Emission Dynamics of Multifunctional Segmented Laser Diode.Segmented LD proposed 30 years ago [l] until now often becomes the subject of R&D being possessed of wider capabhties than the traditional homogeneously pumped LD. Depending on electrical connections, pumping and modulating currents its output characteristics may be altered quahtatively. In microelectronics a lot of microcircuits (ICs) can perform Merent functions dependmg on their connections. Such approach is not usual yet for optoelectronics components but it is reasonable to suppose that segmented LD may become the basis of multdimctional lightemitters. Stationary characteristics of three-sections (GaA1)As SC DH LD with 4pm-wide ridge wavegude were studed in [2]. The present work is concentrated on the dynamical behaviour of h s device.Sections' lengths of the samples were 250, 50, and 250pm respectively. The leakage resistance between them was 3-5kR. Light-current characteristics for Merent connection methods are shown on Fig.1. For short-circuited sections (connection I) L-C curve differs fiom that of homogeneously pumped LD only by jump-like switchrng and a narrow hysteresis loop at threshold.When central section 2 is unpumped (connection II) the power jump at threshold is much htgher and hysteresis loop much wider. When section 3 is u n p q e d (connection E t ) the power jump at threshold is not observed. When section 2 is grounded (connection IV) L-C curve contains pronounced kinks. Typical threshold wavelengths were 86-862nm, 866nm and 865nm for connections I, 11, E I and IV respectively. Above threshold single longtudmal mode operation with side-mode suppression more than 15 dB was observed for connections I, II and I I I . For connection Iv only multimode lasing occured. When section I is grounded (connection V) only amphfied spontaneous emission with spectral FWHM about 25nm is observed (SLD mode).Typical frequency response characteristics (-3dB bandwidth) under du-ect current modulation are the following: LD mode (connection I, I123 = 75mA, P = lOmW) -2.5 GHz; SLD mode (connection V, 123 = 150mA, P =3 mW) -250 MHz.For connections I and II near threshold especially inside hysteresis loops strong selfpulsations were observed. Depending on pumping current the repetition rate of light spikes was in the range 0.5 -2.0 GHz, their pulsewidth was about 5Ops. Th~s process may be effectively synchronized by small sine current supemqosed on pumping current or injected into section 2 (connection II). Above threshold when current increases this process relaxes quickly (Fig.2a).When working point (injection current) is fixed inside hysteresis loop the superposition of bipolar current pulses may switch on/off intensity self-pulsations (Fig.2b). For connection IV intensity selfpulsations are maintained far above threshold with repetition rate increasing with current. But at points that correspont to kinks on L-C curve the pronounced route to chaotic pulsations is observed. The approach to these points is accompanied by period doubhg of the pulsations and ...
