of Fabry-Perot Etalon Filters to Short Optical Pulses

The time response of a Fabry-Perot etalon filter to the short optical pulses has been studied. The transmitting pulse from the etalon filter has been analytically expressed in a series of sub-pulses. Under certain circumstances, the sub-pulses merge together resulting in a broadened output pulse, and the temporal difference between the peaks of the output and input pulses may not equal to the one-way traverse time of light inside the etalon. Studies have also been carried out for the chirped pulse and dispersion etalon, which have led to the expression of the transmitting sub-pulses.

Time delay of Fabry-Perot filters to short optical pulses

In this paper, the time delay, defined as the temporal difference between the peaks of the output and input pulses, of Fabry-Perot filters to short input optical pulses has been investigated theoretically in detail. The results reveal that due to the interference between the multireflected beams inside the etalon, the input pulse widths have intense influence on the time delay. Moreover, the time delay depends on the chirp of input pulse and the difference between the central frequency of the input pulse and the resonance frequency of the fllter.

Influence of the reflectivity distribution of fiber grating on the output characteristics of fiber grating external cavity diode lasers

The dot function approximation of reflectivity distribution of a fiber grating (i. e., supposed that the fiber grating supplies feedback only in bragg reflection wavelength and the reflectivity at other wavelengths is regarded as zero), which is usually used to analyze the output characteristics of a fiber grating external cavity diode laser (FGECDL), has been proved to be unreasonable from physical facts. As a result, a theoretical model including the reflectivity distribution of fiber grating applicable to FGECDLs is presented. Taking the mode suppression ratio (MSR) of FGECDLs as a example for comparison, the results show that MSR obtained by the model is obviously lower than that obtained by the dot function approximation.

Specify various derivatives of output powers with respect to bias current of semiconductor lasers

Starting from the multimode rate equations of the semiconductor lasers, taking into consideration the contribution of the spontaneous emission, an implicit analytical solution to the rate equations has been derived. Using the analytical solution, derivatives, up to the third order, of the laser output power with respect to the bias current have been deduced analytically. It is belived that these expressions are useful in specifying the linearity of the diode lasers when used in lightwave CATV transmission systems.

Variation of Carrier Lifetime during the Dynamic Response of Semiconductor Optical Amplifier to Ultra-short Optical Pulse

The constant carrier lifetime assumption in the time dependent rate equations, which is used to study the dynamic response of semiconductor optical amplifier to ultra-short optical pulse, has been proven to be improper, and a treatment method about the carrier lifetime is presented. The results show that carrier lifetime will change during the dynamic response of semiconductor optical amplifier to ultra-short optical pulse, and the variation of the carrier lifetime relates to the shape of the input optical pulse.

Selection of the fiber grating length in a fiber grating external cavity semiconductor laser

After taking into account the fact that the peak reflectivity of the fiber grating in a fiber grating external cavity semiconductor laser (FGECSL) is required to be lower than unity, the influence of the fiber grating length on the peak reflectivity has been focused on in this paper. Adopting the coupled mode theory, the dependence of the peak reflectivity on the fiber grating length has been studied numerically for various types of fiber gratings. The obtained results have important values on how to select the fiber grating length in a FGECSL.

Selection of time window width and its effects on the numerical simulations of optical pulse propagation in fibers

In order to ensure the accuracy of the split-step Fourier method used to study numerically the optical pulse evaluation in fibers, the selective problem of time window width is focused on in this paper. After giving the selective method of the time window width and the minimum time window width required for corrected calculations of optical pulse propagation in fibers, the shapes of various incident pulses after passing through different fiber lengths have been simulated by selecting different time window widths. The viewpoint that a super-Gaussian pulse distorts in shape on propagation, which was reported by other researchers, has proved to be mistaken.

Studying 980 nm pumped erbium-doped fiber lasers with rate equations

Rate equations have been used to investigate the erbium-doped fiber lasers pumped at 980 nm, and the implicit analytical expressions of some importment parameters have been derived. With these expressions, the output characteristics of erbium-doped fiber lasers can be specified.

Studying two-contact bistable diode lasers with wavelength dependent rate equations

Within the frame of the mean-field single-mode approximation, taking into account the fact that the peak wavelengths of the gain profiles of the pump and absorption regions of two-contact absorption bistable laser diodes (TABLs) are different due to the difference of the carrier densities of the two regions, Lorentzian functions describing the gain profiles of the two regions have been restored in the rate equations applicable to TABLs. Taking into consideration that the output wavelength reflect the peak wavelength of the overall gain, an extra equation has been added to the rate equations. As a result, various characteristics of TABLs including the output wavelength have been investigated.

Influence of facet reflectivities on the output characteristics of laser diodes

Starting from the analytical solutions to the multimode rate equations, the influence of facet reflectivities on the output characteristics of laser diodes have been studied. For laser diodes biased above the threshold, the output spectra and the mode suppression ratios under different facet reflectivities have been simulated numerically. For laser diodes biased below threshold, with the emphasis on the superluminescent diodes (SLDs), the dependences of such important operation parameters as output spectral width (FWHM) and output power on the facet reflectivities have been investigated.