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We describe the first results of hybrid mode locking combining both active and passive mode locking of a semiconductor laser. These functions are integrated into a monolithic device with a 1.3 μm GaInAsP gain region, an active waveguide, and a saturable absorber. The devices have low threshold currents, and exhibit hysteresis in their light/current characteristics. The long integrated waveguides allow mode locking at a repetition rate of 15 GHz without the need for an external cavity. Pulse widths as short as 1.4 ps have been demonstrated using the combined effects of active and passive mode locking.

Some published results on mode locked monolithic lasers are reviewed. Optical spectra of a typical hybrid mode-locked monolithic device for different levels of RF power and frequency are shown and discussed, as are effects of detuning the modulation frequency. Design considerations are examined. These include the length of the device, the use of hybrid mode locking, and the choice of active or passive waveguides. >

The fabrication and performance of a hybrid dual-wavelength light source consisting of InP channeled substrate-buried-heterostructure lasers emitting at 1.3 and 1.5 μm are reported. At 50 mA bias, launched powers averaging 4.3 mW at 1.3 μm and 2.1 mW at 1.5 μm into a 62.5 μm core, lensed, graded-index optical fiber are achieved with coupling efficiencies in excess of 31 and 33% for each wavelength, respectively. The output from this optical fiber is fed, via a biconic connector, to a 8 μm core, single mode fiber with maximum launched powers of 753 μW (1.3 μm) and 450 μW (1.5 μm) recorded.

Proton-bombarded gain-guided stripe-geometry (Al, Ga)As lasers have been made using an SiO 2 proton-implant mask. The Plasma-deposited SiO 2 was anisotropically plasma etched to yield vertical-walled stripes which acted as the high-resolution implant mask, Stripe width is determined solely by photolithography, and consequently strict tolerances can be maintained for optimum laser performance yields. A typical SiO 2 proton mask was 2.5 µm thick and 4.5 µm wide. The electrical and optical characteristics and accelerated aging behavior of these lasers are identical to those of lasers originating from neighboring wafer sites which were wire masked. The use of an anisotropically etched dielectric mask has many advantages over wire or plated metal implant masks, making it ideally suited for use on large wafers.

The first results for hybrid mode locking of semiconductor lasers are reported. Hybrid mode locking combines both active and passive mode locking to produce shorter mode-locked pulses. These functions are integrated into monolithic devices with a 1.3-μm GaInAsP gain region, an active waveguide, and a saturable absorber. The monolithic mode locked lasers are fabricated as arrays of six devices. These devices have low threshold currents and exhibit hysteresis in their light/current characteristics. The uniformity of threshold currents over an array of devices is very good. The long integrated waveguides allow mode locking at a repetition rate of 15 GHz without the need for an external cavity, with pulse widths as short as 1.4 ps being demonstrated.

Monolithic displays in GaP can provide potentially low power, high brightness, red or green display devices. Three basic device configurations (planar, mesa, dome) have been analyzed to determine their relative effectiveness for use in monolithic applications. The basic device structures have been fabricated from GaP wafers prepared by double liquid phase epitaxy. These structures have been studied to identify any inherent technological limitations associated with their fabrication.

Summary form only given. 1.3 mu m GaInAsP lasers were integrated with active waveguides and satirable absorbers to form arrays of monolithic devices. These devices have low threshold currents, and long integrated waveguides have led to picosecond pulse widths at a 15-GHz repetition rate. The integrated active waveguides decrease the effective coupling losses from laser to integrated cavity, and the saturable absorber provides pulse shortening by both active and passive mode locking. Arrays of six monolithic devices were fabricated from semi-insulating channeled substrate buried heterostructure 1.3 mu m GaInAsP laser material. Microwave measurements of the frequency response of these devices show a very large peak at 15 GHz which is one over the round trip time of the device. This peak at 15 GHz was measured to be 12 dB below the response at 50 MHz, while away from the peak the response falls by over 27 dB. This indicates a strong feedback from the integrated cavity, a characteristic of active waveguides. >