Calculation of spectral linewidth reduction of external-cavity strong-feedback semiconductor lasers (original) (raw)

New dynamic multimode model for external cavity semiconductor lasers

IEE Proceedings J Optoelectronics

A new, dynamic, time-domain, numerical model for external cavity lasers, based on the transmission-line laser model (TLLM), is introduced. This is able to show the evolution of spectra from large-signal modulated devices, even when the modulation pulsewidth is less than the external cavity round-trip delay. The model is demonstrated using short and long dispersionless cavities. Results in the time and spectral domains are in agreement with those of previous theoretical and experimental work.

Observations on the dynamics of external cavity semiconductor lasers

Optik, 2012

Dynamics of external cavity semiconductor lasers is known to be a complex and uncontrollable phenomenon. Due to the lack of experimental studies on the nature of the external cavity semiconductor lasers, there is a need to theoretically clarify laser dynamics. The stability of laser dynamics in the present paper, is analyzed through plotting the Lyapunov exponent spectra, bifurcation diagrams, phase portrait and electric field intensity time series. The analysis is preformed with respect to applied feedback phase C p , feedback strength Á and the pump current of the laser. The main argument of the paper is to show that the laser dynamics can not be accounted for through simply a bifurcation diagram and single-control parameter. The comparison of the obtained results provides a very detailed picture of the qualitative changes in laser dynamics.

The complex way to laser diode spectra: example of an external cavity laser strong optical feedback

IEEE Journal of Quantum Electronics, 2005

An external cavity laser with strong grating-filtered feedback to an antireflection-coated facet is studied with a time-domain integral equation for the electric field, which reproduces the modes of the oscillation condition as steady-state solutions. For each mode, the stability and spectral behavior is determined by analysis of the location of side modes in the complex frequency plane. The complex frequency diagrams are shown to be a useful tool to determine the self-stabilization effect of mode coupling and its dependence on laser parameters and external cavity design. The model is used to simulate the large signal time evolution after start from unstable modes.

Small-signal IM response of grating-terminated external cavity semiconductor lasers

IEEE Journal of Selected Topics in Quantum Electronics, 1995

Abstruct-The small-signal intensity modulation response and the CW noise spectrum of a semiconductor laser coupled to an external cavity are known to be enhanced in narrow peaks centerd around the harmonics of the cavity resonance frequency. We have previously shown that each resonance peak of the response exhibits an amplitude discontinuity near the harmonics of cavity resonance frequency. In this paper, we show that each peak of the noise spectrum is bifurcated into a pair of closely spaced peaks of different amplitudes and bandwidths. A comprehensive analytical model is developed to investigate the discontinuity of response peaks and to study the effect of various parameters on their bandwidth and modulation efficiency. It is shown that strong optical feedback, strong gain compression and dc bias above threshold reduce the modulation efficiency but increase the modulation bandwidth.

Center frequency shift and reduction of feedback in directly modulated external cavity lasers

IEEE Photonics Technology Letters, 2000

We show experimentally and theoretically that a center frequency shift occurs when an external cavity laser is directly modulated. The shift may be observed even when the frequency deviation is small compared to the roundtrip frequency of the external cavity and can qualitatively be explained by a reduction in the effective feedback level due to modulation. The frequency shift has been measured as a function of modulation frequency and current, and frequency shifts up to 350 MHz were observed.

Characters of the semiconductor laser with strong feedback

Optik - International Journal for Light and Electron Optics, 2001

This paper investigates the dynamical behaviors of a laser diode (LD) with strong feedback. The spectra, coherence length, and dynamical output power of a LD with different feedback are measured experimentally. It is found that the LD will return back to stable single mode when feedback is strong enough. The Lang-Kobayashi equations are modified to analyze the output of the LD with strong feedback. The good coincidences between the experiment results and the theoretical expectations are found. The results obtained here will give useful information for using the LD as both light source and detector.

Analytical theory of external cavity modes of a semiconductor laser with phase-conjugate feedback

Semiconductor Lasers and Laser Dynamics, 2004

The rate equations describing a laser with phase conjugate feedback are analyzed in the case of non-zero detuning. For low feedback rates and detuning, the stability diagram of the steady state is similar to the laser subject to injection. A stable steady state may loose its stability through a Hopf bifurcation exhibiting a frequency close to the relaxation oscillation frequency of the solitary laser. We also construct time-periodic pulsating intensity solutions exhibiting frequencies close to an integer multiple of the external cavity frequency. These solutions have been found numerically for the zero detuning case and play an important role in the bifurcation diagram.

Small-signal circuit modeling for a grating external-cavity semiconductor laser

Journal of the Optical Society of America B, 1994

A sinusoidal small-signal circuit model is presented for an external-cavity semiconductor diode laser with either weak or strong external optical feedback provided by a grating. It is shown that the effects of optical feedback can be modeled by two voltage sources correlated to the modulated injection current of the diode laser. The magnitudes of these two voltage sources are proportional to the product of the optical feedback level and the modulation amplitude. This result supports the idea of modulating a diode laser by optical injection. The small-signal intensity modulation and FM response characteristics of this circuit model are also presented. The response curves exhibit oscillations with the periods determined by the modulation feedback phase delay. These results agree with the results obtained elsewhere. For a short external-cavity limit, the response curves are reduced to the curves obtained elsewhere for a diode laser without an external cavity.