Takayuki Koguchi

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.

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.

GaInAsP/InP Lateral Current Injection Laser With Uniformly Distributed Quantum-Well Structure

To enhance the internal quantum efficiency of GaInAsP/InP lateral current injection (LCI) lasers, we adopted a structure consisting of five uniformly distributed quantum-wells (QWs). A differential quantum efficiency of 59% and an internal quantum efficiency of 70% were obtained for a cavity length of 750 μm, the latter value is almost twice that of an LCI-Fabry-Pérot laser with a conventional QW structure.

Lateral-Current-Injection Type Membrane DFB Laser With Surface Grating

Toward the light source for on-chip interconnection, a current-injection-type membrane distributed feedback laser with a surface gating structure is demonstrated. In this device, 450-nm-thick GaInAsP/InP layers with lateral-current-injection structure prepared by a two step OMVPE regrowth-method is bonded on a host substrate by using Benzocyclobutene bonding process. A threshold current of Ith=11 mA is obtained with a cavity length of 300 μm and a stripe of 1 μm.

10 Gbps Operation of Top Air-Clad Lateral Junction Waveguide-Type Photodiodes

Toward on-chip photonic integrated circuits (PICs) based on a membrane structure, a lateral junction waveguide-type photodiode fabricated on semi-insulating (SI-) InP substrate was successfully demonstrated. A responsivity of 0.39 A/W was obtained by adopting a bulk GaInAs absorption layer. In addition, a narrow stripe width of 0.85 µm was chosen for the realization of high-speed operation. As a result, a 3 dB bandwidth of 8.8 GHz at a bias voltage of -2 V was attained for a device length of 380 µm, and a clear eye opening was obtained up to 10 Gbps.

Lateral current injection laser with uniformly distributed quantum-well structure

Uniformly distributed quantum-well structure was introduced to a lateral-current-injection (LCI) laser to realize high internal quantum efficiency operation. As the result, superior light output characteristic was obtained with the internal quantum efficiencies of 70%.

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.

10 Gb/s operation of GaInAs/InP top air-clad. Lateral junction waveguide-type photodiode

10 Gb/s operation of GaInAs/InP lateral junction-type photodiode was obtained by adopting a narrow stripe width of 0.85 μm. The responsivity of 0.39 A/W and the 3dB bandwidth of 8.8 GHz at a bias voltage of -2 V were obtained with the device length of 380 μm.

Lateral current injection type GaInAsP/InP DFB laser with a-Si surface grating

Lateral current injection DFB laser with a-Si surface grating was demonstrated, as step to realize membrane laser. The threshold current of 7.0 mA and the differential quantum efficiency of 43% from the front facet were obtained.