The Effects of Amplitude Modulated Signal on the Signal-to-Noise Ratio of Saturation Laser Model with Correlated Real and Imaginary Parts of Quantum Noise
Under the influence of amplitude modulated signal,we use the linear approximation method to study the output power spectrum and signal-to-noise ratio of the saturation laser model driven by the correlated real and imaginary parts of quantum noise and the pump noise.According to the computer data and mapping,we specifically discuss the phenomenon λq of stochastic resonance of the system which happened by the changes of the signal frequency,the correlation λq of real and imaginary parts of quantum noise and the intensities of pump noise.The results show that the system has resonance phenomenon when λq=0.Although the modulated signal has a significant impact on the system,due to the zero correlation between quantum noise and pump noise,there is no phenomenon of stochastic resonance happening when other parameters change.
Under the influence of amplitude modulated signal,we use the linear approximation method to study the output power spectrum and signal-to-noise ratio of the saturation laser model driven by the correlated real and imaginary parts of quantum noise and the pump noise.According to the computer data and mapping,we specifically discuss the phenomenon λq of stochastic resonance of the system which happened by the changes of the signal frequency,the correlation λq of real and imaginary parts of quantum noise and the intensities of pump noise.The results show that the system has resonance phenomenon when λq=0.Although the modulated signal has a significant impact on the system,due to the zero correlation between quantum noise and pump noise,there is no phenomenon of stochastic resonance happening when other parameters change.
On the basis of calculating the steady-state mean normalized intensity fluctuation of a signal-mode laser system driven by both colored pump noise with signal modulation and the quantum noise with cross-correlation between its real and imaginary parts, we analyze the influence of modulation signal, noise, and its correlation form on the statistical fluctuation of the laser system. We have found that when the amplitude of modulation signal weakens and its frequency quickens, the statistical fluctuation will reduce rapidly. The statistical fluctuation of the laser system can be restrained by reducing the intensity of pump noise and quantum noise. Moreover, with prolonging of colored cross-correlation time, the statistical fluctuation of laser system experiences a repeated changing process, that is, from decreasing to augmenting, then to decreasing, and finally to augmenting again. With the decreasing of the value of cross-correlation coefficient, the statistical fluctuation will decrease too. When the cross-correlation form between the real part and imaginary part of quantum noise is zero correlation, the statistical fluctuation of laser system has a minimum. Compared with the influence of intensity of pump noise, the influence of intensity of quantum noise on the statistical fluctuation is smaller.
The time evolution of intensity correlation functionin a single-mode laser driven by the coloured pump noise with signal modulation and the quantum noise with cross-correlation between the real and imaginary parts is studied by using the linear approximation method.In the case of the pump noise self-correlation time 1 << τ , it can be found that: (i)when modulation signal frequency Ω increases, the time evolution ofexperiences a changing process, that is, from the monotonous descending to the descending after the appearance of an initial flat, and finally to the periodically surging with descending envelope; (ii)When the net gain 0 a increases, it experiences a repeatedly changing process, that is, from the monotonous descending to monotonous rise, and to the appearance of a maximum, finally to monotonous descending again.However, in the case of 1 >> τ , the time evolution ofonly exhibits periodically surging with descending envelope.
Using the linear approximation method,we have studied the time vevolution of intensity correlation function C(t) in a single-mode laser driven by the colored pump noise with signal modulation and the quantum noise with cross-correlation between the real and imaginary parts.When pump noise self-correlation time τ changes,we have found that,the time evolution of the C(t) will exhibit various change forms:that is,monotonous descending;monotonous rise;the appearance of a maximum;periodically surging with descending envelope.Furthermore,when the τ is a certain value,the value of the C(t) will lessen with the between the real and imaginary parts of quantum noise correlative increases,but when quantum noise intensity Q increases,the value will increase,and when pump noise intensity P increases,the descending of the C(t) with time has been delayed.
We study the effects of correlations between real and imaginary parts of pump noise on the correlation function and relaxation time of laser intensity in a saturation laser model driven by quadratic pump noise and quantum noise. Using the phase–locking method and the projection–operator method, we derived the stationary probability density, the relaxation time Tc and the intensity correlation function C(s) of the laser intensity, and then performing numerical computations, we find the following: (i) Tc monotonously increases as the correlation strength between the real and imaginary parts of quadratic pump noise λp increases and (ii) C(s) decreases exponentially as decay time s increases and C(s) increases as λp increases. The correlations between the real and imaginary parts of the quadratic pump noise slow down the rate of fluctuation decay of the laser intensity.
Using the linear approximation method, we calculated the steady-state mean normalized intensity fluctuation for a loss-noise model of a single-mode laser driven by a pump noise and a quantum noise, whose real part and imaginary part are cross-correlated. We analyzed the valid range for the linear approximation method by studying the influences on the steady-state mean normalized intensity fluctuation by the cross-correlation coefficient, the intensities of the quantum and pump noise, the net gain, and the amplitude and frequency of the input signal, and we found that the valid range becomes wider when the cross-correlation between the real and imaginary part of quantum noise is weaker, the noise intensities of quantum and pump are weaker, the laser system is far from the threshold and the signal has smaller amplitude and higher frequency.
This paper studies the effects of cross-correlations between the real and imaginary parts of quantum noise on the laser intensity in a saturation laser model. It derives the analytic expressions of the intensity correlation function C(τ) and the associated relaxation time T (C) in the case of a stable locked phase resulting from the cross-correlation λ q between the real and imaginary parts of quantum noise. Based on numerical computations it finds that the presence of cross correlations between the real and imaginary parts of quantum noise slow down the decay of intensity fluctuation, i.e., it causes the increase of intensity fluctuation.