Hitomi Ito

Lateral current injection GaInAsP/InP laser on semi-insulating substrate for membrane-based photonic circuits

A room-temperature pulsed operation was demonstrated using lateral current injection-type lasers composed of a 400-nm-thick GaInAsP core layer with compressively strained 5 quantum wells. A threshold current of 105 mA and corresponding density of 1.3 kA/cm(2) (260 A/cm(2) per well) were obtained with the stripe width of 5.4 microm and the cavity length of 1.47 mm. A fundamental transverse mode operation was obtained with the narrower stripe device of 2.0 microm and the cavity length of 805 microm, while the threshold current and corresponding density were 49 mA and 3.0 kA/cm(2), respectively.

GaInAsP/InP lateral-current-injection distributed feedback laser with a-Si surface grating.

We fabricated a novel lateral-current-injection-type distributed feedback (DFB) laser with amorphous-Si (a-Si) surface grating as a step to realize membrane lasers. This laser consists of a thin GaInAsP core layer grown on a semi-insulating InP substrate and a 30-nm-thick a-Si surface layer for DFB grating. Under a room-temperature continuous-wave condition, a low threshold current of 7.0 mA and high efficiency of 43% from the front facet were obtained for a 2.0-μm stripe width and 300-μm cavity length. A small-signal modulation bandwidth of 4.8 GHz was obtained at a bias current of 30 mA.

Continuous Wave Operation of Thin Film Lateral Current Injection Lasers Grown on Semi-Insulating InP Substrate

New structural designs are adopted to reduce the waveguide loss and increase the internal quantum efficiency of lateral current injection lasers consisting of a thin GaInAsP core layer grown on a semi-insulating InP substrate. This led to a drastic reduction in the threshold current. Room temperature continuous-wave operation has been successfully realized with a threshold current of 11 mA and an external differential quantum efficiency of 33% for a stripe width of 1.7 µm and a cavity length of 720 µm.

Lateral-Current-Injection Distributed Feedback Laser With Surface Grating Structure

As a step toward the realization of injection-type membrane distributed feedback (DFB) lasers, which are expected to be important components of optical interconnections, we realized lateral-current-injection DFB (LCI-DFB) lasers with surface grating structures prepared on semiinsulating InP substrates. First, we designed the surface grating structure to have a high index-coupling coefficient together with a high optical confinement in the quantum wells. Then, we investigated the surface grating structure formed on an amorphous-Si (a-Si) layer deposited on the GaInAsP/InP initial wafer containing five quantum wells. A moderately low threshold current of 7.0 mA and a high differential quantum efficiency of 43% from the front facet were obtained under a continuous-wave operating condition at room temperature for a uniform grating LCI-DFB laser with a stripe width of 2.0 μm and a cavity length of 300 μm. A threshold current of 5.8 mA was obtained with a λ/4 phase-shifted LCI-DFB laser with a-Si surface grating. Furthermore, a small-signal modulation bandwidth of 4.8 GHz was obtained at a bias current of 30 mA with a modulation current efficiency factor of 1.0 GHz/mA1/2.

Injection-Type GaInAsP/InP Membrane Buried Heterostructure Distributed Feedback Laser with Wirelike Active Regions

A current-injection-type semiconductor membrane distributed feedback laser consisting of a 470-nm-thick semiconductor core and bonded by a benzocyclobutene polymer on a silicon-on-insulator substrate was demonstrated for the first time by adopting a lateral current-injection structure. Room-temperature pulsed operation was achieved with a threshold current of 83 mA for a stripe width of 3.2 µm and cavity length of 420 µm.

Lateral Junction Waveguide-Type Photodiode Grown on Semi-Insulating InP Substrate

A lateral junction waveguide-type GaInAsP/InP photodetector was fabricated on a semi-insulating InP substrate by two-step organometallic vapor-phase epitaxy (OMVPE) regrowth. Responsivities of 0.9 A/W at 1500 nm and 0.27 A/W at 1550 nm were obtained. A 3-dB bandwidth of 6 GHz and 6-Gbps error-free operation under non-bias conditions were achieved with a stripe width of 1.4 µm and a device length of 220 µm.

Lateral current injection type GaInAsP/InP DFB lasers on SI-InP substrate

Toward injection type GaInAsP/InP membrane lasers consisting of high index contrast waveguide structure, lateral current injection type distributed-feedback lasers on a semi-insulating InP substrate were realized by an electron-beam lithography and organo-metallic vapor-phase-epitaxial regrowth. Single mode operation with a threshold current of 27 mA and a side-mode suppression ratio of 35dB at a bias current of two times the threshold was obtained at room temperature pulsed condition.

Room-temperature CW operation of lateral current injection lasers with thin film lateral cladding layers

Semiconductor membrane laser with high index-contrast waveguide is promising for achiving low power consumption operation. As a step to realize a current injection (LCI) type membrane laser, GaInAsP/InP lateral current injection type Fabry-Perot lasers with 400 nm thin core layer, including compressively-strained 5 quantum-wells were realized by 2-step OMVPE regrowth on a semi-insulating InP substrate. A RT-CW operation with a threshold current of 12 mA, which corresponds to a threshold current density of 1.7 kA/cm2, was obtained for a sample with a stripe width of 1.4 µm and a cavity length of 490 µm. This LCI structure can be attractive for membrane photonic devices for optical interconnections and on-chip optical wiring.

First lasing operation of injection type membrane GaInAsP DFB laser with lateral current injection BH structure

An injection type semiconductor membrane DFB laser with low index polymer cladding layers was demonstrated for the first time by lateral current injection structure. Room temperature, pulsed lasing operation was realized with a threshold current of 83 mA for the stripe width of 3.2 µm and the cavity length of 420 µm.

Lateral junction waveguide type photodiode for membrane photonic circuits

A lateral junction type photodiode grown on a semi-insulating InP substrate was realized by 3-step OMVPE growth. The responsivity of 0.27 A/W, 3 dB bandwidth of 6 GHz and 7.5 GHz at a bias voltage of 0 V and −2 V, respectively, were obtained for the stripe width of 1.4 µm and device length of 220µm. An error free transmissions up to 6 Gbps at 0 V were confirmed.