Akimasa Mizutani

Lasing characteristics of InGaAs-GaAs polarization controlled vertical-cavity surface-emitting laser grown on GaAs [311] B substrate

We have demonstrated an oxide confinement polarization controlled vertical-cavity surface-emitting laser (VCSEL) grown on a GaAs [311]B substrate. The polarization state was well controlled along the [2~33] crystal direction due to an anisotropic gain in the [311]B plane. We fabricated a small oxide aperture VCSEL with a threshold of 260 /spl mu/A and realized single-transverse mode and single-polarization operation for the first time. The sidemode suppression ratio (SMSR) was 35 dB and the orthogonal polarization suppression ratio (OPSR) was 25 dB. In addition, we have measured polarization and transverse mode characteristics of multi- and single-transverse mode devices under high-speed modulation. In the multimode device of 12 /spl mu/m/spl times/12 pm oxide aperture, we have achieved stable polarization operation of over 25-dB OPSR up to 10 Gb/s and have observed no power penalty due to polarization instability under 2.5-Gb/s pseudorandom modulation. The single-mode device showed stable single-transverse mode and polarization under the modulation conduction up to 5 GHz of sinusoidal modulation. SMSR and OPSR were over 30 and 10 dB, respectively.

A low-threshold polarization-controlled vertical-cavity surface-emitting laser grown on GaAs (311)B substrate

We have demonstrated a GaAs (311)B vertical-cavity surface-emitting laser (VCSEL) with a threshold current as low as 250 /spl mu/A, which is the lowest value ever reported for that on non-(100) oriented substrates. Also, the fabricated VCSEL shows a stable polarization state for wide during current ranges and a large polarization-mode suppression ratio over 30 dB between the [233] and [011] axis modes at 5 mA. The electrical specific resistance of 1.2/spl times/10/sup -4/ /spl Omega//spl middot/cm/sup -2/ at the threshold was reasonably low due to carbon autodoping to AlAs in a p-type distributed Bragg reflector (DBR).

An over 10-Gb/s transmission experiment using a p-type delta-doped InGaAs-GaAs quantum-well vertical-cavity surface-emitting laser

We have fabricated a p-type delta-doped InGaAs-GaAs quantum-well (QW) vertical-cavity surface-emitting laser (VCSEL) with a low-resistance GaAs-AlAs distributed Bragg reflector (DBR). The threshold was as low as 700 /spl mu/A for 10/spl times/10 /spl mu/m/sup 2/ devices. A penalty-free 10-Gb/s transmission experiment with a 100-m-long multimode fiber was performed using fabricated VCSELs. The modulation speed was up to 12 Gb/s, which was limited by an RC constant. Further threshold reduction and high-speed operation can be expected by controlling the doping concentration in p-type delta-doped layers.

Single-transverse mode and stable-polarization operation under high-speed modulation of InGaAs-GaAs vertical-cavity surface-emitting laser grown on GaAs (311) B substrate

We have demonstrated an oxide confinement vertical-cavity surface-emitting laser grown on a GaAs (311)B substrate, and achieved single-transverse mode and single-polarization operation in the entire tested current range. The threshold was 0.6 mA for a 2.7 /spl mu/m/spl times/2.9 /spl mu/m oxide aperture. Even under high-speed modulation up to 5 GHz, the device showed stable single-transverse mode and polarization. Sidemode suppression ratio and orthogonal polarization suppression ratio were over 30 and 10 dB, respectively.

Proposal and Demonstration of AlAs-Oxide Confinement Structure for InP-Based Long Wavelength Lasers

We have demonstrated an AlAs oxidation process for current and light confinement in the AlGaInAs/InP system for the first time. A lattice-mismatched 200-A-thick AlAs layer grown on an InP substrate by metalorganic chemical vapor deposition (MOCVD) was selectively oxidized. The temperature dependence of the oxidation rate was examined. The oxidized AlAs showed good electric isolation characteristics for lateral current confinement. The proposed AlAs-oxide confinement structure formed on an InP substrate may facilitate fabrication and threshold reduction of long wavelength lasers including vertical-cavity surface-emitting lasers.

InGaAs/GaAs Vertical-Cavity Surface Emitting Laser on GaAs (311)B Substrate Using Carbon Auto-Doping.

We have realized a low threshold InGaAs/GaAs vertical-cavity surface emitting laser (VCSEL) grown on GaAs (311)B substrates by metalorganic chemical-vapor deposition. The lasers exhibited a threshold current of 16 mA and a threshold current density of 810 A/cm2 for a 50 µm circular active area device. We obtained low electric resistance of p-type DBRs on GaAs (311)B by using AlAs carbon auto-doping with a hole concentration of 2×1019 cm-3. We also demonstrated a stable polarization operation of (311)B grown VCSELs.

P - type AlAs growth on a GaAs (311)B substrate using carbon auto - doping for low resistance GaAs/AlAs distributed Bragg reflectors

A high p -type hole-concentration AlAs layer has been successfully grown on a GaAs (311)B substrate by metalorganic chemical vapor deposition with using a Carbon auto-doping technique. The doping concentration was well controlled by changing only V/III ratios. The hole concentration was as high as 2 ×1019 cm-3 at a V/III ratio of 6. A very low resistance of p -type distributed Bragg reflector was obtained with a δ-doping technique to GaAs/AlAs interfaces.

GaInAs/AlGaInAs Semiconductor Lasers with AlAs Oxide Current Confinement Structure

An AlAs oxide current confinement structure based on an InP substrate has been demonstrated for the first time to realize low threshold long wavelength surface emitting lasers. The oxidized width is confirmed to be well controllable by choosing suitable oxidation time and temperature. We fabricated an metalorganic chemical vapor deposition (MOCVD) grown 1.65-µ m wavelength GaInAs/AlGaInAs multiple quantum well (MQW) edge emitting laser with the AlAs-oxide confinement structure of 3 µ m-wide and 15 µ m-wide windows. A 3 µ m-wide window oxidized laser having uncoated facets exhibits a threshold of 51 mA for device with a 800-µ m-long cavity. We have obtained a threshold current density of 1.3 kA/cm2 for 3 µ m-wide window devices. The results show a potential application of the proposed structure for low threshold long-wavelength surface emitting lasers.

A COMPLETELY SINGLE-MODE AND SINGLE-POLARIZATION VERTICAL-CAVITY SURFACE EMITTING LASERS GROWN ON GAAS (311)B SUBSTRATE

We realized a completely single-mode and single-polarization 0.98 µm InGaAs/GaAs vertical-cavity surface emitting laser (VCSEL) grown on a GaAs (311) B substrate. The device operates in a single transverse, longitudinal mode and polarization state in the entire tested current range. An oxide confinement structure with a nearly square oxide aperture of 2.5 µm×3.0 µm was formed for transverse mode control. We obtained a side mode suppression ratio of over 35 dB and a polarization mode suppression ratio of over 25 dB between the [233] and the [011] axis modes in the entire driving range. The threshold voltage and electrical specific resistance are as low as 1.5 V and 1.1×10-4 Ωcm-2, respectively. One of the tested devices shows a record low threshold current of 230 µA for non-(100) substrates.

P-type delta-doped InGaAs/GaAs quantum well vertical-cavity surface-emitting lasers

The vertical-cavity surface-emitting laser (VCSEL) operating with low threshold current is a promising way to realize future parallel optical interconnects. In this study, we propose a novel structure of p-type delta-doped InGaAs/GaAs quantum wells for low-threshold, high-speed VCSELs. Edge-emitting lasers having p-type delta-doped quantum wells were grown by metal-organic chemical-vapor deposition and a low-threshold current density of 152 A/cm2 (51 A/cm2/well) was realized. We also fabricated p-type delta-doped quantum well InGaAs/GaAs VCSELs with a low-resistance GaAs/AlAs distributed Bragg reflector, and achieved a low threshold current of 0.37. Further threshold reduction by controlling the doping concentration in the p-type delta doped layers is expected. ©1999 Scripta Technica, Electron Comm Jpn Pt. 2, 82(4): 54–60, 1999