Jean-Marie Peransin

1/f noise in MODFETs at low drain bias

The 1/f noise in normally-on MODFETs biased at low drain voltages is investigated. The experimentally observed relative noise in the drain current S/sub I//I/sup 2/ versus the effective gate voltage V/sub G/=V/sub GS/-V/sub off/ shows three regions which are explained. The observed dependencies are S/sub I//I/sup 2/ varies as V/sub G//sup m/ with the exponents m=-1, -3, 0 with increasing values of V/sub G/. The model explains m=-1 as the region where the resistance and the 1/f noise stem from the 2-D electron gas under the gate electrode; the region with m=0 at large V/sub G/ or V/sub GS/ equivalent to 0 is due to the dominant contribution of the series resistance. In the region at intermediate V/sub G/, m=-3, the 1/f noise stems from the channel under the gate electrode, and the drain-source resistance is already dominated by the series resistance. >

Correlation between electrical and optical photocurrent noises in semiconductor laser diodes

The low and medium frequency (1 Hz/spl les/f/spl les/10 MHz) electrical noise characteristics of 0.98, 1.3, and 1.55 micrometer semiconductor lasers have been investigated. We show that the electrical noise is connected to the optical noise behavior. The correlation between electrical and optical noises is obtained by using the coherence function between these noise sources. This confirms the theoretical predictions issued from Haugs model that this correlation, which originates in the dipole interaction between the optical field and electron-hole pairs, can be extended to the laser diode characterization by using electrical noise measurements. >

Coherence between gate- and drain-current fluctuations in MESFET's and MODFET's biased in the ohmic region

The gate and drain current fluctuations and their coherence have been investigated on MESFETs from NEC and RTC and on MODFETs from NEC, Fujitsu, and Sony. In the frequency range of 10 Hz to 100 kHz the observed spectra show mainly 1/f and generation-recombination noise. Some devices show a complete absence of coherence in that frequency range. Other devices show a coherence as high as 0.55 at low frequencies and a drop at higher frequencies. Some devices show a very low coherence level which increased above a characteristic frequency. The proposed model explains the experimentally observed trends and their physical meaning. The coherence measurement can be used as an additional diagnostic tool for MESFET and MODFET reliability studies. >

Gate current 1/f noise in GaAs MESFET's

Gate current 1/f has been investigated on commercial GaAs MESFETs. It is found that devices with slight differences in drain current noise can have quite a different type of I/sub g/ versus V/sub ds/ and V/sub gs/ and even greater differences in the gate current noise. The 1/f part in the spectrum of the gate current is a better diagnostic tool for characterizing the quality of the junction than the drain current noise. A model that is based on a Schottky barrier shunted by edge currents is proposed to explain the experimental results. >

Electrical and optical noise of high power strained quantum well lasers used in Erbium doped fiber amplifiers

The optical amplifiers are formed by an Erbium‐doped fiber, optically pumped medium by a high power semiconductor laser emitting in the 980 nm region. The pump power is efficiently injected into the Erbium fiber using a precision wavelength division multiplexing fiber optic coupler. The aim of this paper is to propose a noise study of InGaAs/GaAs ridge single quantum well (SQW) lasers as pump lasers.

Spontaneous emission factor and gain evaluation of an optical amplifier by using noise measurements with no input signal

The erbium doped fiber amplifier (EDFA) is presently the key element of a long distance transmission. Experimental results of noise characteristics (1 Hz <EQ f <EQ 500 kHz) of an Er3+ erbium doped fiber amplifier pumped by 1.48 micrometers laser diode are reported in this paper. Several kinds of noise generated in EDFAs (1/f(alpha ) noise, 1 <EQ (alpha) <EQ 3; hopping noise, quantum noise) are very troublesome in the various applications of the EDFA. These noise levels impede to improve the optical coherence and the signal to noise ratio. Several studies have been made in order to introduce the low and medium frequency noise for transmitters but nothing yet concerning the EDFA. This communication deals with optical noise simulations of an EDFA. The output noise depends on the amplified spontaneous emission (ASE) power because no input signal is applied. Thanks to a noise simulation, we have been able to deduce the internal gain G of the doped fiber and the spontaneous emission factor nsp. The correlation between the monitoring photocurrent noise, the output noise and the input noise of the amplifier are given in order to show the influence of the pump laser on the EDFA output and input.

New method of gain and noise factor determination of an erbium-doped fiber optical amplifier by electrical noise measurements

This communication deals with optical noise measurements of an erbium-doped fiber amplifier with input signal. We are able to determine the net gain and the noise factor from only these low frequency electrical noise measurements and new simple relations. It is presented as alternative to optical analyzer measurements and it has no limitation for high input signals.

Noise analysis of the detection unit pixel a-Si:H

We present experimental and numerical simulation results on the noise levels generated in hydrogenated amorphous silicon PIN diodes. THe diodes have the tow structures forming a PIXEL arrangement.A parallel study is developed to compare the noise sources and to precise their location. Firstly we have led the analysis and the modelization of voltage - current curves separately for PIN and NIP diodes. The electrical model valid for both structures is designed. Secondly the noise for these structures is examined for the frequency range from 10Hz to 200kHz. Three different noise generators are extracted from analysis of the spectra. It is shown, that shot noise, 1/f noise and f-1/2 noise sources are present in the dark forward current. The model to explain white noise levels in designed and its validity is verified by experimental data. The dominant typical noise generator for the hydrogenated amorphous semiconductor takes the form of f-1/2 spectra, it is discussed as noise source which is formed by the composition of trap noise generators placed in the intrinsic layer and near the interface N+N-.

Analysis of the optical noise behavior of a LiNbO3 electro-optic modulator

The optical noise of the set: DFB Laser + EOM has been investigated, in a medium frequency range. This noise characterization clearly shows that in most cases the modulator increases the noise level properly relevant to the laser emitter. However, far above threshold, the optical noise at the end of the modulator tends, in some specific cases, to the fundamental noise, that is to say the shot noise level.

Spontaneous emission factor and gain evaluation of optical amplifier noise measurements with no input signal

This communication deals with optical noise measurements of an erbium-doped fiber amplifier. The output quantum noise depends on the amplified spontaneous emission power because no input signal is applied. Thanks to a noise simulation, we have been able to deduce the internal gain G of the doped fiber and the spontaneous emission factor nsp.