Abstract

In the last decade, the use of semiconductor laser diodes for optical communication systems has received increased attention due to their small size, high efficiency, and high speed for direct modulation.¹ In particular, the quenching of one laser by the light of another has been observed for GaAs injection lasers² and other systems. However, high-speed modulation of a laser diode by quenching with a second laser diode has not been addressed so far. A double-heterostructure (DH) stripe geometry GaAs laser with 250-μm cavity length was fabricated on a Si-doped (n+) GaAs substrate. The laser was mounted on a gold-plated heat sink to remove excess heat. A second DH stripe geometry laser, which is perpendicular to the first laser and < 100 μm away, was used as the modulating (sidearm) laser. The sidearm laser was electrically rf modulated and held at a 300-mA dc bias current (below threshold). It should be pointed out that lasing is not required from the sidearm laser. The rf source was a sweep oscillator, operated in a cw mode at 500 MHz at 0.0 dBm and amplified by a Mini Circuits amplifier (model Z HL 2–8) with 0.01-1-GHz bandwidth and 29-dBm power output (~ 1.0 W). The output signal was fed into a comb generator to obtain 150-ps pulses (FWHM) at 500 MHz and then to the rf port of a bias tee through a 16-dB attenuator. The output of the bias tee was then fed into the sidearm laser. The modulated laser was operated single mode at 808.9 nm with 90-mA dc bias current (above threshold). The laser output was detected using an Ortel PD-050-OM ultrafast photodiode detector (50-ps rise time). We observed that the laser output signal was inverted and modulated by the sidearm output. The modulation rate of the laser, as shown in Fig. 1, is ~5.0 GHz. Experimental results indicate that interaction between the lasers is not electrical. Specifically, the voltage across the modulated laser remains constant even when it is quenched to 57 % of its unmodulated output by changing the optical output of the sidearm laser. Further investigations of the mechanism of the interaction as well as optic logic are under way. (12 min)

© 1986 Optical Society of America