LASER LINEWIDTH WITH GAIN COMPRESSION

J. Arnaud, Laurent Chusseau, Fabrice Philippe

Electronics Letters, Volume 27, Issue 25, 5 December 1991, p. 2354 – 2356

ABSTRACT

An exact yet simple expression for the linewidth of laser diodes based on the Nyquist formula is given. The expression applies to the case where the optical gain depends on both the carrier and photon numbers and differs from the expression derived from standard rate equations. Gain compression in conjunction with an electrical conductance may reduce both the linewidth and the intensity noise.

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PHOTONIC NOISE WITH NONLINEAR GAIN

Jacques Arnaud

Electronics Letters, Volume 27, Issue 19, 12 September 1991, p. 1756 – 1758

ABSTRACT

For frequency-independent gain and loss, the circuit theory of photonic noise based on the Nyquist noise sources reduces to a corpuscular theory that postulates independent shot-noise fluctuations of the particle rates. For linear gain, the corpuscular theory coincides with standard rate equations (SREs). When the relative gain compression is comparable with unity, however, SREs are in error by a large factor. The exact theory shows that in the presence of nonlinear gain, photonic noise may be less than shot noise, even when the injected current exhibits shot-noise fluctuations. This new effect cannot be predicted by SREs.

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EVALUATION OF SEMICONDUCTOR OPTICAL PARAMETERS FOR LASER DIODES

J. Arnaud, M. Esteban

Optoelectronics, IEE Proceedings J  (Volume:138 ,  Issue: 2 ), pages 79 – 86, Apr 1991

ABSTRACT

The small-signal modulation and noise properties (electrical voltage, optical power and phase) of laser diodes depend on ten real parameters relating to the semiconductor material employed. Among these, the phase-amplitude coupling factor α is of particular importance. These parameters are evaluated for GaAs at 0.87 μm, GaInAsP at 1.55 μm and InAsSb at 3.87 μm at room temperature. Revised expressions for the optical gain are used. The light-hole contribution, the plasma effect and band-gap shrinkage are taken into account. The latter leads to a significant reduction of α, particularly below the peak-gain frequency. The α-factors for the three materials listed above are found to be, respectively, 2.9, 3.85 and 8.3 for conventional diodes

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CIRCUIT THEORY OF LASER DIODE MODULATION AND NOISE

J. Arnaud, M. Estéban

IEE Proceedings J 03/1990; DOI: 10.1049/ip-j.1990.0012

ABSTRACT

The circuit theory of laser diode modulation and noise is based only on the energy and electron-number conservation laws, and on the well known expression hv(Gb+Ga) for the spectral density of Nyquist noise currents. The conductances G b and Ga represent stimulated absorption and stimulated emission, respectively. This theory leads to results that are in exact agreement with the predictions of quantum optics, even in the case of electronic feedback and non-classical states of light, but the optical field is not quantised. The theory is presented in a general form, applicable to arbitrary optical and electrical configurations, but is exemplified for only a single active element model of laser diode. For independent electron-hole injection, the results are the same as those obtained from standard rate equations, except for a phase-noise term. Important differences do occur for more realistic laser models.

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CIRCUIT THEORY OF MULTIELEMENT LASER DIODES

J. Arnaud, M. Estéban

Optical Society, juin 1989

ABSTRACT

A general theory of noise and small-signal modulation of multielement laser diodes in the saturated regime is established. Nonlinear elements are connected to the ports of a linear-optical circuit oscillating in a single electromagnetic mode. The laser amplitude and phase fluctuations are expressed simply in terms of the scattering matrix of the linear-optical circuit at any baseband frequency and for an arbitrary electronic feedback. The case of a single laser diode and a single detector is treated to demonstrate this method. The correlation between optical power and electrical voltage fluctuations is shown to disappear at large output powers, in agreement with recent experiments.

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LINEWIDTH OF LASER DIODES WITH NONUNIFORM PHASE-AMPLITUDE α- FACTOR

Jacques Arnaud

IEEE Journal of Quantum electronics, vol 25 n° 4, april 1989

ABSTRACT

The linewidth of a laser diode having a phase-amplitude factor α that varies arbitrarily alongt he path is calculated. For simplicity, an ideal single-mode ring-type laser diode with only one wave circulating is considered. The theory is exact in the limit of large injected currents, provided parameters such as the carrier temperature do not vary and the gain or loss per wavelength is small. It is found that when the electron-hole pairs are injected independently of each other (that is, when the pump fluctuations are spatially uncorrelated shot noises) the linewidth is half the value obtained earlier for the linear regime multiplied by (1 + α2)av where the round-trip averaging is affected with respect to the reciprocal of the power gain. Specific examples, in particular a sequence of amplifiers and partially reflecting mirrors, are considered.

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PROPOSAL FOR GENERATION OF AMPLITUDE-SQUEEZED LIGHT (ASL) FROM LASER DIODES WITH ELECTRONIC FEEDBACK

Jacques Arnaud

Electronics Letters, Volume 25, Issue 1, 5 January 1989, p. 1 – 2

ABSTRACT

It is generally believed that the amplitude fluctuations of a light beam initially in the coherent state cannot be squeezed below those of shot noise by the simple arrangement of a beamsplitter and a detector, the current from the detector being fed back to the light source or to a modulator. A simple semiclassical theory shows that arbitrary amounts of squeezing can in fact be obtained if a negative opticalconductance device such as a constant-voltage-driven (nonself-oscillating) laser diode is used in place of a conventional detector.

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CIRCUIT THEORY OF AMPLITUDE NOISE FOR A LASER DIODE WITH ELECTRONIC FEEDBACK

Jacques Arnaud

Europhysics Letters, 8 (4), pp. 345-349, 1989

ABSTRACT

The amplitude noise of a laser diode submitted to electronic feedback is evaluated using a new circuit theory. It is postulated that the electron-hole injection rate equals the photon generation rate at any time, and Nyquist-like noise sources are introduced. Previous results based on quantum mehcanics are recovered. It is found that the amplitude fluctuations of an optical beam in the coherent state can be squeezed below shot noise by feeding back the driving current of a laser amplifier.

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CONTRIBUTION OF SHOT NOISE TO LASER DIODE LINEWIDTH

J. Arnaud

Optic communications, Vol 68, n°6, novembre 1988

ABSTRACT

Yamamoto and others are shown when the pump (or injected current) fluctuations of a laser diode are suppressed, the optical power fluctuations are much reduced, but the laser linewidth remains essentially unchanged. We find that for a realistic extended laser model, the linewidth may in fact be importantly reduced. Our finding is based on a semiclassical theory. With full shot-noise in the injected current, the linewidth is proportional to (1 + α2) av, where α (z) denotes the phase-amplitude factor, and the average is evaluated along the diode z-axis. Without injected current fluctuations, one must substract from this expression half the variance (α2) av – (αav)2 of α. The linewidth reduction thus occurs only if α varies significantly along the diode.

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Les articles de Jacques ARNAUD