In this study, gain-switching characteristics of InAs-InP(113)B quantum dot laser based on multi-mode rate equations are investigated for the first time by applying an external Gaussian pulse beam into the excited state to obtain short pulses. The rate equations including nonlinear gain are solved for direct relaxation model by 4th order Runga-Kutta method. The obtained results demonstrated that width of gain-switching output pulses are long due to dominant effect of ground state photons having long width without optical beam. Furthermore, pulse width increases with the increasing the peak injection current was observed. However, it was found that since excited state photons have narrow width compared to that of ground state, width of output pulses decreases giving a pulse width of around 25 ps owing to dominant effect of excited state with the applying optic beam into excited state. Our results also indicated that differential-gain of excited and groundstates decreases with the increasing of the homogeneous and inhomogeneous broadenings.
In this paper, the investigation of gain-switching characteristics of an InAs/InP Quantum dot laser is performed for direct and cascade relaxation models, theoretically. The model is based on single mode rate equations, which are solved by the Runge-Kutta method. Moreover, the effect of external optical beam irradiation to the excited state are investigated for both relaxation models. Our results showed that for the first time, under the optical Gaussian pulse beam it is possible to generate short pulses with a width of around 30 ps with a high peak power for the direct and cascade relaxation models. It was also found that in the absence of external optical beam irradiation, width and peak power of output pulses for cascade relaxation model are slightly smaller than that of direct relaxation model whereas in the presence of optical beam, they are approximately the same for both models. Obtained results have great importance for the fields where short optical pulse is an important demand such as long-distance optical transmission and medical biotechnology.
Mode-locking characteristic of hybrid soliton pulse source (HSPS) utilizing linearly chirped raised-cosine flat top
apodized fiber Bragg grating (FBG) is investigated by using coupled-mode equations. It is shown that proper mode-locking
range where transform-limited pulses are generated is increased to 1.3 GHz by using linearly chirped raised-cosine
flat top apodized FBG.
A theoretical model for the mode-locked hybrid soliton pulse source (HSPS) is developed by using a time domain solution of coupled-mode equations and rate equations. Numerical simulations show that grating must be both linearly chirped and apodized to be used in HSPS systems with a wide mode-locking frequency range (2.1 to 3 GHz) and transform-limited output pulses.
Mode-locking characteristic of hybrid soliton pulse source (HSPS) utilizing linearly chirped raised-cosine flat top
apodized fiber Bragg grating (FBG) is investigated by using coupled-mode equations. It is found that the fundamental
repetition frequency range of HSPS is significantly extended by using linearly chirped raised-cosine flat top apodized
FBG instead of linearly chirped Gaussian apodized FBG. The range of repetition frequencies over which proper modelocking
is obtained is 2-3.3 GHz with linearly chirped raised-cosine flat top apodized grating whereas this range is 2.1-
2.95 GHz with linearly chirped Gaussian apodized grating.
Mode-locking characteristic of hybrid soliton pulse source (HSPS) utilizing linearly chirped raised-cosine flat top
apodized fiber Bragg grating (FBG) is investigated by using coupled-mode equations. It is found that the fundamental
repetition frequency range of HSPS is significantly extended by using linearly chirped raised-cosine flat top apodized
FBG instead of linearly chirped Gaussian apodized FBG. The range of repetition frequencies over which proper modelocking
is obtained is 2-3.3 GHz with linearly chirped raised-cosine flat top apodized grating whereas this range is 2.1-
2.95 GHz with linearly chirped Gaussian apodized grating.
The intensity modulation (IM) of a hybrid soliton pulse source (HSPS) utilizing linearly chirped Gaussian apodized fiber Bragg grating is described using electric field approach. The HSPS is modeled by a time-domain solution of the coupled-mode equations. It is shown that resonance peak spectral splitting (RPSS) in the IM spectra does not strongly depends on antireflection coated reflectivity, and gain compression factor. It is also found that RPSS disappears by choosing suitable liner chirp rate in Gaussian apodized FBG.
The small signal intensity modulation (IM) of a hybrid soliton pulse source (HSPS) utilizing Gaussian apodized fiber Bragg grating is described using electric field approach. The HSPS is modeled by a time-domain solution of the coupled-mode equations. It is shown that type of external cavity is important effect on resonance peak spectral splitting (RPSS) in IM response as well as effect of laser and fiber Bragg grating (FBG) parameters. The RPSS can be suppressed by using linearly chirped Gaussian apodized FBG as an external cavity insted of Gaussian apodized FBG.
The relative intensity noise (RIN) of hybrid soliton pulse source (HSPS) utilizing different fiber Bragg gratings (FBGs) are described. The HSPS is modeled by a time-domain solution of the coupled-mode equations including spontaneous emission noise, and RIN is calculated using numerical solutions of these equations. RIN reduction up to 4 dB has been demonstrated for the mode-locked HSPS using a suitable window function such as Gaussian apodized and introducing appropriate linear chirp value into gratings.
Intensity noise of mode-locked hybrid soliton pulse source (HSPS) with linearly chirped uniform fiber Bragg grating (FBG) is reported using by coupled-mode equations. Mode-locking is difficult to achieve for some value of rf and dc bias currents because of increasing noise. Hence, transform-limited pulses are not generated over a wide tuning range although these pulses are obtained over a wide tuning range without any noise.
Mode-locked and relative intensity noise (RIN) of hybrid soliton pulse source (HSPS) utilizing Gaussian apodized fiber Bragg grating (with zero dc-index change) is described. The HSPS is modeled by a time-domain solution of the coupled-mode equations including spontaneous emission noise. RIN is calculated using numerical solutions of these equations. It is found that for these gratings soliton type pulse are not generated at the mode-locking frequency. However, these pulses can be generated only at limited tuning range with and without noise. RIN peak does not locate at the fundamental frequency that shows optical resonance due to cavity roundtrip time. Also, obtained soliton pulses are not directly related to magnitude of noise.
The effect of carrier noise on hybrid soliton pulse source (HSPS) is described when it is mode-locked. The model is based on a time domain solution of coupled-mode equations. Relative intensity noise (RIN) is calculated using numerical solution of these equations. It was showed that carrier noise reduces the mode-locking range and near transform limited pulses are not generated because of this noise.
The noise and mode-locking phenomena of a hybrid soliton pulse source (HSPS) utilizing Gaussian apodized fiber Bragg grating is described. The HSPS is modeled by a time-domain solution of the coupled-mode equations including spontaneous emission noise. Relative intensity noise (RIN) is calculated using numerical solutions of these equations. It is found that with and without noise near transform limited pulse are only generated over a limited frequency range even if system is properly mode-locked over a wide frequency range around the fundamental mode-locking frequency. If transform limited pulses are not obtained at the fundamental frequency, there is no noise peak in the RIN spectrum at this frequency.
The noise and mode-locking phenomena of a hybrid soliton pulse source (HSPS) utilizing Gaussian apodized filter Bragg grating is described. The HSPS is modeled by a time-domain solution of the coupled-mode equations including spontaneous emission noise, and relative intensity noise (RIN) is calculated using numerical solutions of these equations. It is found that transform limited pulses are not generated with Gaussian apodized grating even if system is properly mode-locked at the fundamental frequency. If transform limited pulses are not obtained, a noise peak in the RIN spectrum does not occur at the fundamental frequency.
The noise and mode-locking phenomena of a hybrid soliton pulse source (HSPS) utilizing Gaussian apodized fiber Bragg grating is described. The HSPS is modeled by a time-domain solution of the coupled-mode equations including spontaneous emission noise. Relative intensity noise (RIN) is calculated using numerical solutions of these equations. It is found that near transform limited pulses are only generated over a limited frequency range even if system is properly mode-locked over a wide frequency range around the fundamental mode-locking frequency. If transform limited pulses are not obtained at the fundamental frequency, output pulse is not more affected from the noise at this frequency. It is also found that noise reduction is possible by using these gratings.
Mode-locked and noise analysis of hybrid soliton pulse source (HSPS) utilizing uniform fiber Bragg grating is described. The HSPS model is based on a time domain solution of coupled-mode equations including spontaneous emission noise. Relative intensity noise (RIN) is calculated using numerical solutions of these equations. It is found that near transform limited pulses are generated only a few frequencies even if system is properly mode-locked over a wide frequency range. Output pulse is not more affected at the fundamental mode-locking frequency because RIN has not a noise peak at this frequency. It is also found that RIN reduction is possible for mode-locked HSPS by selecting a suitable grating such as Gaussian apodized or linearly chirped.
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