Electrical and optical gain lever effects in InGaAs double quantum-well diode lasers

Abstract

Abstract-In multisection laser diodes, the amplitude or frequency modulation (AM or FM) efficiency can be improved using the gain lever effect. To study gain lever, InGaAs double quantum well (DQW) edge emitting lasers have been fabricated with integrated passive waveguides and dual sections providing a range of split ratios from 1:1 to 9:1. Both the electrical and the optical gain lever have been examined. An electrical gain lever with greater than 7 dB enhancement of AM efficiency was achieved within the range of appropriate DC biasing currents, but this gain dropped rapidly outside this range. We observed a 4 dB gain in the optical AM efficiency under non-ideal biasing conditions. This value agreed with the measured gain for the electrical AM efficiency under similar conditions. We also examined the gain lever effect under large signal modulation for digital logic switching applications. To get a useful gain lever for optical gain quenched logic, a long control section is needed to preserve the gain lever strength and a long interaction length between the input optical signal and the lasing field of the diode must be provided. The gain lever parameter space has been fully characterized and validated against numerical simulations of a semi-3D hybrid beam propagation method (BPM) model for the coupled electron-photon rate equation. We find that the optical gain lever can be treated using the electrical injection model, once the absorption in the sample is known.

Analysis of the effect of optical confinement factor on the distortion performance of gain lever laser diode

“…As the bias current is fixed well above the threshold current, the gain lever is found to reduce. This is in accordance with the theory that gain lever is maximum around threshold current and reduces beyond threshold current [11].…”

“…The total optical gain overcomes the loss of the cavity at lasing threshold. An increase in gain in one section of the laser diode allows equal decrease in gain in other section [11]. When current in shorter section I a decreases, circulating optical power decreases, which results in increase of carrier density N g , in other section.…”

“…A sublinear relation between optical gain and carrier density is obtained. Hence a small amount of increase in carrier density N g , results in modulation depth improvement in such multi section laser diodes [8][9][10][11][12]. The two sections of laser diode are shorted together as shown in Fig.…”

“…Improvement in optical modulation depth is also observed in such devices due to gain lever effect [7][8][9][10][11][12][13][14][15]. The inherent nonlinearity of the two section gain lever laser diode also produces harmonic and intermodulation distortion.…”

Effects of Radiation on Optical Fibers

“…The transmitter contains an integrated multi-quantum-well distributed feedback laser diode(MQW-DFB-LD), an optical isolator, automatic power control (APC) circuits (Tanaka et al, 2002;Zivojinovic et al, 2004;Pocha et al, 2007), automatic temperature control (ATC) circuits, and DC bias circuits. The potential improvements of overall optical system performance depend on studying and analyzing LD transient characteristics such as modulation bandwidth, intensity, frequency noise levels and nonlinear distortion.…”